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A combined experimental and numerical approach for printed circuit rectangular microchannel J-T cooler using argon

APPLIED THERMAL engineering 2021年 182卷 116107-116107页

作者： She, Hailong Cui, Xiaoyu Weng, Jianhua Geng, Hui Chang, Zhihao Univ Shanghai Sci & Technol Sch Energy & Power Engn 516 Jungong Rd Shanghai 200093 Peoples R China Key Lab Multiphase Flow & Heat Transfer Shanghai Shanghai 200093 Peoples R China Shanghai Univ Elect Power Sch Energy & Mech Engn Shanghai 200090 Peoples R China

Considering the small cooling capacity of a Hampson-type Joule-Thomson (J-T) cooler, a multi-layer printed circuit board (PCB) J-T cooler with parallel microchannels was fabricated and investigated in this study. The cooler has four parts: an inlet, a counter flow heat exchanger, a throttle, and an evaporator. A mathematical model is established and iteratively solved with a developed code. Using Ar as the working fluid, the cooling characteristics of the J-T cooler at 2-8 MPa were simulated. The pressure, temperature and velocity of the fluids as well as the temperature of the materials were obtained along the length of the cooler. The discrepancy between calculation and experiment of the cold end temperature is within +/- 2%, and the discrepancy of the outlet pressure is within +/- 4%, indicating the reasonability and reliability of the mathematical model. The model was also used to obtain the heat transfer rate between high- and low-pressure fluids, the enthalpy change, the cooling capacity of the cooler and the axial heat conduction of the material. The results show that the cold end temperature can reach 155.9 K with the gross cooling capacity being 3.66 W at the inlet pressure of 8.02 MPa. It was found that if the axial heat conduction is omitted, the cold end temperature could decrease further by 2.2 K. Finally, the optimisation measures of the cooler are discussed and proposed by analysing the variation law of the J-T coefficient.

关键词： Joule-Thomson Microchannel Multi-layer Mathematical model Experimental and numerical study Cooling capacity

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Compression-assisted decomposition thermochemical sorption energy storage system for deep engine exhaust waste heat recovery

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ENERGY 2022年第PartB期244卷 123215-123215页

作者： Gao, Peng Wei, Xinyu Wang, Liwei Zhu, Fangqi Univ Shanghai Sci & Technol Sch Energy & Power Engn Inst Refrigerat & Cryogen Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Shanghai Jiao Tong Univ Sch Mech Engn Inst Refrigerat & Cryogen Shanghai 200240 Peoples R China Nanyang Technol Univ Sch Mech & Aerosp Engn 50 Nanyang Ave Singapore 639798 Singapore

In the context of the stringent automobile emission legislations, this paper proposes a novel compression-assisted decomposition thermochemical sorption energy storage system for recovering engine exhaust waste heat, which is utilized to produce cooling capacity for a refrigerated vehicle. In this system, the desorption pressure of sorbent can be flexibly adjusted by changing the suction pressure of compressor embedded between the sorption bed and condenser, which ensures the stable operation of system even at relatively low exhaust temperatures. Simultaneously, the decomposition reaction increases suction pressure of compressor, so the coefficient of performance (COP) is thus greatly improved. Furthermore, the sorption bed can output cooling capacity for refrigerated compartment when the vehicle is parked. Currently, vehicle emission standards generally adopt World Harmonized Stationary Cycle test, and 13 engine operating points are selected. At an operating point 3 (a low engine load), i.e. 55% speed and 25% torque, the COP of the novel system at an evaporating temperature of -25 degrees C and a condensing temperature of 45 degrees C is 1.65, 1.5 times higher than that of conventional one. The weighted average COP under 13 operating points is still up to 1.48. Eventually, the novel system promotes the realization of low-carbon and low-cost refrigerated transportation. (C) 2022 Elsevier Ltd. All rights reserved.

关键词： Thermochemical sorption energy storage Compression-assisted decomposition Exhaust waste heat recovery Vehicle emission standards Refrigerated vehicles

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Dynamic modeling of solar-assisted ground source heat pump using Modelica

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APPLIED THERMAL engineering 2021年 196卷 117324-117324页

作者： Chen, Yongbao Chen, Zhisen Chen, Zhe Yuan, Xiaolei Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Tongji Univ Sch Mech & Energy Engn Shanghai 201804 Peoples R China

Traditional rural energy sources, such as straw, firewood, and coal are the main energy resources in developing countries;however, these resources are associated with low efficiency and can cause considerable air pollution. With the rapid development of renewable energy worldwide, existing energy frameworks in rural areas need to be urgently transformed. Developing a universal and reliable dynamic modeling framework for multi-source heat pumps remains an unresolved issue. To this end, this paper proposes an integrated energy system based on a solar-assisted ground source heat pump (SGSHP), which can facilitate the utilization of renewable energy, reduce the electricity consumption, and provide demand response (DR) resources in rural houses. A 150-m2 rural house on the outskirts of shanghai, China was considered as a case building. A novel Dymola modeling framework of an SGSHP system was established, and the heating performance was analyzed. Considering the variation in the energy demand in winter, four practical operation modes were implemented to maximize energy efficiency. The results show that the coefficients of performance of the system are 4.2 and 3.5 with and without solar collectors, respectively. The contributions of solar energy, geothermal heat, and electricity in the system are 27%, 18%, and 55%, respectively. Moreover, approximately 79.6% of AC loads can be shaved during evening peak load time in our proposed energy system.

关键词： Ground source heat pump Solar-assisted energy storage Demand response Dymola simulation

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Experimental investigation on flow boiling characteristics of R1233zd(E) in a parallel mini-channel heat sink for the application in battery thermal management

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INTERNATIONAL JOURNAL OF heat AND MASS transfer 2021年 178卷 121591-121591页

作者： Fang, Yidong Yang, Wenliang Xu, Dan Hu, Lingren Su, Lin Huang, Yuqi Univ Shanghai Sci & Technol Coll Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Zhejiang Univ Coll Energy Engn Hangzhou 310058 Peoples R China

Aiming for the application of refrigerant two-phase cooling on battery thermal management, this study presented an experimental investigation on the flow boiling characteristics of R1233zd(E) in a parallel mini-channel heat sink, which consisted of 21 channels with the length of 140 mm and the cross section of 1.5 x 1.5 mm(2). Under the saturation pressure of 125 kPa, the boiling curve of R1233zd(E) and the heat transfer coefficient were analyzed under different heat fluxes (5-100 kW/m(2)), mass fluxes (150-600 kg/m(2) s) and inlet subcoolings (2.5-8 K). In addition, the flow pattern was captured using high-speed camera. The results showed that the onset of nucleate boiling was delayed with the increase of refrigerant mass flux and inlet subcooling, while the transition of heat transfer was verified by flow pattern visualization. The measured wall superheat was compared with present correlations, showing that the predicted value was always smaller than the experimental results. flow boiling on local points showed that the nucleate boiling was triggered later at the channel located at the center axis of the heat sink, meanwhile the approach of critical heat flux was more obvious at channel outlet. Due to the graduate transition of flow boiling mechanism, refrigerant mass flux had limited influence on the local heat transfer coefficient when the heat flux was lower than 30 kW/m(2), while enhancement on heat transfer could be observed with larger mass flux when the heat flux exceeded 30 kW/m(2). The local experimental data of heat transfer coefficient were compared with 6 correlations from the literatures. It was found that the best prediction was presented by Liu and Winterton model with a MAE of 23.4%, while Kim and Mudawar model showed best agreement under different mass fluxes. A simple modification was conducted on Kim and Mudawar model, and the calibrated model presented a better prediction accuracy with the MAE of 17.6% and 83.2% of total data within the error o

关键词： flow boiling Parallel mini channel heat transfer flow pattern Battery thermal management

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Element different method for three-dimensional radiative transfer within heterogeneous media

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RESULTS IN PHYSICS 2023年 49卷

作者： Li, Yifan Sun, Yasong Zhou, Ruirui Li, Sida Zheng, Aozhou Ma, Jing Northwestern Polytech Univ Sch Power & Energy Shaanxi Key Lab Thermal Sci Aeroengine Syst Xian 710072 Peoples R China Northwestern Polytech Univ Yangtze River Delta Res Inst NPU Ctr Computat Phys & Energy Sci Taicang 215400 Jiangsu Peoples R China Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Changan Univ Sch Automobile Xian 710064 Shaanxi Peoples R China

The ability to accurately determine three-dimensional radiative intensity with high spatial and angular resolution is crucial for the diagnosis of radiative combustion. However, the non-uniform distribution of the refractive index causes the radiation energy to travel along curved paths, making the analysis of thermal radiation challenging. This paper uses the element differential method to calculate radiative heat transfer in a threedimensional heterogeneous media. To address the numerical challenges of strong convection in the radiative transfer equation, an upwind scheme is adopted. The comparison with the results in the literature verifies the correctness and effectiveness of calculating heat radiation transfer based on the element differential method. A cell-by-cell strategy is used to improve computational efficiency and reduce the demand for computer resources. Compared with the overall strategy, the cell-by-cell strategy is proven effective in suppressing non-physical oscillations. Additionally, the method is extended to deal with the issue of intermittent refractive index and achieve a high-resolution description of the angular direction of radiative intensity.

关键词： Thermal radiation Heterogeneous media Element differential method Upwind scheme Cell-by-cell strategy

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Unraveling the disparity of CO2 sorption on alkali carbonates under high humidity

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JOURNAL OF CO2 UTILIZATION 2021年 53卷

作者： Cai, Tianyi Chen, Xiaoping Tang, Hongjian Zhou, Wu Wu, Ye Zhao, Chuanwen Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Southeast Univ Sch Energy & Environm Minist Educ Key Lab Energy Thermal Convers & Control Nanjing 210096 Peoples R China Natl Univ Singapore Dept Chem & Biomol Engn Singapore Singapore Nanjing Univ Sci & Technol Sch Energy & Power Engn MIIT Key Lab Thermal Control Elect Equipment Nanjing 210094 Peoples R China Nanjing Univ Sci & Technol Sch Energy & Power Engn Adv Combust Lab Nanjing 210094 Peoples R China Nanjing Normal Univ Sch Energy & Mech Engn Engn Lab Energy Syst Proc Convers & Emiss Control Nanjing 210042 Peoples R China

CO2 emissions from fossil fuel combustion have been closely associated with the rapid climate change and potential crisis on human society. Na2CO3-based and K2CO3-based solid sorbents have been demonstrated as promising candidates for post-combustion CO2 capture. Despite their physicochemical similarities in many respects, the rationale that endows Na2CO3 and K2CO3 with disparate performance in CO2 sorption is still indeterminate, which motivates us to unravel from the atomic level. Herein, taking moisture effect on carbonation as a starting point, different hydrophilicity and deliquescence between Na2CO3 and K2CO3 are investigated by integrating experimental investigations and theoretical verifications. The results manifest a bigger radius of K+ renders higher cationic hydration on K2CO3 surface, leading to its stronger H2O affinity and easier deliquescence than that of Na2CO3. Under identical humid settings, K+ is observed to diffuse remarkably faster than Na+, accordingly, facilitating a desirable CO2 carbonation performance over K2CO3 sorbents. In this regard, amelioration strategies on Na2CO3 by tuning hydrophilicity are proposed and further demonstrated experimentally. This work provides a fresh perspective to comprehend the carbonation mechanism by solid alkali carbonates as well as practical guidelines for rational sorbents design to boost post-combustion CO2 reduction.

关键词： CO2 reduction Alkali carbonates Deliquesce Density functional theory Molecular simulation

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Controlling the ash adhesion strength of zhundong high-calcium coal by additives at high temperature

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FUEL 2022年 323卷 1页

作者： Liu, Zhongyi Jin, Jing Zheng, Liangqian Zhang, Ruipu Wang, Yongzhen He, Xiang Kong, Shang Zhai, Zhongyuan Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer P Shanghai 200093 Peoples R China Shanghai Marine Diesel Engine Res Inst Shanghai 201108 Peoples R China Linyi Univ Sch Civil Engn & Architecture Linyi 276000 Shandong Peoples R China Shanghai Power Equipment Res Inst Co Ltd Shanghai 200240 Peoples R China Shanghai Boiler Works Co Ltd Shanghai 200245 Peoples R China

Herein, ash adhesion strength has been investigated via a new self-designed tester for solving the severe ash deposition problems of Zhundong high-calcium coal. The results indicate that the ash adhesion strength of Zhundong high-calcium coal appears at 800 degrees C and increases with the temperature rising. The ash adhesion strength increases rapidly at about 1100 degrees C, and reaches 184.933 kPa at 1200 degrees C. Above 800 degrees C, the melting of sulfate results in the ash adhesion strength of Zhundong high-calcium coal. As the temperature increases, feldspar minerals, such as gehlenite and akermanite, form a low-temperature eutectic, causing greater ash adhesion strength. The ash adhesion strength is positively correlated with ash shrinkage. Kaolin and vermiculite can effectively inhibit the formation and melting of sulfate and decrease the ash adhesion strength of Zhundong highcalcium coal. At 1200 degrees C, kaolin and struvite can increase the content of minerals with high melting temperature and decrease the ash adhesion strength. Kaolin additive is more suitable for the Zhundong high-calcium coal combustion below 1200 degrees C and can effectively reduce the ash adhesion strength by 55.9% at 1200 degrees C. Vermiculite additive is well suited for circulating fluidized bed boilers and can almost eliminate the ash adhesion strength below 1000 degrees C. Struvite additive only shows good ash adhesion strength inhibition above 1000 degrees C.

关键词： Zhundong high-calcium coal Ash deposition Adhesion strength Sulfate Additives

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RECENT ADVANCES OF SURFACE WETTABILITY EFFECT ON flow BOILING heat transfer PERFORMANCE

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Frontiers in heat and Mass transfer 2021年 17卷

作者： Cao, Shuang Yang, Hui Zhao, Luxing Wang, Tao Xie, Jian School of Energy and Power Engineering Zhengzhou University of Light Industry Zhengzhou450002 China Beijing Key Laboratory of Multiphase Flow and Heat Transfer for Low Grade Energy Utilization North China Electric Power University Beijing102206 China

flow boiling heat transfer is an effective way to fulfill the energy transfer. The wettability of boiling surface influences the liquid spreading ability and the growth, departure, and release frequency of bubbles, which determines the heat transfer performance. According to the wettability and combination forms, boiling surface are classified into weak wetting surface, strong wetting surface, and heterogeneous wetting surface. Fabricating by physical, chemical method or coating the original surface with a layer of low surface energy, the weak wetting surface has more effective activation point and nucleation center density to improve heat transfer performance at low heat flux. The strong wetting surface always formed by physical or chemical treatment to enhance the rapid rewetting of the wall surface. It has a smaller bubble separation diameter, higher separation frequency and higher CHF. The heterogeneous wetting surface, having the synthetic effects of the strong and weak surface wettabilities, is a hot issue of recent study. But its composition and heat transfer enhancement mechanism are very complicated which need to study thoroughly. Furthermore, the intelligent wetting surface, having the dynamics wettability function, is also briefly analyzed in this paper. Despite the advances in this aspect, the boiling surfaces can be further optimized by fabricate effective wettability to achieve a strong stability, high heat transfer performance and realize the synergistic effect of flow pattern and heat transfer. © 2021, Global Digital Central. All rights reserved.

关键词： Wetting

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Understanding effect of phosphorus-based additive on ash deposition characteristics during high-sodium and high-calcium Zhundong coal combustion in drop-tube furnace

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FUEL 2021年 287卷 119462-119462页

作者： Yu, Zhihao Jin, Jing Hou, Fengxiao Zhang, Yunpeng Wang, Guangxu Liu, Bojianzhi Zhai, Zhongyuan Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai 200093 Peoples R China Shanghai Boiler Works Co Ltd 250 Huangning Rd Shanghai 200245 Peoples R China

Zhundong coal as a high quality steam coal has not been widely utilized due to severe fouling and slagging problems during combustion. To promote clean utilization of Zhundong coal, combustion experiments of Zhundong coal were carried out in the drop tube furnace (DTF). The influence of novel phosphorus-based additive on ash deposition characteristics of Zhundong coal was studied. The appearance and phase composition of the raw coal and mixed coal ash deposits at different flue gas temperatures were researched respectively. The new prediction index of slagging tendency containing phosphorus was proposed, and the balance calculation were performed by FactSage thermodynamic software in different flue gas temperatures, including experimental temperatures selected. The results showed that the values of new indexes for predicting slagging tendency had obvious changes, and the phosphorus-based additive had a significant effect on the ash deposition behavior during the combustion process of Zhundong coal in DTF. Compared with the raw coal, the mixed coal with additive had higher ash fusion points and were in the form of loose, crisp, and porous powder, which was beneficial for soot blowing. When the flue gas temperature was 1000 degrees C or 1150 degrees C, there was much phosphate complex salt as the skeleton in the ash deposits of the mixed coal, such as Na2CaMg7(PO4)(6). Phosphate captured Na and Ca, and effectively inhibited the low temperature eutectic mixtures of Ca with Si and Al, indicating that phosphorus-based additive had good effect on improving ash deposition characteristics of Zhundong coal.

关键词： Zhundong coal Phosphorus-based additive DTF Ash deposition FactSage

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Lattice Boltzmann simulation of non-Fourier heat conduction with phase change

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NUMERICAL heat transfer PART A-APPLICATIONS 2019年第1期76卷 19-31页

作者： Liu, Yi Li, Ling Univ Shanghai Sci & Technol Sch Energy & Power Engn Shanghai 200093 Peoples R China Shanghai Key Lab Multiphase Flow & Heat Transfer Shanghai Peoples R China

The lattice Boltzmann method (LBM) combined with the enthalpy method is a very effective method to solve the solid-liquid phase transition problem. However, when the heat flux is very high or the time of the process is in the same order of magnitude as the relaxation time, it is necessary to consider the non-Fourier effect in heat conduction. At this time, whether the LBM-BGK format based on Bhatnagar-Gross-Krook (BGK) approximation is still valid remains to be discussed. In this paper, the hyperbolic lattice Boltzmann method (HLBM) is combined with the enthalpy method to solve the non-Fourier solid-liquid phase change problem. By solving the non-Fourier heat conduction problem and the Fourier solid-liquid phase change problem, the numerical solution is compared with the analytical solution to verify the accuracy of the algorithm. The effect of different relaxation times on the solid-liquid phase transition is analyzed. In addition, the effect of changes in thermal diffusivity due to state changes on the non-Fourier solid-liquid phase transition is discussed.

关键词： Relaxation time

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