Numerical study of the heat charging and discharging characteristics of a shell-and-tube phase change heat storage unit

• We studied heat charging or discharging performance of a shell-and-tube PCTES unit.
• There are three stages for change of PCM temperature and heat transfer rate.
• Discharging process needs more short time than charging process does.
• Increasing the HTF inlet temperature can decrease the melting or solidification time.
• Increasing the HTF mass flow rate can decrease the melting or solidification time.

The effects of temperature difference between the inlet of heat transfer fluid (HTF) and melting point of phase change material (PCM), the HTF inlet mass flow rate on heat charging and heat discharging performance are numerically studied. The results show that charging and discharging processes have three stages for the change of temperature regarding to time in PCM and heat charging or discharging rate regarding to time: rapidly changing period, slowly changing period and more slowly changing period. With the same configuration and under the same HTF inlet temperature, to complete discharging process needs less time than to complete charging process does. The effects of inlet HTF temperature, the mass flow rate on the characteristics of charging and discharging processes are profound.