Volume 66

Numerical modelling and thermal analysis of a tube-in-tube latent heat thermal energy storage system Avin Rwehikiza Adolf, Tunde Bello-Ochende, Michel De Paepe

Abstract

LHTES systems provide high energy density and management in various applications. This study presents a numerical modelling and thermal analysis of a tube-in-tube LHTES using PCM as the storage medium. A 3D transient heat transfer model based on the enthalpy-porosity method was developed to simulate the coupled processes of conduction, convection, and phase change. A computational model, created with ANSYS FLUENT 2023 R1, was validated against experimental data. The study examined how the initial PCM temperature affects the charging time, heat transfer rate, and energy stored, while maintaining a constant HTF mass flow rate of 234 kg/h and an inlet HTF temperature of 333 K. Increasing the initial PCM temperature was shown to reduce charging time by boosting the initial heat transfer rate and extending the peak thermal response, thereby speeding up early-stage melting. After melting is complete, the heat transfer rate sharply drops to nearly zero. Importantly, while the charging rate varies, the total energy storage capacity remains consistent, with all systems reaching a similar maximum capacity. These results highlight that initial PCM temperature is a vital parameter for enhancing charging kinetics without impacting storage capacity, providing valuable insights for designing efficient TES systems.

Keywords Latent heat thermal energy storage, Phase change material, Tube-in-tube heat exchanger, Numerical modelling, Enthalpy-porosity method