ALBERT

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Jan Seiler, Franz Lanzerath, Christoph Jansen, André Bardow〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Efficient evaporation of water at low temperatures is challenging due to its low saturation pressure. As a consequence, the preferred evaporation by nucleate boiling can only be achieved at the cost of high superheats. However, low superheats can still lead to efficient evaporation by thin-film evaporation. In this work, we experimentally characterize the heat transfer for thin-film evaporation on coated copper tubes, which use capillary action to create a thin film on their surface. The overall heat transfer through the tubes is determined at all filling levels for evaporator inlet temperatures of 10, 15 and 20 °C with varied driving force. Our experiments reveal that poor coatings suffer from dry-out at high driving forces whereas tubes with good coatings remain fully wetted even at high driving force. Furthermore, we show the impact of surface properties on thin-film evaporation: high porosity, surface extension and roughness promote the creation of a thin film on the tube. Thereby, the heat transfer 〈em〉UA〈/em〉-value is increased up to a factor of 10.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Jianxin Xu, Qingtai Xiao, Zhihan Lv, Junwei Huang, Ruoxiu Xiao, Jianxin Pan, Hua Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We propose a new method to measure uniformity of gas-liquid mixing in a direct-contact heat exchanger by moment balance and image analysis. A mapping technique is developed to project the pixels distribution from binary image to 3D domain. We present a rigorous theoretical base of the applied method based on moments and equilibrium theory. An inclination angle with direction is derived to characterize the imbalanced structure caused by heterogeneity of mass distribution, which is used to quantify the global uniformity of spatial distribution of mixtures in any irregular area. A characteristic curve obtained by local inclination angles can be used to test the homogeneous, heterogeneous and pseudo-homogeneous mixtures, leading to a useful parameter to quantify the mixing effects. The uniformity obtained by similar patterns are compared with existing methods. The experimental results show a good fitting curve between mixing effects and heat transfer performance. This test could also be applied for studying a variety of multiphase mixing problems in which assessment of uniformity is required.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Olga Arsenyeva, Julian Tran, Mark Piper, Eugeny Kenig〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pillow-plate heat exchangers (PPHEs) represent a novel equipment type. For their application in industry, reliable preliminary design techniques are required. In this article, the existing methods for heat exchangers design are analysed and the approach for selecting the PPHE design with minimal heat transfer area is proposed. It is based on the mathematical model of thermal and hydraulic PPHE behaviour, in which the overall heat transfer coefficient and pressure drop in PPHEs are expressed through the fluid velocity. The estimation of fluid velocities in PPHE channels is based on the condition that the predefined allowable pressure drop is fully exploited. Two case studies for water heating and crude oil preheat train operating conditions are discussed, in which the flowrates of the fluids on the hot and cold sides differ significantly. The PPHE design with minimal heat transfer area for the considered case studies is presented, with specified pillow-plate geometry parameters and distance between pillow-plate panels. The resulting pressure drops and velocities in PPHEs channels as well as the obtained heat transfer surface areas are compared with existing data for chevron-type plate heat exchangers (PHEs) designed for the same operating conditions. This comparison shows that PPHEs have higher velocities in channels, longer plates and lower heat transfer area. It can be concluded that PPHEs can be successfully used for operating conditions, under which the flow rates for hot and cold fluid are significantly different and the application of chevron-type PHEs with single-pass arrangement is complicated.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Nidhi, K.A. Subramanian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present experimental investigation deals with the study of the effect of oxygen enriched intake air on performance, emission and combustion characteristics of a methanol (M100) fuelled spark ignition engine. The oxygen in the intake air of the engine fuelled with methanol was enriched from 23% (by mass) with base oxygen to 26.5%, 38.7% and 60.4%. The brake thermal efficiency increased drastically with methanol with 38.7% and 60.4% enriched air by 9.9% and 20.5% respectively. The peak pressure and cumulative heat release with the highest enriched air (60.4%) are higher about 2 and 1.27 times than base oxygen percentage (23% by mass). The ignition delay and combustion duration decreased by 35.24% and 57.8% respectively. Carbon monoxide (CO) and hydrocarbon (HC) emissions with the highest enriched air decreased substantially by 48.59% and 30.9%. However, nitrogen oxides (NO〈sub〉x〈/sub〉) emission increased drastically by 112.2% with 38.7% of oxygen but it decreased by 31.5% with 60.4% oxygen enriched air which is lower than base oxygen. A notable conclusion emerged from this study is that a methanol fuelled engine with the oxygen enriched air (60.4%) could emit very lower emissions (CO, HC, NO〈sub〉x〈/sub〉) along with improved thermal efficiency compared to base oxygen (23% by mass).〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Manuel Colera, Ángel Soria, Javier Ballester〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work we present a numerical scheme for the steady-state thermodynamic analysis of gas turbine engines. As usual in the literature, it is based on modelling the gas turbine as a set of independent components connected through nodes, thus giving the user great flexibility to modify the gas turbine’s model and to define and include new components. Additionally, the proposed method provides the same flexibility for the inclusion of new gas properties calculators and nonlinear equations solvers. The simulator also allows identifying the characteristic parameters of the different components of the gas turbine –such as the compressor’s nominal pressure ratio and efficiency– from a batch of operation data. The latter task is accomplished by means of a systematic and computationally economic procedure which allows that the parameters identification be performed component-by-component and does not require any full gas turbine simulations. The scheme has been formulated so that it exploits the full capabilities of today’s computers and mathematical techniques –such as sparse matrix solvers and quasi-Newton methods for sparse jacobians– but, at the same time, remains simple enough to be self-implemented by the interested researchers with the aid of general-purpose mathematical computing software such as Matlab. The simulator has been applied to predict the performance of a real gas turbine, obtaining excellent results.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Ehsan Taheran, Kourosh Javaherdeh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Experimental study has been carried out to investigate the effects of inlet swirl generator on heat transfer and pressure drop of non-Newtonian drilling nanofluid under turbulent flow conditions. The equal volume mixture of water base silver nanofluid and a biological oil diluted by water was used as under test fluid. Thermal conductivity and rheological properties of novel drilling nanofluid were measured and an empirical model for thermal conductivity was proposed. Non-Newtonian power law coefficients of drilling nanofluid at three different temperatures were also presented. Nusselt number and friction factor for three different swirl generators twist angle (θ = 120 °C, 240 °C and 360 °C) were evaluated and thermo-hydraulic performance of non-Newtonian drilling nanofluid (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si17.gif" overflow="scroll"〉〈mrow〉〈mi〉∅〈/mi〉〈mo〉=〈/mo〉〈mn〉0.1〈/mn〉〈mo〉%〈/mo〉〈mo〉,〈/mo〉〈mn〉0.5〈/mn〉〈mo〉%〈/mo〉〈mspace width="0.25em"〉〈/mspace〉〈mi〉a〈/mi〉〈mi〉n〈/mi〉〈mi〉d〈/mi〉〈mspace width="0.25em"〉〈/mspace〉〈mn〉1〈/mn〉〈mo〉%〈/mo〉〈/mrow〉〈/math〉) was calculated at different Reynolds numbers from 4,000 to 10,000. The obtained results stated that the flow behavior depends on the nanofluid concentration, swirl generators geometry and Reynolds number. According to the experimental data, Nusselt number increased up to 86% but enormous enhancement in friction factor (up to 370%) limited the maximum thermo-hydraulic performance augmentation to 35%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Yiran Zheng, Yu Shi, Yunhui Huang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We propose a thermal management system for fast charging Li-ion battery pack combining liquid cooling and phase change material cooling. The main heat dissipating approach is liquid cooling, while composite phase change material wipes out the thermal-opaque area in the battery pack and provides relatively small amount of heat absorption. Alternated flow of coolant is required to guarantee temperature uniformity in the battery pack but is found detrimental to the systematic thermal dissipation. A method to address that issue, adding polyurethane adiabatic interlayers between cooling tubes, is proven to be an effective answer. Via analysing the heat transfer mechanism of the designed thermal management system, the influencing factors on its performance are found and a heat dissipation balancing coefficient is defined to quantify the temperature balancing performance of the system. The simulation for the system under an 8C rate charging condition is conducted, as well as compare tests concerning coolant flowing directions, coolant flowing speeds, filling materials, and the interlayers. Simulation results show that the system in question well controls the temperature of an 8C rate charging battery pack, with the maximum temperature at 38.69 °C and the temperature difference at 2.23 °C.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Eid S. Mohamed〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Exhaust heat from vehicle engines can be one of the promising heat sources to provide additional energy using thermoelectric generation (TEG). However, the objective of this study is to assess the exhaust heat recovery behavior by TEG, evaluation of diesel fuel consumption (DFC) and exhaust emissions. Thirty standard thermoelectric modules (TEMs) were mounted on the two sides (1 × 5) and lower side (4 × 5) arrangement of a light diesel vehicle exhaust channel. A detailed experimental work was carried out to study the performance behavior of TEG system with different engine speeds and over new European driving cycle (NEDC) using chassis dynamometer. Comparative analyses of the exhaust gases flow rate, DFC, exhaust emissions such as THC, CO, CO〈sub〉2〈/sub〉, and smoke emissions have been measured during NEDC with and without TEG actuation. Experimental results observed that the average value of TEG system efficiency is approximately 4.63% under the NEDC conditions. It also found that: by actuation the TEG system, the effectiveness of DFC percentage has been reduced by (1.46%–3.13%), lower exhaust gas emissions were found, too. The experimental result of output power is in good agreement with the theoretical result within 5.16% error at 1500 rpm.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359431118301236-ga1.jpg" width="328" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Kun Tu, Qiang Wu, Haizhou Sun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Owing to the limitation of the available land in China, among various ground source heat pump (GSHP) system configurations, the single-well circulation (SWC) coupled GSHP systems are being intended to provide heating and cooling for building in recent years, especially utilized in this area with suitable hydrogeological and thermogeological conditions. This is due to the fact that the SWC system could not only substantially provide shallow geothermal energy for space heating or cooling in small-scale applications, but also reduce the number of boreholes needed for large-scale geothermal applications. In this work, a mathematical model has been established to analysis the groundwater seepage of SWC system, and analytical solution of steady drawdown was derived. Meanwhile, a numerical model was constructed to evaluate the thermal performance by using SWC coupled GSHP systems. Numerical experiments were performed to observe the evolution of outlet temperature, the distribution of subsurface temperature field, and the long-term development of outlet temperature. It was found that the thermal effective radius (TER) of SWC system is much larger than that of ground-coupled heat pump (GCHP) systems. Also, the temperature field in vertical section caused by the operation of SWC system is funnel-shaped. In addition, the outlet temperature fluctuates annually, and it rather starts a long-term decaying process, until reaching a quasi-steady state after about 8–10 years.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Gang Wang, Gaosheng Wei, Chao Xu, Xing Ju, Yanping Yang, Xiaoze Du〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Different foam metals combined with paraffin and other materials were analyzed to determine their effective thermal conductivity and the macroscopic thermophysical properties of the composite materials. A W-P model composed of six tetrakaidecahedrons and two irregular dodecahedrons was used to simulate the melting heat transfer process in open foam metal at pore-scale under constant temperature. The results show that the porosity and conductivity of the foam metal and the conductivity of the phase change material (PCM) have a significant influence on the effective thermal conductivity of the composite PCM, while the pore size has no obvious influence. The effective thermal conductivity of composite PCMs increased with increasing foam metal thermal conductivity, and increased more rapidly with lower foam metal porosity. The effective thermal conductivity of composite PCMs is related to the ratio of foam metal conductivity to PCM conductivity. The microstructure of the foam metal had an obvious effect on the solid-liquid phase distribution during the PCM melting process, where the heat was transferred mainly through the melted liquid PCM field. Conduction was the dominant heat transfer mechanism, and natural convection in the liquid PCM was weak for the confinement of foam metals. For heat transfer during the PCM melting process, conduction through the skeleton of the porous metal played the most important role. The PCM adjacent to the heating source and foam metal frame melted first, with the fusion zone gradually spreading to the pore center. The melting rate of the PCM increased with increasing boundary temperature and thermal conductivity of the foam metal, but decreased as foam metal porosity increased. During the melting process, the liquid phase fraction did not linearly grow with time; the melting rate was very large at the initial stage, but decreased gradually with time.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 January 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 147〈/p〉 〈p〉Author(s): Adrián Mota-Babiloni, Joaquín Navarro-Esbrí, Víctor Pascual-Miralles, Ángel Barragán-Cervera, Angelo Maiorino〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Coming refrigeration and air conditioning systems must include low GWP fluids and optimized components. An internal heat exchanger (IHX) is a common modification of the basic cycle to enhance its energy performance, and its benefits have been demonstrated with R134a and the recently developed hydrofluoro-olefin R1234yf. This paper assesses the experimental influence of a high effectiveness IHX using R134a, and the low GWP mixture R513A (a mixture of R134a and R1234yf) under different evaporating and condensing conditions (29 points tested in total). Discharge temperature has been increased up to 26 K for both fluids, and the greatest compression ratio is not feasible for R134a. The cooling capacity of the system results increased up to 5.6% for R513A whereas for R134a is around 3%. Furthermore, due to the minimum diminution of power consumption, COP also increases up to 8% for R513A and 4% for R134a. Because of the observed experimental results, high effectiveness IHX is recommended for R513A, especially for high compression ratio operations as long as the discharge temperature does not reach critical values. Finally, it has been found that Klein et al.’s and Hermes’s correlations overestimate the COP benefit and the increase in power consumption should be considered.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): S.H. Hosseini, M.J. Rezaei, M. Bag-Mohammadi, Alireza Zendehboudi, G. Ahmadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Determining the frost layer thickness on plates is very important in heat and mass transfer processes in cryogenic equipment. In this study, the intelligent approaches of multi-layer perceptron trained by Bayesian Regulation (MLP-BR) and adaptive neuro fuzzy inference system (ANFIS) are utilized for predicting the frost layer growth on a vertical plate under natural convection and horizontal and parallel plates under forced convection. Dimensionless groups of the relevant parameters are also formed and used in this analysis. In particular, plate temperature, air temperature, air velocity, relative humidity, and time are taken as the models’ inputs. The self-organizing map (SOM) is applied to examine the influences of inputs on the performance of the selected models. It is shown that the MLP-BR-SOM model provides the best results for the test data samples with AARE of 2.57%, 6.55%, and 8.34% for test data, respectively, for the cases of vertical, horizontal, and parallel plates, respectively. In addition, three new semi-empirical equations comprising of dimensionless parameters are developed for the cases of vertical, horizontal, and parallel plates, with AARE of 12.36%, 27.18%, and 22.076%, respectively. Ultimately, the results are compared with those predicted by the existing empirical equations.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359431118347987-ga1.jpg" width="433" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Eun Jung Choi, Jin Young Park, Min Soo Kim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The aim of this paper is to investigate two-phase heat transfer of HFE-7100 in mini-channels and its cooling performance in order to determine its effectiveness for a fuel cell application. Firstly, characteristics of two-phase boiling heat transfer of HFE-7100 is analyzed. It is demonstrated that two-phase boiling heat transfer coefficient of HFE-7100 in mini-channels is strongly dependent on heat flux and vapor quality but less sensitive to mass flux. Critical heat flux is observed when wall superheat is over 25 K and flow visualization method is used to examine a flow pattern change.〈/p〉 〈p〉In the second part, cooling performance and wall temperature change is investigated. Under heat generation ranges from a fuel cell, wall temperature is maintained at desirable operating temperature of polymer electrolyte membrane fuel cell (60–80 °C) and temperature difference is lower than 0.5 °C. At critical heat flux condition, wall temperature rises to over 90 °C. Also, wall temperature increases from 63.5 °C to 71.6 °C when channel pressure rises from 1.0 bar to 1.5 bar. Lastly dynamic response in wall temperature with the coolant pump control is investigated. It is found that this control method is effective to maintain low temperature difference (less than 1.5 °C) and the intermittent pump operating mode can reduce pump energy consumption.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): M. Rao, A. Fernandes, P. Pronk, P.V. Aravind〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The steel industry is one of the major sources of CO〈sub〉2〈/sub〉 emissions that are released in the manufacture and process of steel as well as in related power production. Focused on reduction of CO〈sub〉2〈/sub〉 emissions in the power production, this paper presents a novel solid oxide fuel cell-gas turbine combined heat and power system fed by coke oven gas. The solid oxide fuel cell-gas turbine system design consists of an adequate gas cleaning section for contaminants removal, solid oxide fuel cell as the main power producer and an anode offgas pressure swing adsorption based CO〈sub〉2〈/sub〉 capture unit. This system is thermodynamically and techno-economically analyzed and compared with a reheat steam turbine. Furthermore, the reheat steam turbine is retrofitted with a CO〈sub〉2〈/sub〉 capture unit. It is then compared to the solid oxide fuel cell-gas turbine system to analyse the difference in system efficiencies.〈/p〉 〈p〉The solid oxide fuel cell-gas turbine system yields an electrical efficiency of 64%, which is significantly higher than electrical efficiency achieved by both, a conventional reheat steam cycle (34.1%) and the retrofitted system (27.0%). Moreover, it depicts a combined heat and power efficiency of 73%. Results also reveal that the solid oxide fuel cell-gas turbine system can achieve a reduction of 50% in CO〈sub〉2〈/sub〉 emissions for equal power production. Furthermore, techno-economic analysis lead to a payback period of 9 years, taking into account state-of-the-art taxes and variation in the cost of components over the lifetime, without taking into account the fuel cost.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Babak Golkar, Sadegh Nikbakht Naserabad, Fatemeh Soleimany, Mansour Dodange, Amir Ghasemi, Hamid Mokhtari, Pooria Oroojie〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The consequences of water crisis in terms of political, social and environmental impacts have been motivated in this paper to recognize the hybrid wet/dry cooling systems of power plant in Iran. The existence of temperature constraints for consumers connected to the hybrid cooling tower, Space constraints for the construction of auxiliary system, devoting attention to high Net Present Value (NPV) of the project over the course of 25 years, Returning the appropriate capital, Optimal Design of air cooler and it's desirable performance over the course of a year were the reasons led to use of the genetic algorithm (GA) in this paper. The GA should optimize the design of the air cooler, according to that, at one functional point of a year, the lowest investment costs and the lowest cost of utilization in one year will happen. The cost of utilization in this project including: water consumption (makeup water of the cycle), fan power consumption (wet and dry block of hybrid cooling system), as well as chemical additives to water. The results illustrated that the proposed algorithm usage, applying a proper control system, taking into account the standards in the written code and determining the optimization intervals according to the manufacturer's data could conclude to the design of an air cooler, which can be constructed by inquiring from the manufacturing companies. The results also indicated that optimized design of hybrid cooling tower could reduce water consumption about 63% over the course of one year, return on investment by 5 years, develop NPV up to 40 M€ and enhance steam turbine power.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Cui Li, Yanzhong Li, Yiwei Cheng, Erfeng Chen, Zhan Liu, Jiaojiao Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents a numerical study on the transient cooldown process of liquid rocket engine by a passive recirculation precooling system. An unsteady mathematical model is developed by considering the interaction of heat dissipation from solid structure with the time- and location- dependent two-phase flow, and the predicted values show good agreements with experiments. The results demonstrate the roles of boiling regimes, and reveal distinct thermal and flow characteristics from single pipe cooldown and bleed precooling. The liquid rewetting front propagates along the flow direction in the vertical feed line and the turbopump related horizontal pipes, with the exception that opposite propagation appears in the upward recirculation line and causes inverted axial temperature distributions and faster cooling of exit. In terms of the time for meeting the turbopump operation requirement, large-diameter recirculation line and high liquid level in the ullage discharging condition are advantageous to the precooling of cryogenic pump, while subcooled liquid and high liquid level in liquid discharging condition prolong the cooldown process and are undesirable. The dependence of cooldown time on subcooling degree, relative liquid level and recirculation line diameter can be described by linear, cubic and exponential functions, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): S. Anitha Kumari, S. Srinivasan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper investigates a comprehensive approach for ash fouling monitoring and an optimized soot-blow mechanism for a thermal power plant reheater. A dynamic nonlinear regression model is designed to monitor the Cleanliness Factor (CF) of reheater and thereby an optimized soot-blow strategy is proposed to determine the critical CF and the duration of soot-blow cycle. The result in this case-study shows that steam consumed per soot-blow cycle is reduced and also the amount of fuel used per day is saved by adopting the proposed soot-blow strategy. The proposed method can be implemented as guidance for soot-blow operation in thermal power plants without any need for additional hardware and with a minimal computation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Yanquan Liu, Leming Cheng, Jieqiang Ji, Weiguo Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High contents of alkali and alkali earth metals (AAEMs) induce severe ash slagging and fouling during coal combustion. In this regard, co-combustion is an effective method to mitigate ash deposition. The ash deposition behavior in co-combusting high-alkali Zhundong (ZD) coal and a bituminous coal, i.e. Shenhua (SH) coal was tested in a 30 kW circulating fluidized bed test system. The results revealed that the condensation of Na〈sub〉2〈/sub〉SO〈sub〉4〈/sub〉 triggered the slag formation of ZD coal in the furnace. The Na-Ca-Fe eutectics were responsible for the melting or partial melting of slags at high temperatures. After blending SH coal with ZD coal, the volatilization of Na was effectively suppressed, and compacted slags practically disappeared at 20% blending ratio of SH coal. In the convective backpass, fine particles (〈10 µm) tended to be deposited on the leeward side of the heating surface because of the eddy impaction. As the blending ratio of SH coal increased, the size distribution of fly ash shifted to a large size range, because of the dilution effect and capture of AAEMs by silicates or aluminosilicates. The minimum blending ratio of SH coal was recommended as 20% to mitigate the ash deposition tendency of ZD coal.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Shou-Guang Yao, Chen Chen, Min Xiao, Miao-Miao Jin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The traditional method of sneak analysis of a thermal system is based on mass flow and cannot reflect system functionality and overall characteristics. Therefore, this study presents a network tree topology model based on energy flow. The heat transfer process in the thermal system is described by introducing the concept of energy flow. According to the design function of the thermal system, hot and cold source of the system are defined as the beginning and end of path search, respectively. All possible paths of heat transfer for the thermal system are obtained. The method is applied in the central cooling system of a ship and compared with sneak analysis based on mass flow. Results of the comparison show that sneak analysis based on energy flow can find new sneak problems on the basis of sneak analysis based on mass flow. Thus, the new method is feasible and effective.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): O. Ribé, R. Ruiz, M. Quera, J. Cadafalch〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Energy recovery elements play a major role in the efficiency and sustainability of building ventilation systems. The use of a sensible or total energy recovery ventilator is a key decision for ventilation systems designers. However, there is a lack of technical tools and developments to support this decision. The authors present a procedure to develop a simple decision tool for designers based on hourly values of the outdoor weather conditions and that can be applied to any kind of building. Results of the procedure are presented in simple-to-use isoline maps and tables. In order to assess credibility of the model used in the procedure, data published in the literature have been used as a reference, showing good accordance. As an example, the procedure has been applied to the Spanish area considering 48 different locations. Results have been presented and discussed. Their analysis shows as the market-accepted recommendation of using energy recovery ventilators in locations with high relative humidity during the summer should be reconsidered.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Beomjin Kwon, Nicholas I. Maniscalco, Anthony M. Jacobi, William P. King〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper reports two-phase cooling in compact cross-flow microchannel heat exchangers with high power density up to 180 W/cm〈sup〉3〈/sup〉. The performance is enabled by high-speed air flow through microchannels and two-phase condensation of refrigerant R245fa. The heat exchangers were realized in 1 cm〈sup〉3〈/sup〉 blocks of copper alloy, using micro-electrical-discharging machining. Two heat exchanger designs were analyzed, fabricated, and tested. The first device has 150 air-side channels of diameter 520 μm, and the second device has 300 air-side channels of diameter 355 μm. In both cases the refrigerant channels are 2.0 × 0.5 mm〈sup〉2〈/sup〉. The heat exchangers were operated with Reynolds number between 7500 and 20,500 for the air flow and with mass flux between 330 and 750 kg/m〈sup〉2〈/sup〉 s for the refrigerant flow. The refrigerant temperature at the channel entrance was 80 °C, which is near the maximum operating temperature for some electronic devices. For comparison purposes, the devices were also tested with single-phase refrigerant flows. This work demonstrates the potential of high power density heat exchangers that leverage advanced manufacturing technologies to fabricate miniature channels.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Kritsada On-ai, Niti Kammuang-lue, Pradit Terdtoon, Phrut Sakulchangsatjatai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effects of centrifugal acceleration and heat inputs on physical phenomena inside a rotating closed-loop pulsating heat pipe (RCLPHP) are considered by implying from the temperature variation of the working fluid, that are amplitude and frequency of temperature variations. The higher amplitude and frequency of the temperature imply to the longer vapor plugs and the higher flow velocity, respectively. From the experiments, when centrifugal acceleration increases, the temperature amplitude decreases. The flow pattern changes from the annular flow to the slug flow. The temperature frequency increases, the working fluid flows with a higher velocity. The flow direction changes from an oscillatory flow to a circulatory flow. Therefore, the thermal resistance decreases. Moreover, when the heat input increases, the temperature amplitude and frequency increase. The flow pattern changes from the slug flow to the annular flow with an intermittent liquid slug with higher flow velocity, thus, the thermal resistance decreases.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Freek Van Riet, Eddy Janssen, Gunther Steenackers, Ivan Verhaert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉Cogeneration (CHP) has great potential to save primary energy in collective residential buildings. However, these savings and their associated financial benefits are influenced by the design of the complete heat production system, which typically includes, besides the CHP itself, an auxiliary boiler and a storage tank. Both scientific literature and design guides focus little on the hydronic aspects of that design, although the performance of a heat production system is extremely prone to it.〈/p〉 〈p〉Therefore, this paper evaluates different hydronic designs of a central heat production system with CHP. First, an overview is given of the state-of-the-art hydronic design concepts that are used in the private sector. Two new concepts are proposed as improvements to the existing ones: one to integrate the CHP and one to integrate the boiler. A morphological chart is developed to classify the features of both the conventional and novel designs. Second, the performance of all the design concepts (and their 54 combinations) are evaluated based on a case study of an apartment block with 24 apartments. This evaluation is made by means of dynamic building system simulations.〈/p〉 〈p〉The results show that maximal primary energy can be saved if the CHP is integrated according to the novel CHP design, which allows a variable flow rate through the CHP. This concept should be preferred in a design process. Multiple hydronic configurations of the boiler, of which one is the novel hydronic boiler concept, resulted in a similar performance. Therefore, designers are advised to make a case-specific comparison to decide which one to take. The morphological chart and methodology elaborated in this paper provide a basis to make that decision.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Bingxuan Lin, Yun Wu, Zhibo Zhang, Dongliang Bian, Di Jin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ignition enhancement in a lean-burn combustor under low pressure is the biggest challenge for high altitude long endurance aircraft. In this study, plasma-assisted ignition using multi-channel spark discharge is proposed according to the theory of critical flame radius (R〈sub〉c〈/sub〉). A time-phased breakdown method is adopted to separate the breakdown stage from the discharge. The arc stage is restrained to reduce energy loss and maintain high voltage. Ignition experiments using single-channel spark discharge (SSD), concentrated multi-channel spark discharge (MSD) and distributed MSD were conducted. The results showed that R〈sub〉c〈/sub〉 is crucial for the ignition. The ignition probability of SSD drops quickly as pressure decreases due to the requirement of a larger R〈sub〉c〈/sub〉. The enhancement of concentrated MSD ignition is obvious at the same initial pressure than that of SSD and distributed MSD. The ignition enhancement is obtained only when the multi-channel combines to create a much larger ignition kernel and exceeds R〈sub〉c〈/sub〉 easily. Still, the ignition capability of MSD at extremely low pressure with lean and stoichiometric mixture does not perform as expected due to the splitting of the flame kernel. MSD can enhance ignition to flame transition but has little influence on the subsequent flame propagation.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359431118353225-ga1.jpg" width="280" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Xiuzhen Li, Dongsheng Zhu, Jinfei Sun, Xun Mo, Shijie Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Twisted oval tube is also a finned tube in a sense, especially when used in crossflow, although the fins of the twisted oval tube are invisible. An experimental research on heat transfer and pressure drop performance of twisted oval tube bundle with staggered layout is conducted. The correlations of Nusselt number and pressure drop coefficient deduced from this paper are well compatible with experimental data, which could provide a theoretical reference of twisted oval tubes for industrial applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Sheng Wang, Hsiu-Hung Chen, Chung-Lung Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An experimental study was carried out to investigate the heat transfer, pressure drop and flow instability characteristics associated with the flow pattern of deionized water during two-phase boiling in a silicon-based manifold microchannel heat sink coated with silicon nanowires (SiNWs) compared to a plain-wall device. The manifold microchannel device featured parallel transverse microchannels etched on a silicon substrate and longitudinal microchannels etched on a glass cover plate. Silicon nanowires were generated on the bottom and the sidewalls of the silicon microchannels. A closed-loop experimental system was constructed to demonstrate thermal and hydraulic performance. Experimental results were presented with mass fluxes ranging from 250 to 1250 kg/m〈sup〉2〈/sup〉 s and subcooled inlet temperatures from 15 K to 65 K. Results for the SiNWs device showed an approximate 20% improvement in heat flux rejection compared to the plain-wall device under the same wall superheat conditions. A subcooled inlet temperature of 65 K associated with a mass flux of 1250 kg/m〈sup〉2〈/sup〉 s is shown to be capable of dissipating an effective heat flux of 431.3 W/cm〈sup〉2〈/sup〉 with a wall superheat of about 85 K. Overall, the SiNW coatings proved positive effects on enhancing the flow boiling heat transfer with slower pressure drop increase, meanwhile the three-dimensional manifold microchannel design is revealed to effectively mitigate flow instability during the entire single and two-phase flow regions. This indicates great potential in utilizing three-dimensional flows by integrating SiNWs surface structures in high heat flux cooling applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Zhiming Xu, Yu Zhao, Jingtao Wang, Hongliang Chang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Inhibition of calcium carbonate (CaCO〈sub〉3〈/sub〉) fouling using sodium carboxymethyl cellulose (SCMC) was investigated in this study, focusing on the effect of the SCMC concentration on the fouling characteristics of CaCO〈sub〉3〈/sub〉 on the stainless steel surface. The fouling characteristics were investigated via pH displacement method, electrochemical impedance spectroscopy, and dynamic experiment analysis. The experimental results indicated that these three methods provided a consistent conclusion: SCMC exhibited a promising performance of fouling inhibition, and the inhibition efficiency and induction period of CaCO〈sub〉3〈/sub〉 fouling increased with increasing SCMC concentration ranging from 50 to 200 mg L〈sup〉−1〈/sup〉. The inhibition efficiency reached 93.2% for SCMC concentration of 200 mg L〈sup〉−1〈/sup〉. Scanning electron microscopy images of CaCO〈sub〉3〈/sub〉 fouling changed from irregular slender needles and clusters to small chips with the addition of SCMC. Moreover, a protective film was formed on the stainless steel surface by adsorption of the constituent of SCMC in the presence of SCMC, directly preventing the deposition of CaCO〈sub〉3〈/sub〉 fouling on stainless steel surface.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Heng Chen, Yao Xiao, Gang Xu, Jidong Xu, Xianhuai Yao, Yongping Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Comprehensive and parametric analyses were conducted to investigate the thermal characteristic of the high back-pressure (HBP) heating process based on a 300 MW coal-fired combined heat and power (CHP) unit. The results indicated that the HBP design promoted the thermal efficiency of the unit by 5.97% (absolute value) and cut down the standard coal consumption rate by 23.52 g/(kW·h), attributing to the exhaust steam recovery efficiency of 57% and the unit generation power increase of 24.58 MW. On the grounds of the first and second laws of thermodynamics, the detailed energy-saving mechanism of the HBP heating concept was synthetically explored by the analyses of energy and exergy flows and graphical exergy, and the results showed that the HBP heating configuration improved the unit performance by reducing the exhaust steam energy loss and the extraction steam flow rate and raising the exergy efficiency of the heat exchange process. The impacts of the primary parameters (unit generation load, unit heating load, supply & return-water temperatures and turbine back-pressure) on the performance of the HBP-CHP unit were also examined and optimization suggestions were put forward. Besides, the heat and power coupling characteristic of the HBP-CHP unit was discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Jia Fang, Zhongwei Meng, Jiansong Li, Yuheng Du, Yuan Qin, Yuan Jiang, Weilian Bai, George G. Chase〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Due to stringent emission standards, diesel particulate filter (DPF) is used to reduce and control particulate matter (PM) emissions for engine manufacturers. The periodical regeneration the DPF by oxidizing the accumulated PM is able to avoid pressure drop build-up and fuel efficiency decrease. This paper discusses the influence of regeneration temperature, regeneration flow rate and regeneration time on both regeneration and emission performance by regeneration test bench. From the temperature distribution profiles, the maximum temperatures were achieved at rear and center part of DPF in all the regeneration tests. When the regeneration temperature was higher than 525 °C, it was benefit to emit the large diameter particles. Increasing the flow rate had negative effect for the maximum temperature, maximum temperature gradient, and regeneration performance ratio. The trends for regeneration efficiency, total mass concentration and emitted particle average diameter were similar under different regeneration flow rates. Increasing regeneration time was benefit for improving regeneration efficiency, but it had negative effect for the performance ratio. The optimization active regeneration operating parameters were achieved after considering both regeneration and emission characteristics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Cheng Chi, Bing Gao, Fan Yang, Ruijin Liao, Li Cheng, Liangxian Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal state and insulation ability of converter transformer are significant to evaluate condition, while the impacts of nonlinear thermal-electric coupling impact are often ignored in the design analysis, and might result in misestimating its actual performance. In this paper, a bilateral thermal-electric coupling method is proposed to investigate the thermal and insulation performance of converter transformer on basis of an actual size. In addition, the influence of non-uniform temperature on the overall winding losses and the nonlinear thermal-electric coupling of insulation system are considered. Firstly, the thermal-electrical parameters coupling characteristics of insulation system in converter transformer are investigated based on the built experimental platform. Results indicate that temperature distribution would change the electrical performance all the time, while electrical-dependent characteristic of oil increases with electric field in U type curve. Then, the impact of non-uniform temperature is discussed based on the built bilateral thermal-electric coupling model, and it is proved that temperature would decrease obviously in considering the losses calculated by bilateral coupling. Finally, the nonlinear thermal-electric coupling performance of converter transformer is studied. It indicates that comprehensive factors of temperature dependence and electric filed dependence have great influences on the insulation properties. Significantly, the electric field of pressboard would decrease by 12.8% under hybrid voltage condition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): F. Favre, O. Antepara, C. Oliet, O. Lehmkuhl, C.D. Perez-Segarra〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Considering that the most common reason for electronic component failure is the excessive temperature level, an efficient thermal management design can prolong the operating life of the equipment, while also increasing its performance. Computational Fluid Dynamics and Heat Transfer (CFD&HT) have proved valuable in the study of these problems, since they can produce reliable fields of fluid flow, temperature and heat fluxes. Moreover, thanks to the recent advances in high-performance computers, CFD&HT numerical simulations are becoming viable tools to study real problems. The conventional approach, which consists of employing body-conformal meshes to the solids and fluids regions, often results costly and ineffective in applications with very complex geometries and large deformation. For these cases, an alternative approach, the Immersed Boundary Method (IBM), which employs a non-body conformal mesh and discretizes the entire domain using a special treatment in the vicinity of the solid-fluid interfaces, has proven more effective. In this work, an IBM was extended to simulate problems with conjugate heat transfer (CHT) boundary conditions taking into account the radiative exchange between surfaces. It was designed to work with any type of mesh (domain discretization) and to handle any body geometry. The implementation was validated and verified by several simulations of benchmark cases. Moreover, the IBM was applied in an industrial application which consists of the simulation of a Smart Antenna Module (SAM). All in all, the carried out studies resulted in a monolithic methodology for the simulation of realistic situations, where all three heat transfer mechanisms can be considered in complex geometries.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Jie Zhao, Da-Zhong Yuan, Da-Wei Tang, Yu-Yan Jiang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Many industrial applications call for high-temperature heat pipes working in anti-gravity modes. In past studies, heat pipes with concentric annular structures were developed with certain levels of anti-gravity working ability in low-temperature ranges. In this study, a concentric annular high-temperature heat pipe (CAHTHP) used for anti-gravity operation was designed and fabricated. Under the anti-gravity working condition, the effects of inclination angle on the CAHTHP frozen startup performance and temperature uniformity were experimentally studied and compared with gravity-operated experiments. The results show that the CAHTHP can achieve stable anti-gravity operation under high flux heating and natural convection cooling. The anti-gravity working condition and the working inclination angle have slight effects on the frozen startup rapidity and temperature uniformity of the CAHTHP. For different inclination angles, the CAHTHP startup times are all similar at approximately 450 s, and the thermal resistance values are all smaller than 0.05 °C/W. Moreover, the anti-gravity frozen startup process variation of the CAHTHP is in good agreement with that of the frozen startup two-region model.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Mohamad Sadeq Karimi, Saeed Salehi, Mehrdad Raisee, Patrick Hendrick, Ahmad Nourbakhsh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The stochastic computations of a NASA gas turbine vane are conducted to investigate the effects of the operational uncertainties on the flow and heat transfer characteristics of the NASA C3X blade. The blade contains ten internal cooling channels to remove heat load. In order to minimize the analysis error the full conjugate heat transfer methodology has been employed to simulate the behavior of external hot gas flows, internal cooling air passages and the solid blade simultaneously. The 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si18.gif" overflow="scroll"〉〈mrow〉〈msup〉〈mrow〉〈mi〉v〈/mi〉〈/mrow〉〈mrow〉〈mn〉2〈/mn〉〈/mrow〉〈/msup〉〈mo〉-〈/mo〉〈mi〉f〈/mi〉〈/mrow〉〈/math〉 turbulence model is used and it is shown the predicted results are in acceptable agreement with the available experimental data. Total pressure, total temperature, turbulence intensity, turbulent length-scale of the inlet and the outlet static pressure are assumed to be stochastic with Beta probability distribution functions. The effects of these uncertainties on flow and thermal fields as well as the blade temperature distribution are studied. The polynomial chaos method with polynomials order 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si19.gif" overflow="scroll"〉〈mrow〉〈mi〉p〈/mi〉〈mo〉=〈/mo〉〈mn〉3〈/mn〉〈/mrow〉〈/math〉 is used to quantify the effects of operational uncertainties. The non-deterministic CFD results are found to be in close agreement with the experimental data. Uncertainties specially in inlet total temperature and turbulent length-scale play key roles on the hydrodynamic and thermal fields around the airfoil also the turbine vane temperature distribution.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Jinlong Xie, Hsiao Mun Lee, Jianhua Xiang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Embedding metal fins into PCMs to improve the thermal conductance of PCM enclosure is widely used in the thermal management of mobile electronics. This paper presented the application of a density-based structure optimization method to redesign the conductive metal structure for better heat diffusion from a concentrated heat source into a PCM enclosure. Two plate fin heat sink structured PCM enclosures with the metal volume fractions of 20% and 30% were the baselines, and the optimized tree shape structures with the similar metal volume fractions of 18.7% and 27.6% were generated for comparison. A transient numerical model based on the Volume of Fluid (VOF) and enthalpy-porosity methods was built to investigate the dynamic thermal behaviors of PCM enclosures. Results illustrated that the optimized tree shape designs outperformed the baseline designs by achieving lower heat source temperature and higher melt fraction in the main PCM melting stage. Increasing metal volume fraction improved the overall thermal conductance of PCM enclosures and hence suppressed the temperature non-uniformity and lowered the heat source temperature. Upwardly orientated PCM enclosure had much better heat transfer performance than that under downward orientation due to its enhanced thermal mixing resulted from the intensified convection flows.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Bin Chen, Li Zhang, Jinlin Han, Xi Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Adding water to the intake air of gasoline engines efficiently improves operations and is highly influential to knock occurrence and NOx emissions. These factors largely benefit from the high latent heat of vaporization as well as the high specific heat of water. In this paper, based on a 1.5 L turbocharged gasoline direct injection engine, those impacts were deeply studied by separating the effect of charge cooling from the influence of increasing specific heat. An experimental test was undertaken to validate the effect of water introduction on the basic engine as well as to confirm boundary conditions and basic parameters for numerical analysis which was based on Ricardo WAVE code. Results indicate that the water introduction technique did improve engine output and thermal efficiency. Engine operations however, were primarily influenced by the impact of increasing specific heat. The charge cooling effect merely reduced the intake air temperature and had a minor impact on in-cylinder thermodynamics. Findings show the impact of water introduction on knock occurrence, engine output, thermal efficiency, and reduction in NOx emissions were mainly boosted by enhancing the specific heat of the operating medium and the effect of charge cooling was found to be insignificant.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Zehui Shao, Ehsan Gholamalizadeh, Albert Boghosian, Behnam Askarian, Zhenling Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the main challenges in multi-chill system issues by considering the uncertainty of cooling demand is total energy consumed and energy buying cost. Therefore, it is necessary to optimize power consumption in these issues. This paper provides a robust optimization method with uncertainty modeling in multi-chiller systems to obtain accurate planning. It should be noted that one of the energy supply sources for multi chiller system is photovoltaic system (in addition to the network). In order to improve cooling demand profile, using demand response program, demand levels are shifted through peak periods of energy consumption to low consumption periods. In this work, the minimization of energy procurement cost of multi-chiller systems from the upstream network is assumed as a target function, taking into account demand response of cooling and uncertainty demand. Also, the effect of cooling demand response on two robust and deterministic strategies has been investigated. Achieved results depict, risk-averse method through robust method is robust against cooling requirement uncertainty, contrasting to risk-neutral method through deterministic approach. In addition, the cost of supplying energy of multi-chiller systems from solar systems is reduced by using the demand response program in both of mentioned methods.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): M.K. Parida, H. Joardar, A.K. Rout, I. Routaray, B.P. Mishra〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The characteristics of multi-fuel VCR engine fuelled with Argemone Mexicana methyl ester, prepared by two step trans-esterification process and its diesel blends (20%, 40%, 60% and 100%) were evaluated with variation of load (3–12 kg) and compression ratio (16–18). In the current analysis engine load, compression ratio and biodiesel blends were taken as input parameters. Response Surface Methodology of Full Factorial Design was used for modelling and analyzing the response parameters with Minitab-14.0 software. Data regression, significance analysis and individual model coefficients were studied for the developed models and presented for validation of the model. Multi objective optimization was carried out for the responses by using the desirability function. Confirmation experiments were executed for validation of optimization results by setting input parameters (Load = 9.8 kg, CR = 18.0, Blend = 20%). Output responses from the mathematical modeling such as BTE 26.77%, BSFC 0.284 kg/kW h, CO 0.0059%, HC 114.84 ppm, NO〈sub〉x〈/sub〉 905.6 ppm respectively were obtained using D-optimal test with composites desirability of 0.97009. The predictions of RSM results were obtained in concurrence with the experimental ones, with errors less than 5% excepting for CO model.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Saeed Mahdavi, Faramarz Sarhaddi, Mahdi Hedayatizadeh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Through the present paper, a solar greenhouse integrated with an Earth-Air Heat Exchanger (EAHE) and Photovoltaic/Thermal collectors (PV/Ts) was theoretically studied in terms of energy and exergy and validated against an experimental study presented in literature i.e. a solar greenhouse with floor area, buried pipe length and PV area of 24 m〈sup〉2〈/sup〉, 39 m and 9.68 m〈sup〉2〈/sup〉, respectively. The comparisons showed a fairly good agreement between the theoretical and experimental results with a relatively high coefficient of correlation around 95%. Afterwards, the given solar greenhouse was optimized in terms of energy and exergy efficiencies while the results indicated that only length of EAHE pipes showed an optimum value equal to 38 m on average. Moreover, the results showed that PV/Ts did not have a significant heating potential for raising the greenhouse air and plant temperatures and only the electricity generation potential of PVs was favorable. However, the EAHE integration seemed promising in raising and lowering the temperatures of greenhouse air by 9 °C and 8 °C in summer and winter, respectively. Moreover, the Temperature Load Leveling (TLL) due to integration of only EAHE was achieved 46% and 58% in summer and winter, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Afshin Najafi-Ghalelou, Sayyad Nojavan, Kazem Zare, Behnam Mohammadi-Ivatloo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Multi-carrier hub energy system (MCHES) satisfies different energy demands such as heating, cooling, and energy demand by using different energy sources simultaneously. In this paper, a robust optimization approach (ROA) is provided for robust scheduling of MCHES considering economic and environmental constraints in the presence of market price uncertainty and multi-demand response programs (DRPs). In ROA, lower and upper levels of market price are considered instead of forecasted market price which guarantees the robust scheduling of the MCHES. The time-of-use (TOU) and real-time-pricing (RTP) rates of DRPs play a vital role in flattening the load curve with the aim of reducing the total operation cost and CO〈sub〉2〈/sub〉 emission. The proposed model is formulated as robust mixed integer linear programming (RMILP) and solved by General Algebraic Modeling System (GAMS) platform which has a great advantage in solving the linear programming models. Finally, to assess the effects of assumed DRPs on robust scheduling of MCHES, three case studies are utilized, and significant results were obtained.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Guo-Hua Shi, Lu Aye, Rui Dai, Xian-Jun Du, Jiang-Jiang Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study investigated a novel LPG vaporisation system utilising direct-expansion solar-assisted heat pump (DX-SAHPV)〈sup〉1〈/sup〉 for supplying residential gas. The DX-SAHPV applies a collector-evaporator to obtain heat energy from both solar radiation and ambient air to produce hot water to vaporise LPG liquid. It can operate in six operating modes depending on the weather and gas load conditions. In this study, a dynamic model and control strategies realising the mode switching were developed to carry out the operating performance evaluation of the system. By applying the typical meteorological year data and the gas load data of a community in Beijing, China, the performance of the DX-SAHPV was evaluated and analysed for the whole year and two selected days. The simulation results show that the system can vaporise adequate LPG liquid for the community throughout the year. The solar energy contribution accounts for approximately 68% of the total heat energy for the water heated vaporisation. It was also found that the DX-SAHP obtains average monthly values of COP ranging from 2.72 to 3.37 and solar collector efficiency varying between 93 and 152%. In addition, which mode the system operates at any time on selected days was predicted and the running time of each mode in each month was discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): T. Arunkumar, D. Murugesan, Kaiwalya Raj, David Denkenberger, C. Viswanathan, D. Dsilva Winfred Rufuss, R. Velraj〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Nanostructured Copper Oxide (CuO) is coated on the stainless steel (SS) 316 substrates using thermal evaporation method. The effect of CuO nanostructured coated absorber plates (NCAP) integrated with Polyvinyl Alcohol (PVA) sponges is investigated in a single slope solar still (SSSS) for desalination. The experiment was conducted in the following configurations: (1) SSSS alone, (2) SSSS with CuO-NCAP, (3) SSSS with PVA sponges and (4) SSSS-CuO-NCAP with PVA sponges. Four identical SSSSs were built with 0.50 m〈sup〉2〈/sup〉 collector area and tested under the same climatic conditions of Chennai, India during the period of March to April 2018. The CuO coated on the SS316 was characterized by Grazing Incidence X-ray Diffraction (GIXRD), Field emission Scanning Electron Microscope (FESEM) and Energy Dispersive Spectrum (EDS). The climatic parameters like ambient temperature, solar radiation and internal temperatures of the SSSS were measured at frequent intervals of time. The efficiencies of the SSSS, SSSS-CuO-NCAP, SSSS-PVA sponges and SSSS with CuO-NCAP-PVA sponges are 37%, 53%, 32% and 41% respectively. The productivity of SSSS, SSSS-CuO-NCAP, SSSS-PVA sponges and SSSS with CuO-NCAP-PVA sponges are 2144 ml/m〈sup〉2〈/sup〉/day, 2995 ml/m〈sup〉2〈/sup〉/day, 1970 ml/m〈sup〉2〈/sup〉/day, and 2318 ml/m〈sup〉2〈/sup〉/day, respectively. Therefore, the addition of the sponges was counterproductive, but the CuO-NCAP significantly increased output.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Joon Ha Lee, Dae Hae Kim, Seong Min Kim, Min Soo Kim, In Gwan Kim, Sung Min Woo, Sung Joo Hong, Chan Woo Park〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A generator is a heart of an absorption refrigeration system. It plays a significant role in the operation cycle by desorbing the water vapor from a lithium bromide (LiBr) solution. The wettability of the solution over the heating tubes has been considered for heat transfer enhancement in a water-LiBr falling film generator. This paper proposes seven types of heating tube bundles modified by surface treatments to improve the wettability. Each heating tube bundle was installed in the falling film generator for each experimental set, and the heat transfer characteristics were observed to evaluate the shell side heat transfer coefficients. Experiments were carried out with the following operating conditions: feed solution temperature (63.5 °C), solution flow rate (4–9 kg/min), feed solution concentration (55–58%), and pressure at the shell side (4.7–6.7 kPa). Hot water was used as a heat source, and the operating parameters were the feed temperature (85–97 °C) and the flow rate (10–28 L per minute). Each heating tube bundle had entirely different heat transfer characteristics, which were distinctly illuminated. The experimental correlations for a shell side heat transfer were developed to estimate the real benefits of using the proposed heating tube bundles. All the obtained empirical correlations were validated within an error limit of around ±20%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Mahsa Amirabedi, Samad Jafarmadar, Shahram Khalilarya〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study deals with application of ethanol and manganese oxide nano-particle at different ratios to gasoline-fueled SI EF7 engine. The blends are prepared in three emulsions namely gasoline-10%ethanol, gasoline-10%ethanol-10ppmMn〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, and gasoline-10%ethanol-20ppmMn〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. In order to prevent the amalgamation of nanoparticles and sedimentation during the test, the ultrasonic cleaner device is utilized to ensure the homogeneity of the composition. To measure the engine power, a 190 kW eddy current dynamometer is coupled and for determination of engine out exhaust gas, AVL gas analyzer is used. The results indicate that ethanol addition by 10% lead to 2.6% increase in brake power (BP), but interestingly 10 ppm Mn〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nano-additive raise the BP to 14.38% and 20 ppm nano-additive led to 19.56% increase of BP. With regard to emissions, ethanol presence in the blend reduces CO and UHC and raises the NOx and CO〈sub〉2〈/sub〉 because the abundant oxygen bonds in ethanol help oxidation process. The best blend in terms of UHC and BSFC reduction is gasoline-10%ethanol-20ppmMn〈sub〉2〈/sub〉O〈sub〉3〈/sub〉. The results also revealed that the peak of CO and UHC occurs at 75 N.m since at 75 N.m the inlet valve is actuated and the excess air is inducted to cylinder.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Philip A. Davies, Guillermo Zaragoza〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The self-cooling greenhouse is a concept to enable crop cultivation in adversely hot climates. It sacrifices a fraction γ of the incident solar energy to drive a refrigeration system, thus lowering the internal temperature below ambient. Heat is actively rejected to a stream of coolant such as air or water. To maintain availability of sunlight for photosynthesis, γ should be as small as possible. Nonetheless, the laws of thermodynamics dictate a minimum value of γ. Using the approach of endoreversible thermodynamics and the theory of selective blackbody absorbers, we determine ideal minimum values achievable for cases of both thermal and photovoltaic solar collection with and without solar concentration. To achieve an internal temperature 10 °C below that of the incoming coolant, a minimum γ = 0.056 is needed using multicolour absorption at maximum concentration 〈em〉C〈/em〉 = 46300 – representing an absolute minimum for either type of solar collection. Without concentration (〈em〉C〈/em〉 = 1) a selective thermal collector permits minimum γ = 0.089 and a single-junction PV solar collector permits minimum γ = 0.15. We discuss briefly implications for development of a real self-cooling greenhouse to approximate the performance of these ideal cases.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Maria T. Plytaria, Evangelos Bellos, Christos Tzivanidis, Kimon A. Antonopoulos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The objective of this work is the investigation of various underfloor solar heat pump heating systems with and without phase change materials (PCMs) in the floor layer. More specifically, a building of 100 m〈sup〉2〈/sup〉 floor area in Athens (Greece) is simulated and evaluated during the winter. The analysis is conducted with TRNSYS software and the results are presented in energy and financial terms. Solar collectors such as flat-plate, photovoltaic and thermal-photovoltaic are coupled to a tank which feeds a heat pump for space-heating purposes. In order to increase the storage capacity, a PCM-layer is placed on the underfloor heating system and different cases are examined by changing the thickness of the insulation in the floor and the area of the collectors. Moreover, this study presents the capital, variable and total cost, the electricity consumption, the coefficient of performance, the solar cover and the indoor temperature of the building for all the systems. The results prove that the use of the PCM-layer on the underfloor heating system reduces the heating load about 40% and the variable costs up to 20% because the electricity consumption can be reduced between 42% and 67%. Moreover, a multi-objective procedure was performed in order to evaluate all the scenarios and it is found that the thermal-photovoltaics seem to be the most appropriate cases due to the extremely low grid electricity consumption. The simple payback period of the system with flat plate collectors without PCM has been found 10.2 years and with PCM 18.3 years.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Qiang Gao, Zhi Wen, Feng Ming, Jiankun Liu, Mingli Zhang, Yanjing Wei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent years, cast-in-place bored piles have been widely used in engineering constructions. However, the applicability of bored pile was constricted by the loss of concrete strength in the cold curing environment of permafrost. A temperature-tracking concrete hydration model was developed to clarify the refreezing process of the bored pile. Based on an initial refreezing time (IRT) on the pile side of at least 30 days, the applicability of cast-in-place bored pile in permafrost regions was discussed. The results show that the IRT increases with the increasing of the mean annual ground temperature (MAGT), the ice content of frozen soil, the molding temperature of concrete, and the pile diameter. The applicability of the bored pile can be expanded by increasing the diameter of the bored pile as well as the molding temperature. Particularly, the influence of diameter is more obvious than that of the molding temperature. The simulations indicate that the bored pile is not recommended to be adopted in perennially cryotic ground where the MAGT is lower than −3.5 °C. The IRT should be adjusted to guarantee both pile quality and schedule.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Ahmed N. Shmroukh, M. Attalla, Amany Abd El-Naser Abd El-Hakim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This study is experimentally targeting to develop an effective novel system to produce fresh water, by sea water desalination using vortex tube. The vortex tube used compressed air as a power source, and produced hot air stream from one end and cold air stream from the other, taking that advantage in water desalination technology, with low consumption of heating energy under vacuum condition. Using four modes of compressor operation, mode I of continuous operation, mode II of five minutes on then ten minutes off, mode III of ten minutes on then five minutes off and mode IV of ten minutes on then ten minutes off. The following results are obtained: the quantity of the desalinated water was, 26% of the initial sea water quantity for mode II, while for mode IV, it was about 34%, for mode III, it was about 51%, while the maximum desalinated water quantity of 68% is obtained at mode I. Finally, the total dissolved solids in the produced desalinated water were about 480 mg/l. Therefore, using Ranque-Hilsch vortex tube in sea water desalination is highly recommended to be used as an effective agent to initiate sea water evaporation and desalinated water condensation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Huan Guo, Yujie Xu, Yi Zhang, Qi Liang, Hongtao Tang, Xinjing Zhang, Zhitao Zuo, Haisheng Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Compressed air energy storage (CAES) systems usually operate under off-design conditions due to load fluctuations, environmental factors, and performance characteristics of the system. Thus, to improve design and operation characteristics, it is important to study off-design performance of CAES systems. The compression process plays an important role in CAES systems. In this paper, we discuss the methodology for modeling off-design operation of a multistage compression process with intercooling of the most promising adiabatic CAES (A-CAES) system. The off-design performances under two proposed kinds of operating regulations are analyzed and compared. These two operating regulations are equal-power-ratio regulation (EPR) and optimizing variable inlet guide vane rotation angle (OVRA) (optimizing all stages simultaneously) regulation. Correlation between parameters such as total power consumption ratio, exergy efficiency, hot water temperature versus mass flow rate ratio, and back pressure is revealed in depth. Based on this research, the optimal operation laws, including pressure ratio distribution and efficiency distribution among all stages, are obtained, and it is found that the primary optimum principle is to enhance the isentropic efficiencies of low-pressure stages to approach design point. Finally, the optimized regulating law for the inlet guide vane rotation angles of the 4 stages is revealed. This study provides strong support for the design, operation, and control of CAES systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): J. Uriarte-Flores, J. Xamán, Y. Chávez, I. Hernández-López, Nelson O. Moraga, J.O. Aguilar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The numerical thermal performance of walls made out with materials available on the Mexican market: red brick (L), solid block (T) and hollow block (B) is presented. Each wall with a passive cooling technique was studied for a period of 24 h (warmest and coldest days) for three cities of Mexico with predominantly warm weather (Merida, Zacatepec and Hermosillo). In order to carry out the thermal analysis of each wall, four configurations were defined as follows: L, T and B stand for red brick, solid block or hollow block as the construction material respectively, and the numbers 1, 2, 3 and 4 stand for an added single layer of plaster (reference case) (1), an added layer of plaster plus a layer of white reflective coating (2), an added layer of insulating material plus a layer of plaster (3), an added layer of insulating material, plus a layer of plaster plus a layer of white reflective coating (4), giving as a result alternate configurations defined as (L1), (L2), (L3), (L4), (B1), … , (T4). In general, results showed that configurations L1, T1 and B1 increased considerably the total thermal load in all the three cities, compared to configurations L4, T4 and B4, respectively. For the city of Merida, Zacatepec and Hermosillo, configuration T4 resulted with the lowest thermal loads: 983.75, 1095.5 and 1540.72 W-h/m〈sup〉2〈/sup〉, while configuration T1 had the highest thermal loads: 1831.22, 1859.86 and 2686.91 W-h/m〈sup〉2〈/sup〉, which represents an increase of 48.8, 41.1 and 42.7% regarding to configuration T4, respectively.〈/p〉 〈p〉Finally, the configuration with the lowest thermal loads and economically viable based on the recovery of investment time was configuration T4, with a recovery time lower than 60 months and a reduction on the thermal loads between 41.1 and 48.8%. On the other hand, the recovery time for configuration B4 went beyond 115 months and the reduction on the thermal loads varied between 34 and 42%.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Morteza Saadat-Targhi, Shoaib Khanmohammadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The current study deals with the thermodynamic modeling, and multi-objective optimization of a pressure reduction station integrated with an organic Rankine flash cycle (ORFC) and a thermoelectric generator (TEG) waste heat recovery system (WHRS). Using the real operating data of a city gate station (CGS), a thermodynamic simulation was developed using EES (Engineering Equation Solver). The exergy analysis as a rigorous method was applied to find the exergy destructive components of the integrated system. Computations indicate that the exergy efficiencies of the indirect water bath heater (IWBH), ORFC condenser and TEG modules are 1.41%, 30.45%, and 16.34%, respectively, which are the lowest asset values among all components.〈/p〉 〈p〉Five main decision variables were defined as objective functions by the parametric study of the integrated system. Results of multi-objective optimization offer a set of non-dominant optimization solutions. A criterion for optimum state selection is carried out with the definition of an ideal point on the Pareto diagram, where point B is picked as a favorable system state.〈/p〉 〈p〉The scattered distribution of decision variables at points (offered by the Pareto solution) represents that 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si93.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mover accent="true"〉〈mi〉m〈/mi〉〈mo〉̇〈/mo〉〈/mover〉〈mrow〉〈mi mathvariant="italic"〉NG〈/mi〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 and 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mi〉T〈/mi〉〈mrow〉〈mi mathvariant="italic"〉NG〈/mi〉〈mo〉-〈/mo〉〈mn〉2〈/mn〉〈/mrow〉〈/msub〉〈/mrow〉〈/math〉 tend to be at the lower bound of their allowable range in all optimum states. Moreover, a comparison between the non-optimal and optimal integrated system reveals that the total exergy destruction rate through the system decreases 337.62 kW, and the thermal efficiency increases 8.57% in the optimal state.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Yousra Filali Baba, Hamid Ajdad, Ahmed A.L. Mers, Yaroslav Grosu, Abdessamad Faik〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents a multilevel comparison between two thermal energy storage materials: quartzite as the most known thermocline energy storage material and magnetite as a new potential candidate. This comparison involves: thermal and thermophysical properties, cycling effect and thermocline thermal energy storage performances. In first, an experimental characterization of magnetite under cycling has been performed, and then magnetite was compared to quartzite from this viewpoint. It has been demonstrated that for the medium temperature range (i.e. from 100 °C to 500 °C), thermal cycling has a positive impact on magnetite characteristics and performances. Thereafter, a numerical model for thermocline storage has been presented and validated. Then, the thermocline behavior and the thermal energy storage performances of both materials during charging and discharging processes have been investigated and tested for various heat transfer fluidscommonly used, including natural oil, synthetic oils and molten salts. This study shows that, for the different HTF tested, no significant difference between the thermocline zone thicknesses can be noted between the two TESM. It has been concluded that for the same storage tank size and the same discharge time, magnetite can store and restore more energy and requires less storage volume although quartzite presents higher efficiencies. For magnetite, this can represent an advantage from an economic and technical standpoint. While for the same storage tank size and the same HTF speed, the magnetite charges and discharges more slowly. On the other hand, the different combinations HTF/TESM tested show that thermocline performances are driven by not only the filler material but also the nature of the heat transfer fluid. In that sense, the molten salt fluids arelargely more efficient for both TESMs than other fluids.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Qun Chen, Meng-Qi Zhang, En-Fu Dong, Yi-Fei Wang, Yu-Qiu Sui〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The variation of heat loads challenges the operation strategy of heat exchanger networks (HENs). Previous individual valve control strategies enlarge the flow resistance, while the individual variable speed pump (VSP) control strategies might cause dangerous working conditions. This paper develops an optimal simultaneous operation strategy of both VSPs and valves in HENs under variable heat loads, which can avoid the extreme VSP operating frequencies and improve the performance of HEN on energy conservation. Optimization experiments with three different control strategies are operated on a practical multi-loop HEN to validate the effectiveness of new operation strategy. The results show that the new simultaneous operation strategy can achieve energy conservation on the premise of safe operation, about 90% power consumption reduction to individual valve control strategy at the heat load 800 W. What’s more, besides boundary conditions, control strategies also influence the optimal operating parameters, which shows the limitation of traditional operation strategy with prescribed set-point temperatures.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Dong Ho Kim, Seok Ho Yoon, Young Kim, Kong Hoon Lee, Jun Seok Choi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents an experimental evaluation of the performance of a thermal storage tank during the charging process using a molten salt as the thermal storage medium. This study was carried out as basic research on molten salt thermal energy storage, and the charging performances of two types of molten salt (HITEC, Solar salt) were empirically assessed. The detailed structure of a storage tank for thermocline was developed for the charging process, and the applicability of the single-tank structure was verified. Single-tank thermal storage data, which is only available in a limited manner in the literature, was experimentally obtained, thus, this study is expected to contribute to the basic design of the single-tank method in the near future.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Xuehui Wang, Bo Li, Yuying Yan, Neng Gao, Guangming Chen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉It is very important to develop a reliable method for the application of the pulsating heat pipe (PHP), however, the currently proposed heat transfer correlations or theoretical models still have some apparent shortcomings, such as great deviation and poor flexibility. Considering the advantages of artificial neural network (ANN) in analyzing complex systems, a fully connected feed forward ANN model was used to predict the thermal resistance of a closed vertical meandering PHP with water. The Number of turns, filling ratio, heat flux, inner diameter and the length ratio of evaporation section were selected as the input parameters. By applying a trial-and-error method, the neuron number in the hidden layer was optimized to be 10. A total of 221 points of experimental data under different working conditions collected from the published literature were applied to build the ANN model. The results showed a good agreement between the experimental data and the ANN model with the MSE and correlation coefficient of 0.0025 and 0.9962, respectively. Furthermore, the influence of the heat flux on the relative deviation was also investigated. It suggested that the ANN model could have better prediction results when the heat flux was within the range of 6500–14,500 W/m〈sup〉2〈/sup〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Fabien Raoult, Stéphanie Lacour, Bertrand Carissimo, François Trinquet, Anthony Delahaye, Laurence Fournaison〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Polydisperse evaporating spray study is complex due to the influence of a large number of physical parameters. Several studies have performed CFD simulations to investigate the cooling performance of water spray systems, but a few have investigated their impact upon heat exchangers. For industrial applications, developing a new and simple approach to simulate polydisperse evaporating sprays upon complex 3D geometries is of great interest. Thus this paper is the first contribution to a CFD numerical tool development to study water spray impact on heat exchangers and presents a CFD water spray model. The spray model is divided into two steps: the spray formation and its dispersion in air flow. The spray development step describes the moment from droplet injection to the position where droplet velocity equals air velocity. This position and the spray dimension are accessed through the droplet trajectory analysis, while the amount of liquid water evaporated is obtained by integrating the droplet size decrease equation. This first part provides boundary conditions for the second step used in a 3D CFD software: Code_Saturne. This CFD code solves the Navier-Stokes equations for the spray with the 〈em〉k〈/em〉-〈em〉ε〈/em〉 turbulence model. Three transport variables are introduced: the liquid potential temperature, 〈em〉θ〈sub〉L〈/sub〉〈/em〉, the total water specific humidity, 〈em〉q〈sub〉w〈/sub〉〈/em〉, which are conservative variables for the evaporation processes; and the total number, of droplets, 〈em〉N〈sub〉c〈/sub〉〈/em〉. The droplet evaporation is added to the 〈em〉N〈sub〉c〈/sub〉〈/em〉 equation through a source term approach. A lognormal law is also used to represent and follow the evolution of the droplet spectra. The model results are compared with experimental results from droplets injected in counter-flow configurations in a wind tunnel. Temperature fields show good agreements with the experimental data. Finally, this paper provides a parametric analysis of water evaporation and air cooling upon a specified surface. The impacts of the relative humidity, spray angle, water mass flow rate and droplet size distribution are investigated. Our approach is an alternative to classical Lagrangian approaches used in spray applications. It provides accurate and consistent results with low computational time in comparison with the literature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Kimberly A. Stevens, Sally M. Smith, Brenton S. Taft〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Oscillating heat pipes have been shown to be an effective means for thermal management. However, the constant, phase-change-powered oscillation can also produce variations in performance. The goal of this research is to quantify performance variation of oscillating heat pipes through repeated tests with closed-loop flat plate oscillating heat pipes. The heat pipes were filled with two different working fluids, butane and R134a, and tested in both double-sided and single-sided cooling configurations, two or three different orientations, and four different power levels, and repeated to quantify the variation in performance, including average thermal resistance, intratest variation (repeatability), intertest variation (temperature fluctuations), and reliability (likelihood of temperature overshoot). Orientation, configuration, working fluid, and power level all influenced the level of variation in performance. In a double-sided configuration, OHPs had lower thermal resistance when oriented vertically. In a single-sided configuration, OHPs had lowest thermal resistance when the evaporator was below the condenser. OHPs were significantly more reliable and experienced smaller temperature fluctuations when in the double-sided than single-sided configuration.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): H. Asgharian, E. Baniasadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cold energy storage during the off-peak hours to supply the cooling demand during the peak hours leads to reduction of the chiller size and energy expenses. In this paper, the performance of an ice bank system based on spherical capsules is experimentally analyzed and the effects of different parameters are investigated using a numerical model. The numerical simulation is performed for optimum design of the energy storage system and the results of numerical simulation are validated against the experimental data. Moreover, temperature distribution inside the ice bank is evaluated, experimentally and numerically, and heat transfer rate from the spherical capsules wall and the liquid fraction inside these spherical capsules are determined using numerical simulations during the charge and discharge processes. The results indicate that utilization of two inlets for heat transfer fluid (HTF) leads to decrease of charging time by 11 min and increase of the efficiency by 37%. Moreover, the best efficiency during the charge and discharge modes are 77% and 51% using 0.04 kg/s mass flow rate, respectively. Furthermore, the results showed that when the capacity of the system increases by increase of spherical capsules from 60 to 120, the system efficiency during the charge and discharge processes increase by 26% and 23%, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Sachin Kumar Gupta, Mayank Mittal〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Low-carbon fuels such as bio-methane, obtained from biomass gasification consisting 96–98% of methane by volume, is a promising alternative fuel for internal-combustion engines. In the present work, methane is used as a surrogate of bio-methane for studying the engine characteristics. First, a comparative study was performed on a single-cylinder, water-cooled, variable compression ratio, spark-ignition engine operating under methane and gasoline fuels with compression ratio (CR) of 8.5:1. Subsequently, the effect of compression ratio was investigated on the performance, combustion including cycle-to-cycle combustion variations through statistical analysis, and emissions, when engine was operated over a wide load range at 8.5:1, 10:1 and 12:1 CRs under methane. It was found that the brake specific energy consumption and emissions were reduced for methane compared to gasoline at all operating loads. Results showed that when the CR was increased from 8.5:1 to 12:1 at low operating load of 5 N-m, brake specific fuel consumption was reduced by 7.2% and the average location of peak in-cylinder pressure (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mi〉θ〈/mi〉〈msub〉〈mi〉p〈/mi〉〈mrow〉〈mi mathvariant="italic"〉max〈/mi〉〈/mrow〉〈/msub〉〈/msub〉〈/mrow〉〈/math〉) was shifted towards the TDC, i.e. 17.4 to 13.5 CAD ATDC, with a decrease in cycle-to-cycle combustion variations. In addition, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"〉〈mrow〉〈msub〉〈mi〉θ〈/mi〉〈msub〉〈mi〉p〈/mi〉〈mrow〉〈mi mathvariant="italic"〉max〈/mi〉〈/mrow〉〈/msub〉〈/msub〉〈/mrow〉〈/math〉 showed linear and quadratic relationships with peak in-cylinder pressure and IMEP, respectively.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): I. Zavala-Guillén, J. Xamán, I. Hernández-Pérez, I. Hernández-Lopéz, C. Jiménez-Xamán, P. Moreno-Bernal, D. Sauceda〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This research presents a thermal evaluation of an absorber-partitioned air channel solar chimney (SC-AP) to determine its feasibility as a building ventilation system in a warm-humid weather. Hourly climatic data from the coldest and the warmest days of each month of 2014 were used to assess the behavior of the SC-AP in Mérida, México. A numerical code based on the Finite Volume Method was developed to evaluate the ventilation potential of the SC-AP. The results indicate that the average mass flow rate of the coldest day is greater than the one corresponding to the warmest day in most of the months; therefore, even under the worst conditions of the year, the SC-AP extracted an average mass flow rate of 0.0832 kg/s. In addition, when the SC-AP is attached to a building, it is able to generate between 7.9 and 11.4 ACH for a residential bedroom of 27 m〈sup〉3〈/sup〉 and more than 3.5 ACH for a classroom of 54 m〈sup〉3〈/sup〉 during the hours with solar irradiance along the year, those values comply with the requirements recommended by ASHRAE.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Ahmet Çağlar〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a novel thermoelectric water dispenser unit is proposed to supply cold and hot drinking water simultaneously. For this purpose, the heat sinks attached to the cold and hot surfaces of a Peltier module are placed into the cold and hot water tanks of the thermoelectric water dispenser. Supplying power to the thermoelectric module, the cold water tank is cooled while the hot water tank is heated at the same time. The cooling and heating performances of the system are examined for three cases: the tanks made of glass walls without insulation; the tanks made of polyethylene walls without insulation: and the tanks made of polyethylene walls with insulation. Results show that water tanks with polyethylene walls have better thermal performance than those with glass walls. Furthermore, insulation of the tanks has a significant enhancement in COP especially on the heating side. Results of this study also indicate that TE water dispenser can compete with conventional types, with the advantages of being environment-friendly, smaller, silent and operable with renewable energy sources.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): V. Gudjonsdottir, C.A. Infante Ferreira, A. Goethals〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Compression-resorption heat pumps (CRHP) utilizing wet compression are a very promising option to upgrade waste heat from industry. CRHPs have the potential to have higher coefficient of performance (COP) than the traditionally used vapour-compression heat pumps (VCHP). However, commercial solutions utilizing wet compression are not available yet. Also, wet compression is a feasible option only if the efficiency of the compressor is sufficiently high, 0.7 or higher, as identified by several authors. In this study, we develop and validate a model of a twin screw compressor that is suitable for wet compression. The model is adapted to calculate the entropy production generation in order to identify where the major irreversibilities are located in the compressor. The effects of clearance size, rotational speed, ammonia concentrations, compressor inlet vapor quality as well as under- and over compression are analysed. The results show that the clearance size and the rotational speed have the largest effects on the entropy production. Additionally, increased ammonia concentration and decreased vapor quality lead to decreased losses. The results indicate that it should be feasible to reach the targeted performance if the clearances size is limited to 50 μm, the rotational speed maintained above 10,000 rpm, the ammonia concentration kept in the range of 30–40 wt.%, and the inlet vapor quality in the range 0.5–0.7.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Jaewan Kim, Jinwoo Oh, Hoseong Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The lithium-ion batteries are widely used for electric vehicles due to high energy density and long cycle life. Since the performance and life of lithium-ion batteries are very sensitive to temperature, it is important to maintain the proper temperature range. In this context, an effective battery thermal management system solution is discussed in this paper. This paper reviews the heat generation phenomena and critical thermal issues of lithium-ion batteries. Then various battery thermal management system studies are comprehensively reviewed and categorized according to thermal cycle options. The battery thermal management system with a vapor compression cycle includes cabin air cooling, second-loop liquid cooling and direct refrigerant two-phase cooling. The battery thermal management system without vapor compression cycle includes phase change material cooling, heat pipe cooling and thermoelectric element cooling. Each battery thermal management system is reviewed in terms of the maximum temperature and maximum temperature difference of the batteries and an effective BTMS that complements the disadvantages of each system is discussed. Lastly, a novel battery thermal management system is proposed to provide an effective thermal management solution for the high energy density lithium-ion batteries.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Y. Wang, Y.M. Ferng, L.X. Sun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A three-dimensional (3-D) CFD methodology is developed to assist in the design of mixing-vane spacer-grids for the rod bundle. An adiabatic experiment and a heating experiment for the 5 × 5 rod bundle are adopted to validate this CFD model. The mesh uncertainty is estimated to be approximately 1.26%. The agreement comparison and the small mesh error strongly reveal that the present CFD model can simulate the thermal-hydraulic characteristics for the mixing-vane spacer-grid with enough accuracy and can be applied to assist in the vane design with confidence. The parameters of mixing vane studied in this paper include the deflection angle, the vane length, and the gap distance. Based on the simulation results, the heat transfer can be enhanced by increasing the deflection angle of mixing vane, which can be compensated by the disadvantage of increasing pressure drop. Effects of increasing angle are more significant on the pressure drop than on the heat transfer enhancement. Therefore, in the vane design, the pressure drop dose put a limitation on the increase in the vane angle for increasing its heat transfer capability. In addition, based on the validation resulting and computing resources, the present CFD model using the geometry of full rod bundle with the multi-grids and without the dimples and springs can provide the enough agreement for the engineering design of spacer-grid with mixing vanes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Paul Byrne, Redouane Ghoubali〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This article presents the evolution of a concept of air-source heat pump for simultaneous heating and cooling (HPS). A heat pump can simultaneously produce heating and cooling energies for collective residential buildings, hotels or highly-glazed office buildings. The heat pump prototypes operate under three main modes. (1) The heating mode produces hot water using heat available in the ambient air. (2) The cooling mode produces cold water and rejects heat to the ambient air. (3) The simultaneous mode produces hot water thanks to heat taken from the cold water, therefore becoming colder. During the simultaneous mode, two thermal energy amounts, for cooling and heating, are produced simultaneously. Therefore, it is interesting for the user that the heat pump operates in the simultaneous mode as much as possible. A winter operating sequence involving a heat exchanger for refrigerant subcooling enhances the performance of the machine. Two prototypes working with R407C and R290 (propane) were built consecutively and tested following European Standard EN 14,511 in a climatic chamber. The experimental results show that the second prototype has a higher performance than the first one regarding exergy aspects thanks to not only the refrigerant choice but also to a better design of components.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Ya-Ling He, Kun Wang, Yu Qiu, Bao-Cun Du, Qi Liang, Shen Du〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Concentrated solar flux distribution in the concentrated solar power (CSP) systems is extremely non-uniform, which can lead to high local temperature and large temperature gradient in solar receivers that will cause great challenges for the safety and efficient operation of the system. This paper introduces the non-uniform flux features in four CSP technologies including the parabolic-trough collector, the linear Fresnel collector, the solar power tower, and the parabolic-dish collector. Challenges including degeneration of the materials, thermal stress and deformation, and overburning are summarized. The corresponding solutions proposed to tackle these challenges are emphatically reviewed, and a recommendation for the optimization of the solar collector is provided from this review, which is that the solar flux distribution and the heat transfer ability of the heat transfer fluid (HTF) should match with each other as well as possible. From this point of view, the existing solutions are classified into two groups. One is optimizing the heat transfer ability of the HTF to match with the flux distribution, which is called the passive approach. The other is homogenizing the flux distribution to match with the heat transfer ability of the HTF, which is called the active approach. This review can help to have a better understanding of the non-uniform solar flux features in CSPs, and provide guidance for solving the corresponding challenges.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Fushui Liu, Zhishuang Li, Ziman Wang, Xiaoyu Dai, Chia-Fon Lee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cavitation significantly influences fuel mixture preparation and combustion of IC engines which are the main power source of transportation. Investigation of cavitation in injector and its effect on spray breakup is very important for reduction of emissions and fuel consumption. To study the cavitation dynamics and primary breakup, highly resolved microscopic imaging technique was employed with an enlarged transparent nozzle and a real-sized nozzle under various throttling conditions. Mechanisms of cavitation generation were investigated through the cavitation generation locations and morphologies. The characteristics of the secondary vapor bubbles were also probed by injecting diesel into the liquid based on the differences of density and refraction between liquid and vapor. It was found that under low pressure, dynamic cavitation which developed and receded bi-directionally was observed close to the inlet. Cavitation in the sac and nozzle inlet was mainly throttling induced under low pressure and redirection induced under high pressure, while cavitation at nozzle outlet was mainly redirection induced. Increasing pressure strengthened cavitation at both inlet and outlet, and made the vapor bubbles more compact and deformed. Decreasing throttling effect enhanced the cavitation before weakening. Besides, vapor bubbles collapsed very quickly at the nozzle outlet due to the abrupt pressure reduction.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Xiang-dong Hu, Lei Han, Yan-guang Han〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The existing formulae for calculating temperature field distribution of frozen soil wall by double-row- and triple-row-piped freezing are deduced for specific arrangements of freezing pipes, where the pipe spacing and row spacing among different rows are assumed the same. And they cannot satisfy the needs of projects construction because the flexible arrangements for double-row- and multi-row-piped freezing are increasingly adopted. In this paper, analytical solutions to steady-state temperature field for double-row-piped freezing with different pipe spacing, row spacing and row staggered distances are theoretical derived based on the linear superposition of formula to temperature field for single-row-piped freezing. Then, with the superposition method mentioned above, analytical solution to temperature field distribution by multi-row-piped freezing in isotropic area is obtained. After that, the triple-row-piped freezing problem is taken as an example to show the application of the derived formula. And the formula to temperature distribution by aligned triple-row-piped freezing generated from the general solution shares the same form as the existing formula. And the calculating result of the formula for a special triple-row-piped problem shows good consistent with the numerical thermal results.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Mohd Shariq Khan, Surya Effendy, I.A. Karimi, Aref Wazwaz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The simulation of liquefied natural gas (LNG) storage tanks is often based on several problematic assumptions, for instance, estimation of boil-off gas (BOG) generation using boil-off rate, vapor-liquid equilibrium in the tank, static liquid level, the use of only lateral area for heat loss calculations, and etcetera. Some of these assumptions are built into selected commercial simulators, creating further challenges in simulating the behavior of LNG tanks. The present study highlights these challenges in the context of a commonly used process simulator, Aspen HYSYS, and provides analytical and intuitive solutions to those problems. The resultant model is validated against an established first-principle model and then exploited for finding improved LNG regasification terminal design and operation strategies. Tank aspect ratio (AR) was studied in relation to plant capacity, recirculation rate, and recirculation line length. An aspect ratio of 1 consistently results in minimum BOG generation, in contrast to the value of 0.5 frequently cited in the literature. During the planned/unplanned shutdown of regasification terminal, higher liquid level in the tank decreases evaporation and thus BOG generation. Minimum recirculation rate that prevents 2-phase flow is found to minimize BOG generation and compressor duty.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Biao Shen, Takeshi Hamazaki, Wei Ma, Naoki Iwata, Sumitomo Hidaka, Atsushi Takahara, Koji Takahashi, Yasuyuki Takata〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Due to the considerably reduced boiling point, organic fluids such as ethanol provide an attractive alternative to water as the working fluid in two-phase thermal management systems for high-heat-flux applications. The state-of-the-art enhancement methods for ethanol boiling normally involve surface structure engineering. Here we report, for the first time, enhancement of nucleate boiling of ethanol using wettability-patterned surfaces. By depositing onto a polished copper surface an array of circular spots of superamphiphobic coating of modified halloysite nanotubes (HNT) with fluoropolymer, which was shown to repel low-surface-tension fluids, we managed to create a meaningful biphilic pattern of alternating hydrophobicity (with ethanol contact angle exceeding 100°) and hydrophilicity (with contact angle close to 0°) on the surface. Boiling heat transfer was found to be improved dramatically on the coated surface. Specifically, the onset of nucleate boiling was found to drop by more than 35%. Moreover, at 20 K surface superheat (above the boiling point), a maximum heat transfer enhancement over 300% compared with a plain copper surface occurred on the surface with a pitch-to-spot ratio close to 2.5. The significantly increased heat transfer rate of the biphilic surfaces could be attributed to facilitated bubble nucleation and stronger agitation effect.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359431118362148-ga1.jpg" width="365" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Ahmad Mustaffar, Anh N. Phan, David Reay, Kamelia Boodhoo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We present a new configuration of concentric annular heat pipe (CAHP). A CAHP consists of two concentric tubes, with the smaller diameter tube positioned inside the larger one so that an annular space is created by sealing the ends whilst the inner space of the smaller tube is open to the surroundings. Evaporation and condensation take place along the length of the annular space. Unique to our CAHP design, the entire inner space of the central tube was designated as the condenser where wet ceramic slurries were to be conveyed through for moisture reduction. A 515 mm-long stainless steel CAHP was constructed for the present study with 76.2 and 38.1 mm outer and inner tube diameters, respectively. A screen wick was attached only to the inner wall of the outer tube. Several experimental parameters were investigated for their effects on axial temperature profile and thermal resistance: 11–43% filling ratios (a measure of fluid inventory inside the annular space), 0–90° angular orientations and 272–302 W heat inputs. An 11% filling ratio was found to be optimum, giving sufficient fluid inventory for wick saturation and compatible with all orientations and heat inputs. For the 11% filling ratio, vapour temperature differentials between heat pipe extremities were 0.4–1.3 K, showing an excellent isothermal condition. Global thermal resistances were calculated to be 0.08–0.31 K/W. As the wet loads were conveyed through the inner tube, vapour was condensed all along the outside surface of the inner tube, releasing thermal energy to the loads through radial heat transfer. The moisture content of the ceramic slurries was reduced from 33 wt% to 21 wt%, at the highest CAHP heat input of 302 W within 35 s residence time, demonstrating the promising potential of the CAHP as an efficient moisture removal technology.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Rui Sun, Yongjun Shi, Zhenfei Bing, Qi Li, Ruihai Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the paper a drop-on-demand deposition system using ultra-high frequency induction heating technology is proposed for the aim of depositing metal materials with high melting point onto the substrate at a low thermal input. The numerical model coupled with electromagnetic field, thermal field and flow field was established to investigate the metal transfer and thermal characteristics of the deposition process. Results indicate that the metal droplet can be deposited onto the substrate at a low thermal input. The effects of current frequency and current density on the deposition temperature and time duration of the deposition were also numerically studied. Analysis of the electromagnetic force and temperature of the pendent molten metal during deposition demonstrates that the current frequency as well as current density influences the time duration by determining the electromagnetic force and the heating rate. The numerical model was verified by experiments, and the experimental results show good agreement with the calculated results. With the advantage of depositing high melting point material while limiting the thermal input for the substrate, the drop-on-demand deposition method using ultra-high frequency induction heating technology is expected to be applied in metal droplet-based applications where the thermal-sensitive materials are used.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Ruiqing Shen, Haejun Park, Qingtong Liu, Qingsheng Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Adiabatic surface temperature (AST) is a useful and convenient concept to characterize the thermal boundary condition that a solid surface is exposed to. Plate thermometer (PT) is often used to calculate AST. However, in an ambient temperature condition, the calculated AST is known to be significantly lower than actual AST. Faced with this challenge, a new method to calculate AST using PT is proposed in the current study. A correlation to determine AST from measured PT temperature in steady state is first developed in a radiation-only environment. Based on this correlation, a correlation for AST is derived for a mixed radiation/convection environment, i.e., for any given convective heat transfer coefficient. AST calculated based on the proposed method is validated against two pool fires.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Kanokwan Buaprommart, Haroun Mahgerefteh, Sergey Martynov, Alberto Striolo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The development and application of a computational model for predicting the thermal radiation and explosion over-pressure in the event of an accidental well blowout during shale gas production is described. The transient discharge rate, the fluid phase composition, temperature and pressure at the ruptured wellhead, serving as the source term for fire and explosion modelling are determined based on the numerical solution of the conservation equations using the Method of Characteristics. Two scenarios covering immediate and delayed ignition of the escaping gas respectively leading to a jet fire or an explosion are considered. The efficacy of the well blowout model is demonstrated by simulating the accidental well-head rupture of a real 4000 m deep shale gas production well at a maximum reservoir pressure of 600 bar. The simulated time variant explosion overpressures and thermal radiation heat fluxes are in turn employed to specify the minimum safe distances to people and equipment during the rapid well depressurisation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Amir Ebrahimi-Moghadam, Ali Jabari Moghadam〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, the effort has been focused on optimal amounts of the geometric and hydrodynamic characteristics of turbulent Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉/water nanofluid flow within the corrugated heat exchangers (HEXs). The optimization is carried out using entropy generation minimization (EGM) approach and genetic algorithm (GA). All of the geometric and hydrodynamic parameters, including corrugation depth (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si12.gif" overflow="scroll"〉〈mi〉a〈/mi〉〈/math〉), corrugation pitch (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si13.gif" overflow="scroll"〉〈mi〉w〈/mi〉〈/math〉), length of the corrugation section (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si14.gif" overflow="scroll"〉〈mi〉L〈/mi〉〈/math〉), height of the corrugation section (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si15.gif" overflow="scroll"〉〈mi〉H〈/mi〉〈/math〉), phase shift angle (〈em〉θ〈/em〉), nanoparticles volume fraction (〈em〉ϕ〈/em〉) and Reynolds number (〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si16.gif" overflow="scroll"〉〈mtext〉Re〈/mtext〉〈/math〉), are taken into account in the optimization process. The results reveal that the addition of Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 nanoparticles to the base fluid significantly enhances heat transfer and also a slight increment in system irreversibility. Adding 4% Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉, with the constancy of the other parameters, causes 5% increment in irreversibility at most. Applying the optimization based on the all of the parameters together results 5.41 mm, 148.84 mm, 1.06 mm, 13.80 mm, 4.35°, 14,757 and 3.19% for optimum values of 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si15.gif" overflow="scroll"〉〈mi〉H〈/mi〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si14.gif" overflow="scroll"〉〈mi〉L〈/mi〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si12.gif" overflow="scroll"〉〈mi〉a〈/mi〉〈/math〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si13.gif" overflow="scroll"〉〈mi〉w〈/mi〉〈/math〉, 〈em〉θ〈/em〉, 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si16.gif" overflow="scroll"〉〈mtext〉Re〈/mtext〉〈/math〉 and 〈em〉ϕ〈/em〉, respectively.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S135943111836037X-ga1.jpg" width="336" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Jun-Seong Kim, Do-Yeop Kim, You-Taek Kim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The organic Rankine cycle makes it possible to accomplish energy recovery from a low-temperature heat source, which is typically not recovered for economic reasons. As the expander for the organic Rankine cycle, the radial turbine is easy to manufacture and has advantages in terms of size and efficiency. The radial turbine design modeler (RTDM), which was developed from in-house code, is a preliminary design program for radial inflow turbines and is different from the commercially available program RITAL. In this study, an experiment on radial inflow turbines is performed using both RTDM and RITAL. As a result, the output and efficiency of the RTDM and RITAL turbines are 36.04 kW, 80.03% and 35.03 kW, 76.01%, respectively. Experimental results demonstrate that the performance of the RTDM turbine is almost similar to the RITAL turbine. We also perform analysis on performance prediction utilizing a deep neural network with two hidden layers based on the experimental data. As a result, the minimum root mean squared errors of the RTDM turbine and RITAL turbine are estimated to be approximately 1.81 and 1.65, respectively. The deep neural network is able to predict the trends of the experiment for the organic Rankine cycle.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Mercedes Ibarra, Antonio Rovira, Diego-César Alarcón-Padilla〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The objective of this work was to simulate the behavior of an Organic Rankine Cycle (ORC) system with two expanders in series at off-design working conditions. The influence of both the intermediate pressure and the volumetric expansion ratio of the expanders on the off-design performance of the ORC was studied and the irreversibilities of the components were analyzed. The performance of the ORC with two expanders for two different designs was also discussed.〈/p〉 〈p〉The thermal efficiency reached using two expanders was higher than the obtained using only one. However, this increase conveyed an increase in the complexity of the design and control of the expanders. As an additional conclusion, it was found that the influence of the intermediate pressure is higher than that of the volume expansion ratio of each expander.〈/p〉 〈p〉The irreversibility of the first expander was mainly due to leaks. However, the performance of the second expander was particularly affected by the difference between the discharged pressure and the condensation pressure. The off-design analysis allowed the definition of a methodology to achieve the desired power with the maximum thermal efficiency, and the identification of the best actuation for the part load operation.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Anand Takawale, Satyanand Abraham, Axel Sielaff, Pallab Sinha Mahapatra, Arvind Pattamatta, Peter Stephan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper reports the results of an experimental study to investigate the performance comparison between two Pulsating Heat Pipes namely, a Flat Plate Pulsating Heat Pipe (FPPHP) and a Capillary Tube Pulsating Heat Pipe (CTPHP). The comparison is made based on the flow regimes and the corresponding thermal performances at heat inputs varying from 20 W to 180 W with filling ratios of 40%, 60%, and 80%. Experiments are performed in the vertical bottom heating mode with ethanol as the working fluid. The pressure inside the PHPs and temperatures at the evaporator and condenser region are measured along with a recording of the internal flow regimes using a high-speed camera. Slug-plug flow is observed to be the dominant flow regime in both the PHPs. However, the amplitude of oscillations is found to be higher in CTPHP as compared to FPPHP. The reduction in thermal resistance of FPPHP and CTPHP due to the presence of working fluid is about 83% and 35% of the corresponding thermal resistances without any working fluid respectively. CTPHP shows better thermal performance than FPPHP due to the presence of lateral conduction arising in the latter which has a detrimental effect on the slug-plug oscillations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Manish Garg, R.V. Ravikrishna〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In-cylinder air-fuel stratification and combustion is evaluated in a CNG-fuelled IC engine using a transient, three-dimensional, computational fluid dynamic (CFD) model. Performance of the stratified mode of operation is compared with the premixed mode. The combustion process is modeled using the extended coherent flame model (ECFM-3Z). For simulating the ignition process, the arc and kernel tracking ignition model (AKTIM) is used. The combustion model is first validated with measured in-cylinder pressure data and other derived quantities such as heat release rate and mass burn fraction for the premixed case. A good agreement is observed between measured and simulated values. It is observed that there is a marginal improvement in terms of overall engine efficiency when the stoichiometric premixed case is compared with the lean stratified condition. However, a major improvement in performance is observed when the lean stratified case is compared with lean premixed condition. The stratified case shows a faster heat release rate which could potentially translate to lower cycle-to-cycle variations in actual engine operation. Also, the stratified cases show as much as 30% lower in-cylinder NO〈sub〉x〈/sub〉 emissions when compared with the premixed case at the same engine load and speed, underscoring the potential of in-cylinder stratification to achieve improved performance and lower NO〈sub〉x〈/sub〉 emissions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Evangelos Bellos, Christos Tzivanidis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The role of renewable energy sources becomes more and more important in modern times. Solar energy utilization in the building sector is one attractive solution for covering heating and electricity needs. In this direction, the investigation of a solar heating-electricity production system ideal for building applications is investigated in this study. This cogeneration system includes hybrid PV (or PV/T) collectors and a heat pump which is driven totally (heat and electricity) by the solar collector. The system is designed properly in order to produce net electricity production except for the need of the heat pump. This system is optimized using an innovative multi-objective procedure with heating and electricity production as the objective functions. The optimization is performed in steady-state conditions for seven different working fluids in the heat pumps. The optimum design points for all the working fluids are compared and finally, R32 is selected as the most suitable choice with R1234yf to be the second one. In the optimum design conditions, 10 m〈sup〉2〈/sup〉 of hybrid PV collector are able to feed the heat pump and finally 4.33 kW〈sub〉th〈/sub〉 of heating and 0.53 kW〈sub〉el〈/sub〉 of net electricity to be produced. The next step in this study is the investigation of the system with R32 for all the winter period in the climate conditions of Athens (Greece). Six different typical days (one for every month from November to April) are examined and the final results are given. For January, which is a representative winter month, it is found that the daily heating and electricity production is 34.9 kWh and 5.13 kWh respectively. Moreover, the mean daily energy efficiency is found 60.53% while the exergy 9.26% for this month.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Ayoub Gounni, Mohamed Tahar Mabrouk, Mohamed El Wazna, Abdelhamid Kheiri, Mustapha El Alami, Abdeslam El Bouari, Omar Cherkaoui〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉New thermal insulation materials made from textile waste based on acrylic and wool were developed using needle punching method. The aim of this work is to investigate the thermal performance of an external building wall outfitted with the developed insulation materials and submitted to the real climatic conditions of Casablanca, Morocco. A numerical finite volume model is developed and validated against the experimental results of a thermally controlled cavity at reduced scale. The numerical model is used to study the thermal performance of the considered wall in winter and summer season and to compute the annual heating and cooling loads. The thermal and energetic performances of the developed insulation materials are compared to the ones of some classical thermal insulation materials (i.e. Rock wool and Expanded polystyrene). Furthermore, a Life Cycle Cost (LCC) analysis is conducted with the local market cost in order to investigate the competitiveness of the new insulation materials and to seek the optimal insulation thicknesses. The results show that the developed thermal insulation materials are a competitive solution in terms of annual loads compared to the conventional thermal insulations. The optimum insulation thicknesses of the new materials and of the considered classical thermal insulations materials are determined using the LCC analysis. The effect of the specific cost of the developed insulation materials is studied and findings show that, the developed insulation can be a competitive solution if their initial cost don’t exceed 590 MAD/m〈sup〉3〈/sup〉.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Yanzhi Zhang, Ming Jia, Pengfei Wang, Yachao Chang, Ping Yi, Hong Liu, Zhixia He〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A decoupling physical–chemical surrogate (DPCS) model was constructed for simulating the multi-component physical and chemical characteristics of practical diesel fuel. In the DPCS model, the physical and chemical characteristics of diesel fuel are surrogated separately, and the physical and chemical surrogates are coupled according to the principles of C/H mass ratio, functional group structure, and carbon balance. By implementing the DPCS model into a Computational Fluid Dynamics (CFD) code, the effect of the multi-component physical and chemical characteristics of diesel fuel on the spray, combustion, and emission characteristics in a constant-volume chamber and an optical diesel engine were explored. The results indicate that the DPCS model can satisfactorily reproduce the diesel vaporization and combustion behaviors under wide operating conditions.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Mehmet Selçuk Mert, Hatice Hande Mert, Merve Sert〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The response surface experimental design methodology was used to investigate thermal energy storage properties of the microencapsulated phase change material (MicroPCM). The capric acid and oleic acid mixture in the presence of hexadecane were encapsulated with styrene-divinylbenzene copolymer shell by emulsion polymerization technique. Response surface design experiments were conducted to determine the effect of three factors, namely, the shell:core ratio, emulsification time and crosslinker percentage at three distinctly different levels. Main effects and interaction effects of the factors on the latent heat of melting (ΔH〈sub〉m〈/sub〉), the amount of produced MicroPCM and the encapsulation ratio were examined using statistical methods. The regression models were derived fully fit the experimental data. According to the statistical analysis results, the most significant effect on the thermal energy storage capacity, the amount of MicroPCM and the encapsulation ratio was attributed to the shell:core ratio. The properties of optimal MicroPCM were investigated by Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). The analysis results demonstrated that optimal MicroPCM with its latent heat of fusion value (123 J/g) and encapsulation ratio (85.85%) can be accepted as a good candidate for thermal energy storage applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Shengchun Liu, Zheng Li, Baomin Dai, Zhifeng Zhong, Hailong Li, Mengjie Song, Zhili Sun〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Using air source heat pump system for residential heating is a practical way to replace coal-fired boiler in China to alleviate the haze problem, and CO〈sub〉2〈/sub〉 is a promising candidate to replace hydrochlorofluorocarbon (HCFC) or hydrofluorocarbon (HFCs) charged into the system. A mathematical model is developed to comprehensively evaluate the energetic, economical and environmental performances of CO〈sub〉2〈/sub〉 heat pump system compared with other three traditional heating methods. The results indicate that the primary energy ratio of CO〈sub〉2〈/sub〉 heat pump is the highest and it is a rational way to utilize renewable energy with the renewable energy contribution ratio of 0.60–0.69. The initial capital cost of CO〈sub〉2〈/sub〉 heat pump is much higher due to the dominant compressor cost. The emission of CO〈sub〉2〈/sub〉 heat pump is lower than that of coal-fired boiler at seasonal performance factor above 2.44. The initial and operation cost can be gradually reduced with the mass production and energy efficiency improvement of CO〈sub〉2〈/sub〉 heat pump. It is believe that air source CO〈sub〉2〈/sub〉 heat pump system can be employed for home heating in China, especial for the hot summer and cold winter region.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): J.M. Barroso-Maldonado, J.A. Montañez-Barrera, J.M. Belman-Flores, S.M. Aceves〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉A crucial aspect of Joule-Thomson cryocooler analysis and optimization is the accurate estimation of frictional pressure drop. This paper presents a pressure drop model for boiling of non-azeotropic mixtures of nitrogen with hydrocarbons (e.g., methane, ethane, and propane) in microchannels. These refrigerant mixtures are important for their applicability in natural gas liquefaction plants. The pressure drop model is based on computational intelligence techniques, and its performance is evaluated with the mean relative error (〈em〉mre〈/em〉), and compared with three correlations previously selected as most accurate: Awad and Muzychka; Sun and Mishima; and Cicchitti et al.〈/p〉 〈p〉Comparison between the proposed artificial neural network (ANN) model and the three correlations shows the advantages of the ANN to predict pressure drop for non-azeotropic mixtures. Existing correlations predict experimental data within 〈em〉mre〈/em〉 = 23.9–25.3%, while the ANN has 〈em〉mre〈/em〉 = 8.3%. Additional features of the ANN model include: (1) applicability to laminar, transitional and turbulent flow, and (2) demonstrated applicability to experiments not used in the training process. Therefore, the ANN model is recommended for predicting pressure drop due to accuracy and ease of applicability.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Fawad Ahmed, Huang Hulin, Aqib Mashood Khan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Numerical modelling can significantly contribute to the performance enhancement and technological advancement of Stirling engines. In this paper, a practically feasible thermodynamic model was developed for beta type of Stirling engines with rhombic-drive mechanism. Quasi-steady flow approach was adopted to analyze the heat transfer and flow friction effects of the heater, cooler, and regenerator on the performance of engine. The numerical model predicts the output power and thermal efficiency while considering the pressure drop in heat exchangers and numerous power and thermal losses. A parametric study is utilized to investigate the impact of operating and geometric parameters on the power output and efficiency of the Stirling engine. A combination of optimized temperature ratio, swept volume, regenerator matrix porosity, phase angle, pressure and engine frequency are assessed. The optimized model is then compared and validated against the experimental data obtained from the General Motor’s prototype of GPU-3 Stirling engine. Substantial improvement on the performance of the engine is achieved by optimizing the operating and geometric parameters of the engine.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Mehdi Bahiraei, Nima Mazaheri, Ali Rizehvandi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The current paper attempts to numerically examine the hydrothermal characteristics and energy performance of a hybrid nanofluid containing graphene nanoplatelet–platinum composite powder in a triple-tube heat exchanger equipped with inserted ribs. The nanofluid flows in the inner annulus side, whereas the cold water and normal water flow in the tube side and outer annulus side, respectively. The ribs are installed on the outer surface of the inner tube. The overall heat transfer coefficient, effectiveness and heat transfer rate of the heat exchanger are enhanced by increasing the nanoparticle concentration and rib height and by decreasing the rib pitch. The pressure drop is more intense in the cases of smaller rib pitch and higher rib height because the particles pass longer routes under these conditions. Based on the heat transfer enhancement, the case with greater rib height and smaller rib pitch at the highest concentration is suggested, because demonstrates the greatest thermal performance for the heat exchanger. Whereas, in the view of the energy efficiency, the heat exchanger with the smaller rib height and lower rib pitch with the highest nanoparticle concentration is recommended since the performance index of this case is greater than that of the other cases.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Dimitrios Korres, Evangelos Bellos, Christos Tzivanidis〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The objective of this work is the investigation of a nanofluid-based compound parabolic collector under laminar flow conditions. The examined nanofluid is Syltherm 800/CuO with 5% volumetric nanoparticle concentration and the examined temperature range is from 25 °C up to 300 °C. The analysis is performed in SolidWorks Flow Simulation Studio using a developed computational fluid dynamics model. Moreover, it is essential to state that this work is conducted under laminar flow conditions because the laminar flow regime is common for the compound parabolic collectors. It is found that the mean value of the thermal efficiency is 1.24% while the maximum 2.76% for inlet temperature equal to 300 °C. Moreover, it is found that the mean and the maximum heat transfer coefficient enhancements were 16.16% and 17.41% respectively, while the maximum pumping work increase was found to be 16.09%. However, the calculated pumping work demand was too low in all cases and this fact indicates that the increase of the pressure drop with the nanofluid is not a limitation in the present problem. In the end, the exergy efficiency enhancement is found to be up to 2.60%, while the overall efficiency enhancement up to 2.76% with the use of nanofluid.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Yandong Hou, Liu Wang, Mingjun Wang, Kui Zhang, Xisi Zhang, Wenjun Hu, Yingwei Wu, Wenxi Tian, Suizheng Qiu, G.H. Su〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The single-phase thermal hydraulic characteristics of liquid metal sodium are very essential for the design and safety analysis of sodium-cooled fast reactor (SFR). In this paper, the pressure drop and heat transfer features of single-phase liquid sodium were experimentally investigated in a 7 rod bundle with the velocity range of 0–4 m/s, heat flux up to 120 kW/m〈sup〉2〈/sup〉 and the absolute pressure range of 0–0.2 MPa. The corresponding Reynolds number ranges from 4000 to 40,000, and the 〈em〉Pe〈/em〉 number varies from 0 to 340. It was found that the critical 〈em〉Re〈/em〉 number for transition-turbulent flow of single-phase liquid sodium is 13,500 in the hexagonal 7-rod bundle. Then the effects of relative axial position, wall heat flux and 〈em〉Re〈/em〉 number on the heat transfer were discussed, respectively. Some existing correlations in the literatures were assessed and compared with the experimental data. Results indicated that these correlations could not predict the current experiments well because of the different geometries and working fluids. The new correlations for the friction factor and 〈em〉Nu〈/em〉 number calculations were proposed based on the current experimental data. For 98.5% of heat transfer data produced by the other researchers, the prediction error of the new correlation is less than 30%. For most of the experimental data, it is less than 20%, which sufficiently proves that the correlation developed in this paper could give a good prediction of the experimental data obtained by other researchers.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): M.M. Sarafraz, M. Arjomandi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present research, an experimental investigation was conducted to identify the behaviour of gallium as a promising heat transfer fluid for cooling a high heat flux surface. Bismuth nanoparticles were dispersed within the gallium to compensate its poor thermal conductivity and to enhance its wettability. A high-fidelity experimental setup was fabricated to provide conditions for measuring the contact angle between the gallium and the surface and also to measure the heat transfer coefficient of a free surface liquid film flowing on the heating surface. Influence of different operating parameters including tilt angle of the surface, heat flux of the surface, surface roughness and time on the contact angle and heat transfer coefficient of the liquid film was experimentally investigated. Results showed that with an increase in the tilt angle of the surface, higher heat transfer coefficient can be achieved, which was attributed to the enhancement of the terminal velocity of the liquid metal. Also, an increase in the roughness of the surface intensified the contact angle of the liquid metal and caused a decrease in the wettability. It was also found that the contact angle of gallium was a function of time such that it decreased with time spanning and reached a constant value.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Guanghui Wang, Dingbiao Wang, Xu Peng, Luole Han, Sa Xiang, Fei Ma〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heat transfer and flow characteristics in the shell side of helically coiled trilobal tube (HCTT) heat exchanger are investigated by experiment and a 3D numerical simulation. Compared to experimental tests and existing empirical formulas, calculated results indicate that the shell-side fluid of HCTT heat exchanger shows a strong ability to rotate and to disturb the boundary layer. In addition, the circumferential and radial velocities near the tube wall are improved, and the velocity vector exhibits a good synergy with temperature gradient. Nusselt number (〈em〉Nu〈/em〉) increases and friction factor (〈em〉f〈/em〉) decreases in shell side of HCTT as the Reynolds number increases. Under the same condition, the augmentation on heat transfer performance of HCTT is about 1.16–1.36 times compared with the helically coiled plain tube (HCPT), while friction factor sharply increases 0.96–1.10 times. The performance evaluation criterion (〈em〉PEC〈/em〉) could be up to 1.32. The Field synergy number of HCTT based on the field synergy principle (FSP) is much higher than that of HCPT and helically coiled elliptical tube (HCET), which indicates effective improvement of flow and heat transfer by HCTT. The correlation equations in the shell side of HCTT heat exchanger are in conformity with the orthogonal experimental design points.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): 〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the consideration of performance reliability, compared with the water cooling and the active air cooling, the passive air cooling technique without using of any pump(s) and blower(s) may be a better solution to the cooling issue of PV panels working under critical condition (high ambient temperature and no wind). In this paper, a new passive air cooling system for PV panels was elaborated. To quantify the performance advantage of this novel system and optimize its structure design, a numerical model was developed and then verified through a series of validation experiments. Following numerical analysis results showed that when the ambient temperature was 30°C, compared to the reference PV panel, the PV array equipped with this kind of passive air cooling system could have a much lower working temperature: 10°C decrease in the case of the solar irradiation intensity reaching to 500 w/m〈sup〉2〈/sup〉 and over 15〈sup〉o〈/sup〉c decrease once the solar radiation intensity jumps to 800 W/m〈sup〉2〈/sup〉. Greater the solar radiation intensity, more benefit can be achieved from this novel passive air cooling system. In addition, the effects of main geometric parameters on the cooling performance of the system were carefully studied. Considering the balance of the cooling capacity and the manufacturing cost, the structure design with a rectangular cooling channel, relatively low channel height and rectangular chimney seems to be the optimal option for the passive air cooling system.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Kai Zhang, Lizhan Bai, Guiping Lin, Haichuan Jin, Dongsheng Wen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, a porous artery structure is proposed to enhance the critical heat flux (CHF) of pool boiling based on the concept of “phase separation and modulation”, and extensive experimental studies have been carried out for validation. In the experiment, multiple rectangular arteries were machined directly into the top surface of a copper rod to provide individual flow paths for vapor escaping. The arteries were covered by a microporous copper plate where capillary forces can be developed at the liquid/vapor interface to prevent the vapor from penetrating the porous structure and realize strong liquid suction simultaneously. The pool wall was made of transparent quartz glass to enable a visualization study where the liquid/vapor distribution and movement can be observed directly. Favorable results have been reached as expected, and a maximum heat flux up to 805 W/cm〈sup〉2〈/sup〉 was achieved with no indication of any dry-out, which successfully validated this new concept. In addition, the effects of the diameter and thickness of the porous copper plate, and the connection method between the porous copper plate and copper fin on the pool boiling heat transfer in the porous artery structure were investigated, and the inherent physical mechanisms were analyzed and discussed.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): J. Ruiz, C.G. Cutillas, A.S. Kaiser, B. Zamora, H. Sadafi, M. Lucas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Drift eliminators play a major role in cooling tower operation. They are designed to reduce the discharge aerosols in their exhaust air stream to a minimum since inhaled airborne particles can cause the well-known Legionnaires disease. However, the pressure drop induced into the air stream increases the power consumption of the system. Accordingly, the design and selection of these elements should be a trade-off between the pressure drop and the collection efficiency. In this paper, six commercial drift eliminators (vane, wire mesh, and honeycomb-type) have been characterized in terms of pressure drop and collection efficiency with the aim of providing reliable information that can be used in drift eliminator design and selection. Fifty-three experiments were conducted regarding the pressure drop and collection efficiency characterization of the eliminators. Generally speaking, for the same type of eliminators the higher the pressure drop, the more efficient it is. Concerning typologies, wire-mesh eliminators perform better than the rest in terms of both pressure drop and collection efficiency. Dimensionless correlations for the pressure drop coefficient and the collection efficiency have been developed for the tested eliminators, showing a good agreement with the experimental results. A selection criterion has been proposed based on the dimensionless parameters that govern the problem and the experimental data of power consumption. It is based on determining the power consumed by the fans of the tower by setting a limit of collection efficiency and the droplet distribution characteristics at the cooling tower outlet area.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Kamil Śmierciew, Jerzy Gagan, Dariusz Butrymowicz〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Ejection system can be driven by free or inexpensive low temperature heat source, either solar or waste heat, as the main source of energy instead of electricity. These systems can be thought as a real alternative to compression devices in air-conditioning technologies. The paper deals with design procedure for the gas ejector based on numerical modelling. Crucial geometry parameters of the ejector and performance lines based on numerical analysis are shown. Also, the velocity and pressure flow fields inside the ejector, temperature and pressure profiles along the ejector are presented and discussed. Effects of geometry modification on the ejector performance are also shown and discussed. Comparison between numerical and experimental results of temperature and static pressure are presented.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Golmohammad Khoobbakht, Mahmoud Karimi, Kamran Kheiralipour〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The objective of the present study is to evaluate the effect of several variables, including different levels of biodiesel and ethanol in diesel blended fuel (biodiesel-ethanol-diesel blends), engine load and rotational speed, on the performance indicators of a diesel engine. Design of experiments was conducted as central composite rotatable designs using response surface method. The results showed that increasing biodiesel and/or ethanol percentages in the fuel blends caused to reduce the engine brake power. A low level of biodiesel and/or ethanol in the fuel blends could enhance the engine brake thermal efficiency in comparison with the pure diesel fuel or high level of biodiesel and/or ethanol in the diesel fuel blends. The highest value of the engine brake power occurred on the condition for pure diesel, engine load of 100% (full load) and rotational speed of 2800 rpm, whereas the highest value of thermal efficiency was observed at D〈sub〉83〈/sub〉B〈sub〉12〈/sub〉E〈sub〉5〈/sub〉 blended fuel, engine load of 80% and rotational speed of 1900 rpm. However, the specific fuel consumption, with a minimum at the pure diesel, full load and engine rotational speed of 2453 rpm, increased with increment biodiesel and/or ethanol percentage in the fuel blends.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Junhui Zhang, Jingyong Liu, Fatih Evrendilek, Wuming Xie, Jiahong Kuo, Xiaochun Zhang, Musa Buyukada〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermogravimetric (TG) and TG-Fourier transform infrared (FTIR) analyses were performed to quantify the comparative performances of cattle manure combustion in air (N〈sub〉2〈/sub〉/O〈sub〉2〈/sub〉) and oxy-fuel (CO〈sub〉2〈/sub〉/O〈sub〉2〈/sub〉) atmospheres at four heating rates. Out of the distributed activation energy model, Flynn-Wall-Ozawa (FWO), Friedman and Starink methods (〈em〉R〈/em〉〈sup〉2〈/sup〉 ≥ 0.86), the FWO method on average led to the highest 〈em〉R〈/em〉〈sup〉2〈/sup〉 value with the lowest activation energy. On average, the combustion in the oxy-fuel atmosphere had the lowest activation energy (180.6 kJ/mol) with the highest 〈em〉R〈/em〉〈sup〉2〈/sup〉 value (0.9812). Our TG-FTIR results showed that CO〈sub〉2〈/sub〉 was the major gas evolution of the cattle manure combustion. Interaction effects of atmosphere type by heating rate on the multiple responses of remaining mass, derivative TG, and differential scanning calorimetry were found to be significant (〈em〉p〈/em〉 〈 0.001). The joint optimization of the three responses was achieved at 424.6 °C in the air atmosphere at the heating rate of 40 K/min.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Ming Xie, Yanlong Zhu, Yi Liu, Yuan Yuan, Heping Tan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Molten salt is widely used in many fields as an important working fluid at high temperature as the increase in the use of new energy sources. In addition to studies on the thermal properties, research on the radiative properties of molten salts is mainly in the wavelength range of 0.3–2.5 μm, but most of emission energy falls in range of 2.5–25  μm at 600 °C. In this study, an emissivity measurement system for a liquid molten salt was developed on the basis of the black body emission method. The spectral emissivities of Hitec and Solar Salts were measured in the wavelength range of 5–25 μm. Moreover, the effects of the radiation of the inner wall of the large crucible and the emission and reflection at the upper surface of the bottom of the small crucible were eliminated. The results showed that the spectral emissivity of a molten salt increases with the temperature. In the wavelength range of 6–8.5 μm, two continuous depressions were observed in the emissivity of the Hitec, whereas there was only one depression in the emissivity of the Solar Salt in the range of 6.5–7.5 μm. The uncertainty of the experiment is less than 5.9% in experimental temperature and wavelength range. The results are supposed to be useful in designing and optimizing the equipment and operating conditions in the concentration solar power (CSP), as well to be helpful in accurately measuring the thermal properties of the molten salt.〈/p〉〈/div〉 〈/div〉 〈div xml:lang="en"〉 〈h5〉Graphical abstract〈/h5〉 〈div〉 〈p〉The spectral emissivity of Hitec and Solar Salts at high temperature, the effects from large crucible and the emission and reflection from the bottom of the small crucible were eliminated.〈/p〉 〈p〉〈figure〉〈img src="https://ars.els-cdn.com/content/image/1-s2.0-S1359431118351123-ga1.jpg" width="493" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 148〈/p〉 〈p〉Author(s): Sayan Biswas, Pei Zhang, Haifeng Wang, Li Qiao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Propagation and extinction behavior of a CH〈sub〉4〈/sub〉/air premixed flame passing through straight and converging-diverging (C-D) microchannels (diameters ranging from 1 to 10 mm) were investigated both experimentally and numerically. The dynamic behavior of flame propagation inside the channels was experimentally studied by using CH〈sup〉∗〈/sup〉 chemiluminescence and direct imaging. Three patterns of flame propagation were observed, 〈em〉i.e.〈/em〉, the flame can survive, partially extinguish and then re-ignite downstream, or completely extinguish. Regime diagrams showing these different patterns as functions of channel geometry and equivalence ratio were generated for both the straight and C-D channels. Numerical simulations were carried out to explain the experimentally observed flame dynamics inside the channels using detailed CH〈sub〉4〈/sub〉/air chemistry. In general, flames were easier to extinguish in C-D channels than in straight channels for a fixed channel diameter and equivalence ratio. Additionally, flames were harder to survive in C-D channels with larger exit-to-throat area ratios. Both heat loss and flame stretch were key factors that can generally cause flame extinction in narrow C-D channels. Heat loss was found to be the primary reason for flame extinction inside the microchannel in comparison with the stretch effect.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Clement Ajani, Stefano Curcio, Racha Dejchanchaiwong, Perapong Tekasakul〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉We developed a theoretical model for the transport phenomena affected by shrinkage in rubber sheet drying. The conjugate approach involving the simultaneous transfer of momentum, heat and mass in the drying chamber and rubber sheet was investigated by computational fluid dynamics. An isotropic, linear elastic model was assumed, and the shrinkage was correlated with the moisture content evolution in the rubber sheet〈strong〉.〈/strong〉 The Arbitrary Lagrangian-Eulerian (ALE) method was used to solve the two-dimensional problem accounting for shrinkage〈strong〉.〈/strong〉 The shrinkage across the rubber sheet thickness was estimated at 9〈strong〉.〈/strong〉1〈strong〉%〈/strong〉 and the moisture content was reduced from 0.4 to 0.05 kg-water/kg-dried sheet at an average holding relative humidity of 60〈strong〉%〈/strong〉 within 46 h. Simulations and experiments showed good agreement 〈strong〉(〈/strong〉R〈sup〉2〈/sup〉 values for moisture content and shrinkage were 0.9809 and 0.9991, while RMSE were 0.0196 and 0〈strong〉.〈/strong〉0091〈strong〉).〈/strong〉 The derived model can be used as a quality index evaluation for rubber sheet and for drying process optimization. Water activity can also identify regions that may be prone to microbial spoilage. The drying time was lower than for traditional sun drying of air dried sheets 〈strong〉(〈/strong〉as high as 152 h〈strong〉)〈/strong〉 or drying in a natural flow chamber 〈strong〉(〈/strong〉72 h〈strong〉).〈/strong〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 February 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 149〈/p〉 〈p〉Author(s): Sampath Emani, M. Ramasamy, Ku Zilati Ku Shaari〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fouling in crude preheat trains is a major cause of thermal inefficiency in petroleum refineries. The limited fundamental understanding of its causes and mechanisms led to ineffective fouling mitigation techniques. It is believed that asphaltenes precipitation and deposition is the major cause of fouling. The present work attempts to simulate the deposition of asphaltenes from crude oil in a multi-pass shell and tube heat exchanger through discrete-phase CFD simulations. The effects of bulk velocity, temperature gradients in the radial direction and particle sizes on asphaltenes deposition are investigated. In an effort to understand the effect of various forces on the rate of deposition of asphaltenes, forces such as gravity, drag, Saffman lift and thermophoretic are applied on the asphaltenes particles. The deposition velocities of the asphaltenes particles are determined based on solving the balance of these forces. The asphaltenes particles mass deposition rate is high in locations of higher particle deposition velocities. The CFD simulations indicate that the dominant forces to encourage particles deposition are gravity and drag. The deposition velocities and mass deposition rates are high for larger particle sizes. Low fluid velocities, higher temperature gradients and larger particle sizes favor higher particle deposition rates.〈/p〉〈/div〉 〈/div〉