Experimental Investigation of Heat Transfer Enhancement in a Two-Pass Square Duct by Permeable Ribs

This investigation presents the heat transfer enhancement results of flow past repeated permeable ribs mounted on the bottom surface of a two-pass square channel. Spatially periodic flow interruption generated by rib arrays mounted on the walls is extensively used for augmentation of heat transfer in turbine blade cooling passages. To remove the local heat transfer deterioration in the vicinity region of the solid ribs, permeable ribs have been proposed in the literature for single pass coolant passages. This study intends to investigate the performance of permeable ribs array placed on the lower wall of a two-pass channel compared to that of the solid rib array. The heat transfer and friction characteristics are investigated for smooth, solid-ribbed, slit-ribbed, and split-slit-ribbed square channels for the Reynolds numbers of 5,500, 12,800, and 16,400. An array of ribs (consisting of fifteen ribs) has been mounted over the total test section, with seven each in the first and second passes, and one in the bend. The performance analysis has been carried out using thermal performance on the basis of constant pumping power and entropy generation principle.