Heat transfer characteristics in channel with square rib at different Mach numbers

Abstract

The detailed flow structures and closely-related heat transfer characteristics were investigated along the wall of a cooling channel with rib tabulator by computation. The two-dimensional Navier-Stokes equations were solved using the density-based algorithm and strongly-coupled with the heat-transfer equation. Three typical Reynolds numbers defined by rib height and Mach numbers were set at 500, 750, 1000 and at 0.2, 0.3, 0.4, respectively. Results show that, As the Mach numbers changing from 0.2 to 0.4, the local Nusselt numbers increase and the average heat transfer effects are enhanced. Based on the instantaneous field of vortices evolvement, the vortexes are first generated near the top surface of the rib by the strong shear effects. Then the vortexes are shed and intensified gradually downstream. Particularly, an important phenomenon is, for the first time, discovered that the high Nusselt number has a consistent correlation with the positive and negative sign alteration of the shear layer on the wall, which satisfactorily explains the mechanisms of heat transfer enhancement due to the flow.