Flow field analysis of air flowing through fin-and0tubes with a pair of delta-winglet vortex generator

Abstract

Paper presented at the 7th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Turkey, 19-21 July, 2010.Among tublar heat exchangers, fin-tube heat exchangers are the most widely used in refrigeration and air-conditioning equipment. The fin shape has been varied from a plain fin to a slit fin and louver fin in efforts to enhance the performance of fin-tube heat exchangers. The performance of vortex generators m the context of heat transfer augmentation has also been investigated. Recently, delta winglet vortex generators have attracted the interest of researchers, partly on the basis of experimental data showing that fin-tube heat exchangers with delta winglet vortex generators experience considerably less pressure loss than conventional fin-tube heat exchangers while the heat transfer capacity is at nearly the same level. Previous studies showed that the efficiency of the delta winglet vortex generator varies widely depending on their size and shape, as well as the locations where they are implemented. In this paper, the flow field around delta winglet vortex generators in a common flow up arrangement was analyzed in terms of flow characteristics and heat transfer using computational fluid dynamics methods. The analyses show that flow mixing due to vortices and a delay of flow separation due to flow acceleration influence the overall performance of the fins. The pressure loss of a fin having delta winglet vortex generators was evaluated to be smaller than that of a plain fin while the heat transfer performance was enhanced at high air velocity or Reynolds number.