最新刊期
卷 46 ， 期 6 ， 2025
- 摘要：With the rapid development of microelectromechanical systems (MEMS) technology, heat dissipation with a high heat flux in a limited space has become a key problem restricting the efficient and stable operation of equipment. Heat-dissipation technology for liquid-liquid two-phase flows in microchannels has emerged as an effective solution to this problem. This paper first reviews the classification of liquid-liquid two-phase flow patterns in microchannels. Compared with other flow patterns, slug flow is a critical flow pattern that significantly enhances the heat and mass transfer performances. This paper summarizes and analyzes the current research progress on the heat transfer of liquid-liquid two-phase slug flows in microchannels. Currently, most studies in this field rely heavily on numerical simulations, with relatively few experimental investigations. Existing numerical models often simplify the complexities of physical phenomena, and many have not been validated using experimental data. Furthermore, these models frequently employ macroscopic numerical methods such as the volume of fluid (VOF) method and finite volume method (FVM) to capture two-phase interfaces. However, the accuracy of these models when calculating the flow field, temperature field, and rates of heat and mass transfer at a two-phase interface requires further verification. Experimental studies tend to focus on minichannels, primarily measuring macroscale global data such as the total pressure drop, overall heat transfer coefficient, and average fluid temperature. There is a notable lack of research involving microscale local and instantaneous data, such as the local heat transfer coefficient and detailed flow and temperature fields. Finally, future directions for the research on heat transfer for liquid-liquid two-phase slug flows in microchannels are discussed.关键词：liquid-liquid two-phase flow;microchannels;heat transfer;slug flow;multiphase flow290|204|0更新时间：2025-12-03
- 摘要：The thermal-management system of a new energy vehicle is a key to ensuring thermal safety and comfort. Battery thermal management and cabin cooling are strongly coupled, resulting in poor dynamic characteristics. Thus, this study examined a transcritical CO2 vehicle thermal-management system, built an Amesim model of a thermal-management system and control system based on the co-control of thermal comfort and battery temperature, and analyzed the thermal-management system under different scenarios and conditions. It was demonstrated that the thermal-management system was able to quickly achieve a comfortable thermal environment of the cabin and ensure a suitable battery temperature under various conditions, with less fluctuation, prompt response, and excellent anti-disturbance performance. Compared to the traditional control method based on cabin temperature, this method could provide excellent cabin thermal comfort at all times, which verified the superiority of a thermal-management system based on this control method.关键词：vehicle thermal management;CO2;thermal comfort;battery cooling215|114|0更新时间：2025-12-03
- 摘要：Battery thermal-management systems based on direct refrigerant cooling are characterized by multiple sources of disturbance, strong coupling, and nonlinearity, making regulation of the temperature difficult through traditional proportional-integral-derivative (PID) controllers. In this study, a dynamic step-down model of a direct cooling thermal-management system was first established based on the first principle, and its linearized model was verified using experimental data. Based on this model, a linear time-varying model-based predictive control strategy was designed and compared with PID control under two operating conditions: battery cooling and the worldwide harmonized light vehicles test cycle (WLTC). Under the condition of constant battery heat generation, the stabilization time for the battery temperature from 50 ℃ to 30 ℃ was 262 s for the model predictive control (MPC) strategy and 952 s for the PID control strategy. At the same time, the MPC reduced the energy consumption by 5.57%. Under the WLTC condition, the temperature fluctuation of the PID control was large, with a maximum deviation of 2.9 ℃, while the MPC was able to respond quickly to a heat load change and stabilize the control temperature at 30 ℃. The standard temperature deviations of the PID and MPC control strategies were 1.7 ℃ and 0.06 ℃, respectively. In summary, the MPC strategy was superior to the PID control in terms of temperature regulation speed, energy efficiency, and robustness.关键词：battery thermal management;direct cooling system;refrigeration system modeling;model predictive control121|145|0更新时间：2025-12-03
- 摘要：A numerical simulation model was used to investigate the impact of refrigerant phase change on the temperature control of lithium-ion batteries. A direct cooling system was designed, and an electro-thermal coupled model was established to simulate heat generation in batteries. The Lee model was used for the phase-change simulation. The model reliability was confirmed through experiments, with deviations under 3%. Simulations were conducted under various conditions to analyze the effects of different boundary conditions on the cooling performance of a harmonica-style cold plate and flow channel structures of parallel and serpentine cold plates. The results indicated that at a 2 C rate, the maximum temperature and temperature difference of a direct cooling system were 7.12% and 58.86% lower than those of a liquid cooling system. When the evaporation temperature increased from 10 ℃ to 20 ℃, the pressure difference of the direct cooling plate decreased from 45.74 Pa to 39.48 Pa. A lower evaporation temperature promoted the refrigerant phase transition. An increased liquid phase fraction at the inlet can lower the highest temperature of the battery module, but may lead to greater temperature differences and excess liquid refrigerant. Increasing the effective contact area of the flow channel with the battery bottom aids cooling, and extending the channel length promotes a complete refrigerant phase change.关键词：battery thermal management;direct cooling system;phase transition;flow channel90|101|0更新时间：2025-12-03
- 摘要：An efficient thermal-management system is crucial for the safe operation of lithium batteries. In this study, an embedded composite cooling plate integrating wavy flow channels with a phase-change material (PCM) and liquid cooling was designed for the thermal management of lithium batteries. From the perspective of recovering the latent heat of a thermally saturated PCM, an evaluation method was proposed to quantitatively analyze the latent heat recovery performances, pumping energy consumptions, and overall performances of different structural configurations. The optimal structural configuration was determined by comparing the overall performances. This configuration included a circular flow shape, circular cross-section, double channels, a cross-sectional area of 36 mm2, and a circular arc angle of 150°. The validity of the established numerical model was experimentally verified. Based on the optimal cooling plate structure, the heat generation of lithium batteries during 3 C rate operation was simulated using a surface heat source, and the effects of several delayed-start strategies for liquid cooling based on the PCM liquid-phase fraction on cooling performance were investigated. The results showed that the best temperature performance could be achieved by switching on the liquid cooling when the PCM liquid phase fraction reached 0.6, achieving a maximum temperature for the cooling plate of 38.32 ℃ and maximum temperature difference of 1.66 ℃, while decreasing the running time of the liquid cooling by 50.50% compared with that of the continuous mode.关键词：embedded composite cooling plate;structural optimization design;phase change;latent heat;battery99|85|0更新时间：2025-12-03
- 摘要：A CO2 heat pump air-conditioning system with single-stage compression secondary throttling and a series gas cooler is proposed to enhance the performance of a CO2 heat pump system. The heating performances of secondary and conventional throttling systems to achieve identical supply air temperatures under different ambient temperature conditions were compared experimentally, and the cycle characteristics when the cooling performance of the system was optimal at different ambient temperatures were investigated. The results showed that the implementation of a secondary throttling system could significantly reduce the energy consumption of the CO2 heat pump system, thereby enhancing the system coefficient of performance (COP). Furthermore, the advantages of the secondary throttling system become more pronounced at lower ambient temperatures. Under conditions where the system supply air temperature was 40 ℃ and the ambient temperature was -20 ℃, the power consumption of the secondary throttling system was 256.1 W and 15.4% lower than that of the conventional throttling system, and its COP was 0.67 and 18.3% higher. Under a fresh air environment at -20 ℃, the CO2 heat pump air conditioning system utilizing the secondary throttling could achieve a heating COP of up to 4.33 when the supply air temperature was 40 ℃. Under a fresh air environment at 43 ℃, the system could reach a cooling COP of 2.46 when the supply air temperature was 23.6 ℃. Additionally, it was observed that the cooling performance of the system significantly deteriorated when the ambient temperature exceeded 35 ℃.关键词：automotive air conditioning;CO2 heat pump system;secondary throttling;system performance;electric vehicles88|110|0更新时间：2025-12-03
- 摘要：In response to the escalation of global warming, low efficiency of traditional heating methods, and high pollution levels, this study investigated a novel wide-temperature-zone heat-pump air-conditioning system for buildings, which employs an eco-friendly non-eutectic working fluid. It integrates the single-stage vapor compression cycle and the auto-cascade heat-pump cycle, enabling efficient heating and cooling from -20 ℃ to 40 ℃ ambient temperature. The viability of the system was tested in Shenyang and compared with that of a conventional R134a air-conditioning system for cooling and a coal-fired boiler for heating. The thermodynamic evaluation indicated coefficient of performance of 3-5.47 in the cooling mode and 1.81 in the heating mode at -20 ℃. Experimental validation confirmed stable operation across a range of -20 ℃ to 40 ℃, with a heating coefficient of performance of 1.4 at -20 ℃. This research provides theoretical support for the advancement of green building development using wide-temperature-zone heat-pump technology.关键词：zeotrope;auto-cascade cycle;wide temperature zone;heat pump air conditioning102|93|0更新时间：2025-12-03
- 摘要：As one method to improve the poor thermal conductivity of porous adsorption materials, metals and carbon-containing materials with high thermal conductivity are utilized in the adsorbent aluminum phosphate. Copper powder, aluminum powder metal particles, and graphene nanoplatelets (GNPs) were added to SFO aluminum phosphate (AlPO-SFO) in three different mass fractions (10%, 20%, and 30%). The effects of these different high-thermal-conductivity materials with different mass fractions on the adsorption and refrigeration performances of aluminum phosphate and thermal conductivity characteristics of the composite adsorbents were studied. The experimental results showed that the GNPs were the most effective thermal additives for the SFO aluminum phosphate adsorbents. Adding mass fractions of 30% GNPs reduced the adsorption capacity by 37% and increased the thermal conductivity by 216%.关键词：adsorption cooling;adsorbent;high thermal conductivity materials;thermal conductivity;adsorption performance56|76|0更新时间：2025-12-03
- 摘要：To simulate and optimize an enhanced vapor-injection system, it is necessary to develop a vapor-injection scroll compressor model with fast calculation speed, high accuracy, good extrapolation accuracy, and few parameters for computation. However, existing models cannot meet these demands simultaneously. In this study, a physics-based explicit form semi-empirical model of a scroll compressor with vapor injection was developed to predict its mass flow rate, input power, and discharge temperature. In this model, the suction mass flow rate was derived by correcting the pressure ratio using the specific heat ratio and multiplying it by the quadratic function of frequency. The injection mass flow rate was based on the assumption of an isochoric mixing process and obtained by expanding the coefficients. The discharge flow rate was the sum of the suction and injection mass flow rates. The input power was based on the assumption of isentropic compression and corrected by pressure, and the discharge temperature model was based on the heat leakage factor. The model was validated based on experimental data, and the results showed that the model had a calculation speed of milliseconds, and was able to accurately predict the performance of the compressor, with the average deviations of the suction mass flow rate and discharge mass flow rate both within 2%, and the average deviations of the injection mass flow rate, input power, and discharge temperature within 5%, 3%, and 3 ℃, respectively. The model can provide reasonable results outside the range of fitted conditions, and the amount of data required for model fitting has been reduced by more than 50% compared to that of existing models.关键词：vapor injection;scroll compressor;semi-empirical model;system simulation98|93|0更新时间：2025-12-03
- 摘要：Pump-driven two-phase thermosyphon loops (TPTLs) have garnered widespread attention to improve the performance and applicability of TPTLs under various conditions. This study compared the heat-transfer performance and operational states of a TPTL using two parallel downcomer branches to switch between gravity- and pump-driven TPTL operation modes. Significant differences were observed in the normal working load range of the TPTL when the working fluid flowed through downcomer branches 1 and 2 (pump off), or only through branch 2 (pump on). The presence of a liquid pump increased the resistance to the fluid flow within the loop. When the pump was turned off, the heat-transfer limit of the TPTL decreased, and it increased when the pump was on. During the oscillatory operational stage, the reservoir was unable to effectively separate the vapor and liquid. When the working fluid flowed through downcomer branch 2 (pump off), the TPTL exhibited a longer fluctuation cycle and greater amplitude compared to those during the flow through branch 1. In the stable operational stage, the reservoir provided better vapor-liquid separation.关键词：two-phase thermosyphon loop;heat transfer performance;operational states;liquid pump;reservoir52|63|0更新时间：2025-12-03
- 摘要：Owing to the limited amount of test data available for flow coefficient correlation fitting, there is a large deviation when applying the correlation formula to the flow coefficient calculation of valves with different diameters. To solve this problem, the flow characteristics of an electronic expansion valve were studied experimentally. The experimental results indicated that the valve diameter, valve opening, and subcooling were the main factors affecting the flow coefficient of the electronic expansion valve. The flow coefficient decreased with an increase in the valve opening. The flow coefficient of a valve with a large diameter (DPF2.0) was greater than that of a valve with a small diameter (DPF1.65) under the same opening degree, and the flow coefficient increased with the subcooling degree. A correlation formula for the flow coefficient that considered subcooling degree Tsub and flow area A was fitted using the experimental data, and the relative deviation was calculated to be within ±5% when using this fitting correlation formula.关键词：electronic expansion valves;flow coefficient;correlation equation;circulating area;degree of supercooling112|80|0更新时间：2025-12-03
- 摘要：This study investigated a liquid-cooled charging-cable cooling system for the high-power DC fast charger of electric vehicles. This system utilized perfluoro as the liquid coolant and a serpentine microchannel heat exchanger as the radiator. A mathematical model of the microchannel heat exchanger of this liquid-cooled charging-cable cooling system was established using the ε-NTU and distributed parameter methods. This model was validated through experiments, which demonstrated good consistency between the calculated values and experimental results. By optimizing the flows on both sides of the heat exchanger, along with its structure and configuration, the heat exchange performance was effectively improved while reducing the power consumption. The system employed a parallel arrangement of 28 rows of tubes, which resulted in a temperature reduction of 1.81-2.49 ℃ for the coolant at the gun head and a maximum temperature decrease of 3.51-6.44 ℃ for the charging cable. The results of this study provide valuable insight into the design of the heat exchangers used in liquid-cooled charging-cable cooling systems.关键词：liquid-cooled charging cable;microchannel heat exchanger;NOVEC649;Optimization calculation68|74|0更新时间：2025-12-03
- 摘要：A novel intelligent defrosting control strategy based on the parallel-plate capacitor principle was investigated to address the issue of the “erroneous defrosting” of an evaporator. A mathematical model of a parallel-plate capacitor was established in the process of frosting and defrosting of the evaporator, and a theoretical analysis of the effects of the air/frost/water intermediate medium proportions on the capacitance value was conducted. The capacitance value showed a gradual linear growth during the frosting process, whereas it first rose and then fell during the defrosting process. This study considered a cold storage evaporator as the research object and constructed a capacitance defrosting control system. The experimental results were consistent with the theoretical analysis results for the capacitance variation trend. The results showed that 32.0 pF and 19.0 pF could be used as the start and stop points for intelligent defrosting control, respectively. The fluctuation range for the central temperature in the cold storage was reduced by 12.0 ℃. The defrosting cycle time was shortened by approximately 4 min. The defrosting efficiency increased by approximately 22%. The defrosting power consumption was reduced by 36.74%, and the total power consumption of the refrigeration system was reduced by 19.8%.关键词：parallel plate;capacitor;defrosting;control strategy;system performance65|59|0更新时间：2025-12-03
- 摘要：TiO2-UF@Tet microcapsules were prepared using a two-step method in which the advantages of organic and inorganic shell layers were combined. The effect of the mass fraction of TiO2 on the performance of the composite-shell phase-change microcapsules was investigated. The morphology, chemical composition, and thermodynamic properties of the phase change microcapsules were investigated using biological microscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, energy-dispersive spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The experimental results showed that the microcapsules formed by TiO2 and UF using the two-step method had a good composite shell structure. The phase-transition temperature of the microcapsules decreased, the latent heat of the phase transition decreased, and the thermal conductivity increased continuously with an increase in the mass fraction of TiO2. The prepared microcapsules had smooth surfaces, a uniform particle size distribution, and an average particle size of approximately 2.0 μm. The phase transition temperature and latent heat of the optimal composition were 3.1 ℃ and 168.5 J/g, respectively, with a coating rate and coating efficiency of 71.64% and 69.08%, respectively. After 100 heating cycles, the phase-transition temperature remained stable and the microstructure was good. These microcapsules are suitable for cold-storage air conditioning systems.关键词：microcapsule;titanium dioxide;urea-formaldehyde resin;composite shell;cold storage61|97|0更新时间：2025-12-03
- 摘要：In this study, homogeneous metal and gradient porosity skeletons were constructed using the three-periodic minimal surface method (TPMS). Based on the pore scale, the finite element method was used to simulate the solidification process for a pure paraffin cavity and investigate the influence of the skeleton structure in the solidification of a composite phase-change material. Comprehensive analyses of the solid-liquid phase change interface, overall liquid phase rate, Nu number of the cold source wall, and cold-storage performance were conducted, and the following conclusion was obtained. When the TPMS skeleton was added to the phase change cavity, it affected the solid-liquid deformation process. The solidification time of the phase change chamber with a porosity of 0.78 is shortened by 94.1% and the cooling rate is increased by 12.98 times compared to the pure paraffin phase change chamber. When the average porosity is 0.84, the porosity gradient increases along the positive x-direction, accelerating the solidification of the cavity, improving the heat transfer efficiency of the chamber. Compared with the pure paraffin phase change chamber, the solidification time is shortened by 93.5%, and the cold storage rate is increased by 12.6 times. Compared with the same porosity and uniform TPMS skeleton phase change cavity, the solidification time is shortened by 12.23% and the cooling rate is increased by 15.3%.关键词：phase change cooling storage;TPMS skeleton;gradient distribution;finite element method;heat transfer coefficient44|91|0更新时间：2025-12-03
- 摘要：To address the casualties caused by hypothermia in cold environments, this study designed a solar-powered rewarming sleeping bag for casualties under extremely cold conditions using the phase change materials ODE@CaF2MPCMs and Cu2O@n-C20, which release heat during phase change at low temperatures. Hot-water simulations and human experiments were also conducted. The results of hot-water simulations at 0 ℃, 4 ℃, and 8 ℃, with an initial phase-change-material temperature of 40 ℃, showed that warm water with an initial temperature of 37 ℃ could be maintained at approximately 36 ℃ for 3 600 s, and the bilateral distribution of phase-change materials had a higher heating rate than that of a unilateral distribution. In human experiments, under -5 ℃, 0 ℃, and 5 ℃ temperature conditions, the average temperature could be maintained at approximately 35 ℃ for 3 600 s, and the unilateral distribution of phase-change materials had better insulation than the bilateral distribution, with an average temperature increase of 2 ℃. At -15 ℃, the average temperature could be maintained above 32 ℃ for 540 min. A temperature-distribution uniformity analysis showed that the maximum coefficient of variation for the unilateral distribution was 0.036 and that for the bilateral distribution was 0.053, indicating a relatively uniform temperature distribution inside the sleeping bag, with the unilateral distribution being more uniform than the bilateral distribution. Comprehensive performance assessments showed that the sleeping bag had excellent insulation but requires optimization for convenience; after 30 repetitions of an experiment at -5 ℃, the temperature effect remained almost unchanged, with only a 0.05 ℃ decrease in the average human body temperature after 30 uses. Moreover, the cost of the sleeping bag is only approximately 400 RMB, and a single heating to 40 ℃ consumes approximately 0.24 kW·h, which is low and shows good economic benefits.关键词：wounded personnel rewarming sleeping bag;Severe Cold Environment;Hypothermia;thermal insulation;heat preservation62|89|0更新时间：2025-12-03
- 摘要：Peripheral blood mononuclear cells (PBMCs) are important immune cells. However, traditional slow-freezing methods delay the proliferation of PBMCs and damage T-cell subsets. Therefore, there is an urgent need to develop an alternative cooling procedure that can effectively preserve the viability and function of PBMCs. In this study, we optimized the cryopreservation of PBMCs using ultrasonic ice seeding and analyzed post-cryopreservation T-cell subtypes using flow cytometry. An ultrasonic ice-seeding apparatus was constructed to achieve contactless ice seeding by combining an ultrasonic generating device and a controlled-rate freezer. The results showed that the cooling procedure involving ultrasonic ice seeding exhibited superior efficacy compared to the conventional slow-freezing approach. Following cryopreservation, the viability and cumulative proliferation of PBMCs were 94.97% and 204.47%, respectively. The proportion of naive T cells (Tn) after cryopreservation and thawing accounted for up to 18.35%. By incorporating ultrasonic ice seeding, the optimized cryopreservation procedure enhanced the post-thaw viability, cumulative proliferative capacity, and proportion of T-cell subtypes in PBMCs, providing a novel and effective approach for PBMC cryopreservation.关键词：peripheral blood mononuclear cells;ultrasonic ice seeding;cryopreservation;T cell;flow cytometry64|70|0更新时间：2025-12-03
- 摘要：To investigate the low-temperature tolerance of Phoenix canariensis seeds and isolated seed embryos, along with the physiological changes that occur during cryopreservation, fresh seeds were dried to 25%, 20%, and 15% moisture content and then cryopreserved at -20 ℃ and -196 ℃ (LN2). The results showed that the survival rate of intact seeds gradually increased with decreasing water content. The survival rate of isolated seed embryo cultures increased with decreasing water content, and the growth rates of seeds and seed embryos dried to 11.6% moisture content were not significantly different from those of the unfrozen groups. The viability of LN2-preserved intact seeds and isolated seed embryos was higher than that of the -20 ℃ preservation group. After cryopreservation, the sucker part of the seed embryos was damaged more severely than the cotyledon after low-temperature preservation; however, this damage did not affect the subsequent growth of the seed embryos. After drying to an 8% moisture content, the superoxide dismutase (SOD) activity of the seeds was lower than that of fresh seeds, and the CAT activity and MDA content increased. After cryopreservation, the SOD activity and CAT activity of the seeds increased, and the MDA content decreased, whereas the MDA content of the seeds increased significantly after drying, indicating that excessive dehydration was not conducive to seed cryopreservation. Phoeni canariensis seeds are highly resistant to low temperatures and can be preserved in liquid nitrogen for long periods.关键词：Phoenix canariensis;low-temperature sensitivity;cryopreservation;seed storage55|49|0更新时间：2025-12-03
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