Thermal performance improvement of a low-temperature thermal energy storage with configuration optimization

To improve the performance of solar heat storage and reduce the energy consumption of the fresh air system in areas with poor solar conditions, this study investigates the thermal storage and release performance of a low-temperature rectangular thermal energy storage unit (RTESU). A validated Computational Fluid Dynamics (CFD) model is used to address the impacts of configuration parameters on the performance of the thermal storage process in the Phase change material (PCM) module, including the number and eccentric arrangement of tubes. Subsequently, the effect of the air channel width on the air outlet temperature and the heat transfer rate is analyzed for the heat-releasing process. The numerical results show that the number and the eccentricity of the heat exchanger tube have significant impacts on the heat storage performance, and a minimum duration of 117 min can be achieved with a tube pitch of 30 mm (corresponding to 5 water tubes) and an eccentric of 5 mm, respectively. The air channel width of 20 mm is found as the optimal width due to its higher heat release efficiency (83.24 %) and lower pressure drop (4.3 Pa). The identification of key structural impacts helped to optimize the RTESU configuration, which performs at a low heat storage time of 117 min and achieves a heat release efficiency as high as 83.24 % to satisfy the need for poor solar conditions.