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工程热物理学报

Journal of Engineering Thermophysics

29 April 2025, Volume 46 Issue 5
    

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  • Research Progress on the Mechanism of Ultrasound Frost Retardation/Defrosting and Its Applications
    WU Yongshuai, WU Siyuan, SUN Yu, ZHAO Rijing, HUANG Dong
    Journal of Engineering Thermophysics. 2025, 46(5): 1379-1400.
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    Frosting usually has a negative impact on device, when ultrasound is used for frost retardation/defrosting, can realize no downtime defrosting, cooling and heating without interruption during defrosting time. But due to its mechanism is not clear, technical difficulties to pragmatize, failed to get popularization and application. This paper reviews the research progress of ultrasound in the field of frost retardation and defrosting from two aspects of its mechanism and pragmatization. Firstly, the ultrasound characteristics is introduced, including commonly used ultrasound wave types and their propagation, ultrasound effects on frost retardation and defrosting, distribution of equivalent force on the cold surface; then, the growth of frost is inhibited by delaying the generation of liquid droplets, delaying the freezing of droplets, crushing the frozen droplets and suppressing the frost branch growing; based on the frost crystal fracture breaking, defrosting effecting factors and defrosting enhancement methods, ultrasonic defrosting mechanism is summarized; and, from the equipment frost retardation/defrosting effects and its energy consumption comparison, practical difficulties and problems, the ultrasound frost retardation/defrosting practical applications is sorted; Finally, a outlook of the ultrasound used for frost retardation/defrosting in the future is given to provide reference.
  • The Performance Study on Hydrogen Production From Medium Temperature Methane Chemical Looping Steam Reforming Using Lithium-based Absorbent
    WANG Xuyun, LI Yang, GAI Zhongrui, RAO Qiong, LIU Mingkai, PAN Ying
    Journal of Engineering Thermophysics. 2025, 46(5): 1401-1408.
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    Lithium silicate serves as a novel CO2 absorbent with moderate absorptionregeneration temperature range (500∼700°C) and excellent cycling stability. In this study, Li2CO3 was selected as the precursor for the preparation of lithium silicate. Additionally, a eutectic co-doping method with potassium elements was employed to enhance its reactivity. Using extrusion-spheronization, we successfully produced absorbent particles with high mechanical strength and cycling stability. The effects of absorption-regeneration temperature, CO2 concentration and particle diameter on the performance of absorbent particles have been studied in detail. Furthermore, mixed with NiO oxygen carriers, sorption-enhanced chemical looping reforming (SE-CLR) experiments were conducted at the range of 500∼650°C for hydrogen production and in situ CO2 capture factors such as reaction temperatures and oxygen carrier to absorbent mass ratios were then investigated The results showcase that at the optimal reaction temperature of 600◦C, the SE-CLR process effectively lowered the reaction temperature by 25°C, achieving a 13% increase in methane conversion rate and hydrogen purity and CO2 capture rate above 90% were attained 
  • Study on Characteristics of Solar-assisted Ammonia-Water Absorption Refrigeration Using Ocean Thermal Energy
    ZHANG Yanmei, WAN Yueru, ZHANG Chengbin
    Journal of Engineering Thermophysics. 2025, 46(5): 1409-1416.
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    This paper proposed a solar-assisted ammonia-water absorption refrigeration system using ocean thermal energy. This paper first introduced the module and working principle of this refrigeration system, and subsequently established and verified its numerical model. Based on this model, the thermo-economic performance of solar-assisted ammonia-water absorption refrigeration system using ocean thermal energy is analyzed and compared with that without solar assistance. The effects of generation temperature and primary rectified temperature on the coefficient of performance (COP) and the exergy efficiency of this refrigeration system are examined and analyzed. The results indicate that the utilization of solar-assisted ocean thermal energy to drive the ammoniawater absorption refrigeration system can obtain 11.6 times more refrigeration capability than that without solar assistance. In addition, the solar assistance can also improve the thermal perfection of refrigeration cycle with 43.3%. The optimal thermal performance of this refrigeration system can be achieved by selecting a combination of generation temperature and primary rectified temperature.
  • Decomposition Characteristics and Prediction Model of Natural Gas Hydrates by Depressurization
    YANG Mingjun, LI Jing, ZHENG Jianan, SONG Yongchen
    Journal of Engineering Thermophysics. 2025, 46(5): 1417-1421.
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    Developing natural gas hydrates is essential for the development of oceanic energy resources. However, the current research on hydrate pressure reduction exploitation has not yet established a systematic and comprehensive theoretical framework. Consequently, there is a lack of key theoretical models to validate large-scale commercial exploitation. This study clarifies the pressure reduction exploitation characteristics of natural gas hydrates through experimental research. By combining the actual distribution of hydrate occurrence in porous media, a hypothesis is proposed that the number of hydrate decomposition particles determines the decomposition rate. Based on this, a model for the skewed normal decomposition gas volume of hydrates is established. Subsequently, a complete non-equilibrium thermodynamic calculation method for hydrate pressure reduction exploitation is proposed, achieving high-precision predictions of dynamic responses including temperature, pressure, and reaction parameters throughout the entire process of hydrate pressure reduction decomposition. The research results effectively address the current shortcomings in hydrate theory and have significant guiding implications for optimizing natural gas hydrate exploitation strategies.
  • Multi-Physics Field-Based Modeling of Linear Fresnel Collector Subsystems
    LU Xiaojuan, RUI Yu, KONG Linggang, FAN Duojin
    Journal of Engineering Thermophysics. 2025, 46(5): 1422-1429.
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    In the field of solar thermal power generation, the control model of the traditional linear Fresnel collector subsystem does not take into account the complexity of the working environment, which leads to poor adaptability and low control accuracy of the collector control subsystem. In order to improve the power generation efficiency of a linear Fresnel thermal power system, a multi-model of the collector system is established based on the complexity of the environment in the western part of China by considering multiple factors and according to the time-varying characteristics of its parameters. Taking the vacuum collector tube, which is commonly used in the current linear Fresnel collector subsystem, as the research object, using COMSOL Multiphysics software, the threedimensional steady state model is established and the multi-physics field is constructed by considering the inlet temperature, the normal direct irradiance, the molten salt flow rate and the wind speed, etc.; the performance of which is analyzed and the data are extracted to carry out the FCM clustering, and the parameter identification by using the forgetting-factor recursive least-squares method is carried out, so as to get the multivariate prediction model for the heat-collector subsystem. The model has been validated and analyzed by the data of the collector field which has been put into use, and the reliability of the model has been confirmed. Certain ideas are provided to improve the performance of the collector subsystem.
  • Research on the Influence of Bypass Adjustment on Matching Characteristics of a Novel Variable Cycle Compression System
    LUO Qiaodan, ZHAO Shengfeng, YAO Lipan, YANG Chengwu, HAN Ge, ZHU Junqiang
    Journal of Engineering Thermophysics. 2025, 46(5): 1430-1444.
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    Based on the requirements of high-altitude, long-endurance drones, this paper presents a novel mode-variable medium bypass ratio compression system structure and conducts a comprehensive analysis of the mechanism by which key adjustment parameters affect the matching characteristics of the compression system. The research findings demonstrate that with an increase in the back pressure of the external bypass, the internal bypass of the compression system exhibits enhanced flow capacity, resulting in improved pressure ratio and efficiency of the CDFS, albeit accompanied by a degradation in the performance of the high-pressure compressor. Decreasing the opening of the CDFS guide vanes significantly reduces the pressure ratio and flow rate of the CDFS, albeit with a negligible effect on its efficiency. Moreover, this adjustment contributes to a certain extent to the enhancement of the high-pressure compressor’s performance. Specifically, when the CDFS guide vanes are closed to 40°, the pressure ratio and flow rate of the CDFS decrease by more than 16%, while the efficiency of the high-pressure compressor increases by 3.95%. Furthermore, augmenting the opening of front variable area bypass injector (FVABI) substantially enhances the flow capacity of both the CDFS and the first external bypass, thereby causing the working point of the CDFS to shift toward the choke boundary. Simultaneously, due to a greater allocation of fluid to the first external bypass, the working point of the high-pressure compressor moves toward the stall boundary. 
  • Experimental and Numerical Study of a Highloaded Subsonic Three-stage Compressor at Design Speed
    REN Xiaodong, LI Xiaoye, WANG Xiaochen, GU Chunwei, CHEN Jiang
    Journal of Engineering Thermophysics. 2025, 46(5): 1445-1452.
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    The subsonic stage is an essential component of gas turbine high-load axial compressors and a dominant factor influencing the performance of multi-stage axial compressors. To meet the development demands of advanced gas turbine compressors, this study conducts experimental and numerical research on a typical high-load subsonic compressor. The compressor design and experimental testing were based on the characteristics of the intermediate stage in industrial gas turbine axial compressors. Subsequently, numerical simulations were conducted to analyze the aerodynamic performance and flow behavior of the compressor, with a particular focus on the leakage flow at the blade tip. The experimental results obtained the compressor’s characteristic curves at different rotational speeds and validated the numerical methods used. Analyses of the flow field at typical operating points revealed that the occurrence of blockage in the compressor is primarily caused by the interaction of shock waves and downstream flow separation in the third-stage moving and stationary blades. Additionally, the blade tip leakage flow in the first-stage moving blades was identified as the main reason for the performance degradation and flow instability during the compressor’s approaching stall process.
  • The Effect of Different Motion Patterns of Lateral Flaps on the Energy Extraction Characteristics of Flapping Foils
    TIAN Chenye, LIU Xiaomin
    Journal of Engineering Thermophysics. 2025, 46(5): 1453-1463.
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    As a new type of fluid energy extraction device, the flapping foils have the characteristics of small environmental impact and high adaptability to low flow velocity conditions. In order to improve the energy extraction efficiency of the flapping foils, a movable lateral flap for the flapping foil is designed in this study. The energy extraction characteristics of flapping foils without flaps, with movable lateral flaps and with fixed lateral flaps are compared based on the numerical simulations. The mechanism of movable lateral flaps to improve the energy extraction efficiency η of the flapping foils is analyzed. Three motion patterns are designed for the movable lateral flaps and the differences in the effects of the movable lateral flaps with different motion patterns on the energy extraction performance are compared at different reduced frequencies f∗. The results show that, the flapping foil using flaps with stationary-start pattern has the best energy extraction characteristics. It obtains the largest energy extraction efficiency η = 48.0% at f∗ = 0.18, which is an improvement of 21.7% compared with the conventional foil. Due to the sudden change in velocity during flap motion, the flaps with sinusoidal pattern and uniform velocity pattern adversely affect the energy extraction of the flapping foils.
  • Analysis of Vortex Structure and Flow Losses in the Annular Casing of Liquid Turbines
    LI Hongyang, MA Yanan, ZHANG Xuehui, CHEN Haisheng, LI Wen, ZUO Zhitao, ZHANG Lei
    Journal of Engineering Thermophysics. 2025, 46(5): 1464-1470.
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    The liquid turbine is an energy-saving device in supercritical compressed air energy storage (SC-CAES) systems, which can replace throttle valves to reduce the temperature of the fluid, increase the liquefaction rate, and significantly enhance the performance of SC-CAES systems. Based on experimental results of the liquid turbine, this paper analyzed characteristics of vortex structure and loss distribution in the annular casing of the liquid turbine using numerical simulation. Results showed that although the annular casing had advantages of easy processing and assembly, it causes about 6% flow loss. Moreover, the complex vortex flow inside significantly interfered with the uniformity of flow in nozzles and rotors, and affected the stability of the output power. Findings of this paper will provide theoretical guidance for the optimization design of high-performance liquid turbines and the development of efficient SC-CAES systems.
  • Large Eddy Simulation Analysis of Vortex Structure and Unsteady Evolution of a Centrifugal Impeller With Staggered Blade
    CHEN Jinbo, WANG Feifan, GAO Bo, ZHANG Ning, NI Dan
    Journal of Engineering Thermophysics. 2025, 46(5): 1471-1476.
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    To investigate the complex flow and vortex structure evolution within the staggered blade centrifugal impeller, Large Eddy Simulation (LES) numerical computation method was employed to capture the unsteady flow field within the impeller flow channel and near the volute togue. Utilizing the Q-criterion vortex identification method, the vortex distribution at two mid-span sections of different impeller schemes was extracted, and the evolution of the vortex structure near the tongue was focused on. The study revealed that staggered blade arrangement generates a large number of multi-scale vortex structures near the inlet flow channel of the posterior blade, dissipating within the flow channel and evolving towards the impeller outlet. The wake vortex band becomes longer and wider as the stagger angle increases. Influenced by both the vortex structures developed within the impeller flow channel and the staggered structures, the shedding time of wake vortices is advanced successively, continuously interfering with the volute togue, resulting in a denser and more complex vortex structure near and downstream of the volute togue.
  • Research on the Influence of Different Yaw Conditions on Vibration and Power of Wind Turbine
    ZHANG Jianwei, WANG Jianwen, YAN Sijia
    Journal of Engineering Thermophysics. 2025, 46(5): 1477-1487.
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    In this paper, a dynamic rotating platform for wind turbines is designed, and the rotating platform is manufactured according to the design scheme. The running program is written by the BASIC language, and the start time of the tested signal is calibrated by the photoelectric sensor. The platform system can dynamically simulate the yaw process of wind turbines, which is more suitable for the actual operation of wind turbines.Using a dynamic rotating platform, the effects of yaw speed and yaw delay time on wind turbine vibration and power were studied. It was found that during the yaw process, the vibration of the wind turbine showed that the slower the yaw speed, the faster the vibration acceleration value increased. The delay time can reduce the vibration acceleration value during the yaw process. When the yaw angle of the wind turbine is 30°, the vibration acceleration value in the Y direction decreases by 0.457 m/s2 after adding the delay time. And it is found that the faster the yaw speed, the greater the influence of the delay time. Finally, a comprehensive analysis of the vibration and power of the wind turbine during the yaw process is carried out. The yaw speed that takes into account high output power and low blade damage is obtained, which provides direct and important experimental basis and new ideas for wind turbine operation safety and yaw control strategy.
  • Numerical Research on Flow Field of the Last Stage Turbine and Axial Exhaust Diffuser
    QIU Bin, FU Jinglun, SONG Yufeng, KONG Xiangling
    Journal of Engineering Thermophysics. 2025, 46(5): 1488-1499.
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    The exhaust diffuser, downstream the last stage turbine, plays a role of guiding the airflow and recovering kinetic energy, which is one of the most important components of the gas turbine. In this paper, the coupled flow field in last stage turbine and exhaust diffuser of an Fclass heavy duty gas turbine are studied by using CFD. The development mechanism of the coupled flow field under different operational conditions was analyzed. The interactions between the flow characteristics of the last stage turbine and exhaust diffuser were clarified. And relationships between the aerodynamic performance parameters of turbine and diffuser were discussed. The results show that there are formulas to calculate the last stage turbine efficiency and the total pressure loss of diffuser by the pressure recovery coefficient of the diffuser under different working conditions. The pressure recovery ability in the diffuser is mainly attributed to the annular diffuser, and the total pressure loss is mostly come from the flow in the conical diffuser. The radial distribution of total pressure and axial velocity at the turbine outlet imposed strong influence on the pressure recovery and total pressure loss of the downstream diffuser. Conversely, the diffuser feeds the turbine stage with the circumferential non-uniform flow field distributions. The circumferential nonuniformity of the flow field in the diffuser is depended on the distribution of the exit swirl angle of the upstream turbine.
  • Study on Loss and Deviation Models for Fan/Compressor Variable Camber Inlet Guide Vane
    YANG Nanshan, FEI Teng, JI Lucheng, ZHOU Ling
    Journal of Engineering Thermophysics. 2025, 46(5): 1500-1511.
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    Empirical model plays an important role in compressor through-flow design. This paper describes loss and deviation models of two-dimensional compressor variable camber inlet guide vane devices. First, a series of plane cascades with different geometry parameters were generated based on the thickness distribution of NACA 65-010 airfoil, and then the numerical calculation was carried out systematically under the condition that the inlet Mach number is 0.4. Based on the calculation results, dealing with the main cascade geometry parameters, such as cascade solidity, blade maximum relative thickness and back blade’s camber angle, the loss and deviation model of cascades at design operating condition is given. Then, taking incidence angle and back blade’s rotation angle into account, the loss and deviation model of cascades at off-design operating condition is given. Finally, through compared with the numerical calculation results of new cascades, it is found that the models can predict loss and deviation well, which indicates that the models have practical value in engineering.
  • Optimization Design of Transonic Compressor Blade Based on Support Vector Regression and Virtual Sample Technique
    HU Handuo, SONG Yanping, YU Jianyang, YIN Shilong, MA Jiaping
    Journal of Engineering Thermophysics. 2025, 46(5): 1512-1519.
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    With the development of artificial intelligence, machine learning technology has been widely used in the field of turbomachinery optimization design. Due to the high cost of obtaining samples whether from wind tunnel experiments or numerical simulations, the reliability of prediction models and optimization results is limited by the number of samples. To solve the small sample problem in the optimization of transonic compressor, support vector regression is selected as the prediction model, which is suitable for small sample learning. Besides, mega-trend diffusion is used to generate virtual samples to improve accuracy. A multi-objective optimization is carried out on the transonic compressor Rotor 37. Applying virtual samples to improve the prediction model, the isentropic efficiency and total pressure ratio of the optimized blade at the design point are increased by 2.3% and 18%, respectively. Moreover, the choked massflow rate is also increased. These results verify the feasibility of the virtual sample technique for aerodynamic optimization design. 
  • Numerical Investigation on Subcooled Boiling Characteristics in Petal-shaped Fuel Rod Bundle Channel Under Cosine Heating Conditions
    CAI Weihua, HUANG Zequan, MENG Xiangfei, ZHANG Wenchao
    Journal of Engineering Thermophysics. 2025, 46(5): 1520-1527.
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    Petal-shaped fuel rods are a new type of fuel element. In order to clarify the subcooling boiling flow and heat transfer characteristics within the petal-shaped fuel assembly under cosine heating conditions. Based on the Eulerian two-fluid model and the wall boiling model, a numerical analytical model of subcooling boiling in a 3×3 petal-shaped fuel rod bundle channel under cosine heating conditions is established. The distribution of vacuole share and heat transfer characteristics in the subchannels at different positions are analyzed. It is found that there is a significant difference between the values of void fraction in different subchannels in axial and circumferential directions. The distribution characteristics are jointly determined by the bubble diameter and bubble nucleation density. The results of the analysis of the heat transfer characteristics show that the heat transfer coefficients of different subchannels show an increasing and then decreasing trend under the influence of cosine heating. In the subcooled boiling region. the boiling heat flow increases with the increase of vacuole share. The related research results can provide a theoretical basis for the application of petal-shaped fuel elements in reactors.
  • Experimental Study on Supercritical Water Flooding in High Water Cut Heavy Oil Reservoirs
    MIAO Yan, ZHAO Qiuyang, WANG Xuetao, LEI Yuhuan, GAO Yunbo, JIN Hui, GUO Liejin
    Journal of Engineering Thermophysics. 2025, 46(5): 1528-1533.
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    Elevated water cut obstructs recovery of heavy oil in later stage of heavy oil reservoir exploitation. This paper simulates such scenarios using one-dimensional sandstone cores filled with saturated oil utilizing hot water flooding. Subsequently, we conducted indoor flooding tests for supercritical water flooding, high-pressure hot water flooding, and superheated steam flooding. Results reveal that supercritical water flooding yields the highest recovery rate (96.27%) and superior in-situ upgrading compared to hot water flooding and superheated steam flooding. The mechanism for enhancing oil recovery via 400°C, 25 MPa supercritical water flooding in a high water cut heavy oil reservoir environment lies in the occurrence of thermal fluid breakthrough phenomenon, miscible flooding, and hydrothermal pyrolysis of heavy oil under supercritical water conditions.
  • Transfer Mechanism of Low-density Lipoprotein in Human Healthy Aorta
    QIAO Yonghui, LUO Kun, FAN Jianren
    Journal of Engineering Thermophysics. 2025, 46(5): 1534-1539.
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    The human aorta is a high-risk area for atherosclerosis, and the distribution pattern of low-density lipoprotein (LDL) is closely related to the formation of atherosclerosis. In this study, three-dimensional geometric models of the two human healthy aortas were reconstructed based on clinical computed tomography images (CTA). The computational hemodynamics method was applied to simulate the spatiotemporal evolution of pulsatile blood flow inside the aorta. The convectiondiffusion transport equation was adopted to predict the movement of LDL in the aorta. The heat transfer process of blood flow was also considered. Results show that LDL is preferentially enriched in the low wall shear stress (TAWSS) area of the aortic wall (r > 0.54). Wall temperature is positively correlated with LDL concentration (r > 0.58). Regions with longer relative residence time (RRT) and lower topological shear variation index (TSVI) all exhibit high LDL concentrations. In conclusion, the numerical simulation method was used to initially reveal the transfer mechanism of LDL in the healthy aorta, which is conducive to measuring and regulating the deposition and polarization of LDL, and provides a theoretical basis for in-depth exploration of the pathogenesis of atherosclerosis.
  • Study of Droplet Collision and Fusion Characteristics in Centrifugal Field
    XIA Yang, WANG Hongda, FAN Jianhua, YAO Xuan, XU Jiawei
    Journal of Engineering Thermophysics. 2025, 46(5): 1540-1548.
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    In pursuit of more efficient droplet mixing, this study proposes a method for evaluating droplet collision and fusion on passive driving microfluidic chips. The method utilizes specific concentration values to mark and capture the distribution of each liquid phase, and employs semiquantitative method to evaluate the efficiency of droplet mixing by discussing the distances between barycenters. The effects of different Reynolds and Bond numbers, as well as wall wetting properties, on droplet collision and mixing are studied. Simulation results show that the Reynolds number (Re) is crucial for the distribution pattern of droplet mixing, and an increase in Re effectively improves mixing efficiency. However, the Bond number only controls the collision location of droplets in specific directions and has a smaller impact on mixing efficiency. Wall wetting property also has a significant effect on droplet movement and collision locations. The mixing efficiency is higher when the contact angle is 60◦ < α < 80◦.
  • Simulation of Hydrogen Diffusion in Confined Channels
    ZHANG Jie, ZHANG Bowei, JIN Hui
    Journal of Engineering Thermophysics. 2025, 46(5): 1549-1558.
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    Hydrogen diffusion in confined channels is widely used in energy storage, chemical production, biomedicine and other fields. When the size of the confined channel is close to the mean free path, the wall surface produces a non-negligible effect on the flow of fluid, and thus hydrogen tends to exhibit transport characteristics different from those of the macroscopic transport. In this paper, hydrogen diffusion within carbon nanotubes in the transition flow regime (0.1 < Kn < 10) was explored using molecular dynamics. The results indicated that factors such as size would affect the diffusion mechanism and self-diffusion coefficient of hydrogen within the confined channel. Although the confinement and surface effects of carbon nanotubes have a limiting effect on the diffusion, the relationship between temperature and diffusion coefficient still follows the Arrhenius equation, and the self-diffusion coefficient and the Knudsen number presented some degree of linear relationship. Based on this, an empirical formula for the self-diffusion coefficient of hydrogen confined in carbon nanotubes in the transition flow regime was proposed, qualitatively illustrating the dependence of the self-diffusion coefficient on the temperature, density and size.
  • Steady-state Heat Current Modeling and Performance Analysis of Alkaline Electrolysis Systems
    JIANG Yichong, LI Qiang, ZHAO Tian, ZHANG Ye, MA Huan, WANG Jingbo, LIANG Zheng, CHEN Qun
    Journal of Engineering Thermophysics. 2025, 46(5): 1559-1568.
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    Hydrogen energy has many advantages, such as helping to absorb renewable energy and promoting large-scale peak regulation of the power grid, there is a huge demand for hydrogen energy in the future energy system. Alkaline water electrolysis is one of the mainstream hydrogen production technologies, and its performance research and optimization are of great significance. In this paper, combined with the component modeling of the alkaline water electrolysis hydrogen production system and the equivalent circuit modeling of the physical processes in the stack, a crossscale heat current model of the system isomorphic to the circuit grid is established, the influence of temperature, pressure and other parameters on the system performance and internal characteristics is studied, and the changes of chamber voltage and stack inlet and outlet temperature are analyzed when the cooling water flow rate and electrolyte flow rate change, It is of great importance for the optimization of thermal management systems and their collaborative simulation with the power grid.
  • Numerical Study on Heat Transfer and Flow Characteristics of SCO2 in Wavy Micro Channel Heat Exchanger
    HU Jun, RAO Yu, ZHANG Yueliang
    Journal of Engineering Thermophysics. 2025, 46(5): 1569-1579.
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    According to the requirements of supercritical carbon dioxide(SCO2) Brayton cycle for compact and efficient heat exchanger, a micro-channel heat exchanger suitable for additive manufacturing is designed. The adaptive flow channel of the heat exchanger can not only match the density change of supercritical carbon dioxide, but also the structural design of wavy channel and fins greatly improve the performance of the heat exchanger. The flow and heat transfer characteristics are studied by numerical simulation, and the influence of mass flow rate on flow and heat transfer is explored. The research results show that compared with the mainstream printed circuit heat exchanger, the compactness of the microchannel heat exchanger is significantly improved; compared with other adaptive channel heat exchangers, the comprehensive performance of the cold and hot side fluids is respectively improved by about 85% and 67%. It has excellent thermal hydraulic performance, which fully proves the innovation and advancement of this heat exchanger in the existing supercritical carbon dioxide heat exchangers.
  • Experimental Study on Heat and Moisture Recovery of Flue Gas Based on Hydrophilic Hollow Fiber Membranes
    NING Zhuo, CHEN Ying, XIAO Liehui, YANG Minlin, HUANG Simin, YANG Yu
    Journal of Engineering Thermophysics. 2025, 46(5): 1580-1585.
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    Aiming at the problems of high cost and low filling rate of flue gas heat and moisture recovery by porous ceramic membrane, a new method using hydrophilic hollow fiber membrane was proposed in this paper. Compared with porous ceramic membrane, hollow fiber membrane has higher cost effectiveness and high packing density. In order to explore the thermal and wet recovery performance of flue gas of hollow fiber membrane components, this study built a thermal and wet recovery experimental platform for flue gas, compared three membrane materials and analyzed the thermal and wet recovery performance of membrane components under different working conditions. In the scope of this study, the maximum recovered water flux and recovered heat flux were 5.8 kg·m−2·h−1 and 13.44 MJ·m−2·h−1, respectively, indicating the excellent recovery performance of the hydrophilic hollow fiber membrane. Increasing flue gas flow and temperature, increasing cooling water flow or reducing cooling water temperature can improve the recovery performance. With the increase of hydrophilicity of membrane materials, the recycling performance of membrane components is improved. This study provides the experimental basis for the application of hydrophilic hollow fiber membrane in the field of flue gas heat and moisture recovery.
  • Multi-objective Topology Optimization of LSM-YSZ Microstructure in SOFC Cathodes
    DU Yufeng, FU Lei, XUE Dingxi, YI Bingyao, LI Guojun, LIU Keqin
    Journal of Engineering Thermophysics. 2025, 46(5): 1586-1593.
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    Due to issues such as interlayer thermal mismatch, uneven heat source distribution, and hindered heat and mass transfer in porous materials at high temperatures, solid oxide fuel cell (SOFC) can experience severe thermal stress, impacting their output power and lifespan. This paper focuses on the straight pore channel microstructure of the LSM-YSZ cathode’s three-phase material in planar SOFCs. By employing a dual-scale asymptotic homogenization method combined with a novel effective medium theory, a multi-objective topology optimization design method for the cathode microstructure is established. The topology optimization design resultes in 5 distinct microstructures with superior performance. The optimized cathode microstructure features LSM particles embedded around a central YSZ scaffold. Compared to typical cathodes, the optimized microstructure not only exhibits a lower coefficient of effective thermal (CET) and higher effective thermal conductivity, but also significantly increases the triple-phase boundary (TPB) density, potentially reaching up to 6 times that of typical cathodes. The results of the cathode microstructure topology optimization provide valuable guidance for the preparation of efficient electrodes.
  • Study on Transpiration Cooling of Microchannel in Liquid Rocket Thrust Chamber
    ZHEN Yunchao, LI Yingge, LIU Xue, JIA Zhenjian, ZHOU Weixing
    Journal of Engineering Thermophysics. 2025, 46(5): 1594-1605.
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    The wall of liquid rocket thrust chamber is washed by high enthalpy flow for a long time, which brings great challenge to the stable and safe operation of the engine. In this paper, micro-scale wire mesh transpiration channel and macro-scale transpiration model of liquid rocket thrust chamber were established respectively to explore the flow heat transfer characteristics under the condition of transpiration cooling. The results show that the increase of coolant flow rate in the pore scale transpiration channel can significantly increase the flow rate in the channel and reduce the outlet temperature, and the small porosity can improve the heat transport capacity of the coolant. Within a certain range, the greater the flow rate of transpiration coolant, the higher the overall transpiration cooling efficiency of thrust chamber; The larger the porosity, the higher the cooling efficiency of thrust chamber contraction section.
  • Accelerating the Design of Near-Field Thermal Modulators With Multilayer Hyperbolic Materials by Machine Learning
    LIAO Tuwei, JU Shenghong, ZHAO Changying
    Journal of Engineering Thermophysics. 2025, 46(5): 1606-1612.
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    Near-field thermal radiation modulation holds broad application prospects in thermal diodes, thermal transistors, and thermal memory devices. However, designing near-field radiation structures is a complex problem characterized by high degrees of freedom and high computational costs. Machine learning offers more convenient and efficient technical support for the design of new materials. This paper focuses on the thermal regulator based on multilayer film structures of different hyperbolic materials, MoO3 and hBN. By combining autoencoders and Bayesian optimization, we optimize the rotation angles of the multilayer films to achieve the maximum rotational thermal modulation ratio. The optimized multilayer structure achieves a contrast ratio of 11.27, which is greater than the best result of the regulation contrast ratio for homogeneous material combinations. The modulation mechanism is analyzed using the energy transmission coefficient and the near-field thermal radiation spectrum. It is found that the significant modulation contrast obtained is mainly due to the mismatch of the hyperbolic volume phonon polaritons in the type I hyperbolic bands of hBN, providing new insights for the design of near-field thermal radiation transfer.
  • The Computational Study of Al-Based Metal-Organic Frameworks Membrane for CO2 Separation
    LIU Jiaxiang, LIU Xiaohui, TAO Wenquan, LI Zhuo
    Journal of Engineering Thermophysics. 2025, 46(5): 1613-1618.
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    In this study, the GCMC and MD simulation methods were performed to study the CO2/N2 and CO2/CH4 separation performance of the Al-based metal-organic frameworks (MOFs) membrane. The flux and selectivity of the membranes were estimated by calculating the adsorption and diffusion of the gas molecules in the MOFs. The results show that CAU-10 and its derivatives have good affinity with CO2, and the CO2/N2 separation performance of CAU-10-F and CAU-10-pydc membranes exceed the Robeson upper bound. By analyzing the diffusion energy barrier of gas molecules in different membranes, the strategy that using mixed ligands to synthesize the MOFs was proposed, and the F_pydc membrane based on the strategy was designed with improved permeability and selectivity. This study provides a new idea for development of high-performance MOFs membranes.
  • Impact of Phonon Ballistic Transport on Electrical Performance of GaN Transistors
    SHEN Yang, CAO Bingyang
    Journal of Engineering Thermophysics. 2025, 46(5): 1619-1623.
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    This paper investigates the self-heating effects in Gallium Nitride (GaN) Transistors using a combination of TCAD electrothermal simulations and phonon Monte Carlo (MC) simulations. By reconstructing the channel temperature distribution predicted by MC simulations within TCAD, the impact of phonon ballistic transport on the degradation of device drain current is analyzed. The results indicate that the decrease in drain current due to self-heating is primarily associated with the cross-plane ballistic effect. Although the ballistic effect related to the heat source size comparable to phonon mean free path (MFP) significantly increase the temperature near the drain side under the gate, this region’s electron velocity becomes saturated under high electric fields, rendering it almost unaffected by the temperature rise.
  • An Electrochemical-Thermal Coupling Model for Lithium Ion Batteries Based on Explicit Scheme
    LI Weizhuo, BAO Zhiming, GAO Qingchen, DU Qing, JIAO Kui
    Journal of Engineering Thermophysics. 2025, 46(5): 1624-1633.
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    In this work, an electrochemical-thermal coupling model suitable for large scale thermal management simulation is developed based on the open-source platform, OpenFOAM. The electrochemical sub-model is coupled with the three-dimensional thermal sub-model in a one-dimensional explicit scheme, and the coupling process traverses each grid of the thermal computational domain. This allows the model to quickly and accurately describe the voltage and temperature changes at different C-rates. Using this model, the effects of battery resistance changes, heat generation mechanism, and cell inconsistency on the temperature distribution of a module are further explored. The results show that the ohm heat is the main heat source at high C-rates, and the maximum temperature difference decreases as the inconsistent cell moves from the outermost to the middle.
  • Thermophysical Properties Reinforcement of Ternary Carbonate Materials by Nanoparticles
    XU Meiyang, WEI Gaosheng, CUI Liu, DU Xiaoze
    Journal of Engineering Thermophysics. 2025, 46(5): 1634-1639.
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    Molten salt is widely used in the field of solar thermal utilization due to its advantages of wide liquid temperature range and high heat storage capacity. The significant disadvantage of molten salt is the low thermal conductivity, and the addition of nanoparticles can effectively strengthen the heat transfer ability of molten salt. In this paper, ternary carbonates are used as the base salt, and zero-dimensional Al2O3 nanoparticles, one-dimensional multi-walled carbon nanotubes, and two-dimensional graphene nanosheets with different combinations of multidimensional nanoparticles are added to prepare new composite molten salt materials, and the thermal diffusivities of the composite carbonates in the liquid state are measured by the laser flash method at different temperatures, so as to analyze the effect of multidimensional nanoparticles on the reinforcement of ternary carbonates’ thermophysical properties. The experimental results show that zero-dimensional alumina nanoparticles and two-dimensional graphene sheets have synergistic strengthening effects. With the addition of zero-dimensional alumina nanoparticles and an additional 0.5% mass fraction of 2D graphene nanosheets, the thermal diffusivity of the composite carbonates can be enhanced by up to 54.08%, and the prepared composite carbonates have better stability.
  • Screening and Thermophysical Properties Study of Mixed Molten Salts With Same Cation
    WANG Yuanyuan, LU Yuanwei, HE Cong, WU Yuting, ZHANG Cancan
    Journal of Engineering Thermophysics. 2025, 46(5): 1640-1645.
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    To develop heat transfer/storage molten salt materials that matched the third-generation solar thermal power generation technology, NaNO3, NaOH, and Na2CO3 molten salts with the same cation were selected as the research objects. Phase diagram calculation for the NaNO3-NaOHNa 2CO3 ternary system was carried out based on thermodynamic theory and phase diagram software, and the preferred mixed molten salt was determined by experiment. The results indicated that there was one eutectic point in the ternary system calculated by the Direct method, while the FactSage software simulation predicted that there were four eutectic points in the ternary system. The mixed molten salt corresponding to the eutectic point (E4) with the lowest melting point was selected as the preferred molten salt. The melting point of preferred molten salt was 246.44°C, the decomposition temperature was 649.5°C, and the average specific heat capacity was 1.68 J·g−1·K−1, which met the requirements as the medium and high temperature heat transfer/storage material.
  • Application of AI Technology to Improve the Accuracy of Non-contact Temperature Measurement
    SHAO Yice, FENG Chuangxin, WANG Hong, ZHU Xun, CHEN Rong, DING Yudong, LIAO Qiang
    Journal of Engineering Thermophysics. 2025, 46(5): 1646-1651.
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    Temperature measurement is an essential part of epidemic prevention. Due to the strong infectivity of COVID-19, contact temperature measurement cannot be used. However, external factors interfered with non-contact temperature measurement, resulting in low accuracy. In this paper, the effect of various factors on non-contact temperature measurement is comprehensively considered, and two compensation correction models based on the Support Vector Machine (SVM) and the Artificial Neural Network (ANN) is established. A large number of temperature measurement data are obtained by simulating human body temperature acquisition, and then the data are used to train the model. Finally, the correction results of the two models are compared and evaluated. The results show that the correction operation time of the SVM model and ANN model is very short. Both models can effectively improve the accuracy of non-contact temperature measurements. The accuracy and stability of the SVM model are better, but with the increase in sample size, the ANN model shows the potential to improve the correction accuracy further. 
  • Study on the Mechanism of Functionalization on Thermal Transport of Carbon nanotube Nanofluids
    TIAN Wenshuang, BAO Yanqiong, QIN Guangzhao, ZHENG Xiong
    Journal of Engineering Thermophysics. 2025, 46(5): 1652-1660.
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    Carbon nanotube (CNT) nanofluids show significant potential for energy systems due to their exceptional thermal conductivity, but colloidal instability hinders practical applications. While the introduction of functional groups on CNT serves as an effective strategy to enhance the dispersion stability of CNT nanofluids, its impact on thermal transport remains unclear. This study integrates experiments and molecular dynamics simulations to analyze thermal conductivity in pristine, CNT-OH, and CNT-COOH nanofluids. Contrary to expectations, chemical functionalization reduces heat transfer efficiency. Thermal resistance analysis, hydrogen bonding quantification, and water mobility calculations reveal that functional groups introduce interfacial phonon scattering and disrupt nanoscale heat pathways, despite improving hydrophilicity and stability. The work highlights a critical trade-off: functionalization stabilizes colloids but degrades thermal performance by perturbing atomic-level energy transfer mechanisms. These findings establish design principles for optimizing nanofluids, emphasizing the need to balance stability enhancements with thermal property preservation in next-generation energy systems.
  • Study on the Radiation Characteristics of Chlamydomonas Reinhardtii Considering Multi-component Complex Structure
    LI Xingcan, JIANG Miao, LIN Li, LÜ Chenghao, XIE Bowei
    Journal of Engineering Thermophysics. 2025, 46(5): 1661-1667.
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    In this paper, a multi-component complex structure cell model considering microalgae organelles as well as shapes is proposed, and the theoretical calculations are carried out by the DDA method and verified by comparing with the experimental data, meanwhile a lateral comparison analysis is carried out with a variety of simplified models. The results show that the calculation accuracy of the multi-component complex cell model is higher, the error of the absorption crosssection and scattering cross-section is reduced by more than 18% compared with the homogeneous sphere model and core-shell sphere model, and the scattering phase function is in good agreement with the experimental results. In addition, the theoretical calculation error can be reduced when the influence of the growth base liquid at continuous wavelength is taken into account.
  • Key Role of Atmosphere Control in the Pyrolysis-Gasification Process for Municipal Sewage Sludge
    MA Mingyan, XU Donghai, YANG Lijie, WANG Shuzhong, HE Yaling
    Journal of Engineering Thermophysics. 2025, 46(5): 1668-1673.
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    Pyrolysis-gasification process is a promising technology for the sustainable management of municipal sewage sludge. However, the elemental composition and structural properties of sludge biochar, which are significantly influenced by the pyrolysis atmosphere, play a crucial role in the subsequent gasification process. This study aims to uncover the impact of pyrolysis atmosphere on the reactivity of biochar gasification by evaluating the sludge biochar obtained under different pyrolysis atmospheres. The results revealed that a CO2-enriched atmosphere notably increase the C content of the pyrolysis biochar. The C/H and C/O ratios of biochar under a 30%N2 +70%CO2 are 1.27 and 1.88 times higher than those under 100% N2, respectively. The CO2 atmosphere promoted deoxygenation and aromatization, enhancing the graphitic structure of biochar. In gasification, biochar from a 100% CO2, at low heating rates (10 and 20 °C/min), shows 1.14 and 1.15 times higher overall and local gasification indices compared to that from 100% N2. This research highlights the importance of the interplay between biochar preparation and gasification heating rates, which is key to optimizing gasification reaction parameters for efficient sludge management.
  • Extension of High Load Operation of Premixed Charged Hydrogen/Diesel Dual Fuel Engine at Low Speed
    SHI Jinhong, WU Zhifei, ZHANG Lijun, LIU Chunli, XU Ming
    Journal of Engineering Thermophysics. 2025, 46(5): 1674-1682.
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    Extension of high load operation of premixed charged hydrogen/diesel combustion mode at low speed was investigated on a modified four-cylinder diesel engine, which proposes port fuel injection of hydrogen and direct injection of diesel. The results show that break thermal efficiency is consistent with the original engine, SOOT emission reduces 16.5%, NOx emission increases 13.5% and the maximal pressure release rate rise to 1.15 MPa/°CA at 1000 r/min speed-60% load operation, 6 L/min flow rate of hydrogen. With the increasing of engine load, NOx emission increases rapidly and the maximal pressure release rate exceeds standard value under the same engine speed and hydrogen flow rate, which limit the operation range to a higher load. Under the condition of in-cylinder two stage direct injection combined with EGR, the general optimization direction of load extension of premixed charged hydrogen/diesel engine is obtained by reducing pilot quantity, retarding pilot timing and increasing EGR. Compared with the original engine, NOx emission reduces 37.5% and the maximal pressure release rate is reduced to 1.0 MPa/°CA at pilot quantity 1.8 mg/cyc, pilot timing −22°CA and EGR ratio 22%.
  • Study on Potassium Release Characteristics During the Combustion Process of Pine Wood and Papermaking Sludge
    LÜ Jianju, WU Dongyin, ZHAO Jing, WEI Xiaolin, TENG Qinzheng, YANG Benchao
    Journal of Engineering Thermophysics. 2025, 46(5): 1683-1691.
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    During the thermal utilization process of high-alkali fuels, gas-phase alkali metals will deposit on the surface of heat exchanges, endangering the safe operation of the equipment. Biomass is a typical high-alkali and zero-carbon fuel. Papermaking sludge has biomass characteristics, and the potassium content of the sludge used in this paper is relatively close to that of common pine wood. In this paper, the physicochemical properties and occurrence forms of alkali metals were studied based on methods such as thermogravimetry and stepwise extraction of pine and papermaking sludge. Then, tunable diode laser absorption spectroscopy technology was used to study the release characteristics of alkali metals in different occurrence forms during the combustion process of pine and papermaking sludge. The results showed that the potassium content in pine wood and papermaking sludge was basically the same, with 887.3 mg·kg−1 and 961.5 mg·kg−1, respectively. However, the amount of gaseous potassium released during pine wood combustion was much higher than that in papermaking sludge. The release of gaseous potassium from pine wood reached a maximum of 86 μg·m−3 after entering the flame for 41 s. The release curve of gaseous potassium from papermaking sludge showed a saddle shape with a maximum of 15 μg·m−3 at 48 s and 18 μg·m−3 at 62 s, respectively.
  • Visualization of the Effect of Pre-chamber Structure Parameters on Ammonia Combustion Characteristics
    SHI Song, TIAN Jiangping, YE Mingyuan, YIN Shuo, YANG Hongen, CUI Zechuan
    Journal of Engineering Thermophysics. 2025, 46(5): 1692-1700.
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    In this paper, the combustion process of ammonia pre-chamber jet ignition is visualized using high-speed photography. The experimental results show that: a larger pre-chamber volume can provide a larger ignition energy, leading to a reduction in the ignition delay and combustion duration; the pre-chamber volume is the most influential factor for the ignition position of the mixture in the main combustion chamber, and the larger the pre-chamber volume is, the closer the ignition position is to the pre-chamber. Under good combustion conditions, a pre-chamber with a small aperture has better combustion characteristics, and despite the prolonged ignition delay, the combustion duration can be significantly shortened, especially in high-temperature environments.
  • Study on Distribution Characteristics and Influencing factors of NH3/NO Molar Ratio in Catalyst Nanopores Under Diffusion Mass Transfer
    LI Peiyuan, XIN Qi, JIANG Ye, YANG Yang, ZHENG Chenghang, YANG Zhengda
    Journal of Engineering Thermophysics. 2025, 46(5): 1701-1707.
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    NH3/NO molar ratio is an important parameter of SCR process. Under the background of deep peak shaving of thermal power generation, the denitration efficiency can be effectively improved and ammonia slip can be reduced by adjusting the appropriate NH3/NO molar ratio. The diffusion process of NH3/NO in a single pore structure was simulated by molecular dynamics simulation method, and the NH3/NO molar ratio under different pore positions and time conditions was quantitatively counted. The results show that the NH3/NO molar ratio increases after diffusion, which explains the reason why the NH3/NO molar ratio is less than 1 in the actual ammonia injection; With the increase of temperature, the component diffusivity increased, and the NH3/NO molar ratio increased; NH3 is more sensitive to the change of hydroxyl site density. With the increase of site density, the diffusivity decreases, and the NH3/NO molar ratio decreases; Increasing the pore width is conducive to the full diffusion and weakens the effect of diffusion on the NH3/NO molar ratio. The above conclusions provide theoretical guidance for optimizing the NH3/NO molar ratio at the macro level from the micro perspective.
  • Study of the Ultra-High Pressure Spray Dynamics in the Full Field Under High Ambient Density Condition
    AN Chen, LIU Long, LUO Hongliang, WANG Lu
    Journal of Engineering Thermophysics. 2025, 46(5): 1708-1718.
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    To understand the dynamics of ultra-high pressure injection spray under high ambient density conditions, the spray characteristics in the near and far fields are investigated using longdistance microscope and schlieren, respectively. The effects of nozzle diameter, injection pressure, and ambient density on spray characteristics are discussed in detail. Moreover, the zero-dimensional spray models are compared with experimental data. The results indicate that Zhou’s penetration model, with a modified K1 parameter, demonstrates good agreement with the measured results. Additionally, the near-field spray dynamics are analyzed. Different from the far-field spray development, the injector with a smaller nozzle diameter exhibits longer penetration due to a faster pressure rise at the SAC and nozzle hole. Furthermore, the evolution of spray penetration could be structured into pre-acceleration stage and main-acceleration stage due to the trapped effect of residual diesel on fresh diesel. The near-field spray is mainly influenced by the initial in-orifice fluid state and injection parameters, rather than the interaction between the spray and gas. Finally, taking the nozzle diameter into consideration, an empirical correlation for near-field penetration is developed. 
  • Study on NO formation in Ammonia/Methane Laminar Premixed Flames
    JI Feiyu, LI Qing, MA Liuhao, DU Jianguo, WANG Yu
    Journal of Engineering Thermophysics. 2025, 46(5): 1719-1727.
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    Using ammonia (NH3)/hydrocarbon mixture for combustion is regarded as an effective way to realize carbon peaking and carbon neutrality, but there exists the challenge of high NOx emission. In the literature, there is a lack of basic flame experimental investigation on NO formation in ammonia combustion. Therefore, this study built an experimental setup for calibration-free, moisturized and quantitative NO concentration measurement in a McKenna NH3/CH4 laminar premixed flame. The effects of equivalence ratio and ammonia doping ratio on the characteristics of NO formation were investigated, and the key reaction paths affecting NO generation under different working conditions were analyzed. The results showed that: at low equivalence ratios, the NO concentration along the axial direction showed a sharp increase to peak at about 2 mm and then leveled off; But at high equivalence ratios, the NO emission concentration increased to peak and then decreased with the increase of axial height; For a certain equivalence ratio, the NO concentration showed an increasing and then decreasing trend with the increase of ammonia doping ratio; With the increase of the equivalence ratio, the NO concentration decreased and the peaking condition gradually shifted to the low ammonia doping ratio; Compared with the experimental results, the prediction of Okafor mechanism is accurate at low equivalence ratio, while further study is needed at high equivalence ratios. 

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