Comparison of an Experimental and Numerical Investigation of a Packed-Bed Latent Heat Thermal Storage System with Encapsulated Phase Change Material
Abstract
A laboratory scale packed bed latent heat thermal energy storage (TES) system was designed and built to study its charging and discharging behavior. Encapsulated sodium nitrate spherical capsules were used as the storage material and air was used as the heat transfer fluid. A two-dimensional two-phase model was developed by assuming that the PCM capsules behave as continuous, homogeneous, and isotropic porous medium, and not as a medium composed of independent particles. The heat transfer coefficient was calculated based on the phase change process inside the capsule by enthalpy formulation model. The flow inside the system was predicted by solving the extended Brinkman equation. The developed model was used to analyze the temperature distribution inside the capsules placed at different axial positions of the bed. The effect of mass flow rate on the charging and discharging times and melt fraction of the packed bed during the charge and discharge processes were also analyzed. The results obtained from the model matched well with the experimentally observed results.
Keywords
Phase change material, Packed-bed latent heat storage, Encapsulated capsule