Effect of Twist Ratios on Heat Transfer for Circular-Cut Twisted Tape Inserts in U-Shaped Pipe

To study the turbulent flow of fluid in circular-cut twisted tape inserts with inserts of varying twist ratios, a numerical simulation has been conducted. The heat transfer phenomenon of fluids in the tubular pipe is analysed with the help of a k omega turbulent model. During the numerical simulation, study was conducted where the Reynolds numbers (Re) was kept in the range 3700 <= Re <= 23650 under a constant temperature condition and twist ratios 3.0, 3.25, 3.5, 3.75, 4.0 and without insert separately. The length of the inserts is 800 mm on both sides with water as the working fluid. Numerical results show that the Wall Temperature, Bulk Temperature, effectiveness (epsilon), Nusselt number (Nu), the friction factor (f) and the thermal performance (eta) show a downward t rend with the twist ratio of the inserts. The vorticity exhibits aAstable pattern in absence of inserts while demonstrating irregular pattern at cut-positions when there are circular-cut twisted tape inserts. The results also show that the heat transfer behavior depends not only on the difference in the geometrical shapes of the insert but also on their twist ratio. For the twist ratio 3, Afriction factor enhances 5.01-5.96 times compared to without insert and also the effectiveness improves 1.88 times. InAcase of thermal enhancement, its performance is 1.31-1.92 times better than without insert.