Numerical study of winglets vortex generator effects on thermal performance in a circular pipe

Abstract

Various technologies have been developed to enhance heat transfer and, ultimately, to develop more efficient compact heat exchanging devices. In this research, heat transfer and wall friction in a pipe, with vortex generators (VGs) insert, are numerically investigated. The effects of different attack angles and blockage ratios of VGs fitted inside a smooth pipe are investigated. CFD simulations, with and without VGs insert, were conducted for an air flow with Reynolds numbers in the range 6000–33000 and for a constant heat flux on the pipe model surface. Four VGs are fitted in a circular pattern on the inner surface of the pipe. The different sets of delta winglets were characterized by four attack angles β (0°, 15°, 30° and 45°) and three blockage ratios B (0.1, 0.2 and 0.3). The Nusselt number and friction coefficient results show the influence of the VGs insert on thermal performance. The results indicate that the best set of parameters for thermal performance enhancement (TPE) is β = 30° and B = 0.1. The internal flow behavior and the distribution of the Nusselt number, friction coefficient and turbulent kinetic energy, were explored to explain the effects of the VGs, with different configurations, on the overall Nusselt number, friction coefficient and thermal performance enhancement. The extent of the turbulent wake, in the axial direction, was estimated to explain the different performance of the configurations considered.