• Effect of rib height on heat transfer and friction factor in a square channel roughened by inclined ribs with a gap
• Author  :  Aditi Neekhara, Pooja Tiwari and Shailesh Gupta
• Pages   :  223-229
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• Abstract

This work concentrates on experimental investigation of forced convection heat transfer and friction factor (pressure drop) characteristics of a rib-roughened surface with varying rib height of discrete inclined ribs. The test section of the square duct (AR=1) is roughened on its top and bottom wall with Inclined square ribs having a gap on its length. Reynolds number (Re) based on duct hydraulic diameter varied from 5,000 to 40,000, relative roughness pitch (p/e) is 10, relative gap width (g/e) is 1 and relative gap position (d/W) is taken as 1/3. The rib attack angle (α) is taken as 600 .The effects of five rib height to hydraulic diameter ratios (e/Dh) of 0.047, 0.060, 0.074, 0.087 and 0.10 on heat transfer in terms of Nusselt number and friction loss in the form of friction factor are experimentally investigated. The results show that there is significant effect on the Nusselt number and friction factor when (e/Dh) has changed. It is observed that the heat transfer augmentation in the channel increase with decrease in the rib height to hydraulic diameter ratio (e/Dh) (from 0.10 to 0.060) but only at the cost of the pressure drop across the test section. Maximum heat transfer enhancement is associated with ribs of (e/Dh) = 0.060 which also produces the maximum pressure drop penalty in the range of parameters investigated. The thermal hydraulic performance for all (e/Dh) ratios is also presented. The thermal hydraulic performance of ribs with (e/Dh) = 0.060 has found maximum and is about 2.18.

Keywords: Nusselt number, Friction factor, Rib height to hydraulic diameter ratio, Reynold’s number, thermal performance

Article published in International Journal of Thermal Technologies, Vol.7, No.4 (Dec-2017)