Study on thermal performance improvement technology of latent heat thermal energy storage for building heating

Thermal energy storage technology incorporating phase change materials (PCM) is a feasible option to take advantage of off-peak electricity tariff for achieving the function of “peak load shaving” and energy efficiency economically in electric heating systems. However, the low thermal conductivity of phase change materials in these systems limits its application. In this work, a design of non-uniformly distributed fin configuration was proposed, considering the optimization of the non-uniform arrangement and coil structure to enhance heat transfer. A two-dimensional CFD model has been developed and validated with test data. The coil inner diameter, tube pitch, row spacing and fin height were optimized based on the simulated temperature variations and visualizations of the PCM during charging and discharging processes. Results demonstrated that the mass of fully melted PCM is increased by 24.5%, and the outlet water temperature is about 3℃ higher for the optimal non-uniform finned coil structure. Additionally, the influence of the device overall dimensions on the PCM utilization rate is also demonstrated in this study. After optimization, the heat energy discharged-charged ratio can be increased by 39.6% to achieve a better thermal energy discharging efficiency. The results may provide valuable references for appropriate latent thermal energy storage design solutions in practice.