NUMERICAL INVESTIGATION OF THERMAL PERFORMANCE OF A TUBE FITTED WITH REGULARLY SPACED TWISTED TAPE ELEMENTS

摘要

This work presents a numerical investigation on thermal performance of a tube fitted with regularly spaced twisted tape elements in turbulent flow regime. Two different twisted tape widths of 46 mm and 44 mm which are lower than the tube inside diameter of 50 mm are used, in order to reduce excessive pressure drops associated with full width twisted tape elements. The numerical analyses were performed with various free space ratios (5=0.0, 1.0, and 2.0) at a constant twist ratio (TR) of 5. Uniform heat flux was applied to the external surface of the tube and Reynolds numbers varied from 5918 to 46875 in the numerical calculations. The numerical results obtained from a plain tube were 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. 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.