Experimental Study on Heat-Transfer Enhancement in Turbulent Natural Convection along a Vertical Flat Plate. 2nd Report, Effect of Backward-Facing Step.

Abstract

Heat transfer and Fluid flow of turbulent natural convection with a backward-step were investigated experimentally, and the effect of step size on heat transfer was discussed. The wall temperature and the fluid flow were visualized using a liquid crystal and fluorescent paint to clarify the behavior of heat transfer coefficients. It was realized from a series of experiments that low-temperature streaks appear on the backward-heat-transfer plate and that they a significant role in heat-transfer enhancement. These patterns are generated by low-temperature fluid lumps, which possess three-dimensional and unstable structures. Moreover, the maximum heat-transfer point is not consistent with the reattachment point of the separation flow, and these points shift downstream with increasing step size H.