A novel bionic packed bed latent heat storage system filled with encapsulated PCM for thermal energy collection

Abstract

• A bionic structure brings a more homogeneous temperature difference and a smaller pressure drop compared with conventional systems. • The parameters related to heat transfer and phase transition acquired from numerical study were validated by experiments. • A non-local thermal equilibrium model was employed to characterize the temperature distribution of PCM and HTF in porous media. • The enhancement of flow resistance and heat exchange performance was evaluated. The main content of this work is to propose a novel bionic solution to overcome the nonuniformity of flow and temperature distribution, which is an inherent problem and restriction for conventional latent heat storage devices. By learning from animal circulatory systems, the inner space and flow channel network are distributed hierarchically as arteries, veins, capillaries and ventricles. A conceptual configuration of the bionic system is presented, and its numerical model is established to demonstrate the flow and heat transfer phenomena. The encapsulated PCM that is used in this study is fabricated and parameters related have been measured by experiments. A numerical model of a 3D continuous PCM bed is established to help research the flow of HTF through the surfaces of PCM particles and the heat transfer between them. Then, a model of a simplified bionic device is developed where the PCM region is set as a porous domain. The results show the flow and temperature fields are distributed uniformly, along with a much smaller global pressure drop. By allocating the thermal load on cascaded layers with stepwise PCMs, a more homogeneous global temperature difference can be achieved.