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Beschreibung: 〈p〉Publication date: 25 March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 169〈/p〉 〈p〉Author(s): Hanfei Guo, Hafiz Muhammad Ali, Ali Hassanzadeh, Yanbao Ma〈/p〉

Beschreibung: 〈p〉Publication date: Available online 25 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering〈/p〉 〈p〉Author(s): Jianlu Zhu, Wei Zhang, Shengnan Liu, Yuxing Li, Miaoer Liu, Quanshen Yin, Bin Xie, Xichong Yu, Yan Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In the field of LNG simulation study, most optimization studies have concentrated on the LNG processes at steady-state simulation, and only a few studies have reported the dynamic simulation of the LNG process, which is closer to actual operating conditions. The main purpose of this study was to design a dynamic model of propane pre-cooling double nitrogen-expander LNG process based on an actual LNG plant, to investigate the dynamic behavior of this process, which had been considered suitable for FLNG process in previous studies. Furthermore, this is one of the first studies to verify the dynamic simulation of this process through the actual operation of an LNG plant. First, the dynamic models of the main equipment used in this process were developed. Second, a dynamic simulation of this process was performed, and the dynamic behaviour was investigated. Finally, to verify the accuracy of the dynamic simulation, different types of dynamic conditions were added to the simulation to investigate the behaviour of the process, including disturbances in the feed gas flow rate and shutting down of the propane system. Further, the dynamic responses and average errors between the experimental and simulated values were obtained and discussed. The results indicated that the two-stream heat exchange model can be used to replace the multi-stream heat exchange model for dynamic simulation, with the average error of dynamic simulation being under 10%, the control system can resolve the problem of excess cooling capacity and make the entire system run stably in the case of feed gas flow rate disturbance, the whole system returns to stability within 100 min in the case of the propane system shutdown. The results can provide feasible prediction and verification methods for the construction of large experimental and liquefaction production devices in the future.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering〈/p〉 〈p〉Author(s): Shangshang Wei, Xiufan Liang, Taimoor Mohsin, Xiao Wu, Yiguo Li〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉An analytical dynamic model can deepen our understanding of system characteristics. However, no system-scale dynamic model of integrated parabolic trough concentrating solar power (CSP) plants currently exists due to lack of a dynamic model of heat exchanger trains and proper integration of different subsystems. To solve the problems, this work developed a new analytical dynamic model of heat exchanger trains. Furthermore, a simplified analytical model of an integrated parabolic trough CSP consisting of a parabolic trough solar field, thermal energy storage, and power block subsystem is first proposed here. To demonstrate the fidelity of the integrated model, the simulation presented here was compared with the simulation built on a software platform and the corresponding measured data from the Andasol II plant. All the validation results of a steady-state case and two dynamic cases prove that the proposed model can capture the system dominant processes with satisfactory accuracy and computational efficiency. Considering the advantages of reliability, simplicity, and robustness, the integrated model can be applied to design and test system controllers of CSP plants, and various other areas related to the CSP.〈/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-S1359431119346319-ga1.jpg" width="261" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 23 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering〈/p〉 〈p〉Author(s): Takehiro Esaki, Noriyuki Kobayashi〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉To be able to use a chemical heat pump (CHP) practically, it is necessary for the reactor and heat exchanger to perform well. Herein, we examine the heat input/output and coefficient of performance (COP) for reactor modules of a CHP under a calcium chloride (CaCl〈sub〉2〈/sub〉) hydration reaction. Various reactor modules were investigated, including plate-tube heat exchangers that comprise of reactors with packed beds of different widths, along with expanded graphite and porous nickel (Ni) metal plates. We found that the heat input/output characteristics could be improved by reducing the heat and mass transfer resistances in the packed-bed reactor. During the heat release, when the reactor and evaporator pressures were the same, the heat transfer rate had a higher impact on the heat output than the water transfer rate. On the contrary, the water transfer rate had a higher impact on the heat input than the heat transfer rate, when the reactor and condenser pressures were the same during heat storage. Furthermore, a COP of 0.43 was achieved for chemical heat storage, at the required temperature, using a plate exchanger with a porous Ni metal plate. Conclusively, a preferred reactor module is one that demonstrates high heat input/output and COP, so that the heat and mass transfer rates can be improved to enable the hydration of large quantities of CaCl〈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-S1359431119314966-ga1.jpg" width="359" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: Available online 22 January 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering〈/p〉 〈p〉Author(s): Mengzhao Chang, Jeong Hwan Park, Hyung Ik Kim, Suhan Park〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉The spray characteristics of two direct-injection gasoline injectors with different hole arrangement under flash boiling conditions were studied. The spray development and spray characteristics, such as the spray tip penetration, spray angle, rate of collapse, and spray area during the injection process of the two injectors were studied via high-speed shadowgraph techniques. The sprays were divided into three regions based on the rate of collapse at room temperature and atmospheric pressure, that is, the subcooled region, and flash boiling region (transition region and flare flash boiling region). In addition, the spray characteristics of injector N under different superheated degree and ASOI were determined in detail. The experimental results showed that the spray plumes of the injector (N) with small hole spacing easily interacted, causing the earlier collapse of the spray structure. Injector (N) with small hole size had a good effect on atomization, and the effect of flash boiling on spray characteristics was low. The flashing spray characteristics are not only affected by the degree of superheat, but also by the ambient pressure alone. The spray characteristics of injector N and injector W in the transition region are ideal for the GDI engine. This may provide new opportunities for the GDI engine combustion system and injection strategy design.〈/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-S1359431119343662-ga1.jpg" width="243" alt="Graphical abstract for this article" title=""〉〈/figure〉〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 25 March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 169〈/p〉 〈p〉Author(s): Shang Mao, Ankang Kan, Ning Wang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Vacuum insulation panel, composed of a core material and a barrier, is a very efficient thermal insulation material. Compared with conventional insulation materials, the vacuum insulation panel is proposed to achieve a better insulated performance. However, its thermal conductivity will be seriously increased and insulated performance will be significantly decreased since the additional heat is transferred through the barrier; that is called thermal bridge effect. This paper emphasized on effective thermal conductivity to evaluate the performance of vacuum insulation panel. Two criteria, i.e., the linear and point thermal transmittance are introduced to evaluate the comprehensive performance of vacuum insulation panel. A heat transfer model was used to analyze the thermal bridge. Then, a fast and effective method for measuring thermal bridge is presented, which is supported by numerical simulation analysis. The results indicated that thermal bridge not only could increase with the increasing of the mental foil (main aluminum) thickness, but also could exhibit higher heat losses with the reducing of thickness of the vacuum insulation panel. Overall, the effective thermal conductivity of vacuum insulation panel could increase by 110.8% when the barrier contains 10 μm mental foil and the size of vacuum insulation panel is 300 × 300 × 10 mm〈sup〉3〈/sup〉. This research provides a reference for measuring the thermal bridge and could also disclose the quantitative behavior of physical parameters in thermal bridge.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 25 March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 169〈/p〉 〈p〉Author(s): L. Jiang, R.Q. Wang, A. Gonzalez-Diaz, A. Smallbone, R.O. Lamidi, A.P. Roskilly〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Due to relatively high energy consumption of absorption technology, adsorption carbon dioxide capture is gathering the momentum in recent years. This paper aims to further improve the thermal performance of a 4-step temperature swing adsorption cycle by integrating internal mass recovery and heat recovery. Exergy efficiency is evaluated by using adsorption characteristics of activated carbon and compared in terms of four different situations i.e. basic cycle, heat recovery cycle, mass recovery cycle, heat and mass recovery cycle, which could illustrate the advantages and disadvantages of different recovery technologies. Results demonstrate that heat recovery and mass recovery technologies are quite conducive to improve the up limit of cycle thermal efficiency. Under the conditions of different desorption/adsorption temperatures and pressures, exergy efficiencies using recovery technologies could be improved by up to 2.86 times when compared with that of basic cycle. Besides, in real application unused percentage of adsorption reactor and metal ratio have large influence on the cycle performance while mass recovery rate has a relatively small influence. One potential application of the proposed recovery technologies is direct air capture in building ventilation system since a largest improvement could be achieved at a low carbon dioxide concentration.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 25 March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 169〈/p〉 〈p〉Author(s): Feng Wang, Yuling Zhou, Weibo Yang, Meiqin Ni, Xiaosong Zhang, Caihua Liang〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉Spraying method to prepare superhydrophobic surface is more efficient than the wet chemical etching used before, and is more suitable for outdoor coil of air source heat pump. However, durability in frosting/defrosting cycles and anti-frosting performance should be clarified before applying the sprayable superhydrophobic coating to solve the frosting problem. Superhydrophobic surface was prepared in this paper, by spraying SiO〈sub〉2〈/sub〉 coating on aluminum surface. Frosting and defrosting tests were carried out to verify its durability and anti-frosting performance. The self-jumping of condensate droplets were focused on at early stage of frosting. Moreover, a theoretical model was developed to analyze the influence of the superhydrophobic surface characteristics on self-jumping of condensate droplets. The durability of the sprayable surface was greatly improved compared with the etched surface. Continuous self-jumping of condensate droplets was achieved at early stage of frosting, and theoretical analysis indicated that reducing contact angle hysteresis was the key to achieve self-jumping. Compared with the surface having equal contact angle but larger angle hysteresis, self-jumping reduced the surface coverage of droplets on the sprayable surface, as a result, decreasing the frost layer thickness by 33% after frosting for 60 min, which indicated that the sprayable surface had excellent anti-frosting performance.〈/p〉〈/div〉 〈/div〉

Beschreibung: 〈p〉Publication date: 25 March 2020〈/p〉 〈p〉〈b〉Source:〈/b〉 Applied Thermal Engineering, Volume 169〈/p〉 〈p〉Author(s): Yongqiang Han, Yiming Zhang, Teng Zuo, Ruolong Chen, Yun Xu〈/p〉 〈div xml:lang="en"〉 〈h5〉Abstract〈/h5〉 〈div〉〈p〉In this paper, an R245fa organic Rankine cycle experimental prototype system with a 5-cylinders radial piston expander is presented to recovery waste heat from exhaust gas of diesel engine. In order to explore the system behavior and research the effective adjustment method, the performance was tested and analyzed with multiple operating parameters: pump speed, generator load, energy of waste heat source and working fluid filling quantity. Moreover, energy and exergy analysis were provided to evaluate the system energy loss. Combining simulation study of expander in GT-SUITE, the internal friction and leakage were calculated to illuminate the energy degradation processes of expansion. The experiments proved the feasibility of radial piston expander for organic Rankine cycle coupled to vehicle engine. The results demonstrate that expander power output can be optimized by adjusting pump speed under different heat sources and moderate filling quantity indicates the largest expander power output. The gross thermal efficiency and exergy efficiency of the organic Rankine cycle system can reach up to 2.02% and 10.5%, respectively. Overall system exergy losses are 4.24–4.63 kW and expander contributes about 1 kW. In the processes of expansion, entropy increment leads to larger energy degradation than working fluid flow loss and mechanical frictional loss. Under the influences of multiple energy losses, the maximum expander mechanical power output 279 W can be obtained.〈/p〉〈/div〉 〈/div〉