Fully developed periodic laminar flow and heat transfer in an isothermal wall tube with 45�° upstream rectangular winglet vortex\ngenerators (RWVG) with closed end are investigated numerically. The fluid flow and heat transfer characteristics are proposed for\nReynolds numbers based on the diameter of the tube, Re = 100 to 2000.The RWVGs with an attack angle of 45�° are mounted with\nin-line arrangement on both sides of a plate and the closed tip pointing upstream is inserted in the middle of the tested tube to\nproduce longitudinal vortex flows through the tested section. Effects of different blockage ratios (b/D, BR) and pitch spacing ratios\n(P/D, PR) on heat transfer, pressure loss, and the thermal enhancement factor (TEF) in the round tube are studied.Theresults show\nthat the longitudinal vortex flows can induce impinging flows on a tube wall leading to an extreme increase in heat transfer rate\nover the round tube for all cases. Additionally, the rise in the BR and the reduction of PR result in the increase of both the Nusselt\nnumber and friction factor values. The optimum TEF in the range studied is around 2.9 at BR = 0.15, PR = 1, and Re = 2000.
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