Discharging characteristics modeling of cool thermal energy storage system with coil pipes using n-tetradecane as phase change material

The dynamic discharging characteristics of cool thermal energy storage system with coil pipes are studied by a discharging process model according to the energy balance of the phase change material and the heat transfer fluid. The n-tetradecane is taken as phase change material (PCM) and the aqueous ethylene glycol solution with 25% volumetric concentration is used as heat transfer fluid (HTF). It is presented that the variations of the phase change material temperature, heat transfer fluid temperature, melt fraction and cool release rate with time during the discharging process. The effects of the inlet temperature and the flow rate of the heat transfer fluid, and the diameter of coil pipes on the outlet temperature of the heat transfer fluid, melt fraction and cool release rate are discussed. The results indicate that the higher flow rate of the heat transfer fluid or the higher inlet temperature of the heat transfer fluid results in the higher cool release rate and the less time for discharging process. Compared to the inlet temperature and the flow rate of the heat transfer fluid, the diameter of coil pipes has little influence on the discharging characteristics.