Experimental study on heat transfer characteristics in square duct with double V-ribbed tape
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Abstract
The paper presents an experimental study on turbulent flow and heat transfer characteristics in a square duct fitted diagonally with double V-ribbed tapes. The tested duct has uniform heat-fluxed walls and the flow rate of air used as the test fluid is presented in terms of Reynolds number (Re) from 4,000 to 25,000. The insertion of the ribbed tape is performed with three blocked ratios of rib-to-duct height (b/H, BR) = 0.10, 0.15 and 0.20, two pitch ratios of rib pitch to duct height (P/H, PR = 1 and 2), attack angle (a) = 45o, pointing upstream of the flow with respect to the main flow direction. Influences of blocked ratios and pitch ratios on thermal and flow friction characteristics of the inserted duct are investigated. The experimental result of heat transfer in the form of Nusselt number and pressure drop in term of friction factor are compared between the duct mounted with double V-ribbed tapes and the smooth duct. The experimental result shows that at smaller rib pitch spacing (PR = 1) and higher blocked ratios (BR = 0.20) provides highest heat transfer rate, friction factor and thermal enhancement factor (TEF) is about 1.65 at the lowest value of Reynolds number.
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