The effect of hydrodynamic flow unsteadiness on heat transfer enhancement in a channel with square ribs

Abstract

The heat transfer coefficient has been measured in the channel with square ribs for the case of periodic flow rate variation. New technique for heat transfer coefficient measurements has been applied in the study. It allows simultaneous surface heating and estimation of its local temperature. Two different patterns of heat transfer coefficient behavior in the gap between the ribs have been obtained. The first pattern corresponds to enhancement of both local heat transfer coefficient and average heat transfer if compared to its steady flow values. The second pattern exhibits considerable gain in heat transfer in the near-wake of the rib and its deterioration in other measurement regions. The reasons for such effects have been described on the basis of smoke visualization of flows.