Unsteady heat transfer from a sphere at low Reynolds and Strouhal numbers

Abstract

Heat transfer from a sphere in a traveling sound wave is studied using an axi-symmetric formulation. The effect of a reversing flow on the flow behavior is examined and formation of separation regions and vortex shedding at flow reversal is found even for Reynolds numbers on the order of one. Time dependent thermal displacement and induced transient flows were found to increase the minimum value for transient heat transfer significantly above the conduction limit as predicted by a quasi-steady analysis. The heat transfer is found to decrease with Strouhal number for Reynolds numbers greater than two. Transient effects for the range of low Strouhal numbers are found to be significant for the determination of time-averaged unsteady heat transfer.