COMPARISON OF WING-TYPE VORTEX GENERATORS FOR HEAT-TRANSFER ENHANCEMENT IN CHANNEL FLOWS

Longitudinal vortices can be generated in a channel flow by punching o r mounting small triangular or rectangular pieces on the channel wall. Depending on their forms, these vortex generators (VG) are called del ta wing, rectangular wing, pair of delta winglets, and pair of rectang ular winglets. The heat transfer enhancement and the flow losses incur red by these four basic forms of VGs have been measured and compared i n the Reynolds number range of 2000 to 9000 and for angles of attack b etween 30 and 90 deg. Local heat transfer coefficients on the wall hav e been measured by liquid crystal thermography. Results show that wing lets perform better than wings and a pair of delta winglets can enhanc e heat transfer by 46 percent at Re=2000 to 120 percent at Re=8000 ove r The heat transfer on a plate.