Development and experimental investigation of a modular, honeycomb shell-and-coil PCM-based latent heat thermal energy storage unit assisted with heat pipes. Dynamic simulation of melting process by using object-oriented modeling

This study investigates a modular latent heat thermal energy storage (TES) unit designed to enhance energy storage efficiency using coconut oil as the phase-change material (PCM). The research aims to address the challenge of efficient heat transfer in compact TES systems for applications like solar energy and waste heat recovery. The unit features a novel honeycomb shell-and-coil structure with aluminum helical coils and copper heat pipes, facilitating heat transfer to the PCM via circulated heat transfer fluid. Experiments were conducted under two regimes: 34.5 °C inlet temperature with 1.2 L/min flow rate and 33 °C with 1.7 L/min. Results demonstrate a volumetric energy density of 38 kWh/m 3 and a maximum charging rate of 0.5 kW. Performance was evaluated using the normalized heat transfer performance coefficient (NHTPC) and volumetric energy density (VED), showing competitive efficiency compared to other TES designs. A dynamic model, developed using object-oriented modeling in Modelica, accurately predicts temperature and heat flux, validated against experimental data with a maximum discrepancy of 6 %. This work introduces a scalable, modular TES design and a novel NHTPC vs. VED comparison methodology, offering significant potential for optimizing thermal energy storage systems in the future. • Modular honeycomb TES with heat pipes boosts heat transfer efficiency. • Achieves 38 kWh/m 3 energy density using coconut oil as PCM. • Dynamic model in Modelica validated with experimental melting data. • Proposes NHTPC vs. VED for enhanced TES performance evaluation. • Visualizes PCM melting dynamics through transparent 3D-printed shell.