Effect of perforated fins on the heat-transfer performance of vertical shell-and-tube latent heat energy storage unit

Abstract

Annular finned tube has been widely employed in the latent heat thermal energy storage (LHTES) field to accelerate the charging/discharging process. Nevertheless, the obstruction of fins on the liquid flow restrains natural convection development in the LHTES unit. In the present work, we propose several three-dimensional perforated-fin models to enhance the heat storage performance. The perforated fin structure is studied in detail by varying the hole diameter and hole location. It is observed that the two hole-parameters have significant effects on the charging performance of the LHTES unit. With the increase of the hole diameter, natural convection is reinforced, but thermal conduction is weakened simultaneously. Besides, the farther the hole is from the fin root, the stronger the thermal conduction is, while the weaker the natural convection is caused. The findings reveal that although the perforated fin is conducive to enhancing natural convection, it weakens thermal conduction compared with the solid-fin model. There is an optimal perforated-fin structure for achieving the maximum enhancement on the heat transfer. The structure, in which the hole diameter is 3 mm, hole location is L = 8 mm, and hole number is 6, reduces the complete melting time by 5.49% compared with the solid-fin model, and the heat storage capacity is commendably enhanced by 0.21%. Consequently, the perforated fins are worthy of being employed in the annular finned tube LHTES unit.