摘要

In this paper, the effect of V-cut twisted tape inserts on heat transfer and friction factor characteristics in a double pipe heat exchanger have been experimentally investigated for three twist ratios (TR = 5, 10 and 15), different combinations of depth and width ratios (DR=1/2, WR=1/2; DR=1/3, WR=1/2; DR=1/2, WR=1/3) and inlet temperatures (50°C, 60°C and 70°C). Water has been used as hot fluid (flowing through in-tube side, where twisted tape inserts is used) as well as cold fluid (flowing through annulus side). The obtained results show that the Nusselt number increases and the friction factor decreases with increasing Reynolds number for the same twist ratio. The average Nusselt number and friction factor of water flowing in the inner tube with twisting ratios of 5, 10 and 15 for same depth and width ratio (DR=1/2 and WR=1/2) respectively, enhance 1.51 to 2.52, 1.37 to 2.03, 1.09 to 1.57 times and 1.55 to 1.87, 1.45 to 1.77 and 1.36 to 1.62 times respectively, that for the plain tube. Higher depth ratio (DR=1/2) and lower width ratio (WR=1/3) yield higher heat transfer and friction factor than those V-cuts twisted tape with lower depth ratio (DR=1/3) and higher width ratio (WR=1/2). The value of thermal performance factor (TPF) is greater than unity for all cases. This indicates that using V-cuts twisted tape inserts is considered a better choice in practical application.