Abstract

Heat transfer enhancement is a constant objective in the design of heat exchangers. Several techniques have been implemented to achieve it. Passive techniques use the fluid ' s energy to improve the heat exchanger surface performance. As a passive technique, vortex generators produce a relatively low impact on drop pressure. They are a disruptive element of the boundary layers and when facing the flow, they create secondary flows responsible for the enhancement of heat transfer. Vortex generators can be implemented on surfaces using different methods, but a mechanical punching operation is probably the best option to create them. The oper-ation produces a hole on the surface which plays a crucial role in the heat transfer process. There is a lack of studies where the influence of punched holes on the rectangular channels ' performance has been researched. Numerical methods allow to develop such analysis. As a novelty, this paper numerically analyzes the influence of two built-in punched vortex generators on a rectangular channel with a similar disposition and inside the laminar flow regime. Four dispositions with a variable transversal pitch are studied, for a total of 22 different models. The results are discussed using a modified non-dimensional parameter. The best overall performance was obtained using the arrangement with punched holes in front of the vortex generators. When compare to the others, that arrangement allowed to double the overall performance. A heat transfer enhancement ranging from 1 to 14% was obtained as a Reynolds number function. In contrast, the pressure drop increased from 3 to 17%.