In this study, a 294 L high-low temperature test chamber with two power batteries in the test area is investigated. The temperature rise and heat dissipation of the batteries in the chamber at a constant temperature of 45 ℃ are simulated through CFD, and the flow field of the high-low temperature test chamber is analyzed and optimized. The results show that for the air distribution pattern on the same side as the upper air supply and lower air return, the perforated plate in the upper part of the test area is helpful in improving the uniformity of the flow field. A vortex phenomenon occurs between the two power batteries. Increasing the distance between the shelf and bottom of the test chamber and appropriately increasing the return air grille area can reduce or even eliminate this phenomenon and thereby improve the flow field uniformity. When the distance between the shelf and bottom of the inner chamber increases to 0.2 m and the height of the return air grille increases to 0.15 m, the overall inhomogeneity of the flow field in the test chamber decreases from 1.73 to 0.4, and the vortex phenomenon between the batteries disappears.

In this study, physical models of six-row and four-row arrays of a low-ambient-temperature air-source heat pump with and without wall obstruction are established. A three-dimensional numerical simulation of the ambient flow field of the low-ambient-temperature air-source heat pump under nominal working conditions at 261.15 K is carried out. In this study, the inlet air temperature of the evaporator surface and the heat transfer rate of the low-ambient-temperature air-source heat pump under different horizontal wind speeds are investigated. The location of the unit under the worst conditions is determined, and the influence of cold air backflow on the heat transfer performance is analyzed. The ambient wind hindered the diffusion of cold air at the fan outlet and increased the deflection angle of the fan outlet, resulting in the accumulation of cold air in the upper part of the fan, and the cold air reflux phenomenon in the unit was more obvious inside and on the lee side the array. The results showed that when the horizontal distance between the units was 0.6 m, the horizontal wind speed increased from 0 to 5 m/s. The lowest inlet air temperature of the array unit is 2.44-3.69 K lower than the ambient temperature; the average heat transfer decreases by 1%-6.2%, and the average inlet air temperature is 0.78-1.57 K lower than the ambient temperature. When the distance between the unit and wall is 0.6 m, the horizontal wind speed increases from 0 m/s to 5 m/s, respectively; the lowest inlet air temperature of the array unit is 3.51-4.14 K lower than the ambient temperature; the average heat transfer rate decreases by 5.9%-11.5%, and the average inlet air temperature is 1.29-1.98 K lower than the ambient temperature. On this basis, an array air-source heat pump was simulated under different lateral spacings and distances from the wall. The results showed that increasing the lateral spacing or distance from the wall enhanced the heat transfer of the array low-ambient-temperature air-source heat pump unit. When the lateral spacing increases to 1.8 m, the average heat transfer rate of the array unit can reach more than 96.5% of the baseline heat transfer rate of the array unit. When the distance from the wall is increased to 1.8 m, the average heat transfer rate of the array unit can be more than 91.3% that of the baseline unit. A horizontal spacing or a spacing from the wall of 1.2 m is a better installation spacing, which provides a theoretical basis for on-site installation.

The miniaturization and performance improvement of components continuously increase the power of electronic devices. Superior heat-dissipation performance is important for the reliability of electronic devices. In this study, an experimental pump-driven refrigerant two-phase cold-plate-cooling system was developed. Four two-phase cold plates with different materials (Cu and Al) and channel heights (10 mm and 15 mm) were designed and processed. The heat-transfer performance of the cold plates, together with their flow resistance characteristics, pump power under different heat fluxes (4.4-22.2 W/cm²), refrigerant cooling capacities (3-11 kW), and heat source positions were studied. The results indicated that the heat-transfer performance of the two-phase cold plate was superior. The maximum heat transfer coefficient was 26 kW/(m²·℃) when dealing with a concentrated heat source with a heat dissipation of 1000 W and a heat flux of 22.2 W/cm². The temperature difference between the heat source surface and the refrigerant was less than 15 ℃ when the total pressure drop of the system was less than 20 kPa and the power consumption of the refrigerant pump was less than 20 W. A natural cold source can be used for heat dissipation to achieve energy savings. The heat transfer characteristics of the two-phase cold plate can be described by the fin efficiency correlation and the Kandlikar heat transfer correlation. The deviation between the temperature difference calculated by the theoretical formula and the measured value was less than 1 ℃. The results of this study can guide the design of cold-plate channels.

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.

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 T_sub 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.

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.