Because of the limited experimental studies on transcritical CO₂ refrigeration systems at low evaporating temperatures, an experimental platform of a two-stage transcritical CO₂ compression refrigeration system with an ejector was designed and built. We evaluated the performance of the proposed refrigeration system under the following experimental conditions: evaporating temperature within the range of -33 ℃--29 ℃, gas cooler outlet temperature of 30 ℃-40 ℃, and high pressure of 8.20 MPa-9.70 MPa. The results show that the variation trend of the experimental results is consistent with that of the theoretical thermodynamic calculation results, and the application of the ejector can significantly improve the performance of the two-stage transcritical CO₂ compression refrigeration system. The maximum increase rate of the coefficient of performance (COP) of the refrigeration system by the ejector is 29.37%. Under experimental conditions, the optimal high pressure of the two-stage transcritical CO₂ compression refrigeration system with an ejector is 8.80 MPa, and the corresponding optimal COP is 1.63. The cooling capacity and COP of the two-stage transcritical CO₂ compression refrigeration system with an ejector increase with increasing evaporating temperature, and the gas cooler outlet temperature significantly affected the performance of the refrigeration system. As the gas cooler outlet temperature increases from 30 ℃ to 40 ℃, the COP of the refrigeration system decreases by 61.4%. The research results provide a reference for research on two-stage transcritical CO₂ compression refrigeration systems with ejectors.

A high-efficiency condensation dehumidification system utilizing copper foam driven by a Stirling refrigerator was developed to address the demands for high-efficiency heat transfer and a compact lightweight design in space stations. An experimental study was conducted to investigate its heat and mass transfer characteristics under various conditions. The experimental parameters were set as follows: air inlet temperature ranging from 20 ℃ to 30 ℃, relative humidity between 50% and 80%, cold plate temperature from 8 ℃ to 13 ℃, and inlet wind speed from 0.4 m/s to 1.4 m/s. The results indicated a positive correlation between the increase in the air inlet temperature and the enhancement of both the heat and mass transfer coefficients. Specifically, when the air inlet temperature increased from 20 ℃ to 30 ℃, the heat transfer coefficient increased by 10.5%, whereas the mass transfer coefficient exhibited a more substantial increase of 57.1%. Furthermore, variations in the relative humidity of the air inlet distinctly affected the heat and mass transfer coefficients: the heat transfer coefficient decreased by 31.6% with an increase in the relative humidity, whereas the mass transfer coefficient increased by 11.4%. Although reducing the temperature of the cold plate can effectively improve heat transfer, it leads to the accumulation of condensate water and reduces the efficiency of heat and mass transfer. Therefore, an appropriate cold plate temperature must be selected. Additionally, the efficiency of heat and mass transfer was markedly enhanced with increasing inlet wind speed. However, a continuous increase in wind speed resulted in higher system energy consumption. Thus, a balance between efficient heat transfer and high system energy consumption was essential. Based on extensive experimental data, the heat transfer model was refined using regression analysis. The standard deviation between the theoretical and experimental values was 8.21%, and the maximum deviation was 19.76%, demonstrating the strong predictive accuracy of the model.

In this study, a phase-change heat-storage water tank with a flat-plate storage plate was designed with phase-change materials. A heat-storage water tank model was constructed using the same staggered arrangement. Experiments and simulations were used to investigate the heat storage and discharge performances of a flat-plate-filled phase-change heat-storage water tank and the influence of the discharge flow rate on the heat release performance of the change materials. The role of different discharge flow rates in improving the heat release performance of phase change materials is discussed. The results show that filling a 98 L water tank with 12.15 L of phase change materials in a flat plate manner increased the heat storage capacity of the water tank by 17.91% while improving the stability of the system operation. By analyzing the flow rates under different heat release modes, it was found that at a discharge flow rate of 100-175 L/h, the heat release ratio of the phase change materials was maintained above 88%. The hot water supply volume reached 135 L. However, the heat transfer between the fluid and the phase change materials was no longer timely when the flow rate increased. The heat release ratio of the phase change materials gradually decreased to 81.5%, and the hot-water supply volume decreased to 125 L. To improve the heat discharge performance of phase change materials in a heat-storage water tank, it is necessary to ensure sufficient external heat transfer conditions and fundamentally improve the heat exchange capacity of the phase change materials.