Design and optimization of an eccentric tube heat exchanger based on bionic fins

Abstract

Latent heat thermal energy storage based on phase change materials (PCMs) is an effective approach for improving the utilization efficiency of intermittent thermal energy sources. However, the low thermal conductivity of PCMs leads to slow melting and non-uniform heat transfer, which significantly limits the charging performance of thermal storage units. In this study, an eccentric-tube phase change heat exchanger with bionic fins was proposed to enhance the melting behavior of PCM. A two-dimensional cross-sectional transient numerical model was established, and the enthalpy–porosity method was employed to simulate the melting process of lauric acid. Five fin configurations were designed under approximately equal fin area conditions. Four eccentric distances (0, 4, 6, 8 mm) were considered to investigate the coupled effects. Results show that the tree-shaped fin achieves the shortest complete melting time of 2184 s at e=0 mm, 3.0% shorter than the straight fin. As the eccentric distance increases to 8 mm, the complete melting time decreases by 20.9% to 1728 s. The combination of tree-shaped fin and e=8 mm reduces the complete melting time by 23.2%.