最新刊期
卷 46 ， 期 2 ， 2025
- 摘要：Battery thermal management systems are crucial components of pure electric vehicles. The promising application of liquid immersion technology in electronic equipment has also garnered increasing attention for its potential in battery thermal management. Power battery immersion liquid-cooling technology involves directly immersing the battery in dielectric liquid to dissipate heat through convection or phase-change heat transfer. This study analyzes the impact of temperature on battery performance and compares the advantages and limitations of different thermal management systems. The importance of immersion-based battery thermal management is emphasized. Key technical challenges and recent research advancements are reviewed in detail, including coolant selection, module design, and considerations for battery life and safety. Finally, commercially developed immersion cooling products for demonstration and exploration are introduced.关键词：power battery;battery thermal management;immersion liquid cooling;coolant;module design44|0|0更新时间：2025-04-15
- 摘要：The rapid development of microelectronic devices has driven a trend toward miniaturized and lightweight electronic devices with high heat flux. Porous structures are increasingly used in heat dissipation due to their ability to expand the heat transfer area, enhance nucleation sites for boiling, and regulate surface wettability, significantly improving boiling heat transfer. Microchannel heat dissipation technology based on porous structures has emerged as an effective and promising method to enhance heat sink performance. Recent advancements highlight three common configurations: porous structures on microchannel surfaces, porous materials within microchannels, and porous microchannel skeletons. These structures encompass coatings, microcavities, metal foams, porous fins, and ribs. This article reviews progress in microchannel heat dissipation using porous structures, evaluates the benefits and drawbacks of these configurations, addresses challenges such as balancing heat transfer and pressure drop, and proposes optimization strategies to overcome these issues.关键词：microchannel heat sink;porous structure;heat transfer enhancement;pressure drop;optimal design20|1|0更新时间：2025-04-15
- 摘要：Transcritical CO2 heat pump air-conditioning systems have gained prominence in new energy vehicle thermal management due to their energy-saving and environmentally friendly characteristics. However, the relatively low coefficient of performance (COP) in cooling mode remains a significant obstacle to developing transcritical CO2 heat pump air conditioning systems. To enhance system performance, five technical approaches are proposed: internal heat exchangers (IHX), expanders, vortex tubes, ejectors, and combined multiple evaporation steps with vapor injection. The performances of these methods were evaluated through one-dimensional theoretical calculations under vehicle operating conditions. Results indicate that optimizing discharge pressure is critical for all methods, with varying degrees of COP improvement. Expanders provide the most comprehensive benefits, ejectors perform well under specific design conditions, IHX shows notable enhancements in cooling mode, and vortex tubes and combined multiple evaporation steps with vapor injection exhibit broad adaptability across working conditions. These findings offer valuable insights for practical engineering applications and support the adoption of transcritical CO2 heat pump systems in new energy vehicles.关键词：new energy vehicles;transcritical CO2;heat pump air-conditioning system;performance improvement methods19|1|0更新时间：2025-04-15
- 摘要：In northern China, public buildings commonly use direct-expansion air-conditioning systems for cooling and district heating networks for heating, necessitating separate terminals for each function. This study proposes a multi-connected air conditioning system capable of utilizing refrigerants and water for direct heating with hot water from district heating systems. The system integrates three-fluid heat exchangers within indoor units, enabling seamless switching between direct-expansion air-conditioning and district heating systems. Using an office building in Beijing as a case study, the system was evaluated under summer cooling design conditions, and its heating performance during winter and transitional seasons was analyzed. Results reveal that during winter, the system requires user-side water temperatures below 54 ℃, while in transitional seasons, the direct-expansion mode delivers unit capacities exceeding peak heating demands with energy efficiency surpassing 3.5 over 49% of operating hours. This system simplifies existing configurations by providing a single terminal for year-round heating and cooling, enhancing efficiency and thermal comfort.关键词：multi-connected air conditioner with refrigerant and water;three-fluid heat exchanger;air conditioning system;district heating system;space heating12|2|0更新时间：2025-04-15
- 摘要：To reduce energy consumption in temperature- and humidity-independent air-conditioning systems and enhance solar energy utilization, this study developed a solar-assisted desiccant wheel and adsorption cooling system (SDCS-A) using TRNSYS 18. System performance under Guangzhou's climatic conditions was analyzed by varying collector areas and tank volumes together with evaluating metrics such as system coefficient of performance (COPsys), solar fraction (Fs), and primary energy consumption (Ep). These results were compared with those of a solar-assisted desiccant wheel and vapor compression cooling system (SDCS-C). Findings indicate that changes in collector area significantly influence Fs and Ep, with Fs increasing by an average of 12.18%, while variations in tank volume predominantly affect COPsys, with a maximum difference of 0.1. Compared to SDCS-C, SDCS-A achieved 6.51% higher monthly average COPsys, a 21.05% increase in Fs, and a 21.45% reduction in Ep during the cooling season. Furthermore, the system's performance across different climates was evaluated, demonstrating that Guangzhou offers more stable and higher monthly COPsys values than Beijing, Shanghai, and Lhasa.关键词：solar energy;desiccant wheel;adsorption cooling;performance analysis;TRNSYS10|0|0更新时间：2025-04-15
- 摘要：Helium throttling refrigeration technology is a key cooling method used in liquid helium temperature zones in space. Research on the rapid cooling of chillers coupled with large heat capacity loads is important for the efficient operation of large heat capacity loads. To clarify the cooling characteristics of helium throttling chillers under different rapid cooling schemes, cooling experiments with no additional measures scheme, room-temperature valve bypass scheme, and thermal switch scheme were conducted based on GM pre-cooled helium Joule-Thomson chillers under different heat capacity loads. The experimental results show that the load-free pull-down times of the three schemes were 39.8 h, 20.5 h, and 19 h, respectively. Based on thermodynamics and heat transfer theories, the changes in the radiation, convection, heat conduction, and throttling source terms during no-load cooling were quantitatively analyzed, and the reasons for the difference in cooling time of helium throttling chillers under different schemes were explained. With a simulated load of 0.136 kg of copper, schemes of the room-temperature valve bypass and hot switch were adopted, and the corresponding cooling times were 25.5 h and 20 h, respectively. The experimental results show that the cooling effects of the thermal switch and room-temperature valve bypass scheme are essentially the same for the cooling of a small heat capacity load. Therefore, thermal switch cooling has significant advantages for large-heat-capacity load cooling.关键词：helium Joule-Thomson refrigerator;rapid cooling;large heat capacity;heat switch;bypass11|0|0更新时间：2025-04-15
- 摘要：Displacer-type pulse-tube cryocoolers use a displacer for phase adjustment and recovery of acoustic power, leading to high refrigeration efficiency. Despite their potential, there is limited research on highly efficient displacer-type pulse-tube cryocoolers with large cooling capacities near -100 ℃. This paper presents the design of a 100-watt displacer-type pulse-tube cryocooler for low-temperature freezers and evaluates its performance, focusing on displacement motion and compressor efficiency. A validated numerical model was employed to analyze the coupling between the pulse tube and compressor and the internal phase relationship of the cold finger. Results show that under operating conditions of a 3.0 MPa charging pressure, 64.9 Hz frequency, 20 ℃ cooling water temperature, and 500 W input power, the cryocooler achieved a cooling capacity of 160.3 W at -100 ℃ with a relative Carnot efficiency of 22.2%. The displacer led the compressor piston by 59°, the internal phase distribution of the pulse tube was optimal, and the compressor exhibited a high efficiency of 78%. This cryocooler is the most efficient displacer-type pulse-tube cryocooler in its temperature range.关键词：pulse tube cryogenic cryocooler;Hypothermic storage;refrigeration performance test;Displacer;compressor10|1|0更新时间：2025-04-15
- 摘要：The refrigeration industry is advancing towards environmentally friendly, efficient, and safe alternative refrigerants. To analyze compressor performance with various refrigerants, this study proposes a modified semi-empirical model with 13 characteristic parameters. Experiments were conducted with R22, R507, and R744 under variable operating conditions to identify parameters and validate the model. The experimental and simulated results showed strong agreement, with average relative errors of 2.07% for input power and 1.17% for mass flow rate. Using a typical operating condition, the losses and efficiencies of different refrigerants were compared at various frequencies. Results indicate that R744, with the lowest pressure, leakage, and power losses, demonstrated superior performance. While R507 and R22 showed similar efficiencies, the efficiency of R507 declined significantly at frequencies above 50 Hz due to increased pressure losses. This study provides a theoretical basis for optimizing compressor designs for various refrigerants.关键词：operating characteristic;semi-empirical model;twin-screw compressor;refrigerant substitution10|2|0更新时间：2025-04-15
- 摘要：Because the piston volume of a scroll compressor with variable base circle involute can be reduced under the premise of obtaining the same cooling capacity, it can satisfy the compact and lightweight requirements of vehicle air conditioning compressors. To improve the isentropic and volumetric efficiencies of the scroll compressor, a mathematical and geometric model of the scroll disc with a variable base circle involute was established. With the variable index k and the modified increment δ0 as variables, the internal flow field of the scroll compressor is numerically simulated, and fluid dynamic analysis is conducted. The numerical results show that when the parameters of the variable base circle line are k=1 and δ0=-0.03 mm, the specific dissipation rate of the fluid in the compressor working chamber is 180.28 s-1, which is 103.11 s-1 lower than the 283.39 s-1 of the flow field in the fixed base circle compressor. The isentropic efficiency of the scroll compressor can be improved by reducing energy loss due to the turbulent kinetic energy dissipation. The performance of the scroll compressor for electric vehicle air-conditioning was tested. Compared with the fixed base circle scroll compressor, the input power of the variable base circle scroll compressor with k=1 and δ0=-0.03 mm decreases by 1.392%, and the performance coefficient COPel increases by 4.204%.关键词：scroll compressor;modified base circular line;turbulent dissipation;flow field analysis;performance test10|1|0更新时间：2025-04-15
- 摘要：This study investigates the magnetocaloric properties and refrigeration performance of batch-prepared (La, Ce)(Fe, Mn, Si)13Hy alloys. After heat treatment and hydrogenation, the Curie temperatures of M1, M2, and M3 were 292.9 K, 287.8 K, and 283.9 K, respectively, decreasing with higher Mn content. Arrott plots indicated an itinerant-electron metamagnetic transition. M2 exhibited the highest isothermal magnetic entropy change of 12.0 J/(kg·K) under a 2 T magnetic field, with a full width at half maximum of 11 K. Relative cooling capacities (RCP) were 110.2 J/kg, 132.0 J/kg, and 110.0 J/kg for M1, M2, and M3, respectively. Adiabatic temperature changes measured under a 1.5 T magnetic field were 3.48 K, 3.14 K, and 2.96 K for M1, M2, and M3, respectively. A maximum refrigeration temperature span of 16.9 K was achieved by cascading the alloys at an ambient temperature of 295 K.关键词：batch preparation;(La, Ce)(Fe, Mn, Si)13Hy magnetocaloric materials;magnetocaloric properties;refrigeration performance8|2|0更新时间：2025-04-15
- 摘要：A composite cold storage phase change material (PCM) based on Na2SO4·10H2O and Na2HPO4·12H2O was developed to meet the temperature requirements of cold storage air conditioning. The phase change temperature was 8.3 ℃, with a latent heat of 151.3 kJ/kg, representing a 14.24% increase in latent heat compared to previous works. Additionally, a novel thermal energy storage device utilizing spherical encapsulated PCM within a packed bed was proposed. A three-dimensional physical model of the packed bed was constructed using EDEM software to study the effects of sphere capsule size, inlet temperature, and heat transfer fluid (HTF) flow rate on the system's thermal performance. Results show that reducing the sphere capsule size, lowering the HTF inlet temperature, and increasing the HTF flow rate accelerate the thermal energy storage process and reduce charging time. For instance, when the HTF inlet temperature increases from 2 ℃ to 4 ℃, the packed bed's cold storage capacity and density decrease by 5%, the average cold storage rate drops by 41.93%, and the pressure drop remains relatively constant. However, the effect of sphere capsule size on thermal energy storage capacity and density lacks a clear trend and depends on specific engineering applications. These findings offer theoretical guidance for the practical application and broader use of packed-bed thermal energy storage systems for air conditioning.关键词：cold storage phase change material;disordered pack;packed bed;cold storage characteristics11|0|0更新时间：2025-04-15
- 摘要：As a core heat exchange component in forced-draft cooling towers, the performance of packing material significantly impacts the power consumption of the equipment. In this study, an experimental platform for crossflow cooling tower packing was developed to examine the effects of wind speed, water spray density, and packing height on the heat and mass transfer performance and resistance characteristics of herringbone corrugated packing. Empirical formulas were derived to analyze fan power consumption in crossflow cooling towers. Results reveal that heat and mass transfer performance improves with increased wind speed and water spray density and decreased packing height. Wind speed was found to be the most influential factor; increasing wind speed from 0.96 m/s to 2.05 m/s raised the mass-transfer coefficient by 70%. At low water spray densities, increasing the density significantly enhanced heat and mass transfer. Air resistance in the packing zone increased with air velocity, approximately proportional to the 1.68-1.91 power of wind speed. When the cooling water volume flow rate was 70 m3/h, sacrificing 20% of heat exchange capacity and reducing the inlet-outlet temperature difference from 5 ℃ to 4 ℃ reduced power consumption by approximately 71%. To maintain a power consumption ratio of 0.035 kW·h/m3, lowering the approach temperature from 4 ℃ to 3 ℃ required a 31% reduction in cooling water volume flow rate.关键词：crossflow cooling tower;herringbone corrugated packing;heat and mass transfer;air resistance;power consumption ratio8|0|0更新时间：2025-04-15
- 摘要：To address the issue of unreasonable buried pipe length design in ground-source heat pump projects, a three-dimensional dynamic simulation platform was developed. The reasonableness of the buried pipe length was evaluated by comparing the simulated outlet temperature with the designed outlet temperature based on specifications. Using a building in Beijing as a case study, the effects of soil thermal properties and borehole-related parameters on the design error in buried pipe length were analyzed. A sensitivity analysis further examined the impact of these factors. Results indicate that the relative error in buried pipe design length increases with rising soil thermal conductivity, soil volumetric heat capacity, borehole depth, and borehole spacing. Relative error ranges were 10.7%-27.3%, 8.0%-23.8%, 7.3%-12.5%, and 12.5%-17.4% for the respective factors. Sensitivity analysis revealed soil thermal conductivity as the most significant factor influencing pipe length, with a quantitative index of 0.909. Other influential factors, in descending order, were soil volumetric heat capacity, borehole spacing, number of borehole columns, and borehole depth.关键词：ground-source heat pump;ground heat exchanger;design length of the buried pipe;sensitivity analysis12|1|0更新时间：2025-04-15
- 摘要：Capillary mat heat exchangers are increasingly used in transportation energy tunnels owing to their large heat-transfer area and uniform temperature. Thermal energy tunnels, a new type of energy tunnel, differ from transportation energy tunnels because of the heat source inside such tunnels. To examine the feasibility of applying capillary mat heat exchangers in thermal energy tunnels under endothermic conditions, heat transfer performance was experimentally investigated using a 1∶1 intermittent operating mode. The results showed that the higher the initial air temperature (T0) in the tunnel, the greater the heat flux. With the inlet temperature of circulating water (tin) fixed at 5 ℃, as the temperature difference between T0 and tin increases by 10 ℃, the heat flux increases by 45.9%. The heat flux also increases with the increase of circulating water velocity (u); whereas u increases up to 0.1 m/s, the heat transfer rate saturates and approaches 187.22 W/m2. The lower the tin is, the greater the heat flux. When the T0 is 50 ℃ and the u is 0.075 m/s, for every 1 ℃ increase in the tin, the heat transfer rate decreases by 2.04%.关键词：thermal energy tunnel;tunnel air temperature;capillary mat heat exchanger;heat transfer performance9|1|0更新时间：2025-04-15
- 摘要：Superhydrophobic surfaces, a new type of green material, exhibit promising application prospects in the field of anti-/de-icing. In this paper, the kinetic behavior of impinging droplets on surfaces with different temperatures (-25-16 ℃), different inclination angles (0°-60°), and different wettability (hydrophilic and superhydrophobic surfaces) is investigated through experimental comparisons. The variations of the droplet morphology, spreading factor, spreading time, and contact time are analyzed. The results show that the impinging droplets exhibit different kinetic behaviors after spreading due to the different inclination angles and wettability. The maximum spreading factor and spreading time on hydrophilic surfaces increase with the inclination angle. The variation of the spreading time on superhydrophobic surfaces follows the same trend as that on hydrophilic surfaces, while the maximum spreading factor decreases with an increase in the inclination angle, especially at Ts-25 ℃; Compared to hydrophilic surfaces, the impinging droplets have shorter spreading times on superhydrophobic surfaces, which can reach about 10 times at Ts=-25 ℃. Increasing the wall inclination angle breaks the symmetric bounce of the droplets on the horizontal superhydrophobic surface, thereby shortening the contact time of the droplets. This suggests that increasing the inclination angle can effectively inhibit the freezing of water droplets.关键词：droplet impact kinetics;surface wettability;surface inclination;surface temperature;anti-/de-icing11|1|0更新时间：2025-04-15
- 摘要：Refrigerant leakage is a frequent and costly fault that deteriorates the normal operation of a chiller; however, it is difficult to measure directly. This study proposes a data mining- and key-feature-based approach for the soft measurement of refrigerant leakage. Random forest importance ranking and distance correlation coefficients were used to select the characteristic features, and a support vector regression (SVR) soft measurement model was established to measure leakage quantitatively. The proposed model was validated through a leakage experiment conducted on a screw chiller with a rated cooling capacity of 1 440 kW and a refrigerant charge of 330 kg. The results showed that the SVR soft measurement model established on the three selected key features achieved significantly improved performance. The model had a root mean square error (RMSE) of 0.844 kg and a mean absolute error (MAE) of 0.734 kg, outperforming the other three feature subsets.关键词：refrigerant leakage;feature selection;soft measurements;random forest;support vector regression8|4|0更新时间：2025-04-15
- 摘要：The drying process of a heat pump clothes dryer (HPCD) has complex characteristics such as strong coupling (the thermal cycle of the refrigerant side is coupled with the drying cycle of the air side), time variation (the system operating parameters change with drying time), and integration (limited space integrating evaporator, condenser, fan, compressor, etc.), and such complexity makes theoretical analysis of the drying performance of HPCD difficult. Based on certain simplifications, this study analyzes the effects of different compressor capacities and fan airflows on the moisture extraction rate per unit time (MER) and moisture extraction rate per unit energy consumption (SMER) of the HPCD. Under the same airflow, the SMER increases first and then decreases with the condenser discharge air temperature and evaporator discharge air temperature, when the discharge air temperature of the condenser is between 20 ℃ to 80 ℃ and the discharge air temperature of the evaporator is between 10 ℃ to 50 ℃. For the HPCD analyzed in this paper, when drying a half load (5 kg) of clothes, theoretical calculations identified an optimal condenser discharge air temperature of 53 ℃ and an evaporator discharge air temperature of 27 ℃ that maximized the SMER. The optimal temperatures are related to the COP of the heat pump system and the mass and heat transfer capacity of air with clothes. Under the same evaporator discharge and condenser discharge temperatures, within the airflow range of 0.02~0.08 kg/s, the SMER first increases and then decreases with the airflow. There is an optimal working airflow of 0.047 kg/s that maximizes the SMER, which is related to the drum power and the airflow resistance characteristic of the clothes dryer. According to methods for measuring the performance of tumble dryers for household use, testing verified that the theoretical analysis results were consistent with experimental tests. This research method and its conclusions provide theoretical guidance for the design and optimization of HPCD.关键词：heat pump clothes dryer;drying performance;evaporating temperature;Condensing temperature;compressor15|3|0更新时间：2025-04-15
- 摘要：Large cold storage systems play a significant role in economic development with substantial energy consumption and environmental impacts. To promote the green, low-carbon, and efficient development of cold storage, this study mainly focuses on refrigerant substitution, refrigeration system optimization, and the application of transcritical CO2 systems with ejectors in large cold storage systems. The performance and energy consumption characteristics of different refrigeration systems were compared through a comprehensive annual hourly energy consumption analysis based on the cold storage demands at different temperatures and under various climatic conditions. The results show that the COPs of a transcritical CO2 system integrated with specifically optimized ejectors are higher than that of the R507A system in all four cities for low-temperature (-32 ℃), medium-temperature (-8 ℃), and high-temperature (0 ℃) cold storages. However, it exhibited performance advantages over the R717 system only in cold climate zones, with the highest system COPs of 2.45, 4.86, and 5.98 for low, medium, and high-temperature cold storages, respectively. Considering the system′s annual energy consumption, the application of CO2 transcritical systems in low, medium, and high-temperature cold storages in Beijing achieved energy savings of 7.9%, 10.1%, and 10.5%, respectively, compared to the R507A system. The energy savings of the R717 system were slightly higher than that of the CO2 system in low-temperature cold storage, but the CO2 system had more obvious advantages in medium- and high-temperature cold storage. The energy consumption of the CO2 transcritical system also varied across climate zones. In the cold climate zone, the energy savings reached 9.3%, outperforming the R717 system, while in the hot climate zone, its energy savings dropped to 2.8%, slightly lower than that of R717. With the appropriate selection of temperature range and climate zone, the overall operational efficiency and energy-saving performance of the transcritical CO2 system can surpass those of the R717 system. This study conducted a comprehensive analysis of the operational performance and energy consumption distribution characteristics of the CO2 system and highlighted its applicability in different scenarios, providing important references for promoting and applying the system, which is crucial for achieving dual carbon goals.关键词：CO2 transcritical system;ejector;cold storage;energy saving;CO2 emission reduction14|0|0更新时间：2025-04-15
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