Heat transfer characteristics of topological latent heat storage systems based on optimization objectives

Abstract

In order to improve the heat storage efficiency and shorten the heat storage/release time in latent heat storage (LHS) systems, topology optimization of heat transfer problems has been applied to LHS systems. The choice of the optimization objective determines the structure of the topology fins. In this paper, the topology generation process was analyzed using the mean temperature, the mean square deviation (MSD) of the mean temperature, and the multi-objective entropy depletion as the optimization objectives. In this way, a method for selecting the optimization objectives according to the design requirements was obtained. The multi-objective topological structure (Case 3) with uniform tree-shaped fins (Case 4) and gradient tree-shaped fins (Case 5) was applied to the LHS system, and the finite element analysis method was used to construct a mathematical model of the LHS system to comprehensively analyze the heat storage/release process. The results showed that the complete melting times for Case 3, Case 4, and Case 5 were 751 s, 1005 s, and 920 s, respectively. At 751 s, the average heat storage capacities for Case 3, Case 4, and Case 5 are 296.81 W, 216.94 W, and 238.92 W, respectively. Compared to Case 4, Case 3 decreased the complete melting time by 25.27 % and increased the average heat storage capacity by 36.82 %. At heat-releasing times of 500 s, 1000 s, 1500 s, and 2000 s, the maximum differences in liquid phase rates for the three models were 10.93 %, 11.97 %, 11.51 %, and 9.57 %, respectively. From the perspective of the field synergy, Case 3 showed a better heat transfer path and the optimal heat transfer effect considering the temperature, liquid phase rate, heat storage/release time, and heat storage/release capacity. In addition, the dimensionless criterion equation affecting the liquid phase rate was obtained by segmented fitting of the heat transfer process of the topology-optimized LHS system. The findings of the study can facilitate the promotion of topology-optimized structures for practical engineering applications in LHS systems.