Evaluation and development of a predictive model for conjugate phase change heat transfer of energy storage system partially filled with porous media

Abstract

The present study proposes a predictive model to explore the effect of partially filled porous media on the conjugate heat transfer characteristic of phase change material (PCM) with interfacial coupling conditions between pure fluid region and porous region. The enthalpy-porosity method, local thermal non-equilibrium model and Darcy-Forchheimer law are comprehensively considered to describe the convective heat transfer process in porous media. The modified model is then validated by benchmark data provided by particle image velocimetry (PIV) experiments. The phase change behavior, heat transfer efficiency and energy storage performance are numerically investigated for different partial porous filling strategies in terms of filling content, position, height of porous foam and inclination angles of cavity. The results indicate that due to the resistance in porous region, the shear stress exerted by the main vortex (natural convection) in pure fluid region and the momentum transferred, a secondary vortex phenomenon appears in the porous region near the fluid/porous interface. Moreover, such discontinuity of permeability and fluid-to-porous thermal conductivity results in the cusp of phase change interface at the horizontal fluid/porous boundary. Among four partial porous filling cases, the lower porous filling one has more desirable heat transfer performance, and the 3/4H lower porous filling configuration is the best solution for optimization of the latent heat thermal energy storage (LHTES) systems. For tilted cavity, the increase of inclination angle positively affects the heat transfer efficiency as well as the energy storage rate of the LHTES system, where the performance of 3/4H lower porous filling configuration is further highlighted.