Topology optimization for heat transfer enhancement in thermochemical heat storage

Thermochemical heat storage has a promising application prospect due to its high energy density and ability of seasonal energy storage with little heat loss. However, most of thermochemical heat storage systems suffer from very poor thermal conductivity that limit the heat transfer rate and hinder the implementation of this technology. This study presents a novel solution to the poor heat transfer problem in a multi-tube thermochemical heat storage unit through topology optimization of highly conductive fins. For the formulation of the topology optimization problem, the dehydration process of Ca(OH)(2) was considered, and a density-based approach was employed. Results indicated that the topology optimized geometry had a superior heat transfer performance and a 43% improvement was achieved with respect to the normally used longitudinal design in terms of reaction time. It was found that during the dehydration process of Ca(OH)(2), heat conduction was the dominant factor while convection heat transfer was only observed in a small region near the porous gas channel. Furthermore, the effects of the number of heat transfer fluid (HTF) pipes were explored. It was shown that bifurcations of intermediate branches tend to vanish with the increase of the number of HTF pipes and the charging process can be further enhanced through a more uniform HTF pipe distribution. Finally, the reconstructed model was validated, and the optimized fins were tested under the hydration process of CaO, which further confirmed the superiority of the topology design. (C) 2020 Elsevier Ltd. All rights reserved.