Abstract
Fin-and-tube heat exchangers are an integral part of several thermal systems of mass utility such as air conditioners and heat pumps. The demand of the aforesaid thermal systems has increased multi folds over the past decade. In order to improve the heat exchange capacity of fin-and-tube heat exchangers, deploying longitudinal vortex generators is an effective method. As geometry of the vortex generators is an important design parameter, the thrust of this investigation is to come up with the most favorable geometry of winglet type generators. The selection of favorable winglet geometry requires thermo-hydraulic assessment to identify energy-efficient design(s). Multiple favorable positions are considered, for installing the winglets around the tubes, before arriving at the favorable geometric design(s). After ascertaining the promising designs, their applicability is examined over a range of Reynolds number which spans from 2122 to 6367. Later part of the study discusses the change in the thermal and flow characteristics, of the heat exchanger, due to variation in the winglet geometry. A study of the flow structures makes it evident that the spread of the longitudinal vortices widens, with eventual dissipation, in the flow direction, which has a discernible effect on the heat flux distribution over the fin surface. The study pertaining to the local changes suggests that the surfaces of both fins as well as the tubes undergo heat transfer augmentations, and the degree of augmentation grows with the decreasing aspect ratio of the vortex generators.
