A STUDY ON THE EFFECTS OF FIN COLLAR SHAPE ON THE HEAT TRANSFER PERFORMANCE OF FIN-TUBE HEAT EXCHANGERS

摘要

A numerical study is conducted to investigate effects of a triangular space in fin-tube heat exchangers on heat transfer performance. The triangular shape is formed by two adjacent fin collars and a copper tube where the fin collar does not contact the copper tube. It affects on not only thermal resistance between a copper tube and fin collars but also air side heat convection. Size of the triangular space depends on its production process and is not constant. In the numerical simulation, the triangular shape was assumed as an equilateral triangle. The ratio of the triangle edge length to fin pitch is varied from 0 to 40 %. A thermal conductance was set on contact surface of the tube and fin collar. Due to a decrease of the thermal conductance value, heat transfer rate also decreases. Size of the triangular space affects to both air side convection and total contact resistance between the tube and fin collar. Increase of the triangular space increases non-contact area of the fin collars with tube and decreases heat transfer rate. On the other hand the air side heat convection is encouraged. The triangular space changes the fin collar shape and air flow pattern around the tube. Heat transfer rate enhanced about 1 % due to the increase of the triangular space.