Thermal Performance of Cold Storage Packed Bed for Air Conditioning with Modified Composite PCM Based on Eutectic Hydrated Salts

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 ℃, and the latent heat of phase change was 151.3 kJ/kg. Compared with previous work, the latent heat value increased by 14.24%. Additionally, a novel thermal energy storage device using spherical encapsulated capsule PCM within a packed bed is proposed. A three-dimensional physical model of the packed bed is established using EDEM software to investigate the effects of sphere capsule size, inlet temperature, and flow rate of the heat transfer fluid (HTF) on the thermal performance of the packed bed thermal energy storage system. The results indicate that reducing sphere capsule size, lowering the HTF inlet temperature, and increasing the HTF inlet flow rate all accelerate the thermal energy storage process, reducing the thermal energy storage time. When the inlet temperature of HTF increases from 2 ℃ to 4 ℃, the cold storage capacity and density of the packed bed decrease by 5%, the average cold storage rate decreases by 41.93%, and the pressure drop remains relatively constant. However, the influence of sphere capsule size on parameters such as thermal energy storage capacity and density does not exhibit a clear pattern, and their impact should be determined based on specific engineering applications. These findings provide theoretical guidance for the practical application and widespread use of packed bed thermal energy storage systems in air conditioning.