An Experimental Investigation of Heat Transfer Enhancement in a Rectangular Duct with Plate Fins

In this study, using an ideal heat exchanger model, a detailed evaluation of performance parameters in the turbulent regime for the enhancement of heat transfer by using winglet-type vortex generators is carried out. The heat transfer, friction characteristics, and the second law analysis of the convective heat transfer for turbulent flow through a rectangular channel containing built-in wing-type vortex generator have been investigated experimentally in the range of Reynolds numbers between 3000 and 30,000. The installation of the wings is organized, in such a way that periodically interrupted enlarged and contracted channel flow domains are established. Wings were aligned at various angles of beta = 7-20 degrees positively and negatively with the direction of main air flow direction. The highest heat transfer performance was found for a beta = 15 degrees winglet angle. Each winglet pair induces longitudinal vortices behind it, and strong mixing effects occur in a buffer region between divergent and convergent channel arrangements. It was observed that the enhancement of heat transfer caused the increment of the friction coefficient. In addition, the relation of the entropy generation number to effectiveness has been studied under optimal design conditions for divergent and convergent channels on the basis of entropy generation minimization.