Heat Transfer Performance of a Fin with Two Fences and Tube Heat Exchanger. Study in the Low Reynolds Number Range.

Abstract

A three-dimensional steady numerical computation was made for a component model of fin and tube type of compact heat exchangers situated in a uniform flow. In this study, in order to find a clue to design high-efficient heat exchangers, numerical computation was made in the case where two fences are attached on the plate fin surface and their geometrical effects such as their locations, their heights and their attack angles on flow and heat transfer characteristics were investigated especially 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. This hole simulates the hole of the plate fin to be produced in practical application, when a fence is produced by punching from the original plain fin plate. Two fences with holes were found to show several important effects on flow and heat transfer structures and to work well in heat transfer augmentation. They reduce the dead water area downstream the tube so that heat transfer enhancement was obtained there. Heat transfer enhancement was also attained on the fin surfaces around them. As a result, total heat transfer performance becomes 17% up compared to the normal plain fin case.