ALBERT

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Jingqi Tan, Jianjian Wei, Tao Jin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Onset and damping processes that characterize the transition of a thermoacoustic engine between the stationary and periodic oscillating states have attracted much research effort. In this work, the onset and damping characteristics of a closed two-phase thermoacoustic engine are investigated, where a regenerator is inserted between the cold and hot heat exchangers to reduce the irreversible loss caused by heat transfer. Additionally, a branch resonator, which consists of a load tube and a gas reservoir, is introduced to form the closed system and to adjust the acoustic field. A lumped parameter model is proposed to quantitatively analyze the performance of the thermoacoustic engine. Upon optimization, an onset temperature difference as low as 8.2 °C can be achieved in the experiments with R134a as the working fluid, which is the lowest one ever reported in the literatures. Besides, hysteresis phenomenon is found during the onset and damping processes. The present work aims to provide better understanding of the onset and damping behaviors of a two-phase thermoacoustic engine.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Bin Zou, Yiqiang Jiang, Yang Yao, Hongxing Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Since various optical factors, including sunshape and optical errors, coexist in practice, their coupling effects on the PTC’s optical performance deserve in-depth explorations. Previous studies mainly focused on individual effects of several typical optical errors or simple description of optical errors using a unified Gaussian model. Thus, this study is committed to investigating the coupling effects of multiple optical factors on the PTC’s optical performance based on the theoretically individual characterization of each optical factor. The Monte Carlo Rays Tracing method was adopted, and the effective sunshape model was established for sampling of incident rays by convolving the incident sunshape model with the specularity error model. It is revealed that larger circumsolar ratio and specularity error produced more uniform heat flux distribution on the absorber. The advantage of high optical quality reflectors in improving optical efficiency was more outstanding in clearer weather. As circumsolar ratio was more than 0.2, improving specular quality to very high degree (〈3 mrad) reduced instead the optical efficiency. When tracking error and slope error were maintained respectively less than 4 mrad and 2 mrad, the weakening of optical efficiency was limited. The optical efficiency was more sensitive to slope error than to tracking error. The offset direction along positive Y-axis caused at maximum 2.19 times increase in heat flux density than that without optical errors, which causes threat of overheating to the absorber. When alignment error and tracking error were in the opposite direction, the optical loss could be compensated, whereas that in the same direction enlarged the optical loss. The slope error weakened the compensation effect and aggravated the weakening effect.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Jiaxu Wang, Xuefeng Liu, Siwei Chen, Hanghang Jiang, Guanyu Fang, Wenjing Chen, Shiming Deng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The current work study the heat dissipation characteristics and airflow distribution in a power cabin. By simplifying the cable structure, a 1:5 reduced-scale model was constructed based on the Archimedes number. Computational fluid dynamics (CFD) simulations were applied to the prototype power cabin. The 3D steady-state Reynolds average Navier-Stokes (RANS) equation is used to solve the ventilation flow, where the turbulence model is realizable k–ε. The CFD simulation of the prototype has been verified by the reduced-scale model. On this basis, several conclusions were drawn. The airflow distribution in the power cabin and cable arrangement cause a difference in the temperature distribution between the cables. The strong turbulence at the air inlet causes a significant temperature drop. The mechanical fan can effectively cool the cable to a certain extent, but cable temperature control should take into account the effects of ampacity and ventilation, as well as cable location.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Wenwu Zhou, Lin Yuan, Xin Wen, Yingzheng Liu, Di Peng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present study explored and examined the piezoelectric (PE) jet: an active cooling concept that can be actuated in demand, which had an oscillating flow and extremely low power consumption. The heat transfer and flow characteristics of the PE jet were quantified at various Reynolds numbers (〈em〉Re〈/em〉 = 5000, 10,000, 18,000) and spacings (〈em〉H〈/em〉/〈em〉D〈/em〉 = 4.5, 5.5, 6.5; corresponding gap 〈em〉G〈/em〉/〈em〉D〈/em〉 = 0.1, 1.1, 2.1). The temperature sensitive paint technique was used to study the heat transfer, and the particle image velocimetry technique was applied to resolve the flow characteristics and to further correlate the heat transfer results. Measured results show that the impingement cooling of the PE jet increased as the 〈em〉Re〈/em〉 increased and as the 〈em〉H〈/em〉/〈em〉D〈/em〉 decreased. Compared with a circular jet, the PE jet exhibited a greatly improved heat transfer at 〈em〉H〈/em〉/〈em〉D〈/em〉 = 4.5 (i.e., 〈em〉G〈/em〉 = 0.1〈em〉D〈/em〉), with a maximum of 20% enhancement in area-averaged 〈em〉Nu〈/em〉. Due to the fan oscillation, the turbulent kinetic energy level in the PE jet was significantly higher than in the circular jet, which greatly promoted the heat transfer at a narrow gap. In general, the new PE jet can provide superior heat transfer performance at a small gap and a high Reynolds number.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Sanaz Tabasi, Hossein Yousefi, Younes Noorollahi, Mohamad Aramesh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, the performance of a photovoltaic panel integrated with a reflecting mirror is investigated. In this regard, the effects of panel and mirror tilt angles, and the mirror length on the system performance are modeled. The cell temperature rises have also been considered. Moreover, by a 3D model, the lighting and shading statuses are studied in detail, and all the possible conditions are presented and modeled. The resulting model can calculate the amount of incident solar energy on the panel and the generated electrical power in every moment during a year. This amount is dependent on the system configuration and capacity and its location. A 250-W photovoltaic panel and the city of Tehran have been considered the basics of calculations to assess the model results. By employing the genetic algorithm method, the optimum configuration has been found to have 69.084° and 0° tilt angles for the panel and the mirror, respectively, at the mirror length of 2 m. This configuration can generate 2.38 GJ (613.89 kWh) of electrical energy annually. It was also found that the optimum configuration had 0.024 GJ of annual energy losses due to the effects of cell temperature rise.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Su Min Hoi, An Liang Teh, Ean Hin Ooi, Irene Mei Leng Chew, Ji Jinn Foo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The flow across the plate-fin heat sink under the influence of 2D planar space-filling square fractal grid-induced turbulence at Reynolds number 〈em〉Re〈sub〉Dh〈/sub〉〈/em〉 of 2.0 × 10〈sup〉4〈/sup〉 is numerically characterized. Fractal thickness ratio 〈em〉t〈sub〉r〈/sub〉〈/em〉, plate-fin inter-fin distance 〈em〉δ〈/em〉 and grid-fin separation 〈em〉ℓ〈/em〉 are numerically explored and optimized via Response Surface Optimization (RSO) with the objective of maximizing the Nusselt number 〈em〉Nu〈/em〉. Results reveal that, thanks to highly interactive, small and comparable turbulence length scale 〈em〉L〈sub〉t〈/sub〉〈/em〉, strong turbulence intensity 〈em〉T〈sub〉u〈/sub〉〈/em〉 and high velocity adjacent to the fin surfaces, thermal dissipation of plate-fin heat sink enhances significantly. An optimum fractal grid and plate-fin geometrical combination having 〈em〉t〈sub〉r〈/sub〉〈/em〉 = 9.77, 〈em〉δ〈/em〉 = 0.005 m and 〈em〉ℓ〈/em〉 = 0.01 m is proposed. It delivers 〈em〉Nu〈/em〉 of 3661.0 which is 6.1% and 16.3% greater than the reference case and least favorable configuration, respectively. Sensitivity analysis discovered that 〈em〉δ〈/em〉 effectively dominates the thermal dissipation improvement while 〈em〉t〈sub〉r〈/sub〉〈/em〉 contributes the most on the pressure drop. Interestingly, fractal grid may not necessarily augmenting plate-fin forced convective heat transfer. Without proper-tuning the fluid flow structures within the fins may worsen the thermal dissipation instead of strengthening it. In short, the interaction between plate-fin heat sink and the fluid flow structures within the fins contributes greatly to heat transfer performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Mark Baldry, Victoria Timchenko, Chris Menictas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Metal additive manufacturing technologies are increasingly being adopted for rapid prototyping and to build geometrically complex designs for thermal management. This paper develops and experimentally validates a numerical model to design a high performance, small-scale heat sink for use with a thermoelectric cooling cap. The design was constrained by a heat load of 2.15 W, and a target average base temperature of 45 °C as a compromise between avoiding burn injury and reducing heat dissipation requirements. Over successive numerical iterations, an optimal natural convection heat sink was developed with an estimated thermal resistance of 10.9  K·W〈sup〉−1〈/sup〉 and base temperature of 44.4 °C. This design featured an internal cavity in a tapered pin array, and was able to achieve a steady state base temperature that was 11.7 °C cooler than a conventional design, with 51% less surface area and significantly less material.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Nae-Hyun Kim, Cheol-Hwan Kim, Yousaf Shah, Wei Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In a parallel flow heat exchanger, significant mal-distribution of flow occurs due to phase separation. In this study, various insert devices (perforated tube, perforated tube with perforated plate, orifice and perforated tube, concentric perforated tube) were investigated to obtain an improved flow distribution in a 36 channel parallel flow heat exchanger. The test section was made to closely simulate an actual heat exchanger. Tests were conducted for upward flow for the mass flux from 57 to 241 kg m〈sup〉−2〈/sup〉 s〈sup〉−1〈/sup〉 and quality from 0.2 to 0.4 using R-410A. Of the investigated insert devices, concentric perforated tube yielded the best flow distribution. Insertion of the concentric perforated tube reduced the thermal degradation from 61% to 14%. Furthermore, the preferred number of holes of the concentric perforated tube was dependent on the mass flux. At a low mass flux, an insert having small number of holes was preferred, whereas the reverse was true at a high mass flux. At a low mass flux, the effect of inlet vapor quality on flow distribution was significant. At a high mass flux, however, the effect of vapor quality on flow distribution was minimal. Possible explanations on the flow distribution behavior were provided through flow visualization in the header.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Rohit Singla, Kanchan Chowdhury〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Cryogenic air separation plants producing pressurized gaseous oxygen (PGOX) near 40 bara at purities 99.8% and 95% and gaseous nitrogen at 5 bara above 99.99% purity are analyzed. Oxygen is compressed either by external compression process (EC) or by internal compression (IC). IC is gasification of pumped liquid oxygen in the main heat exchanger (MHX). IC plants require appropriate combinations of pressure and flow of air and size of the MHX to vaporize PGOX with reasonable specific power consumption (SPC). Based on exergy and economic analyses of the ASU after simulating the plant in Aspen HYSYS®™8.6, the values of parameters which give high exergy efficiency with low capital and operating expenditures are determined. SPC of IC is 7–8% higher than that of EC. Addition of crude argon column improves the purity of oxygen from 96.3% to 99.8%. Recovery of oxygen improves by 5% with 3–4% reduction of SPC for both types of plants. Capital requirement for both EC and IC plants is about 50% higher with argon separation than without it. HP air between 33% and 31% of total air flow at 70 bara and 80 bara respectively is the most preferred range of operation of IC plants for 95% purity of oxygen. The corresponding flow of HP air is 5% lower for 99.8% purity of oxygen.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Medhat M. Sorour, Wael M. El-Maghlany, Mohamed A. Alnakeeb, Amgad M. Abbass〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An experimental investigation was conducted in order to study heat transfer between a vertical free surface jet and a horizontal stainless steel heated plate. The jet was composed of water-〈em〉SiO〈sub〉2〈/sub〉〈/em〉 nanofluid with an average particle size of 8 nm delivered from a fixed nozzle diameter of 6 mm. The results covered a wide range of jet Reynolds number up to 40000, ten nanoparticle volume fractions (0% ≤ 〈em〉φ〈/em〉 ≤ 8.5%), five jet aspect ratios (〈em〉z/d〈/em〉 = 0.5, 1, 2, 4 and 8) and plate radius to jet diameter ratio (〈em〉r/d〈/em〉) up to 12.5. The experimental results illustrated that the enhancement of the average Nusselt number increases with the volume fraction and Reynolds number. Therefore, the volume fraction can significantly provide a heat transfer enhancement of the average Nusselt number up to 80% for a volume fraction of 8.5% compared to pure water. Conversely, the effect of nozzle to plate aspect ratio (〈em〉z/d〈/em〉) is not significant. Finally, a new heat transfer correlation has been proposed for the average Nusselt number as a function of Peclet number, a nanoparticle volume fraction, a plate to jet diameter ratio and a nozzle to plate aspect ratio.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Grayson Lange, Luca Carmignani, Subrata Bhattacharjee〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Radiative emission from a flame is an important component of the heat transfer balance between flame and surroundings. When the residence time of the oxidizer increases radiation plays an important role, and a practical example is given by microgravity flames where the lack of buoyancy creates larger time scales of the problem. With a strong opposed-flow, however, radiation could become a secondary effect. This study presents experimental measurements of thermal radiation from downward spreading flames over thin sheets of PMMA (polymethyl methacrylate) in a normal gravity environment and no forced flow. Radiation data from these downward spreading flames can serve as a baseline for future microgravity experiments. The presented experiments are performed in an apparatus called Flame Stabilizer where a spreading flame is turned stationary in laboratory coordinates by moving the sample upwards at the same velocity as the downward spreading flame. A radiometer, capable of line of sight measurement, is mounted on a x-y-z position controller and used to map the radiation emitted by the flame and the burning solid perpendicular to the fuel surface. After establishing repeatability and consistency of the results, a family of radiation profile curves is generated to map the radiation field. The experiments are then repeated by varying fuel thickness; larger fuel thicknesses are found to generate stronger radiation signals as the flame size becomes bigger. Furthermore, the radiative response to the presence of char in a flame is illustrated by comparing the PMMA results with a cellulosic fuel. With the unburnt solid in the flame region, radiative emissions significantly increase.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): X. Zheng, Z. Lin, B.Y. Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Desiccant coated aluminum fins are an important part of desiccant coated heat exchangers (DCHEs). The overall performance of DCHE-based systems benefits from improved heat and mass transfer characteristics of desiccant coated aluminum fins. In this paper, a new type of nano-silver powder supported FAPO-34 composite fin is proposed. Samples with different mass percentages of nano-silver powder were fabricated and related characteristics including thermal conductivity, cycle water uptake and adsorption/desorption performance were investigated. Our experimental results show greatly improved thermal conductivity of nano-silver powder supported composite sheets. Analysis of the adsorption testing confirmed that the nano-silver powder improved dynamic adsorption performance, and adsorption rate coefficients of composite sheets increasing by 6–103% compared with that of a pure FAPO-34 coated sheet. The composite samples also exhibited better dynamic desorption performance, in that their desorption rate coefficients increased to be 1.3–2.3 times as great as those of the pure FAPO-34 sample.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Xinpeng Zhao, Sohrab A. Mofid, Majed R. Al Hulayel, Gabriel W. Saxe, Bjørn Petter Jelle, Ronggui Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Highly transparent and low thermal conductivity materials have attracted great interest for the applications in window insulation in recent years. Accurate characterization of the thermal properties including thermal transmittance (U-value) and thermal conductivity of window insulation materials is very important for developing next-generation materials. The conventional hot box method, which is commonly used to measure the U-values of building materials, requires sample sizes 〉 1.0 m〈sup〉2〈/sup〉 to minimize the influence of parasitic heat loss on the measurement accuracy. This characterization challenge hinders the development of novel window materials which are not yet available for large-scale deployment. To address this issue, a reduced-scale hot box system (RHS) was designed to measure both the U-value and the thermal conductivity of specimens that can be more readily made, with sizes 〈 0.2 m × 0.2 m. The developed reduced-scale hot box system has a very simple testing system and can avoid the challenging thermal insulation requirement of the conventional hot box. The fast turnaround of the reduced-scale hot box system can help facilitate the development of novel insulating materials for energy-efficient windows.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Thi-Thao Ngo, Chi-Chang Wang, Jin H. Huang, Van-The Than〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents an inverse method for predicting the heat source and temperature during Gas Metal Arc Welding (GMAW). A combination of finite element thermal model and optimized technique is used to give inverse solutions. Simulated results show that the estimated temperatures and heat source are in good agreement with the exact solutions. Experiments are then performed to measure real temperature data which are further utilized for inversely predicting the heat source and temperature field. The experimental inverse results indicate that the predicted temperatures have a good correlation with the measured data, and the heat source is carried out for different welding conditions. To verify accuracy of the inverse results, a comparison of temperature at validated point is implemented. In addition, the temperatures at the welding area which are difficult to directly measure are also obtained. The proposed method may be applied to optimize welding condition for other welding processes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Mingyue Ding, Chenzhen Liu, Zhonghao Rao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to enhance the heat transfer performance of phase change material (PCM) for thermal energy storage (TES) in tiny devices, such as battery thermal management, light-emitting diode and electronic device cooling, TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O nanofluids and the microchannel were combined in this paper. Two crystal forms of TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O nanofluids were prepared by using a two-step method. And paraffin was used as PCM. The stability and thermophysical properties of the above two nanofluids were tested and compared. It can be found that R TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O nanofluid has better stability, and its thermal conductivity increases maximally by 3.27%, while the value is 2.88% of A TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O. Besides, R TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O nanofluid increases the viscosity by a maximum of 4.87%, while A TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O increases by 7.45%. Considering these properties, R TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O nanofluid was chosen to study the heat transfer characteristics in the microchannel within a TES unit. The results indicate that R TiO〈sub〉2〈/sub〉-H〈sub〉2〈/sub〉O nanofluid with 1.0 wt% increases Nu by 19 ∼ 41% and 6 ∼ 14% during the melting process and solidification process respectively. In addition, the melting time of paraffin decreases by a maximum of 32.90% and the solidifying time of paraffin decreases by a maximum of 22.57%. During the whole TES process, there is an increase in pressure drop of no more than 8%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Amir Sharafian, Paul Blomerus, Walter Mérida〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Fugitive methane emissions from the liquefied natural gas (LNG) supply chain have revealed uncertainty in the overall greenhouse gas emissions reduction associated with the use of LNG in heavy-duty vehicles and marine shipping. Methane is the main constituent of natural gas and a potent greenhouse gas. Recent measurements have shown that the LNG offloading process had the largest contribution to methane emissions in the refueling portion of the supply chain. However, there are limited studies analyzing the LNG offloading process for small-scale applications. This study investigates six methods used to offload LNG from a tanker truck to an LNG refueling station and their contribution to methane emissions. A verified thermodynamic model is created by comparing numerical results with the experimental data collected from an LNG offloading process in a refueling station. The modeling results show that the LNG transfer by using a pressure buildup unit causes methane emissions as high as 104 g/kg LNG. In contrast, LNG transfer by using a pump and controlled pressure buildup unit provides the lowest risk of methane venting. Also, the results of parametric study indicate that rigid foam insulation can be considered as an economical alternative to vacuum jacketed pipes in LNG refueling stations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Cheng Zeng, Shuli Liu, Liu Yang, Xiaojing Han, Ming Song, Ashish Shukla〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉For some renewable energy such as solar energy, the mismatch between the side of generation and demand should be tackled by thermal energy storage techniques with high energy density and low thermal losses. Thermochemical energy storage is a promising technology to meet these requirements. Within a thermochemical energy storage system, reactor is one of the critical components to achieve the optimal performance. While few studies have investigated the three-phase reactor applied in open thermochemical system in building’s application. This study presents a numerical description of a three-phase thermochemical reactor with air, solid thermochemical material and water flow. Zeolite 13X has been selected as the working thermochemical material and experimental tests have been conducted to obtain the temperature profiles in both the charging and discharging processes. A two dimensional numerical model of the reactors has been developed, verified and validated. A good agreement has been obtained by comparing the numerical and experimental results with the root mean square percent error ranging from 6.02% to 12.29%. Additionally, parameters sensitivity analysis has been conducted for reference diffusivity, heterogeneity factor, and initial water uptake of the zeolite. The numerical model and the investigation provide the tool for reactor design optimisation, charging and discharging processes evaluation and reactor performance improvement.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Dan Dan, Chengning Yao, Yangjun Zhang, Hu Zhang, Zezhi Zeng, Xiaoming Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An effective battery thermal management system is crucial for electric vehicles because the performance of lithium ion battery is sensitive to its operating temperature. In this study, a thermal management system equipped with micro heat pipe array (MHPA) is designed. An equivalent thermal resistance model is developed for MHPA based on thermal circuit method. The accuracy of the proposed model is validated by comparing the simulation results with experimental data under steady and dynamic and operating condition. A validated lumped thermoelectric model is adopted for prismatic lithium ion battery. The proposed thermal resistance model is combined with the battery model in order to predict the transient temperature distribution of a battery pack based on MHPA cooling. Simulations are conducted for air-cooled MHPA thermal management system. Temperature rise and temperature gradients of the designed cooling system are compared with direct forced convection. Simulation results demonstrate that the MHPA-based battery thermal management provides a quick response to ensure the temperature stability during rapid changing operating condition.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Farkhondeh Jabari, Behnam Mohammadi-ivatloo, Mousa Mohammadpourfard〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Recently, seawater desalination and power generation units are optimally co-scheduled because of interconnection between electricity and water networks. A typical water-energy hub grid consists of the conventional thermal power plants and the combined water and power (CWP) generating units. In the CWP plants, the waste heat of the flue gases exhausted from the power generation process is utilized for water treatment. If the water and power generation company aims to maximize its daily profit, the electricity price uncertainty will affect the optimum operating point of the generating units. In other words, the fluctuations of the energy prices cause the power generation patterns of thermal and CWP units to change. Hence, this paper implements a robust optimization strategy on water-power nexus model to handle the uncertainty of the electricity price with no need for its probability distribution and membership functions. The lower and upper bounds and the forecasted prices are used for solving the robust mixed-integer non-linear program and making the risk-averse decisions against the uncertainty. It is indicated that the proposed approach is suitable for the price taker water-power cogeneration companies, which seek the optimal schedule of their thermal and CWP units for a certain operating period.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Zhiyao Yang, Ming Qu, Omar Abdelaziz, Kyle R. Gluesenkamp〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Liquid desiccant systems (LDS) have recently seen an increase in research interest as they can utilize low-grade heat resources and separate the sensible and latent cooling loads by efficiently removing moisture in the air without cooling it to the dew point. However, simulation and analysis of LDS had remained complex and demanding due to the limited resources of LDS simulation tools. This work presents the new LDS module developed in the Sorption system Simulation program (SorpSim), which is an open-source and flexible platform for steady-state simulation and analysis of various sorption systems. First, the new LDS module containing a finite-difference model and an effectiveness-NTU model for the heat and mass transfer in LDS dehumidifier/regenerator component was introduced. Then the simulation results of the new module were verified using data from the literature. Finally, a case study was carried out in SorpSim where an LDS cycle was built and simulated using the new module. The impacts of design and operating parameters on the simulated LDS performance were investigated. The parametric study revealed that a high source temperature improved moisture removal rate (MRR) but reduced the system coefficient of performance (COP); the COP increased monotonically with the desiccant solution recirculation ratio, while the MRR peaked at a ratio of 85%; and an internal solution heat exchanger with UA of 800 W/K was found to be sufficient for optimal performance under high recirculation ratios. The case study demonstrated the LDS module’s capability to facilitate the analysis of LDS design and operation. The LDS module can be further coupled with other component models in SorpSim to simulate and analyze various liquid-desiccant-based systems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Mohammad Parhizi, Ankur Jain〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Phase change materials (PCMs) are used commonly for thermal energy storage and thermal management. Typically, a PCM utilizes its large latent heat to absorb and store energy from a source. The rate of energy stored (W) and energy storage density (J/m〈sup〉3〈/sup〉) over a certain time period are both important performance parameters of a phase change based energy storage system. While significant experimental research has been carried out to improve thermal conductivity of PCMs, there is a lack of theoretical understanding of how thermal conductivity and other thermophysical properties affect these performance parameters. This paper presents a theoretical heat transfer model to predict the rate of energy storage and energy storage density as functions of PCM thermal properties. Using perturbation method based techniques, expressions for these parameters are derived for two geometries, first for a simplified assumption of constant temperature at the source-PCM interface, and then for a more realistic scenario of time-dependent interface temperature. Results indicate that while increasing thermal conductivity results in improvement in rate of energy stored, the energy storage density does not change for a Cartesian system and actually decreases for cylindrical system. This shows that using a high thermal conductivity PCM may not be ideal when energy must be stored compactly because while this increases the total energy absorbed, it also results in greater rate of melting, which reduces the energy storage density. Results also provide guidelines for material selection for phase change based energy storage systems. For example, a trade-off in the choice between materials of disparate thermal properties is identified in terms of whether the rate of energy stored or energy storage density is paramount. Differences in the performance of Cartesian and cylindrical systems is investigated. Theoretical results presented in this work highlight various performance trade-offs related to the thermal properties of the PCM and help understand the impact of thermal conductivity enhancement on phase change energy storage performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Xudong Wang, Daqian Zhang, Xiaojia Wang, Zhiwei Kong, Yali Shao, Baosheng Jin〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the increasing thermal input of chemical looping combustion (CLC) reactor, the monitoring and diagnosis of its internal boundary conditions become important issues for operation safety. Based on the discrete heat transfer model of reactor wall, Kalman filter and fuzzy inference were combined as fuzzy inference-based augmented Kalman filter (FI-AKF) and fuzzy inference-based Kalman filter coupled with weighted recursive least squares algorithm (FI-KFW) for the real-time monitoring of CLC reactor. Simulations were carried out to validate the feasibility of these two methods. Under both normal and abnormal conditions, the FI-KFW could exhibited satisfying performances for the internal heat flux monitoring. Number of the measurement points and intensity of measurement noises were changed numerically to investigate their effects on the monitoring results of FI-KFW. Results demonstrated that FI-KFW had strong ability to resist the ill-posedness of the monitoring process and it was capable for the real-time monitoring of the chemical looping combustion reactor, which could offer reliable information for operation diagnosis.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Yongming Han, Chenyu Fan, Meng Xu, Zhiqiang Geng, Yanhua Zhong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The production data of complex chemical processes are multi-dimensional, uncertain and noisy, and it is difficult to directly control raw materials consumption and measure the product quality. Therefore, this paper proposes a production capacity analysis and energy saving model using long short-term memory (LSTM) based on attention mechanism (AM) (AM-LSTM). The weights of the results sequence in the hidden layer, which have great influence on final results in the output layer, are calculated by the AM. Then the production prediction model is built using the LSTM to extract features of the input data and multiple time series results of the hidden layer. Compared with the common LSTM, the multi-layer perceptron (MLP) and the extreme learning machine (ELM), the applicability and the effectiveness of the proposed model is validated based on University of California Irvine repository (UCI) datasets. Finally, the proposed model is applied to analyze the production capacity and the energy saving potential of the purified terephthalic acid (PTA) solvent system and the ethylene production system of the complex chemical process. The experimental results verify the practicability and accuracy of the proposed model. Furthermore, the results offer the operation guidance for production capacity improvement through saving energy and reducing the energy consumption.〈/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-S1359431118343485-ga1.jpg" width="170" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Sabino Caputo, Federico Millo, Giulio Boccardo, Andrea Piano, Giancarlo Cifali, Francesco Concetto Pesce〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper investigates the potential of coated pistons in reducing fuel consumption and pollutant emissions of a 1.6 l automotive diesel engine. After a literary review on the state-of-the-art of the materials used as Thermal Barrier Coatings for automotive engine applications, anodized aluminum has been selected as the most promising one. In particular, it presents very low thermal conductivity and heat capacity which ensure a high “wall temperature swing” property. Afterwards, a numerical analysis by utilizing a one-dimensional Computational Fluid Dynamics engine simulation code has been carried out to investigate the potential of the anodized aluminum as piston Thermal Barrier Coating. The simulations have highlighted the potential of achieving up to about 1% in Indicated Specific Fuel Consumption and 6% in heat transfer reduction. To confirm the simulation results, the coated piston technology has been experimentally evaluated on a prototype engine and compared to the baseline aluminum pistons. Despite the promising potential for Indicated Specific Fuel Consumption reduction highlighted by the numerical simulation, the experimental campaign has indicated a slight worsening of the engine efficiency (up to 2% at lower load and speed) due to the slowdown of the combustion process. The primary cause of these inefficiencies is attributed to the roughness of the coating.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Zilong Wang, Hua Zhang, Binlin Dou, Guanhua Zhang, Weidong Wu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heat storage tanks are one of the key components in solar thermal utilisation systems. In this study, the effect of the inlet stratifier on the thermal stratification in a heat storage tank with phase-change materials (PCMs) was investigated. A heat storage tank with a volume of 60 L and aspect ratio of 1.68 was developed based on the phase-change temperature of 331.15 K for sodium acetate trihydrate. The thermodynamic characteristics of the heat storage tank were measured at an initial temperature of 353.15 K and inlet water temperature of 278.15 K. Moreover, a computational fluid dynamics (CFD) model of the heat storage tank was established to simulate the discharge process. In addition, the CFD model was verified with experimental data. The impact of the PCM position on thermal stratification was thoroughly analysed for various flow rates. Furthermore, performance parameters including the Fill Efficiency (FE), Richardson number (Ri), and MIX number were considered. The results show that the equalizer enhances the thermal stratification effectively in the phase-change heat storage tank and stabilises the heat output characteristics of the water tank. Furthermore, in the water discharge process (t* = 0.1–0.7), the distances between the isothermal surfaces (279.15 K) and isothermal surfaces (352.15 K) in PCM4, PCM3, PCM2, and PCM1 increase by 6.56, 7.2, 8.98, and 12.34 cm, respectively. Thus, the mixing of hot and cold water strengthens with higher PCM position, which improves the thermal stratification in a heat storage tank. The half-life of the PCMs (melting rate reaches 50%) is prolonged with increasing inlet flow rate. For an inlet flow rate of 1 L/min, the half-life of PCM4 is t* = 0.5. For an inlet flow rate of 5 L/min, the half-life of PCM4 is t* = 0.95. Moreover, the simulated results of the FE and Ri are slightly higher than the experimental values, whereas the simulated MIX number results are below the experimental values. Finally, the simulated and experimental root mean-squared error results increase with lower PCM positions and increasing inlet flow rates.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Y.H. Diao, L.L. Yin, Z.Y. Wang, Y.H. Zhao, L. Liang, F.W. Bai〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present study, the thermal performance of a latent heat thermal energy storage device based on flat miniature heat pipe arrays with straight rectangular fins during the charging process is numerically investigated using porous media to reduce computational resources and time. Air is selected as the heat transfer fluid (HTF). The influence of a thermal storage unit (TSU) with one heat transfer component (HTC) on the melting rates of the phase change material (PCM) is simulated at different inlet temperatures and flow rates of HTF. The heat transfer between two HTCs that form a tandem is analyzed and compared, and the effect of different arrangements of the two HTCs on the charging process is then studied. Results indicate that the inlet temperature and the volume flow rate of the TSU influence the charging process. The average outlet temperature and charging power, which grow in a power function relationship with the volume flow rates, increase linearly with the inlet temperatures. The average charging power of the HTF through HTC-2 is reduced by approximately 63.71% compared with HTC-1 when the two HTCs form a tandem. The average charging power of the TSU with two HTCs connected in tandem is higher than that of the parallel TSU at the same inlet temperature and volume flow rate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Bruno Marcotte, Michel Bernier〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents an experimental validation of a thermal resistance and capacitance (TRC) model for double U-tube boreholes with two independent circuits. In the TRC model, the borehole cross-section is divided into four quadrants each with two nodes representing the fluid and the grout, respectively. Ground heat transfer is evaluated in each of the 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si8.svg"〉〈mi〉n〈/mi〉〈/math〉 vertical sections using the infinite cylindrical source analytical solution with appropriate temporal superposition. Finally, internal tube-to-tube and tube-to-borehole thermal resistances are evaluated with the multipole method. The TRC model is validated against results obtained using a small-scale borehole (90.39 cm long with a 9.45 cm diameter) positioned in a sand tank of known properties. The borehole is made of ceramic which enabled the precise positioning of thermocouples at the mid-height cross-section. Data are acquired at a high frequency (1 s) to capture transient effects. In the first set of results obtained for a quasi-steady state, isotherms over the mid-height cross-section compare favorably well with the ones obtained using the multipole method. In the other two tests, the borehole is subjected to varying inlet (flow rate and temperature) conditions. It is shown that the TRC model is in good agreement with the experimental data except when there is a severe steep change in inlet temperature or when there is no flow.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Taehoon Kim, Donghwan Kim, Sungwook Park〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In engine simulation, coarse mesh size is usually used to analyze a variety of cases utilizing chemistry which consists of many species and reactions. However, it is difficult to predict spray morphology exactly with coarse mesh. In this study, a model to predict structure deforming flash boiling spray even for the coarse mesh has been developed. A flash breakup model combined with a modified version of a gas-jet model was utilized to analyze propane flash boiling spray. The gas-jet direction was calculated by averaging the directions of spray from each nozzle. A high-velocity region near the axis of gas-jet flow confined the plumes to form a single plume. Gasoline spray was analyzed to determine proper Kelvin-Helmholtz-Rayleigh-Taylor (KH-RT) model constants. Gasoline spray characteristics such as spray tip penetration and morphology were captured using the final model constants. Using the KH-RT model constants, the flash breakup model was validated for propane flash boiling spray. Sauter mean diameter (SMD) of simulation and experiment showed similar results. However, spray morphology could not be captured by the simulation using only the flash breakup model. A modified gas-jet model was applied to the simulation along with the flash breakup model to improve spray morphology. Using the modified gas-jet and flash breakup models, spray structure penetrating through the central axis was successfully predicted and this resulted in a better spray tip penetration prediction. SMD trend depending on ambient pressure was captured and maximum error between experimental and simulation results was 11%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Ruikang Wu, Yiwen Fan, Tao Hong, Hao Zou, Run Hu, Xiaobing Luo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heat removal of high-power electronic devices has become the bottleneck that restricts the working performances. For ultrahigh heat flux density, even a thin layer of thermal interface material will dominate the temperature rise along the whole heat dissipation path. The existing liquid cooling only consider the cooling of the top surface of the electronic devices/chips, causing insufficient utilization of the cooling potential. In this paper, an immersed jet array impingement cooling device with distributed returns was designed, fabricated, and tested. In the proposed cooling device, the chip is immersed in the coolant and the coolant is ejected onto all the immersed surface of the electronics through the impinging jets, enabling to provide body cooling for high-power electronics. To prevent the jet interference between adjacent jets, distributed extraction returns were set between the adjacent jets for coolant to exit the impingement domain without flowing past the surrounding jets. The measured average temperature of the high-power chip with input heat power 550 W and flow rate 1000 ml/min is 77.0 °C, where the effective heat flux is 110 W/cm〈sup〉2〈/sup〉, and the inlet coolant temperature is maintained to be 40 °C. The average temperature of the high-power chip under the input heat power of 800 W (160 W/cm〈sup〉2〈/sup〉) is 78.7 °C with the flow rate reaching 2000 ml/min. The effective heat transfer coefficient of 41,377 W/m〈sup〉2〈/sup〉·K in maximum was achieved. The present body cooling is expected to provide high heat removal ability and be used for ultrahigh heat flux density electronics.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Manoj Kumar, Debashis Panda, Suraj K. Behera, Ranjit K. Sahoo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As a major component of cryogenic turboexpander, the design and performance estimation of a radial inflow turbine determines the effectiveness of the system. To explore the performance, this paper focuses on to investigate the effect of mass flow rate and operating temperature on isentropic efficiency, temperature drop, enthalpy drop, pressure variation, and power output of a cryogenic turboexpander. Firstly, the mean-line design of a radial inflow turbine is conducted by considering different loss models. Sobol sensitivity analysis is performed to identify the major geometrical parameters which have a significant effect on the performance of the turbine. Based on the geometrical data sets, an 〈em〉ANN〈/em〉 and 〈em〉ANFIS〈/em〉 models are developed to predict the ranges in which maximum efficiency of the turbine is obtained with minimum losses. The designed turbine is validated with available data in the literature. Secondly, an experimental set-up with extended measuring points for data collection is developed to investigate the performance of a turboexpander at cryogenic temperature. A detailed experimental analysis is carried out to compare the temperature drop, isentropic efficiency, and power output of the turboexpander for mass flow rate in the range of 0.03–0.08 kg/s and the inlet temperature of 130, 140, and 150 K. It is noticed that the highest temperature drop is obtained for the inlet temperature of 150 K. Thirdly, based on the experimental data, an 〈em〉ANN〈/em〉 and 〈em〉ANFIS〈/em〉 model is developed to predict the optimal range in which the turboexpander have maximum isentropic efficiency and temperature drop. The results deduce some valuable experimental data and also accumulate the design methodology of radial inflow turbine for cryogenic applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Kaswar Ali Al-Ameri, Shohel Mahmud, Animesh Dutta〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This work proposes a new configuration of solar still system and includes three experimental comparative studies on a 17 cm high longitudinal distillation unit with one distillation partition. The study targets to figure out the optimum conditions that maximize the productivity of the distillation partition. Also, the work includes determining the amount of the rejected waste energy from the unit with respect to the input energy for the optimum case obtained in the study. The investigated comparative cases include gravitational effect vs. Capillary effect of brackish water flow in the distillation partition wick, the performance when the unit is insulated vs. uninsulated, and using single wick vs. double wick layer inside the distillation partition. The work was conducted indoor, and electrical power (30 W, 50 W, 70 W, 90 W, and 110 W) was supplied to the unit separately. The results show that the gravitational brackish water flow, insulating the unit with 1″ thickness styrofoam, and using double cotton wick layer are the optimum operating conditions that maximize the productivity of the distillation partition. Under these conditions and when 110 W is supplied inside the distillation unit, the distillation efficiency of the unit is 15.64%, the distillation partition efficiency is 16.48%, and the heat supply efficiency of the unit is 19.61%. Also, the study proves that the distillation efficiency of the unit, the distillation efficiency of the distillation partition, and the efficiency of heat supply of the unit increases with increasing the input power to the unit.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Xiao Qian, Dongji Xuan, Xiaobo Zhao, Zhuangfei Shi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The excessively high temperature of lithium-ion battery greatly affects battery working performance. To improve the heat dissipation of battery pack, many researches have been done on the velocity of cooling air, channel shape, etc. This paper improves cooling performance of air-cooled battery pack by optimizing the battery spacing. The computational fluid dynamics method is applied to simulate the flow field and temperature field of the battery pack for different battery spacing. The battery spacing and corresponding CFD simulation outputs (maximum temperature and temperature difference) are used to train the Bayesian neural network. Compared with CFD simulation results, the relative errors are 0.08% and 3.2%. With this neural network model, the optimal battery spacing arrangement is found which is [17,24,22,0.22,0.23,0.176,0.176] and the temperature difference and the maximum temperature of the batteries are respectively 5.986(K) and 300.511(K). The results show this neural network model can accurately describe the relationship between the battery spacing and the battery temperature. This optimization process represents an effective and time-saving method to design the battery spacing distribution to improve the cooling performance of battery pack.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Evaldas Greiciunas, Duncan Borman, Jonathan Summers, Steve J. Smith〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A Concept Heat Exchanger (HE) design manufactured using the Additive Layer Manufacturing (ALM) technique Selective Laser Melting (SLM) is proposed and numerically evaluated. It is composed of a HE corrugation which introduces inter-layer flow conduits between the parallel HE layers of the same fluid. These pathways are provided by hollow elliptical tubes which serve several functions: to disturb the flow to promote heat transfer, to provide additional heat transfer area and to minimise flow maldistribution inside the HE core. The corrugation is incorporated into a counter-flow prototype HE unit model meaning to exploit the installation volume and design freedom made possible via ALM. Three Computational Fluid Dynamics (CFD) models are utilised to evaluate the performance of the proposed HE unit. Firstly, a traditional two step HE design methodology is utilised which works by initially evaluating a fully symmetric channel of the proposed HE corrugation (termed single channel). Then the results this model are incorporated into a simplified HE unit model. The second approach evaluates the HE unit performance based on a fully detailed CFD analysis that fully resolves flow and heat transfer inside the HE core. The third modelling approach involves splitting the inter-layer HE unit model into parts, which results in HE header models and allows simplification of the HE core into a single corrugation period width HE core model (termed superchannel). The results of these models are then compared to a conventional pin–fin HE unit model, formed by blocking the elliptical inter-layer conduits. It was found that in all the HE unit models the pressure drop is similar whilst the heat transfer was enhanced by between 7% and 13% in terms of the overall 〈math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si68.svg"〉〈mrow〉〈mi mathvariant="normal"〉Δ〈/mi〉〈mi〉T〈/mi〉〈/mrow〉〈/math〉 by the inter-layer channels (increasing with the Reynolds number). All simulations were completed using a CFD package OpenFOAM.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: September 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 160〈/p〉 〈p〉Author(s): Ehsan Sourtiji, Yoav Peles〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A concept to power micro synthetic jets using bubble growth and collapse is introduced and studied over a range of operating frequencies (0.1–2.5 Hz) and heating powers (3–4.5 W). The microfluidic device has no moving parts and uses the interfacial layer between the vapor and liquid phases which substitutes the requirement for a physical flexible membrane. A micro heater inside a chamber (3.5 mm in radius and a height of 220 µm) was connected to a main microchannel through a nozzle with a 300 µm opening. Periodically powering the micro-heater triggered bubble explosion and implosion in the chamber, which in turn generated the synthetic jet. Sequential images of bubble nucleation, growth and collapse were captured using high-speed camera photography and a microscope. A momentum coefficient was used to characterize the synthetic jet. It was found that its average value exceeds unity for a large range of operating frequencies suggesting that this synthetic jet can improve the performance of a range of micro-system performance, such as micro-mixing in microfluidic devices.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Haobing Zhou, Fei Zhou, Qian Zhang, Qianzhi Wang, Zebin Song〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To maintain the maximum temperature within the optimum range and to improve the temperature uniformity of cylindrical lithium-ion battery, a liquid cooling method based on the half-helical duct was proposed. The effects of inlet mass flow rate, pitch and number of helical duct, fluid flow direction and diameter of helical duct on the thermal performance of battery at 5 C discharge rate were analyzed numerically. The results showed that the maximum temperature and temperature difference decreased with an increase in the inlet mass flow rate. When the pitch and the number of helical duct changed at the optimal inlet mass flow rate of 3 × 10〈sup〉−4〈/sup〉 kg/s, there was no obvious improvement in the cooling performance. If the flow direction was varied according to six kinds of cases, the maximum temperature and the temperature difference for the Case4 all displayed the lowest values. If the diameter of half-helical duct varied from 2.0 mm to 3.8 mm, the temperature difference would retain within 4.3 °C, but the maximum temperature would approach to 30.9 °C, slightly higher than 30.5 °C. In comparison to the thermal management with jacket liquid cooling method, the thermal management with half-helical duct liquid cooling method might be better and more effective owing to the low fluid volume and no stagnant zone.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Jingtang Peng, Zhili Chen, Taojie Zheng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new solar heat collecting and snow melting device for purified water utilization was originally designed and developed. The heat and mass transfer model was established and verified by experiments. Results show that the snow melting efficiency of the cases at 100% and 80% of the system volume is higher than other amount cases. The heat conducting working medium filling level has relatively large influence on the snow melting efficiency of the device, and the optimal working medium filling level is above 3/4 of total volume of the circulating system. In actual use, replenishment of working medium in the system shall be conducted in time before the working medium level decreases to 1/2. The water outflow and snow feeding mode has evident influence on the snow melting efficiency. When the 2-h water outflow mode is used, the snow melting efficiency is the highest, reaching 39.2%. The heat and mass transfer model of the device performs better in simulation calculation and is useful for estimation of snow melting efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Naeem Abas, Ali Raza Kalair, Mehdi Seyedmahmoudian, Muhammad Naqvi, Pietro Elia Campana, Nasrullah Khan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉CO〈sub〉2〈/sub〉 is becoming increasingly important as a mediating fluid, and simulation studies are indispensable for corresponding developments. In this study, a simulation-based performance investigation of a solar water heating system using CO〈sub〉2〈/sub〉 as a mediating fluid under sub-zero temperature condition is performed using the TRNSYS® software. The maximum performance is achieved at a solar savings fraction of 0.83 during July. The as lowest solar savingss fraction of 0.41 is obtained during December. The annual heat production of the proposed system under Fargo climate is estimated to be about 2545 kWh. An evacuated glass tube solar collector is designed, fabricated and tested for various climate conditions. Moreover, a detailed comparison of the system’s performance at sub/supercritical and supercritical pressures shows that the annual heat transfer efficiency of the modeled system is 10% higher at supercritical pressure than at sub/supercritical pressures. This result can be attributd to the strong convection flow of CO〈sub〉2〈/sub〉 caused by density inhomogeneities, especially in the near critical region. This condition resuls in high heat transfer rates.〈/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-S1359431119301450-ga1.jpg" width="267" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Hadi Sadeghi, Masoud Rashidinejad, Moein Moeini-Aghtaie, Amir Abdollahi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Today’s world energy-related challenges, ranging from anthropogenic climate change to continuous growth of demand for different energy forms, have enforced planners of energy systems (ESs) to concentrate on more optimal and eco-friendly operation and/or expansion planning methodologies. In this context, increased interdependencies of gas, heat and electricity ESs have recently encouraged the planners to design operation and/or expiation strategies in an integrated manner in favor of a new concept, the so-called “Energy Hub” (EH). Although this concept has been employed so far in a multitude of studies, but its real nature, advantages, difficulties, importance or inevitability aspect, and eventually, its application areas in power industries have remained as open questions from various viewpoints. On the other hand, the difference in the planners’ perceptions of the EH concept has caused emerging various definition and models for this. At this point, it is worth reviewing the frameworks proposed for planning the ESs based on the EH approach, while understanding the application areas of the EH, its components, the nature behind presented definitions, and the hierarchy of events/factors drawing the planners attention to this approach, can help to find the answers of the questions. In doing so, this paper presents a state-of-the-art review of existing research works focusing on the operation and/or expansion planning problems of ESs in the context of EH. Reviewing results and findings can be helpful for both researchers new to this field of study by extraction of the distinguishing borders between underlying concepts and presenting an in-depth review on the latest studies, and experts in this research field by summarizing the details of a wide range of relevant works and extracting research gaps.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Zeng Deng, Jun Shen, Wei Dai, Ke Li, Qinglu Song, Wenchi Gong, Xueqiang Dong, Maoqiong Gong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a hybrid microchannel and slot jet array heat sink is designed and fabricated to achieve a better thermal performance of the high-power laser diode arrays. A standard commercial laser bar with wavelength of 808 nm is packaged on the heat sink and experiments are performed to assess the cooling performance of the hybrid heat sink. In the experiments, the forward voltage method is used to measure the chip temperature and the structure function method is applied to obtain the thermal resistance of the heat sink. Using the deionized water as coolant, the heat sink deals with a heat flux of up to 506 W/cm〈sup〉2〈/sup〉 and the thermal resistance of the heat sink is only 0.23 K/W when the flow rate is 0.8 L/min (The average jet velocity is 13.3 m/s). The optical power can be up to 135.5 W corresponding to the wall plug efficiency of 64.2%. Compared with the published solutions related to cooling similar laser chips, the thermal resistance reduces by over 15%, indicating that this hybrid heat sink is an interesting solution to improve the cooling of the high-power laser diode arrays.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Xiaojia Li, Guangqiao Xu, Guilong Peng, Nuo Yang, Wei Yu, Chengcheng Deng〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Solar steam generation technology can utilize abundant and renewable solar energy for many applications. In this work, we proposed a low-cost high-efficiency solar steam generator by using wick materials with wrapped graphene nanoparticles, and the energy efficiency can reaches up to 80%. Instead of traditional smearing method, the chemical wrapping method was used for better coating the graphene nanoparticles on the wick materials. Through the SEM morphological results, the graphene nanoparticles are shown to be evenly wrapped across the fibres of the wick material, which have better dispersity and stability. The evaporation rate, instantaneous energy efficiency and the solar absorptivity of three wick materials with/without nanoparticles under different conditions were compared and analyzed. Among the three different wick materials, the fine fluffy cloth can provide more three-dimensional contact area for wrapping graphene nanoparticles and thus contribute to better evaporation. Additionally, the influence of two different reduction methods and different concentrations of graphene oxide solution on the energy efficiency was also analyzed. Our work offers a simple and effective way of using nanotechnology in practical application for better solar-to-heat conversion.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Juan C. Tudon-Martinez, Alberto Cantu-Perez, Andrea Cardenas-Romero, Jorge de J. Lozoya-Santos〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A zero dimensional thermodynamic model (0D-model) is used to represent the conservation equations of energy in an industrial box furnace for designing purposes. Thus, this paper proposes a 0D model-based design approach for industrial box furnaces which results very processing time efficient, minimizing the design analysis time period that can exist when two-dimensional (2D) or Computational Fluid Dynamics (CFD) modeling is used. 2D or CFD models can be highly accurate but with also high computational load; the time spent in an industrial design from the concept to the prototype can take several months where the bottleneck is the simulation phase. The modeling results in the proposed approach consists on analyzing the fuel energy power requirement required to achieve a desired temperature profile, given the most important design parameters such as physical furnace dimensions, composition material in the insulation section, thermal load properties, fuel/air ratio conditions, etc. In this case, the proposed approach for a 0D-model based furnace design has been validated with different operation set-ups and compared with simulation data provided by a complex 2D model as well as with experimental data from an industrial box furnace. Quantitatively, the modeling result was up to 96.77% of fit with respect to the simulator behavior, taking less than 5% of processing time considered by the complex 2D model.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): R. Anish, V. Mariappan, Mahmood Mastani Joybari〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Renewable energy sources are incapable of supplying continuous power due to their intermittent availability. To tackle this, energy storage systems incorporating phase change materials can be utilized. Among the several techniques, shell-and-finned-tube configurations show promising heat transfer performance and have greater engineering applicability. This study experimentally investigated the heat transfer mechanism in a horizontal shell-and-multi-finned-tube energy storage unit. Variation of average temperature and storage effectiveness as well as effects of inlet heat transfer fluid temperature and flow rate on the phase change of erythritol were experimentally investigated. It was found that the effect of inlet temperature was more significant than the flow rate (12–32% and 7–17%, respectively). Moreover, natural convection was found to significantly influence the heat transfer during melting where the melted material initially occupied the upper region of the unit and then moved from top to bottom. The outcomes of the present work help understand the effect of natural convection to be effectively utilized for the design and optimization of such storage configurations.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Peng Xiao, Zhong Yifeng, Wang Peng, Luo Dan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉As a lightweight building material, hollow-glass-beads-filled cement-based composites (HGB-CBCs) have important applications in building energy saving and fireproofing. In order to reveal the mechanism of thermal conduction in HGB-CBCs, a heat conduction micro-model of HGB-CBCs was established based on the variational asymptotic homogenization method (VAHM). Then, the heat conduction micro-model was used to quantitatively investigate the influence of the micro-structural parameters and constituent properties on the effective thermal conductivity of HGB-CBCs with two different types of unit cells. Numerical results show that the heat flux fields recovered by VAHM perfectly agree with those by RVE-based FEM, but more smooth. The heat flux will drop slowly and almost linearly far away from the glass bead, while the heat flux in HGB will drop sharply, indicating HGB has great thermal resistance. HGB-CBCs with greater volume fraction and smaller wall thickness of HGB provides better thermal insulation effect. The longer and more complicated heat transfer paths around the wall of HGB are beneficial to the decrease of effective thermal conductivity, which can provide guidance for engineers who want to use HGB-CBCs as thermal-insulating composite materials in the civil engineering.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Chunmeng Xu, Lukas Graber〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to improve the electric current rating of a vacuum-insulated disconnect switch, a copper-water thermosyphon has been embedded into an electrical bushing to achieve significantly higher effective thermal conductivity and lower hotspot temperatures of the bushing. The temperature profiles of a thermosyphon bushing conductor under different heat loads and filling ratios have been characterized by experiments. For the purpose of estimating the performances of any thermosyphon bushing with various dimensions, working fluids and filling ratios, a thermal network model with lumped thermal capacitors has been established. Characteristic features of thermosyphon bushings like the thick pipe walls and the distributed Joule heat sources are represented in the model. This model successfully predicted the effective thermal conductivity and hotspot temperatures of a thermosyphon bushing prototype designed for a vacuum-insulated disconnect switch. Because of the compact designs of thermosyphon bushings, they can be implemented in a wide range of power equipment, such as vacuum switchgear, disconnect switches, plasma chambers, and high-power physics experiments.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Xiaofei Yue, Weidong Liu, Yuan Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Water droplet freezing and melting on three micro- or hierarchically-structured silicon surfaces and a smooth silicon wafer were studied experimentally. The surface temperature was kept at −13.8 °C during freezing and increased gradually to room temperature after turning off the bath circulator. The freezing behaviors including the freezing delay, solidification front movement, and the droplet profile were obtained through the photographic method. The results show that the tiny black silicon particles on hierarchical structures facilitate a longer freezing delay. The solidification stage lasted for 5–17 s depending on the surface structures, during which the freezing rate was larger in the initial seconds. Droplet on three micro-structured surfaces formed a tip with the angle of 122 ± 2°, smaller than that on the smooth silicon which was 136 ± 3°. The melting onset temperature for samples 1–3 was about 4.4 °C while melting happened on smooth silicon needed a smaller degree of superheat.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): T.I. Bhaiyat, S. Schekman, H.Y. Lim, Y.H. Jeon, T. Kim〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Louvered fin-and-tube heat exchanger cores, operating inside of an automotive climate control system (ACCS), are used to control temperature and humidity in a passenger cabin. The thermal performance of these cores is typically sensitive to flow features inside the core, which have been well studied for uniform flow fields as well as some non-uniform and inclined flow-fields upstream of the core. The compact geometry of an ACCS unit results in the flow-fields upstream of the core being different from those used in previous studies. When measuring the performance of a louvered fin-and-tube heater core inside a commercially manufactured ACCS unit, up to a 60% reduction in the core’s thermal performance compared to the performance when exposed to a uniform upstream flow is detected. Such a drastic performance reduction has not been reported in the literature. As such a systematic breakdown is made to elaborate how some key and specific ACCS unit features designed for the sake of compactness could play a detrimental role in reducing the overall thermal performance of a given louvered fin-and-tube heater core. By mimicking the actual ACCS features the performance deterioration in the commercial unit could be largely replicated. The individual contributing effects of the various fluidic features such as flow separation and recirculation are determined. Only 50% of the measured 60% deterioration, however, could be accounted for, suggesting that other ACCS unit properties not assessed in detail in this study may also adversely affect the core’s performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Hang Li, Xiangbang Kong, Chaoyue Liu, Jinbao Zhao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The nickel-rich silicon-graphite lithium-ion cells, for example the LiNi〈sub〉0.8〈/sub〉Mn〈sub〉0.1〈/sub〉Co〈sub〉0.1〈/sub〉O〈sub〉2〈/sub〉/Silicon-carbon (NMC811/Si@C), have been used in the commercial power batteries to meet the higher capacity requirements now. However, the battery with higher energy is more destructive as thermal runaway occurs. In order to improve the safety of the battery, it is essential to study the thermal stability of this kind of battery. In this work, the differential scanning calorimetry (DSC) and adiabatic rate calorimetry (ARC) have been used to conduct a detail thermal stability analysis for this type of battery of different charge state, the thermal stability mutation of Si@C material has been observed firstly when the SOC is great than 55%. Besides, a reasonable thermal runaway reaction sequence of the battery of NMC811/Si@C is proposed. Moreover, based on the time to maximum reaction rate (TMR), the effective recommendations for the use of NMC811/Si@C lithium ion battery are provided.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Xin Ma, Chenghui Zhang, Ke Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A simple, yet accurate hybrid model of scroll compressor (SC) used in micro-compressed air energy storage system (MCAES) is put forward in this paper. The modeling process starts with basic thermodynamic and fundamental physical principles but captures only few key operational characteristic parameters to predict the exhaust temperature, exhaust flow rate and the input torque of the SC, and then the appropriate input and output variables are selected according to the control demands of the system. Compared to the existing models, the hybrid model is more streamlined, and is better to meet the control requirements of the system, considering both accuracy and practicability. The developed model is identified and corrected based on both the experimental data and manual. The testing results show that the maximum error between the predicted results and the experimental data is less than 10%, indicating that the model can predict the system performance accurately. Finally, further efficiency analysis is advanced based on the proposed hybrid model, and the optimal operation range of the compression process is suggested. The hybrid model proposed in this paper lays the foundation for the subsequent capacity design, performance analysis and optimization control of MCAES.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Dietmar Siegele, Fabian Ochs, Wolfgang Feist〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents the detailed steady-state measurement results of a novel speed-controlled exhaust-air to supply-air heat pump combined with a ventilation system. Compared with conventional systems, the heating power can be more than doubled to approximately 2.5 kW using recirculation air. Therefore, such cost-effective systems can be utilized not only in high-energy-efficient buildings but also in buildings with higher heating loads, such as in case of renovations. A functional model was developed and tested in the laboratory. The measurement results demonstrated an overall system performance of over 4.5 for minimal heating power at +10 °C and 2.5 for maximum heating power at −7 °C. A simplified physical model for refrigerant cycle was presented and validated. It provided results with a measurement accuracy of 8%. The model was used to demonstrate further optimization potential. According to these results, a 5% improved system performance can be achieved by increasing the condenser size.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Ali Al-Janabi, Miroslava Kavgic〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Hysteresis is a crucial energy performance factor for the phase change material (PCM)-enhanced building envelope. This study aims to (1) compare a recently developed hysteresis method against its precursor enthalpy-temperature method, (2) perform local sensitivity analysis on hysteresis input parameters, and (3) investigate the feasibility of integrating PCMs within a suspended ceiling using the hysteresis method in EnergyPlus 8.9. Therefore, it provides new knowledge and information required for better comprehension and implementation of the hysteresis object in EnergyPlus. A building at the University of Manitoba is used as a case study because of its curtain-wall façade system, which is becoming popular worldwide despite increasing concerns over its lack of thermal storage properties. The results show a discrepancy between the hysteresis and enthalpy-temperature methods, which may vary considerably with the intensity and duration of the transmitted solar radiation. Furthermore, the peak melting and freezing temperatures, latent heat during the phase change process, solid-state density, and material thickness are essential hysteresis input parameters. Integration of PCMs resulted in heating and cooling energy savings ranging from 1.9% to 11.4% and 5.5% to 37.4%, respectively, as well as a reduction in discomfort hours from 10% to 29% depending on the zone and PCM type.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Mayank Maheshwari, Onkar Singh〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Various options for improving the performance of gas/steam combined cycle, the performance enhancement can be achieved by increasing the turbine inlet temperature and/or increasing the cycle pressure ratio along with intercooling for reducing compression work and reheating for increasing the expansion work. The present paper analyses eight novel configurations of the intercooled gas turbine based combined cycles having the gas turbine blade cooled using closed loop cooling scheme. Combined cycle configurations differ in respect to cooling medium being steam or ammonia-water, intercooling, reheating, single/dual/triple pressure heat recovery steam generator, steam turbine, and ammonia water turbine. The comparative evaluation of combined cycle arrangements is based on thermodynamic modeling using first law and the second law of thermodynamics for the inlet temperature to turbine of 2000 K and ambient temperature of 303 K. Study aims at furnishing results for understanding the implications of modifications on the cycle performance. The results show that maximum 1142 kJ/kg of work is obtained for ammonia concentration of 0.6 while the maximum cycle efficiency of 53.87% and second law efficiency of 58.46% is obtained for ammonia concentration of 0.7 at cycle pressure ratio of 40 for combined cycle with triple pressure heat recovery vapor generator having ammonia-water cycle at high pressure& intermediate pressure and Rankine cycle at low pressure.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Xiaoqiang Jiang, Aqiang Lin, Adil Malik, Xinye Chang, Yuanyuan Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Heat transfer and vacuum in the condenser are affected by the flow characteristics in the low-pressure steam turbine exhaust passage. In this study, the Eulerian-Eulerian equilibrium two-phase model is applied to investigate the contribution of multi-factor components on aerodynamic performance of twin exhaust passage. Results show that the share of steam phase is reduced in the exhaust passage with consideration of the built-in pipelines. Total-pressure loss in the exhaust hood is about four times of that in the throat. The sensitivity of local loss existing in the exhaust hood on the whole loss is higher than that in the throat. Considering the factors of LSBs and pipelines, both the static-pressure recovery coefficient of 15.44% and effective specific enthalpy-drop of 0.145% are the best performance. By evaluating the steam turbine economic, however, static-pressure recovery coefficient and specific enthalpy drop are 1.25 times and 0.475 times of that without pipelines, respectively, relative to built-in pipelines. Therefore, a recommendation on the consideration of twin exhaust passage, last stage blades, steam extraction pipelines, low-pressure heater, and wet steam can obtain a representative aerodynamic characteristic.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Chaobin Hu, Xiaobing Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Influences of heat losses on the performances of thermal systems driven by internal combustions are unavoidable. Methods to compensate the heat losses are very important for improving the fidelity of numerical predictions. In this paper, a thermal compensated model was put forward for predicting the combustion of energetic materials in a gun propulsion system. Different from the existing models, the heat exchanges between the combustion products and the inner walls of the chamber were considered in the energy conversion equation. The modified two-phase fluid flow model governing the combustion was solved by using a Godunov type of numerical scheme. The exchanged heat was obtained by predicting the transient heat transfer in the barrel based on a finite element method. Based on the modified model and the coupled computational framework, the combustion of energetic materials in a launching process was studied and the influences of the heat losses on the combustion were discussed. The results indicate that the modified model can effectively compensate the heat losses for thermal systems. The work provides an accurate method to compensate heat losses for evaluating the system performances.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Wanwan Fu, Ting Zou, Xianghui Liang, Shuangfeng Wang, Xuenong Gao, Zhengguo Zhang, Yutang Fang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this work, a novel phase change temperature-tuned composite phase change material (PCM) for the PCM floor was developed by using sodium acetate trihydrate-urea non-eutectic mixture as PCM and fumed silica (SiO〈sub〉2〈/sub〉) as both supporting material and temperature regulator. The thermoregulation mechanism of SiO〈sub〉2〈/sub〉 and the properties of the resulting composite PCM were studied. The results showed that the addition of SiO〈sub〉2〈/sub〉 could adjust melting temperature of the non-eutectic mixture from 34.36 to 48.45 °C, reduce supercooling degree and prevent leakage. With SiO〈sub〉2〈/sub〉 mass fraction of 30%, the composite PCM had a suitable melting temperature (35.75 °C), high latent heat (151.6 kJ·kg〈sup〉−1〈/sup〉) and low supercooling degree (1.14 °C). Meanwhile, the composite PCM possessed a good form stability and excellent thermal reliability and favorable thermal conductivity. Considering the above, the novel composite PCM has a great potential for the PCM floor. It is also expected that the present work can provide a new insight into tailoring phase change temperature of PCMs.〈/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-S1359431119308440-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): M.A. Sharafeldin, Gyula Gróf, Eiyad Abu-Nada, Omid Mahian〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of metallic copper nanoparticles on the thermal efficiency of an evacuated tube solar collector was studied. Different volume concentrations of copper nanoparticles e.i. 0.01%, 0.02% and 0.03% were examined to explore the effect of nanoparticles on evacuated solar collector performance. The tests were performed at three volume flow rates of 0.6 L/min, 0.7 L/min and 0.8 L/min. The results demonstrate a 50% increase in the output temperature. Also, the heat energy incremented from 417 W to 667 W, which is equivalent to 34% area reduction for the same energy production. The remarkable enhancement in the heat removal factor to reach a value of 0.97. Copper nanoparticles played a significant role to increase both the absorbed energy and the removal energy parameters. Their maximum values were found for a volume concentration of 0.03% and at the volume flow rate of 0.8 L/min to be 0.83 and 21.66, respectively. Finally, environmental analysis is carried out to find the role of copper nanoparticles in CO〈sub〉2〈/sub〉 reduction. The comparison between current results with reported results in the literature for other types of nanoparticles, show the high potential of copper nanoparticles for solar collector applications.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): J.L. Wang, Y.B. Tao, Ya-Ling He〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Three-dimensional external finned tube heat exchanger has been widely applied in waste heat recovery system. However, the current researches mainly focus on its fluid flow and heat transfer characteristics. The condensation of sulfuric acid and water vapors on heat exchanger surface, which can cause severe low temperature corrosion and reduce equipment efficiency, has rarely been reported. In this study, a heat and mass transfer model for flue gas on finned tube surface was developed to investigate the sulfuric acid and water vapor condensation characteristics and their distributions. The effects of flue gas velocity and temperature, acid and water vapor concentrations, and surface temperature were examined. The results show that the distribution of acid solution concentration on finned tube surface mostly depends on the distribution of fin surface temperature. At the windward side (especially near the minimum flow cross section region), both fin surface temperature and condensed acid solution concentration reaches the maximum value. Increasing velocity leads to vapors condensation rate and acid solution concentration increasing. The acid solution concentration decreases with flue gas temperature or tube wall temperature increasing. The present work could provide effective theoretical guidance for anti-corrosion design of finned tube heat exchanger.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Guodong Xia, Yuanzheng Lv, Dandan Ma, Yuting Jia〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The microchannels with triangular corrugations usually have high heat transfer ability, but the possible continuous two-phase instable boiling with periodically moving gas-liquid interface may cause the oscillations of pressure drop and temperature of walls, and lead to some control issues and security risks. In this paper, acetone is chosen as the working fluid, and an experimental setup with multi-sensors is built. The straight and triangular corrugated microchannels are applied for comparisons and analysis. Both microchannels have same hydraulic diameters of 104.3 μm. After experiments at the working conditions of 〈em〉G〈/em〉 = 250–1100 kg/m〈sup〉2〈/sup〉 s and 〈em〉q〈sub〉eff〈/sub〉〈/em〉 = 208–1050 kW/m〈sup〉2〈/sup〉, the similarities and differences about continuous instable boiling between two types of microchannels are found. A prediction model with equations and principles are developed, and the wall temperature at inlet is chosen as the judging criteria. The analysis results show that the wall temperature at inlet dominant the instable boundaries, and which can be affected by the working conditions and structural parameters. The prediction model also indicates that the increasing of flow resistance at inlet, decreasing of inlet temperature and heat transfer coefficient at inlet can reduce the area of instable boiling by about 40%, and decrease the slopes of instable boundaries by 24.2–51.7%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: Available online 12 August 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering〈/p〉 〈p〉Author(s): Vicente Macián, Vicente Bermúdez, David Villalta, Lian Soto〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The application of a low-temperature combustion concept, such as RCCI combustion under real engine operating conditions is extremely complex. However, the implementation of the dual-mode dual-fuel (DMDF) strategy allows operating in low-medium load with the RCCI combustion and in high load with dual-fuel diffusive combustion. This allows taking advantage of the benefits of RCCI combustion as the simultaneous reduction of PM and NOx emissions. However, there are still serious challenges that required to solve, such as the high-pressure rise rate and the excessive CO and HC emissions. In this sense, this work shows how the implementation and an adequate adjustment of the cooled LP-EGR rate significantly minimize these problems and also shows how the LP-EGR has a greater impact on the DMDF than on the CDC concept.〈/p〉 〈p〉This work has been performed in a modern medium-duty diesel engine fueled with standard gasoline and diesel fuels, with which a cooled LP-EGR loop has been coupled. A TSI Scanning Particle Sizer (SMPS 3936L75) was used to measure the particles size distribution and the Horiba MEXA-ONE-D1-EGR gas analyzer system to determine gaseous emissions. A parametric variation of the LP-EGR rate was experimentally performed to analyze the effect over each combustion process that encompasses the DMDF concept (fully premixed RCCI, highly premixed RCCI and dual-fuel diffusion) and its consequent impact on gaseous and particle emissions. In addition, results were compared against the CDC concept to state the benefits of the DMDF concept. Among the different results obtained, it can be highlighted that during the RCCI strategy the increase in LP-EGR rate provided a reduction in NOx emissions. Nonetheless, unlike that fully premixed RCCI in highly premixed RCCI combustion, the PM emissions increased with this increment in the LP-EGR rate, shifting the size distribution of particle toward larger sizes, but decreasing the HC and CO emissions. Finally, with the exception of the high HC and CO emissions in fully premixed RCCI, in all the combustion strategies of the DMDF concept, a reduction of the analyzed pollutants was observed when compared with the CDC mode.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Matteo Marchionni, Lei Chai, Giuseppe Bianchi, Savvas A. Tassou〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The paper presents a modelling methodology for Printed Circuit Heat Exchangers (PCHEs) in supercritical CO〈sub〉2〈/sub〉 (sCO〈sub〉2〈/sub〉) power systems. The PCHE model can be embedded in models of the full sCO〈sub〉2〈/sub〉 power unit for optimisation, transient simulation and control purposes. In particular, the purpose of the study is to assess the potential and limitations of lower order models in predicting the overall heat transfer performance of PCHEs. The heat transfer processes in the channels of the PCHE recuperator are modelled in 1-D and 3-D using commercial software platforms. The results show that predictions from the two modelling approaches are in good agreement, confirming that the 1-D approach can be used with confidence for fast simulation and analysis of PCHEs. Using the 1-D approach, the model was validated against manufacturer’s data for a 630 kW PCHE recuperator, and subsequently used to simulate the performance of the heat exchanger at design and off-design operating conditions. Performance maps produced from the simulations, enable visualization of the influence of operating conditions on the heat transfer performance and pressure drops in the heat exchanger. Dynamic simulations under transient operating conditions show that the thermal expansion of the working fluid caused by a fast reduction in density and increase in pressure in the system, can be a concern, requiring careful management of the start-up process to avoid sudden changes in temperature and thermal stresses.〈/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-S1359431119304004-ga1.jpg" width="500" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): M. Gortych, Z. Lipnicki, B. Weigand〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉 〈p〉The main purpose of this paper is to examine experimentally and theoretically the process of heat accumulation and heat release for PCM (〈em〉phase change materials〈/em〉) in an annular space.〈/p〉 〈p〉The theoretical part of this work provides a solution of the problem of liquid solidification in an annular space under the influence of free convection. Here a simplified quasi-steady-state model for solidification has been applied. The new simplified model describes the solidification phenomenon with an imposed boundary condition on the solidification interface by applying a heat transfer coefficient. From the developed model, the influence of various dimensionless parameters on the phase change problem can be seen clearly.〈/p〉 〈p〉Measurements and observation of the thickness of the solidified layer were performed in a newly built apparatus. In addition, this paper is also concerned with the role of the contact layer in the solidification process. Results are showing the thickness of the solidification layer depending on time and the distribution of the local heat transfer coefficient on the surface of the solidification front. The obtained experimental and numerical results show good agreement.〈/p〉 〈p〉The examined solidification process makes it possible to use the results obtained for the design of new heat accumulators. The presented method to analyse heat accumulation is important for power engineering. It opens up the possibility to reduce the size of heat accumulators, thus, possible leading to a reduction in their production costs.〈/p〉 〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Huiling Duan, Yuan Zheng, Chang Xu, Yuanfang Shang, Fan Ding〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A plasmonic blended nanofluid formed by mixing Au nanoparticles with different shapes in water is proposed in this paper for direct solar absorption. Optical and thermal properties of the plasmonic blended nanofluid are studied numerically and experimentally. Resonant characteristics of Au plasmonic nanoparticles are tuned by particle shapes. Compared with single-component nanofluid, the extinction spectrum of this plasmonic blended nanofluid is broadened. The matching of extinction spectrum and solar radiation spectrum is tuned by adjusting the proportion of components in blended nanofluid. Photothermal properties of three types of plasmonic blended nanofluids are measured experimentally. Due to the higher extinction coefficient, the blended nanofluid exhibits higher temperature rise. A simplified heat transfer model is established to verify experimental results. Simulation results are consistent with experimental results. Before experiment, photothermal properties of different nanofluids can be qualitatively compared by using the simulation model, which can effectively reduce the number and cost of experiments.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Hu Shi, Bin He, Yinyun Yue, Chaoqing Min, Xuesong Mei〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In order to investigate the cooling effect of forced fluid circulation on the ball screw feed drive system of a precision boring machine tool, theoretical modeling of and experimental study on temperature control of screw shaft along with heat generation and dissipation interactions are focused in this paper. Thermal behavior measurements are conducted on the machine tool to detect the temperature of the feed drive system equipped with oil cooling circulation real-timely. Based on the heat generation and forced convention analysis of ball screw system, temperature distribution of screw shaft in the axial direction is modeled mathematically. Relationship between the heat convection coefficient and cooling system parameters is established to formulize the surface temperature distribution considering the flowing speed of cooling medium as time-invariant. Numerical simulation was conducted showing that the geometric dimension of flow passages and the speed of cooling flows significantly influences the thermal behavior. The fuzzy PID control strategy is employed to regulate the temperature of screw shaft with the flow rate of cooling fluid adjusted by a valve controlled hydraulic system. The relations between temperature rise and flow rate are formulated indirectly while taking the heat generation under the no-cooling working condition as disturbance. Measurements with feed drive system operating at different feed rates are preformed and the proposed temperature regulation method proves to reduce about 3 °C in temperature variation through experimental results based control system simulation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Xin Li, Fengzhong Sun, Xuehong Chen, Chuanfei Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The chip mufflers are widely installed around the natural draft wet cooling towers (NDWCTs) to lessen the noise, which significantly influence the tower inflow air field. To study the impact and mechanism of the chip muffler on the tower performance, a three dimensional numerical model for a wet cooling tower with different layouts of chip muffler is established. The ventilation rate 〈em〉G〈/em〉 and the average exit water temperature 〈em〉t〈sub〉a〈/sub〉〈/em〉〈sub〉2〈/sub〉 of tower are computed to analyze the tower performance. Results indicate that the chip muffler around half the tower weakens the tower cooling efficiency. The specific effect of the chip muffler on the performance is as follows. With the increase of the distance between the chip muffler units 〈em〉B〈/em〉 and the distance between the chip muffler and cooling tower 〈em〉L〈/em〉, the 〈em〉G〈/em〉 increases while the 〈em〉t〈sub〉a〈/sub〉〈/em〉〈sub〉2〈/sub〉 decreases. On the contrary, with the increase of the installation angle of the chip muffler 〈em〉θ〈/em〉, the 〈em〉G〈/em〉 decreases while the 〈em〉t〈/em〉〈sub〉a2〈/sub〉 increases. Thus, the chip muffler with a 〈em〉θ〈/em〉 of 0°, a 〈em〉B〈/em〉 of 150 mm, and a 〈em〉L〈/em〉 of 5 m can lead to a optimum tower performance. This paper can lay the foundation for the optimization of the chip muffler research.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Bowen Zhang, Jie Mei, Chunyun Zhang, Miao Cui, Xiao-wei Gao, Yuwen Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉A new methodology is proposed for predicting the bank thickness covering and protecting the refractory brick walls of the smelting furnaces. The inverse method predicts the bank thickness changing with both time and coordinates, by using a two-dimensional physical model of the furnace that is more general and challenging than the previous studies. Moreover, the thermal conductivities of the phase change material are identified simultaneously because they are poorly known, which is more challenging and practical. The inverse problem is solved by the Levenberg-Marquardt Method (LMM). The direct problem of the smelting furnace and the sensitivity matrix coefficients of the LMM are calculated by ABAQUS, using a complex user-defined element that is set up based on the complex-variable-differentiation method (CVDM) and the user element subroutine (UEL). Finally, numerical examples are given to examine the performances of the approach for predicting the bank thickness covering the refractory brick walls of the smelting furnaces.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Shuang Cao, Zheng Miao, Jinliang Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Liquid charge ratio is defined as the total liquid volume charged in an organic Rankine cycle (ORC) system divided by the total internal volume of the system, which influences the two-phase (vapor-liquid) phase distribution to dominate the component operation. In this paper, the effect of liquid charge ratio on ORC performance is explored for a ~10 kWe ORC system. It is shown that ORC can operate with liquid charge ratios in the range of 35–50%. At an optimal liquid charge ratio of 42.5%, the system attains the maximum thermal efficiency, power efficiency and net efficiency of 7.74%, 7.02% and 5.62%, respectively. When the system operates below the optimal liquid charge ratio of 42.5%, the liquid flushing may occur to induce pump cavitation and unstable flow due to insufficient liquid suction during pumping process. Alternatively, when the system operates above the optimal liquid charge ratio of 42.5%, more liquid is occupied in the condenser, decreasing the effective heat transfer area to elevate the condensation pressure, thus the system efficiency is worsened. This paper presents the important criterion for optimal liquid charge ratio for ORC operation.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Yuying Liu, Guanghai Liu, Haiyang Hu, Bo Kong〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the present work, strategies for the grouping of wavenumber subintervals were extended to deal with the compatibility of multi-scale multi-group full-spectrum k-distribution model with non-gray wall boundaries. The main idea is to enhance the correlated-k characteristics of absorption spectra of H〈sub〉2〈/sub〉O-CO〈sub〉2〈/sub〉 mixtures and emission spectra of non-gray wall within each divided group. The improvements in the calculation accuracies of radiative heat flux on the wall resulting from the new grouping strategy were evaluated using a series of 1D cases, in which combustion gases with strong inhomogeneities of temperature, pressure and molar ratio of water vapor to carbon dioxide were bounded by non-gray walls. The non-gray walls are assumed to be different metal materials with various surface states and temperatures. Finally, evaluation of the wavenumber subinterval grouping strategy was presented based on calculation of thermal imaging for directional radiation transfer from hot supersonic exhaust plume to a metal plate.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Wenjie Zhou, Yong Li, Zhaoshu Chen, Liqiang Deng, Yunhua Gan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The effect of the passage area ratio of liquid to vapor on the heat transfer performance of ultra-thin heat pipe (UTHP) in horizontal state was experimentally investigated in this work. The wick was sintered with a layer of 100- and 180-mesh copper mesh. The passage area ratio of liquid to vapor of UTHP was adjusted by changing the wick width. The capillary limits of UTHPs with various wick widths were analyzed theoretically. The effects of the wick width and filling ratio parameters on the thermal performance of UTHPs were studied experimentally. The maximum heat transport capacity of UTHPs were compared with the calculated capillary limits. The results indicated that the optimum filling ratio of the UTHP gradually decreased with increasing wick width. An appropriate wick width was beneficial to enhance the UTHP's thermal performance by increasing the vapor-liquid circulation efficiency during heat transfer. When the wick width was 4 mm, the maximum heat transport capacity of UTHP could reach 8.5 W, which was 4.25 times that of UTHPs with 2 and 7 mm wide wicks. From the capillary limit calculation and sample testing, the optimum passage area ratio of liquid to vapor of the experimental UTHP was 67.28%.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Wandong Bai, Dong Liang, Wei Chen, Minking K. Chyu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Turbine blades are designed to have rather complex internal cooling structures such as ribs and pin-fins, which are installed individually or concurrently in the serpentine channel. In this paper, pin-fin array heat transfer and pressure drop under the ribs induced non-uniform entry condition——entrance effect, have been experimentally investigated using the transient liquid crystals technique. Three configurations respectively installed 60°, V-shaped and W-shaped ribs at the upstream of pin-fin array and a baseline without ribs (representing a uniform entry condition) were tested in the Reynolds number range of 7000–40,000. A numerical simulation was also conducted to obtain more understandings of flow behaviors. The results showed that the entrance effects induced by the three shaped ribs have unique physical characteristics because of the generating of different secondary flow patterns. The entrance effect led to spatially non-uniform heat transfer distributions on pin-fin endwalls, however, its influence was only limited to the upstream region. The entrance effect not only enhanced the overall heat transfer, but also reduced the pressure drop of pin-fin array, hence, resulting in higher thermal efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): K. Arshad Ahmed, E. Natarajan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The present work investigates the incorporation of internal toroidal rings in an absorber tube of a solar parabolic trough collector (SPTC) with an objective to enhance the thermal performance. To produce substantial effect on the heat transfer rate, nine different cases of absorbers have been considered. The fully developed turbulent heat transfer characteristics of the absorber tube have been numerically studied and validated under varying inlet temperatures and flow rate of the heat transfer fluid (HTF). Realizable k-ε two-equation turbulence model with enhanced wall treatment has been used with ANSYS FLUENT 15 commercial codes. The influence of toroidal rings on heat transfer and fluid flow are evaluated and presented. The absorber with toroidal ring having a diameter ratio (H) of 0.88 and pitch size (p) of 2d is the thermally efficient optimal case. While the absorber with H = 0.92 and p = 2d is the energy efficient optimal case, with H being the ratio of inner to outer diameter of the toroidal ring and 2d being the distance between the adjacent rings, which is equal to two times the inner diameter of the absorber tube. When the inlet temperature of HTF is 600 K, the increase in efficiency for the thermally efficient and energy efficient optimal case are found to be 3.74% and 1.88%, while the increase in Nusselt number is found to be 2.33 and 1.49 times higher than the smooth absorber tube (SAT), 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-S1359431119322707-ga1.jpg" width="294" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Tianjiao Li, Yuan Yuan, Biao Zhang, Jun Sun, Chuanlong Xu, Yong Shuai, Heping Tan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Non-intrusive flame detection technique, such as radiation imaging, can measure large flame in boilers or engines. Flame light field imaging is a new type flame detection method based on radiation imaging. Using this method, a multi-view flame light field image can be obtained in a single capture, and the three-dimensional temperature field of the flame can be calculated using a reconstruction algorithm. In this study, experiments are conducted to verify the temperature reconstruction method using the Lucy–Richardson and nearest neighbor filtering joint deconvolution algorithm based on the refocused flame light field images. It was found that, in terms of the temperature trend and range, the results for different flame sections can be reconstructed to be comparable to the results using the non-negative least squares method. Although the flame shapes are non-axisymmetric corresponding to working conditions, the temperature reconstruction method using refocused light field images can effectively reflect these changes.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Ye Wang, Guoqing Zhang, Xiaoqing Yang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Liquid cooling technologies for large battery modules are facing challenges of optimizing their structure due to the many variable factors. In this work, a simplified yet effective strategy coupling single-factor analysis with orthogonal test is proposed to overcome this barrier in large battery modules. We systematically study the influence of the inlet velocity, channel number and contact angle on the cooling performance and thereby optimize the structure. The influence rank of the factors follows the order of “contact angle” 〉 “inlet velocity” 〉 “channel number”, indicating that the contact angle has the most significant influence on the cooling performance, which should be fixed at about 70°. Channel number shows slight influence on the cooling performance in large battery modules. The suitable values of the inlet velocity and channel number are variable within the ranges of 0.2–0.5 m·s〈sup〉−1〈/sup〉 and 1–2, respectively, based on different specific applications, particularly those targeting higher cost-efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Fei Ma, Peng Zhang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The conventional solar collectors are usually indirect absorption solar collectors which convert solar energy into thermal energy through a coating surface with high optical absorbency. The direct absorption solar collector, which absorbs the incident radiation directly by the working fluid with high extinction coefficient, shows a better performance than that of the indirect absorption solar collector. The phase change slurry as a novel composite phase change material can work as both heat transfer fluid and energy storage medium due to the large heat capacity and fluidity. In the present study, the phase change slurry is applied in the direct absorption solar collector to further improve the solar collector efficiency, and a numerical model is built to investigate the performance of a parallel plate direct absorption solar collector. The optical properties of the particle of phase change material and the phase change slurry are analyzed based on the theories of the Mie scattering and modified independent scattering. The extinction coefficient of the phase change slurry increases with the increase of solid volume fraction and the absorption index of the particle. The effects of different parameters on the efficiency of the direct absorption solar collector are discussed. The collector efficiency increases first and then decreases with the increase of absorption index of the particle. The solid volume fraction shows different influences depending on the absorption index of particle. The melting of solid particle also plays an important role in the collector efficiency and the temperature distribution. The performances of different types of solar collectors are compared, and the phase change slurry based direct absorption solar collector shows the highest photothermal conversion efficiency. The results are helpful in extending the applications of phase change slurry and direct absorption solar collector as well as in improving the solar collector efficiency.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 5 November 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 162〈/p〉 〈p〉Author(s): Wenke Zhang, Linhua Zhang, Ping Cui, Yan Gao, Jiying Liu, Mingzhi Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Both initial cost and land area can be saved while ground source heat pump (GSHP) system employs energy pile as the ground heat exchanger (GHE), and the energy pile exchanges heat with the surrounding underground medium. Groundwater seepage exerts influence on the heat transfer, and this is because the convection of groundwater alleviates the heat or cold accumulation around pile and then improves the heat transfer effect of energy pile. The existing researches regards the velocity of groundwater seepage as the one-dimensional vector, or the available models are not accurate enough though three-dimensional groundwater seepage is considered. The paper describes the spiral line heat source models with three-dimensional groundwater velocity, and the analytical solutions of temperature response are obtained. Afterwards, the performance of GSHP system is studied based on the proposed models, and the factors that have impacts on the coefficient of performance (COP) of heat pump unit are explored. The differences are explained while every factor employs different cases, but the common results of all cases are that the COP is indeed improved by groundwater seepage, and therefore the advantages of groundwater seepage should be noted. The researches of the paper attach importance to the seepage role, and the findings of the paper are favorable for the further development of GSHP technology.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): S.K. Chen, Y.M. Chen, N.E. Todreas〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The accuracy of the prediction of the pressure drop in a bare rod hexagonal bundle by the upgraded Cheng and Todreas correlation has been demonstrated to be excellent using the 32 bundle experimental bare results available in the literature.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Jianzhong Zhu, Xiao Wu, Jiong Shen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉With the increase of renewable sources participating into the power grid, the traditional thermal power generation is responsible for the frequent power regulation where the disturbance rejection ability should be enhanced during the operation. The boiler-turbine unit is a non-strictly proper multivariable plant with uncertainties, external disturbances and hard constraints, which make the conventional control strategy hard to meet the operating requirement. To this end, an advanced control strategy of generalized active disturbance rejection control (GADRC) is proposed in this paper, consisting of multivariable extended state observer (MESO) and anti-windup compensator. A simple transformation approach is proposed, which can convert the output disturbances involving the feedthrough item into the input lumped disturbances, so that their impact can be estimated by the MESO and compensated by the proposed GADRC. In addition to this, a setpoint filter is developed in the control structure to remove the tracking offset caused by the unknown disturbances and a novel anti-windup strategy is presented to handle the input saturation problem and alleviate the resulting fuel waste issue. The robust stabilities of the proposed GADRC including feedback control and anti-windup control are guaranteed using frequency domain method and Circle criterion, respectively. Simulation studies compared with other methods demonstrate the effectiveness of the proposed control strategy on the boiler-turbine unit, especially in complex cases of external disturbance and model-plant mismatches.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Guangan Chen, Yuanbin Zhao, Wendong Li, Wenjing Ge〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The aerodynamic field around high-level water collecting natural draft wet cooling tower (HNDWCT), especially that below its special high-level water collecting devices (HWCDs), strongly affects the tower efficiency. Therefore, the aerodynamic fields below HWCDs and its evolution characteristics have been studied, then the corresponding impact on the performance of HNDWCT has been clarified in detail. The results demonstrate that the incidence angle and speed of crosswind have great influence on the air flow state below HWCDs, thus the air distribution in heat and mass transfer zones and air mass flow rate through tower, resulting in the degradation of tower cooling performance. To mitigate the adverse effect of crosswind on tower cooling performance, cross wall has been investigated as a means to improve tower air flow structure. It has been found that the cross wall with appropriate porosity is beneficial to increase the tower efficiency. While, the optimum porosity depends on the crosswind speed and its incidence angle, which ranges from approximately 0.33–0.53. Furthermore, the structure of heat and mass transfer zones of HNDWCT, especially the rain zone, are different with that of usual natural draft wet cooling tower (UNDWCT), which causes the different effect of impermeable cross wall.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Amatalraof Abdullah, Ismail Bin Said, Dilshan Remaz Ossen〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The high energy consumption for air conditioning in buildings is a serious concern due to its consequences on the earth's ecological life. This study presents a new passive cooling design for buildings inspired by the morphological and physiological cooling mechanism in the nasal turbinate of camels. The main cooling unit consists of clay cylinders shaped like onion rings covered by two layers of jute fiber and installed in a wind tower. The clay plates were manufactured, and the wind tower was built in one of the desert cities in Yemen to experimentally examine and evaluate the performance of this design for ten consecutive days starting from 9 a.m. till 9 p.m. The results confirmed the applicability of the bio-inspired design to efficiently decrease the air temperature by an average of 14.6 °C and increase the relative humidity of the air by 57.5% on average. With only 1.20 m height, this design was able to drop the temperature by 19.8 °C achieving a considerable cooling efficiency in comparison with the rest cooling designs with the high heights that installed inside wind tower. The zero-energy cooling design can be a viable alternative for the highly-consumed mechanical cooling equipment.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Youhong Liu, Yifu Luo〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This paper presents influence investigation of pulsed purge film on flow and thermal characteristics of a turbine endwall. Three-dimensional transient Reynolds-averaged Navier-Stokes equations coupled with SST 〈em〉k〈/em〉 − 〈em〉ω〈/em〉 turbulence model are utilized in this study. Varied slot orientation angles 〈em〉α〈/em〉, mass flow ratios (MFR) and 〈em〉Strouhal〈/em〉 (〈em〉St〈/em〉) numbers are selected as research parameters. The results indicate that endwall film cooling effectiveness varies as orientation angle 〈em〉α〈/em〉 increases. Optimum film cooling effectiveness is obtained at 〈em〉α〈/em〉 = 45° for cosine wave injection. MFR increases the level of film cooling effectiveness throughout the cascade channel. At the same MFR, square wave injection has the worst cooling effect. In a time period, instantaneous film cooling effectiveness changes drastically. The distribution of the instantaneous film cooling effectiveness is affected by 〈em〉St〈/em〉 number and cooling outflow pattern. As 〈em〉St〈/em〉 increases, the laterally-averaged film cooling effectiveness changes differently for cosine and square waves in the whole cascade channel.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Xiaocui Xie, Hua Liu, Chang He, Bingjian Zhang, Qinglin Chen, Ming Pan〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉This article presents a three-dimensional CFD model to describe the counter-current air-water flow across the staggered tube bundles in a bench-scale closed wet cooling tower by combining VOF multiphase method and SST 〈em〉k-ω〈/em〉 turbulence model. The proposed model can investigate the interfacial heat-mass transfer and complex interaction mechanisms among multiple tubes. Through adding the shear force term and water evaporation in the model, the circumferential distribution of the falling film and air humidity fields are obtained, and the effects of the spray density and the air velocity on the falling film flow mode, air humidity, and transfer process are studied. The results show that, the thinnest water film and maximum evaporation rate are obtained when the circumferential angle is 75° and the spray density is 0.048 kg m〈sup〉−1〈/sup〉 s〈sup〉−1〈/sup〉, respectively; the air Reynolds number has a greater influence on multiphase heat and mass transfers than that of the spray water Reynolds number.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): E. Hosseinirad, M. Khoshvaght-Aliabadi, F. Hormozi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent years, the use of vortex-generators in low scale channels has been examined by several researchers. However, non-uniform vortex-generators have not yet been investigated, and this is the main motivation behind the current numerical study. Hence, simulations are carried out for water flow through a mini-channel equipped with various non-uniform transvers vortex-generators (TVGs). Also, experiments are conducted to validate the obtained results. The findings reveal the following trends: (i) non-uniform TVGs affect temperature contours and flow fields of water, (ii) the fluid mixing generated by long TVGs is greater than that of short TVGs, particularly at the upstream, (iii) when Reynolds number is large enough, the TVGs create 3D swirl flows which intensify the heat transfer effectively, (iv) locating long TVGs at the upstream of mini-channel enhances the thermal performance as well as the pressure drop, (v) maximum values of 0.63 and 2.06 are recorded for the relative ratios of Nusselt number and friction factor through the model with long to short arrangement of TVGs, (vi) at lower Reynolds number region, the best overall hydrothermal performance is seen for the model with long to short arrangement of TVGs, while at higher Reynolds number region, it belongs to the uniform model, (vii) maximum values of 0.49 and 1.43 are recorded for the considered performance indexes at Reynolds number of 50.〈/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-S135943111932486X-ga1.jpg" width="219" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Carolina B. Carvalho, Mauro A.S.S. Ravagnani, Miguel J. Bagajewicz, André L.H. Costa〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Design optimization of air coolers is often presented limiting fan calculations to the required power, without considerations of fan capabilities or commercial viability. In this article, new design optimization procedures are presented to include the selection of a commercial-type fan and, thus, the air flow rate as a variable. The resulting model is a mixed integer nonlinear programming (MINLP) problem, which is solved globally, using three different enumeration procedures, and the performance among them is compared. The proposed approaches are illustrated by two case studies. Results showed that the smart enumeration scheme can provide the global solution in an acceptable computational time even when considering large problems.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Hassan Jafari Mosleh, Rouhollah Ahmadi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉One of the efficient solar energy harvesting technics is the parabolic trough concentrated solar power plant. However, if the concentrated solar power plant were not equipped with a storage system, the power plant capacity factor would be deficient. Latent thermal energy storage system using phase change material (PCM) is a high energy density storage system to provide durable energy with a constant temperature. In this study, first, a dynamic analysis is performed implementing TRNSYS software on the parabolic trough concentrated solar power plant located in Shiraz, Iran. Consequently, this system is assisted by the latent thermal energy storage system to improve its performance and capacity factor. Several high-temperature PCMs, namely H250, NaNO〈sub〉3〈/sub〉, KNO〈sub〉3〈/sub〉, and KOH, are examined in the latent thermal energy storage system. The simulation depicts that owing to the operational condition of Rankin cycle in this study, using NaNO〈sub〉3〈/sub〉 in the latent thermal energy storage system is the best option with a higher solar fraction (34.14%) among other examined PCMs. In this case, the solar fraction has been enhanced by 90.5% in comparison with the solar power plant without the latent thermal energy storage system. The economic analysis illustrates that the payback period, IRR and NPV of the added LTES system are obtained as 11 years, 15.6% and, 617825$, respectively. The result of the sensitivity analysis on NPV revealed that the electricity price has the most effect on NPV and enhancing the electricity price has a positive impact on NPV.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Luwen Qin, Junye Hua, Xiaobao Zhao, Ye Zhu, Dong Li, Zhigang Liu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, Micro-Particle Image Velocimetry (Micro-PIV) system has been used to visualize the flow properties of deionized water flowing across circular, ellipse and diamond micro pin-fin arrays with Reynolds number situated between 100 and 400. While Fluent 15.0 is used to simulate the velocity distribution, streamline patterns and temperature distribution around micro pin-fin arrays. Micro-PIV results and simulation outcomes have been compared to investigate the flow and heat transfer characteristics of micro pin-fin arrays. Among three types of pin-fins, backflow occurs firstly at the tail of circular pin-fins and wake vortices form gradually, then the structure of the vortex gradually lengthens. The velocity and pressure transformation along the single pin-fin is a decompression acceleration region at first and turns into a pressurization deceleration from the middle to the tail of pin-fin. The area of higher temperature region of vortices at the back of circular pin-fin is the largest, which results in better heat transfer performance.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Mehmet Canalp Kulahli, Songül Akbulut Özen, Akin Burak Etemoglu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this study, a novel parabolic reflector for a Parabolic Trough Collector (PTC) is presented. The reflector contains a varying focal length in lengthwise direction while still maintaining a fixed focal line. Due to this geometry, heat flux around the absorber not only varies circumferentially but also axially. A new geometric design parameter is defined which is the ratio of focal length at the ends, and the effects of it on the thermal behavior are investigated numerically. To represent the heat flux realistically a method is presented by employing a custom code to construct the novel reflector in SolTrace (a ray tracing software), and heat flux profile around the absorber is calculated. This flux is applied to a Computational Fluid Dynamics (CFD) model as a source term and simulations are realized. The coupled model is validated with the experimental results regarding the LS-2 module. Besides the parametric analyses about geometric factor, flow rate optimization analyses are also. As a result of the parametric analyses, a 0.21% rise is achieved for thermal efficiency and a 0.63% increase is achieved for net energy gain as a result of the flow rate optimization study.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: October 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 161〈/p〉 〈p〉Author(s): Sanskar S. Panse, Prashant Singh, Srinath V. Ekkad〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉High porosity metal foams are known for providing high heat transfer rates, however, the concomitant higher-pressure losses have been a concern towards the realization of enhanced thermal hydraulic performance. Present study aims towards developing metal foam-based cooling configurations subjected to forced convection in a channel by employed very thin and high porosity Aluminum foams, where the goal is to achieve maximum foam volume participation in heat dissipation. To this end, a comprehensive experimental study has been carried out to investigate the effect of foam pore density (pores per inch: PPI) and channel aspect ratio (AR) on the thermal hydraulic performance of thin metal foams. High porosity (93%) thin aluminum foams with pore densities of 5, 20 and 40 PPI were studied, where the convective heat transport was facilitated through air forced through the channel. For the 40 ppi foams, three foam heights of 3.175 mm, 6.35 mm and 19 mm were tested, for 20 ppi foams, two foam heights of 6.35 mm and 19 mm were tested, and for the 5 ppi foams, one height of 19 mm was tested. These three different foam heights yielded in channel ARs of 16:1, 8:1 and 8:3, respectively. Heat transfer gain due to metal foams was evaluated against a geometrically identical smooth channel as well as with the Dittus-Boelter correlation for developed turbulent flow in circular ducts. Experimental data reveals that, for a given AR, an increase in pore-density resulted in both, increase in heat transfer as well as pressure drop. Amongst all three channel configurations, the 40 ppi foams had highest heat transfer, where the gain with respect to smooth channel for 〈em〉Re〈/em〉 5000 was ~21, 12 and 9.5 times, for 8:3, 8:1 and 16:1 channels respectively. Increase in channel AR (thinner foams) demonstrated an increase in heat transfer performance for a given pumping power. The thermal hydraulic trends observed for thin and high pore-density foams proved them to be viable candidates for compact electronics cooling.〈/p〉〈/div〉 〈/div〉

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: 25 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 154〈/p〉 〈p〉Author(s): Zhiming Xu, Zhimin Han, Aodi Sun, Xiaoyan Yu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Industrial flue gas contains a large amount of ash, which usually accumulates on the heat exchanger wall and forms particulate fouling. This paper presents a numerical simulation study on the particulate fouling characteristics on the floor heat transfer surface in a rectangular channel. In particular, we investigate the effects of the inlet velocity, concentration, wall temperature, and particle diameter on the fouling mass of the fly ash particles. It is found that increasing the inlet velocity and decreasing the concentration lead to a decrease in the asymptotic total fouling mass of the fly ash particles. For a 5 μm particle, the asymptotic total fouling mass decreases with the increase in the wall temperature, whereas for 9 μm and 15 μm particles, the asymptotic total fouling mass remains almost constant with the increase in the wall temperature. The asymptotic total fouling mass for the 5 μm particle is the smallest, followed by the 9 μm particle. The 15 μm particle possesses the highest asymptotic total fouling mass among the three particles.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 154〈/p〉 〈p〉Author(s): Guohui Zhang, Wanlong Liu, Hansong Xiao, Wenxing Shi, Baolong Wang, Xianting Li, Yang Cao〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In recent years, variable refrigerant flow (VRF) systems have gained popularity in commercial and residential buildings. It is extremely significant to obtain the real performance of VRF systems in order to improve design. However, the measurement of the field cooling or heating capacity of air-cooled VRF systems has not yet been thoroughly addressed. In this paper, a novel field measurement method for the capacity of VRF systems is proposed based on the energy conservation of a compressor set. The compressor set consists of the actual compressor, oil separator, and capillary with the corresponding pipelines. The validation results indicate that the compressor set energy conservation method yields 15% accuracy for cooling capacity and 13% accuracy for heating capacity. Furthermore, the novel measurement method was applied to a VRF system in an office building over four weeks during the heating season. The field test results demonstrate that the average part-load ratio of the VRF system was 0.33, which revealed that the sizing of the VRF system was relatively excessive.〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 154〈/p〉 〈p〉Author(s): Gihoon Kwon, Dong-Wan Cho, Deok Hyun Moon, Eilhann E. Kwon, Hocheol Song〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Pyrolysis of chicken manure was conducted at the fundamental level as a practical example of valorizing animal waste. In particular, to tailor three pyrogenic products (gas, oil, and biochar) via manipulating carbon distribution, carbon dioxide (CO〈sub〉2〈/sub〉) was particularly used as reactive gas medium. Carbon distribution from the liquid phase of pyrogenic oil to the gaseous pyrogenic products while suppressing dehydrogenation was mainly identified in the CO〈sub〉2〈/sub〉 environment. In detail, the more generation of CO was observed in the CO〈sub〉2〈/sub〉 environment, which was ascribed to the homogenous reactions between the liquid phase of pyrogenic products and CO〈sub〉2〈/sub〉. In reference to pyrolysis in an inert (N〈sub〉2〈/sub〉) condition, carbons in pyrolytic oil was used to form CO by the homogeneous reactions. As such, the amount of pyrolytic oil was substantially reduced in the CO〈sub〉2〈/sub〉 atmosphere, which subsequently led to the enhanced generation of CO. Such identified CO〈sub〉2〈/sub〉 effects in pyrolysis of chicken manure were noticeably enhanced due to the catalytic effects imparted from the inorganic constituents including CaCO〈sub〉3〈/sub〉 in the chicken manure sample. Note that the catalytic effects imparted from CaCO〈sub〉3〈/sub〉 was experimentally validated by means of comparing the gas evolution patterns from pyrolysis chicken manure and acid-washed chicken manure in the CO〈sub〉2〈/sub〉 environment. Despite the same mass of biochar both in the N〈sub〉2〈/sub〉 (inert) and CO〈sub〉2〈/sub〉 environments, the chicken manure biochar sample created in the CO〈sub〉2〈/sub〉 environment exhibited the well-developed pore matrix, which led to the high CO〈sub〉2〈/sub〉 sorptive performance. In detail, chicken manure biochar fabricated in the CO〈sub〉2〈/sub〉 environment exhibited three times higher the CO〈sub〉2〈/sub〉 uptake performance as compared with the case of N〈sub〉2〈/sub〉.〈/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-S1359431118364901-ga1.jpg" width="387" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Description: 〈p〉Publication date: 25 May 2019〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 154〈/p〉 〈p〉Author(s): Shixue Wang, Kaixiang Li, Yuan Tian, Junyao Wang, Yukang Wu, Shan Ji〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Thermal issues are increasingly critical for the scaling-up and integrated deployment of lithium-ion batteries (LIBs). To make battery temperature control more accurate, a concept of thermal inertia was proposed to cylindrical power batteries in the current study. Experimental results showed that the thermal inertia of the battery can greatly affect the thermal behavior during battery discharging process, based on which a battery thermal model was created by COMSOL Multiphysics with infrared imaging technology adopted to experimentally investigate the thermal inertia for a LiFePO〈sub〉4〈/sub〉 (LFP) battery. It is evidenced that the model and the corresponding simulation can provide helpful guidance for the thermal behavior control and improve thermal performance. Furthermore, the temperature distribution and variation of the slack period (after discharge) were studied, including internal temperature, surface temperature and temperature difference. Results showed that the battery radius (R) and discharge rate (C) were the major factors that influenced the thermal inertia. In addition, a thermal inertial calculation model was proposed for predicting battery thermal inertia under different operating conditions.〈/p〉〈/div〉 〈/div〉