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 ℃, 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.