Experimental Investigation of Effect of Different Configurations of Semi Circular or Half Round Ribs on Heat Transfer Enhancement in a Rectangular Duct

This research study investigates the impact of various configurations of half round shaped ribs on thermal performance and frictional effects through a rectangular duct. The ribs were provided only on inner surface of the rectangular duct's bottom wall. Six distinct configurations of half round ribs varying from continuous to hybrid arrangement were used. The range of Reynolds number was kept between 13,500 and 34,800; while the ratio of rib pitch and height was kept constant as 8. The ratio of height of rib to hydraulic diameter of duct (also known as blockage ratio) was kept at 0.114. The results of experimental investigation showed that the Nusselt number ratio obtained was ranging from 1.36 to 2.74, while the friction factor ratio ranges from 1.70 to 4.51. The overall enhancement ratio for all configurations obtained ranges from 1.06 to 1.80 times that of plain duct. Among all rib configurations, the hybrid rib configuration shows superior ratio of Nusselt number and intermediate increase in ratio of friction factor as compared to all the other rib configurations. Hybrid rib configuration shows overall enhancement ratio values ranging from 1.45 to 1.80 times as compared to that of duct without ribs within the above specified Reynolds number. From this study, the results showed that the hybrid configuration of ribs shows superior overall enhancement ratio in thermal manner over the remaining tested rib configurations.