Heat transfer distribution of swirling flame jet impinging on a flat plate using twisted tapes

Impinging flame jets have wide applications in industrial and domestic heating purpose. The aim of the present study is to study the effect of swirl on flame jet impingement heat transfer characteristics. Four twisted tapes of twist ratios 2, 3.2, 4.5 and 7.5 (corresponding swirl numbers of 0.79, 0.49, 0.35 and 0.21) are used to experimentally obtain the swirling flame jet. The effect of twist ratio at Reynolds number varying from 500 to 2500 and equivalence ratio varying from 0.7 to 1.5 for burner tip to impingement plate distances of 2 and 4 is studied. The effect of swirl is compared with that of no tape in the tube burner by estimating the average heat flux distribution and coefficient of variation of heat flux for two impingement regions - within two times the burner diameter from the stagnation point and four times diameter from the stagnation point. From the experimental study, it is found that swirl enhances the heat flux distribution by 40-140% at low Reynolds number. At higher Reynolds number the effect of swirl is negative and is found to decrease the average heat flux distribution by 10-40%. (C) 2015 Elsevier Ltd. All rights reserved.