Experimental study and synergistic performance analysis of phase change material assisted cold thermal storage system for energy efficient air cooling

Cold thermal energy storage (CTES) system integrated with phase change materials (PCM), provide a cost-effective and promising method for increasing the effectiveness of air conditioning systems. The charging and discharging performance of a CTES is crucial for cooling supply and user thermal comfort experience. This study experimentally investigates the performance of a CTES that utilizes RT-18 HC as a PCM to enhance cold storage performance. A parametric study with in-depth thermal analysis was conducted to examine the influence of refrigerant flow rate (0.45, 0.70, and 0.95 kg/min) and supply air flow rate (0.55, 0.75, and 1.0 m/s) on PCM temperature dynamics. The study also investigates the melting and solidification mechanisms of RT-18 HC based CTES along with the cooling capacity and coefficient of performance (COP) of system. The results indicate that increasing the refrigerant flow rate from 0.45 kg/min to 0.70 kg/min reduces the average air temperature passing through the cooling coil from 25.2 °C to 20.3 °C. It was also found that higher flow rates accelerate the solidification time of PCM during charging, however the heat transfer effectiveness was relatively reduced during the discharging process. The optimal operating conditions of the proposed system were attained at a refrigerant flow rate of 0.70 kg/min, resulting in an average daily cooling capacity of 927 W and a COP of 1.67, with a PCM melting time of 5417 s. Under these optimal conditions, the maximum improvement in PCM melting time, air-cooled temperature, and system performance coefficient reached 13.40 %, 19.45 %, and 35.77 %, respectively. Overall, this study provides crucial insights by presenting a practical, compact design and optimal operational parameters to enhance the performance of cold thermal storage systems.