Study on temperature distribution optimization and enhanced heat transfer in shell and tube phase change accumulator

The phase change accumulator can effectively solve the problem of intermittency and fluctuation in the utilization of new energy, thus improving the efficiency of thermal system. This paper focuses on the internal temperature stratification phenomenon in shell-and-tube phase change thermal energy storage units, as well as the “melting dead zone” problem that arises during the melting and solidification processes. A novel stratified fin structure of phase change accumulator is proposed, and its heat transfer characteristics during the melting and solidification processes are simulated. Experimental validation of the optimal fin structure in the phase change thermal energy storage system was conducted. The results indicate that the phase change time and the time required for temperature uniformity in the stratified structure of the thermal energy storage system are independent of the arrangement of the tube bundles. Within the tested temperature range, increasing the temperature of the heat transfer fluid significantly enhances the heat transfer efficiency of the storage unit and reduces the phase change duration. The implementation of a stratified structure effectively mitigates local overheating issues within the storage system, resulting in reductions of 31.6 % in the melting duration and 30.4 % in the time required for temperature uniformity.