Two-dimensional simulation of a cylinderical latent heat thermal energy storage system

Phase change material-based latent heat thermal energy storage (LHTES) systems offer an effective way to improve the energy storage capacity and efficiency in building heating. In this paper, a two-dimensional computational model is developed to study the thermal behaviour and heat transfer characteristics of a cylindrical LHTES system. This model is based on the thermal conduction in the phase change material. It is first validated with the experimental data and then used to study the thermal behaviour and heat transfer characteristics of a cylindrical LHTES system for consecutive charging and discharging processes. Contours of temperature distribution and liquid volume fraction in the phase change material are studied and compared with the experimental data. It is found that the thermal conduction assumption is sufficient to model the discharging process as the predicted results agree well with the experimental data. However, during the charging process, the charging time calculated using the thermal conduction model is approximately 30% longer than the experimental charging time. It proves that the convective heat transfer caused by buoyancy in the liquid phase plays an important role in the LHTES system. Further research is required to better understand the heat transfer between heat exchanger surfaces and phase change materials, and in particular, the interactions between the solid and liquid phases of the phase change material.