Experimental and simulation analysis on thermal stratification characteristics in solar storage tanks with phase change materials

• A 3D transient water tank model is created and validated by experimental measurements. • Thermal stratification of the water tank with PCM units under dynamic operating conditions was investigated. • Multiple thermal stratification evaluation parameters are applied. • The transient simulation results were used to visualize the generation mechanism of thermal stratification inside the DHW tank during the heat storage process. Among the various ways to improve energy storage and utilization in solar thermal energy storage systems, the water tank is often considered as an effective heat storage utilization. In this study, sodium acetate trihydrate (SAT) is coupled with a solar domestic hot water (DHW) storage tank as a phase change material (PCM). The thermal stratification of latent heat storage water tanks with different locations of PCM units and inlet flows was researched experimentally and numerically. The results show that in the charging process, as the inlet flow increases, the thickness of the thermocline gradually increases, with the degree of mixing in the tank aggravation. The Richardson number gradually increases as the PCM units are moved closer to the inlet. The RMSE between the experimental and simulated values reached the minimum at a flow rate of 3 L/min. The system has taken as the optimal working condition with better thermal stratification when the PCM units are placed at PCM1, and the flow rate is 3 L/min. This study provides theoretical and experimental guidance for the optimal design of DHW storage systems.