Published Paper Details:

The improvement of the performance of heat exchangers with gas as the working fluid becomes particularly important due to the high thermal resistance offered by gases in general. In order to compensate for the poor heat transfer properties of gases, the surface area density of plate heat exchangers can be increased by making use of the triangular fins. In addition, a promising technique for the enhancement of heat transfer is the use of longitudinal vortex generators. The longitudinal vortices are produced due to the pressure difference generated between the front and back surface of the vortex generator. The longitudinal vortices facilitate the exchange of fluid near the walls with the fluid in the core and hence, the boundary layer is disturbed. It causes the increase in temperature gradient at the surface, which leads to the augmentation in heat transfer. An innovative design of triangular shaped fins with rectangular or a delta wing vortex generator mounted on their slant surfaces for enhancing the heat transfer rate in plate-fin heat exchanger is proposed. The performance of the proposed design is evaluated for different flow rate of hot fluid and cold fluid of the wing and constant bath temperature boundary condition. The study is being carried out for wing vortex generator to the fin surface by brazing.. The flow regime is assumed to be laminar because, usually the fin spacing is so small and the mean velocity is such that the Reynolds numbers of interest are below the critical Reynolds number. The working fluid considered is air and water. At higher Reynolds numbers, more fluid passes through the channel in the same interval which causes a reduction in the value of mean temperature. Combined span wise average Nusselt number is computed by averaging the local Nusselt numbers all around the periphery. In the downstream direction, the temperature of the fluid increases and so the combined span wise average Nusselt number decreases continuously for the plate-triangular fin without any vortex generator. The churning action mixes the fluid near the surface with the comparatively colder fluid in the core region. It increases the temperature gradient near the walls and hence, the combined span wise average Nusselt number increases. The heat transfer enhancement can reduce the size of the heat exchanger for a given heat load or exit temperature. The only price to be paid for enhancing heat transfer using longitudinal vortex generators is the additional pumping power required to force the fluid through the heat exchanger. This quantity is also computed to confirm that the increase is sufficiently small. The analysis is also carried out by varying the size of the wings and using the in-line arrangement of the wings.