Configuration optimization of regularly spaced short-length twisted tape in a circular tube to enhance turbulent heat transfer using CFD modeling

This work presents the configuration optimization of regularly spaced short-length twisted tape in a circular tube for turbulent heat transfer in air using computational fluid dynamics (CFD) modeling. The configuration parameters include the free space ratio (s), twist ratio (y) and rotated angle (alpha). The computational results are in good agreement with experimental data. The results indicate that the larger rotated angle yields a higher heat transfer value and a greater flow resistance, whereas the smaller twist ratio results in better heat transfer performance using a twist ratio ranging from 2.5 to 8.0 except for a large rotated angle and a high Reynolds number (e.g., alpha = 360 degrees and Re = 20,200). However, the minimum resistance factor occurs if the twist ratio is in the range of 4.75-5.75. The optimal design of regularly spaced short-length twisted tape in a circular tube for turbulent air flow is y = 4.25-4.75, alpha = 180 and s = 28-33 with a Reynolds number that varies from 10,000 to 20,200. If the heat transfer rate is more important, the second design of y = 4.25-4.75, alpha = 270 degrees and s = 28-33 in the range of Reynolds numbers from 10.000 to 20,200 can be used as a reference for industrial application. (C) 2010 Elsevier Ltd. All rights reserved.