Thermal investigation of PCM-based high temperature thermal energy storage in packed bed

The behavior of a packed bed latent heat thermal energy storage system is analyzed in this paper. Molten salt is considered for the heat transfer fluid (HTF) with phase change material (PCM) capsules as the filler. The model developed uses the concentric-dispersion equations, except the phase change phenomena of PCM inside the capsules is analyzed by using enthalpy method. The equations are numerically solved by finite-difference approach, and the results obtained are validated against experiments from the literature. The effects of PCM capsule diameter (d_p), fluid inlet velocity (u_f) and storage tank height (H) on the temperature profiles of packed bed have been investigated. Also presented and discussed in a detail description of the charge efficiency for various working conditions. The results indicated that decreasing the size of PCM capsule and fluid inlet velocity, or increasing the storage height, results in an increase in the charge efficiency.