heat transfer and pressure drop characteristics in a circular tube fitted with and without v-cut twisted tape insert

the effect of v-cut twisted tape insert on heat transfer, friction factor and thermal performance factor characteristics in a circular tube were investigated for three twist ratios (y = 2.0, 4.4 and 6.0) and three different combinations of depth and width ratios (dr = 0.34 and wr = 0.43, dr = 0.34 and wr = 0.34, dr = 0.43 and wr = 0.34). the obtained results show that the mean nusselt number and the mean friction factor in the tube with v-cut twisted tape (vtt) increase with decreasing twist ratios (y), width ratios (wr) and increasing depth ratios (dr). subsequently an empirical correlation also was formulated to match with experimental results with ± 6% variation for the nusselt number and ± 10% for the friction factor.