Thermal and fluid flow characteristics in a tube equipped with peripherally-cut dual twisted tapes

This article presents an experimental analysis of the turbulent flow of water in a heat exchanger tube fitted with peripherally-cut dual twisted tapes (PDTs) under a constant wall heat-flux condition. The peripherallycut dual twisted tapes with different cutting pitch ratios (l/y = 0.5, 0.75 and 1.0) were tested for Reynolds numbers in the range of 5400 to 14,000. The experimental results showed thatNusselt number and friction factor of the tubes fitted with PDTswere considerably higher than those of the plain tube and those of the tubes with single twisted tape (ST) and dual twisted tapes (DTs). It was found that PDTs with l/y = 0.5, 0.75 and 1.0 gave higher heat transfer rate than the typical DTs, with average Nusselt numbers greater by 12.1%, 7.8% and 3.8%, respectively. For the range investigated, PDTs with the smallest l/y ratio offered the highest thermal performance factor of 1.14