Simultaneous evaluation of charge/discharge times and energy storage/release capacities in multi-tube latent heat energy storage with metal foam-enhanced PCM

Abstract

Phase change materials (PCMs) play a critical role in energy storage systems due to their high latent heat capacity, enabling efficient thermal energy storage and release during phase transitions. The low thermal conductivity problem of PCMs causes the heat transfer to decrease during energy storage and release processes and the heat energy to be distributed nonuniformly in the system. Multi-tube latent heat energy storage (LHES) with phase change materials (PCMs) have been implemented to improve heat distribution within PCMs. The novelty of this study was the simultaneous assessment of charge/discharge times and energy storage/release capacities for determining the optimal tube geometry, number, and layout in LHES with metal foam-enhanced PCM. In this context, single, double, triple, and quadruple multi-tube designs consisting of basic geometries (circle, square, triangle) for LHES with metal foam-enhanced PCM have been realized. RT42 was used as PCM and two-dimensional and time-dependent numerical analyses based on the enthalpy-porosity method were carried out for these configurations. In addition, the non-equilibrium thermal model was chosen for energy analyses because it offers a more realistic approach. The melting and solidification analysis findings were evaluated in terms of charge/discharge time, PCM temperature distribution, and energy storage/release capacity. Depending on the physical phenomena in the melting and solidification processes and the heat transfer surface areas of the tube geometries, different geometries have shown high performance in charge and discharge times. The lowest charging time was obtained for the triangle-tube designs and reduced charging time by 7.7 % to 10.4 % compared to circle-tube designs. However, the lowest discharge times were obtained for square-tube configurations in the solidification process and the discharge time was decreased by 13.6 % to 27.8 % compared to circle-tube designs. The energy storage and release capacity during melting and solidification processes did not increase proportionally with the number of tubes. In the quadruple-tube model, heat energy was distributed more uniformly within the PCM container. However, for the non-uniformly arranged triple-tube model, higher energy storage and release capacities were achieved at the end of the charging and discharging periods. Considering the energy storage and release performances, it was observed that the most suitable configuration for both melting and solidification processes was the triple triangle-tube. The triple triangle-tube design revealed enhancements in energy storage capacity of 0.41 % to 12 % and energy release capacity of 0.15 % to 9.93 % compared to other single and multiple-tube designs. © 2024 Elsevier Ltd