Investigation on thermal performance of different wire coil twisted tape inserts in a tube circulated with water

Abstract

This study gives the combined outcome of twisted tapes (TT) and perforated twisted tapes (PTT) with twist ratios of (TRS) 3, 4 and 5 and wire coils (WC) coil ratios (CR) of 3 and 4 in a circular tube, where water has been circulated as the working fluid. The convective heat transfer coefficient (h) and friction factor (f) characteristics are examined in the turbulent flow regime (3000 ≤ Re ≤ 16,000) in order to obtain the thermal performance. These characteristics obtained with the combined effect of TT and PTT associated with WC in a plain tube are 65.06%–101.13%, 75.67%–177.81% and 2.75%–30%, 9%–28% respectively when compared with the circular tube. These enhancements are due to reversed flow caused by wire coils with swirling and impinging flow from the twisted tapes. In addition, high turbulence is created while the fluid is passing through the perforations of PTT. With the wire coil at TR = 3 and CR = 3, the maximum thermal enhancement factor at stable pumping power is 2.03 and 2.66 for TT and PTT, respectively. For all wire coils, twisted tapes and plain tubes, the correlations of Nusselt number and friction factor are established.