Enhancement of heat transfer by a fin with two fences and tube heat exchanger

A three-dimensional steady numerical computation was made for a unit element of finned-tube heat exchangers mounted in a uniform flow. In this study, numerical computation was made in the case where two fences are set on the plate fin surface by punching and the effect of the fences on the flow and heat transfer characteristics were investigated in the low Reynolds number range. The effect of a hole, open in the plate fin behind the fence, on heat transfer and flow structures was also examined. Two fences with holes were found to show several important effects on the flow and heat transfer characteristics and to work well in heat transfer augmentation. They reduce the dead water area of the fin downstream the tube so that heat transfer enhancement was obtained there. Heat transfer enhancement was also attained at the brim of the hole, especially for the fin surface that was not mounted the fence. As a result, total heat transfer performance becomes 17% higher compared to the normal plain fin case.