Numerical Investigation of Heat Transfer Enhancement and Pressure Drop in Heat Exchanger Tube fitted with Dual Twisted Tape Elements

摘要

This study presents a numerical investigation on heat transfer and fluid flow characteristics of a tube fitted with dual twisted tape elements in turbulent flow regime. The commercial software, FLUENT 13, is chosen as the CFD tool for this work. The numerical analyses are performed with three different diameter ratios defined as the ratio of twisted tape diameter to the inside diameter of the tube (d/D=0.2, 0.3, and 0.4) at a constant twist ratio (TR) of 5. Uniform heat flux is applied to the external surface of the tube and Reynolds numbers varied from 3920 to 28268 in the numerical calculations. The numerical results obtained from a plain tube are compared with those from the studies in literature for validation of numerical technique. The use of twisted tape elements leads to a considerable increase in heat transfer and pressure drop over the plain tube. The highest overall enhancement efficiency of 27% is achieved for the case d/D = 0.2 at a Reynolds number of 3920. Consequently, the numerical results reveal that the best operating regime of all twisted tape elements was found at low Reynolds number, leading to more compact heat exchanger.