Thermal performance analysis of phase change material based thermal storage system using a generalized numerical model with volumetric expansion and shrinkage

Abstract

Prediction of shrinkage voids during solidification of phase change material (PCM) with unequal liquid and solid densities is critical to design and assess the thermal performance of latent heat thermal energy storage system. In this paper, the solidification of phase change material with shrinkage void formation is numerically investigated using the modified source-based enthalpy method. This study aims to develop a capability to predict the size and location of shrinkage voids during solidification by developing generalized governing conservation laws that account for large differences in density, specific heat, and thermal conductivity between solid and liquid phases of phase change material. The proposed numerical model incorporating volumetric shrinkage and expansion is validated with the reported experimental results. Further, the present model is used to study the effect of solidification shrinkage on the heat transfer performance of the latent heat thermal energy storage system using paraffin wax. The shrinkage during the discharging period is found to affect the thermal performance of the thermal energy storage significantly. The maximum difference in total heat extraction from the thermal energy storage is obtained as 15% between the cases of with and without shrinkage. Moreover, the proposed model is used to analyze the behaviour of latent heat thermal energy storage system under multiple cycles of solidification and melting, incorporating volumetric shrinkage and expansion. The developed methodology will provide detailed insight into the thermal performance of latent heat thermal energy storage system with shrinkage and expansion, leading to an improved material selection and design of the storage systems.