Numerical study on the heat storage and flow characteristics in a packed bed thermal storage with phase change particles

Abstract

Packed bed latent heat storage (PBLHS) is considered as a promising method to store thermal energy. Here, a 2-D axisymmetric numerical model is established to simulate the melting of spherical phase change material (PCM) particles with air voids. First, the effective thermal conductivity (ETC) of the PCM considering natural convection was calculated, and was found to be strongly correlated with the liquid fraction, γ, and the Rayleigh number, Ra. Based on this, a 3-D PBLHS model based on the coupled discrete element modeling-computational fluid dynamics (DEM-CFD) approach was proposed, and the effects of varying the inlet temperature and mass flow rate were analyzed. The results show that increasing the inlet temperature and flow rate of the heat transfer fluid significantly improves the heat storage and flow characteristics of the packed bed. In addition, the effects of varying the particle size and packing configuration of the bed were investigated. The results show that the radial temperature and velocity distributions of the radially layered model (RLM) were the most uniform among the different packing models. Furthermore, the average charging rate of 3.18 × 10³ W was 17.8 % higher than that of the randomly packed model (RPM), indicating significant heat storage enhancement.