Periodically fully-developed heat and fluid flow behaviors in a turbulent tube flow with square-cut twisted tape inserts

This article reports a numerical study of enhancing heat transfer and thermal performance of in a circular tube inserted by square cut twisted-]tapes in comparison with that inserted by classical twisted tapes. The study was carried out for a turbulent periodic flow in a three-dimensional constant heat flux-]wall tube. The influences of square cut twisted-]tape geometries including perforated width to tape width ratios (WR = w/W = 0.5, 0.6, 0.7, 0.8 and 0.9) and perforated length to tape width ratios (LR = L/W = 0.7, 0.8 and 0.9) were determined. The main findings are that the heat transfer and pressure loss increase with decreasing perforated width to tape width ratio (WR) and perforated length to tape width ratio (LR) while thermal enhancement factor (TEF) increases as WR increases. The highest thermal enhancement factor (TEF) of 1.37 is achieved by using square-]cut twisted tapes at the largest perforated width to tape width ratio (WR = 0.9) and the smallest perforated length to tape width ratio (LR = 0.7) at Reynolds number (Re) of 7000. The highest thermal enhancement factor (TEF) is around 1.32 times over than that given by the classical twisted tape. (C) 2016 Elsevier Ltd. All rights reserved.