Investigation of heat transfer enhancement inside developing gravity-driven films along a vertical permeable plate subject to nonuniform suction

Abstract

Flow and heat transfer through the boundary layers of a falling liquid film on a vertical permeable plate subject to nonuniform suction flow are analyzed in this work. The continuity, momentum, and energy equations are transformed to nonsimilar equations and solved using a validated implicit and iterative finite difference method. Increases in the Froude number, Galilei number, and the dimensionless average suction velocity are found to increase the skin friction coefficient, the Nusselt number, and the heat transfer enhancement ratios. These enhancement ratios are noticed to increase at the plate exit as the suction velocity power-law index increases. The Froude number for uniform suction case required to attain the same enhancement ratios due to nonuniform distribution of this suction flow is found to increase as the Galilei number, average suction velocity, and power-law index increase. It is found that the upper most values of the enhancement factors in heat transfer and Froude number are m + 1 folds when the suction power-law index is equal to m. This work demonstrated that significant heat transfer enhancement inside developing gravity-driven liquid films is attainable when properly distributing the suction velocity along the plate.

Combined effect of roughness and suction/blowing in a laminar micro-channel flow

“…Suction and blowing, two active techniques, have been widely studied in boundary layers, but less so in channel flows. For example, Khaled [15] studied the effects of nonuniform suction in a falling liquid film. Chen [16] studied forced heat transfer over a flat plate subjected to suction and blowing and continuously moving in a quiescent or flowing fluid.…”