Local Heat Transfer and the Effects of Turbulence on Interrupted-fin Surfaces

Project Overview Interrupted-fin surfaces are used to enhance the air-side heat transfer performance in many compact heat exchangers. While many empirical correlations are available in the open literature for offset-strip and louvered-fin geometries, local heat transfer behavior on individual fins is not as well understood. A redesign of these surfaces may result in higher heat transfer. Inlet flow manipulation is another way to increase heat transfer. Increases in turbulence intensity have been shown to cause significant increases in flat-plate turbulent heat transfer and a reduction in the critical Reynolds number (Blair, 1983a and b, and Hancock and Bradshaw, 1983). If an increase in turbulence intensity causes vortex shedding to begin at a lower Reynolds number or causes the resulting vortices to be larger, heat transfer should show a significant augmentation (See DeJong and Jacobi, 1995; DeJong and Jacobi, 1999; and Gentry and Jacobi, 1995). However, it is uncertain whether or not these effects will be seen in the more complicated interrupted surface geometries. Thus, this project has two related objectives. First, local heat transfer behavior interrupted surface arrays is being analyzed. Second, the effects of an increase in turbulence intensity on heat transfer and pressure drop for these geometries is being quantified.