Modeling and Simulation of Thermodynamic Behavior in a Packed Bed Thermal Energy Storage System

Abstract

This research article studied and simulated a packed bed thermal energy storage system to elucidate its thermodynamic behavior. A transient mathematical model for turbulent flow in a hybrid media, comprising both porous and transparent components, incorporating forced and natural convection, has been formulated. Comsol Multiphysics CFD software was employed for the numerical solution. The Local Thermal Non-Equilibrium (LTNE) methodology was utilized to assess heat transfer in both solid and fluid phases and to ascertain the thermal exchange coefficient between them, which is a critical characteristic for evaluating stored energy. Simulations were conducted on an axisymmetric cylindrical tank filled with pebbles (solid material) and circulated by a thermal oil, serving as a heat transfer fluid (HTF). The presented model was validated and approved using experimental data. The velocity distribution and temperature profiles of the solid phase and fluid phase in the system during the charging process were ascertained and shown. The influence of porosity and particle size on the thermal performance of the TES system was assessed and reported. The findings indicated that the duration needed to charge the tank diminishes with an increase in both porosity and particle size.