Design and Operation of a Novel Cross Fin in Hot-Water Production System for Buildings

The importance of phase change heat storage (PCHS) in solar thermal applications is limited by the low thermal conductivity of phase change materials (PCMs) and the uneven temperature distribution during heat transfer. This study proposes to use composite fins for heat exchange in the PCHS module and integrate them into a hot-water production system (HWPS) for building heating. The effectiveness of the novel fin structure is assessed through thorough numerical simulations and experimental validation. An examination of melting fractions, temperature distribution, and flow characteristics of the molten PCMs across various fin structures indicates that increasing the lengths and quantities of the cross fins can alleviate the challenge of incomplete melting at the end of the charging process. Notably, expanding the surface area of the cross fins results in a 7.37-fold increase in the average thermal storage rate and a 781.25% enhancement in the average temperature response compared to the original design. These findings show that the new composite fin design greatly improves the heat storage performance of an HWPS, which is of great significance for building energy conservation.