Numerical Simulation of Charging Performance of Combined Sensible-Latent Heat Storage System with a Macro-Encapsulation Method

In recent years, heat storage system combining sensible and latent heat materials has received more and more attentions. In this paper, we proposed the hybrid configuration with a macro-encapsulation, and analyzed its charging performance with different influencing factors by CFD simulation. In the case, the sensible heat storage materials are magnesia brick or HT concrete and the phase change materials (PCMs) are mixed molten salts. Firstly, we analyzed the heat transfer characteristics of the hybrid configuration in charging process. Then, we analyzed the effect of heating power on charging performance. The maximum temperature of the heating surface shall not exceed 500°C as the constraint condition, the heat storage capacity increases at first and then decreases with the heating power. Then, we compared the charging performance of different solid structure and the hybrid configurations. Whether magnesia brick or HT concrete, the charging performance of the solid structure is better than that of the hybrid configuration, because the thermal conductivity of the molten salt is significantly lower than that of the two sensible heat storage materials. Then, we compared the charging performance of different molten salts. The hybrid configuration with lower melting point molten salt has better performance because of more intensity natural convection. Finally, we analyzed the charging performance of the hybrid configuration used the composite phase change material (CPCM) with high thermal conductivity and specific heat. From the result, the charging performance increases by 22.5% compared with the solid structure. These results indicate that the hybrid configuration with the macro-encapsulation method is a potential form of thermal energy storage, but it needs to be further optimized.