Effect of the Streamwise Orientation of a Pair of Vortex Generator on the Flow and Heat Transfer Characteristics in a Plain Channel

Abstract

For a rectangular channel flow, a variant of delta winglet vortex generator (VG) in common flow up (CFU) orientation is presented to enhance the thermal performance factor by decreasing the friction losses. The new vortex generator is a simple reversal of a standard CFU orientation such that the leading edge and suction side of the conventional CFU orientation of the winglet become the trailing edge and pressure side for the reverse common flow up (RCFU) orientation of the winglet, respectively. Numerical simulations were carried out for a three-dimensional, steady, laminar, and incompressible rectangular channel flow with and without the two VG configurations. Performance analysis was done for global Nusselt number and friction factor for different inter-winglet spacings of the VG pair at a Reynolds number of 1478. An increase of 2.3% in the thermal enhancement factor was achieved in RCFU compared to CFU orientation at an inter-winglet spacing equal to 0.02 times the channel height. At the highest inter-winglet spacing equal to 0.6 times the channel height, the CFU orientation exhibited a gain of 3.2% in the enhancement factor over the RCFU orientation. Heat transfer downstream of the vortex generator was shown to be impacted in the reverse configuration (RCFU) due to stronger vortex formation compared to a standard CFU configuration at the least inter-winglet spacing.