Natural convection heat transfer in the separation region of a backward-facing step. (Heat transfer from step).

Abstract

An experimental study has been conducted to investigate the fluid flow and heat transfer of natural convection past a backward-facing step. The step and the vertical plates upstream and downstream of the step are heated uniformly with a constant heat flux, and water is used as a test fluid. The flow and temperature fields over the step are visualized. The result shows that the high-temperature fluid ascending from the upstream plate separates from the step after flowing over a certain distance from the step edge, while the low-temperature fluid above the step rushes onto the step surface after the separation. The local heat transfer coefficients of the step are also measured, and the results reveal that the above separation and inrush of a high- and low-temperature fluid yield the minimum and maximum heat transfer coefficients of the step. It is also found that the locations of the minimum and maximum heat transfer coefficients are determined solely with the local Grashof numbers of the step.