ABSTRACT There are many applications in engineering industry that require heat addition or removal and a wide variety of heat exchange devices are used for different applications. Performance of improving coefficient of heat transfer becomes essential in all applications. Most of thermal devices like high temperature gas turbines, heat exchangers, electronic equipment, convective heat transfer plays a major role in most of the engineering applications. To attain higher coefficient of heat transfer, it is necessary that the surface of heat transfer flow is to be made turbulent. However, energy for producing such turbulence must come from the blower or fan and the maximum turbulence leads to excessive power requirement to make the air flow through the duct. Therefore, maximum turbulence must be produced in the region which is very near to surface of heat transfer i.e. in the laminar sub-layer only and this is done by using vortex generators. Vortex generator is responsible for creating the turbulence in the flow of fluid. The analysis is carried out to enhance the heat transfer coefficient with installing the rectangular winglet type of vortex generator in rectangular duct. These vortex generators are provided on bottom plate of the rectangular duct. These vortex generators cause stream wise longitudinal vortices in the test section which disrupt the growth of the thermal boundary layer and enhances heat transfer rate. Influence of geometrical parameter of rectangular winglet vortex generator such as winglet height, wings attack angle on heat transfer coefficient is studied. Air is taken as the working fluid; the flow regime is assumed to be laminar. By varying the above parameter, the heat transfer coefficient is calculated and by comparing all the result optimum height of rectangular winglet and attack angle is achieved