Flow and heat transfer control to improve the performance on fin-tube type heat exchanger by vortex generator

Abstract

Consulta en la Biblioteca ETSI Industriales (8331)

[EN] The following document is a description of the study and research performed on the development of the optimal design of vortex generators on fin-tube type heat exchangers. It is important to improve the performance of fin-tube type heat exchangers, because they are used in many industrial fields like intercoolers of gas-turbines, refrigeration and son on. The optimal design is required in order to achieve a more compact size of the heat exchanger and to be more energy efficient. Since the thermal conductivity of gas is significantly smaller than the liquid¿s, many researchers have investigated gas flow and heat control to find a way to improve the performance of the heat exchanger, for example, by using vortex generators on the fin surface. Vortex generators can produce turbulence and longitudinal vortices inducing strong swirling motion and controlling the separation point on the tube surface, and therefore achieving an augment of the impinging area of the flow on the tube. This is effective to augment the heat transfer rate. There are numerous types of vortex generator configurations, (as shown in figure 1.a.) wing-type, winglet-type, triangle type, louver-type and their combinations. However, the experiments conducted until now have been under low Reynolds Number, (Re = UD/¿, U: inlet velocity, D: tube diameter, ¿: kinematic viscosity of the fluid) and because a high Reynolds Number is required in the air side of fin and tube type heat exchangers, while using devices such as intercoolers, it is necessary to perform experiments under high Reynolds Number. But the main reason why the experiments should be held as mentioned earlier, is to determine the best vortex generator configuration. For the case being, louver type vortex generator has been chosen. This type of vortex generator has a simple but effective configuration, it is easy to manufacture because it only requires a pressing, and it offers great improvement in both increasing the impinging area around the cylinder and creating turbulence that increases the heat transfer coefficient.