Experimental and numerical investigation of discharging process of direct contact thermal energy storage for use in conventional air-conditioning systems

Direct contact thermal energy storage (TES) for use in conventional air-conditioning systems is proposed to reduce the operational energy demand. Thermal performance of a novel kind of phase change material (PCM) prepared for use in conventional air-conditioning systems with the proposed direct contact TES tank, is evaluated. A 3-dimensional (3D) numerical model is built using ANSYS FLUENT to investigate dynamic characteristics of the discharging process of TES system. The model is validated by comparing the numerical with the experimental results. The effects of heat transfer fluid (HTF) flow rate, HTF inlet temperature, liquid PCM volume fraction, complete discharging time, discharging capacity of the tank, and temperature distribution in direct contact TES tank are investigated. The results indicate that increasing the HTF flow rate speeds up the discharging capacity and the discharging time of the direct contact TES system reduces. When the flow rate increases from 0.503 m3/h to 0.936 m3/h, the melting PCM increases from 63.33 vol.% to 70.74 vol.% within 600 s. The discharging capacity increases with HTF inlet temperature; however, the whole discharging capacity does not change obviously by changing HTF inlet temperature.