The Effect of Diameter and Position of Transverse Cylindrical Vortex Generators on Heat Transfer Improvement in a Wavy Channel

Abstract

The present study investigates the effect of outer diameter (10 mm and 15 mm) and 5 positions of cylindrical vortex generators (CVGs) installed to the wavy channel in order to improve heat transfer parameters in conjunction with low-pressure drops. The wavy channels with and without CVGs are compared in terms of the local heat transfer coefficient, mean Nusselt number, Colburn factor, friction, and thermal performance for Re in the range of 857 to 8001. Furthermore, the effect of the cooling air flow direction (forward and backward) is assessed. Inserting the CVGs to the channel causes the enhancement of Nusselt numbers and Colburn factors for all CVGs positions and Re in comparison with the channels without CVGs. The maximum thermal performance factor TPFB = 0.8229 was achieved for the channel with CVGs position ‘5’ and 15 mm diameter, backward air flow, and Re = 1677. The backward air flow is more efficient compared with forward air flow since the cooling air gets into the valleys to a greater extent, and thus, better mixing of the fluid occurs. The numerical investigation, conducted with Ansys Fluent software, is compared with the experimental one acquired by holographic interferometry at good agreement of the local heat transfer coefficients. Finally, new correlating equations for the mean Nusselt number were created.