Abstract: Phase change materials (PCMs) are the core media in latent heat thermal energy storage system， and phase change temperature， thermal conductivity and energy storage density of PCMs are the three most critical factors for selecting PCMs. These effects of three key factors of PCMs on heat transfer rate of thermal energy storage system are analyzed by means of relative thermal resistance variation according to thermal resistance modeling， respectively. The results indicate that when the thermal conductivity of PCMs is increased to about 2 folds， the heat transfer improvement of the system is significantly effective. After increasing to 5 folds， the effect of increasing the thermal conductivity to enhance the heat transfer rate of the system is almost invalid. During the charging process， the lower of PCMs’ phase change temperature is， the higher heat transfer rate becomes， and it’s just on the contrary during the discharging process. The increase of energy storage density has no effect on the heat transfer rate of the system， but the time of heat charging/discharging power is extended by corresponding multiple.

Key words: PCMs; heat transfer rate; thermal conductivity; phase change temperature; energy storage density