A research on melting, energy storage, and entropy generation in a vertical shell-tube latent heat storage system with different fin models and laminar flow regimes

Abstract

This numerical study investigates the melting time, energy storage, and second-law efficiency of a latent heat thermal energy storage (LHTES) system consisting of a vertical shell and tube heat exchanger using aluminium metal foam (MF) and fins with different geometries. RT58 paraffin wax phase change material (PCM) was used as the heat storage material, and heat input to the system was provided by hot water flowing through the inner tube in a laminar regime (Re = 1000 and 2000) and T inlet = 358 K. Rectangular, triangular, and parabolic fin models with the same total surface area were compared under different fin lengths. The analyses were carried out using the enthalpy-porosity approach and the Darcy–Brinkman–Forchheimer model. The results show that fin geometry and dimensions are decisive factors in PCM melting time, energy storage capacity, and entropy generation (EnG). While rectangular fins provided the shortest melting time, parabolic fins stood out with a more homogeneous melting profile and lower overall EnG performance. The best performance was obtained with the longest parabolic fin (P3) model. This model provided 4-19% lower thermal EnG compared to other geometries. Re = 2000 significantly shortened the full melting time of the PCM by increasing heat transfer compared to Re = 1000. The results show that the combined use of MF and fins in vertical shell and tube LHTES systems increases energy storage efficiency and reduces thermodynamic irreversibilities.