Heat transfer enhancement of a channel via vortex-based fluidic oscillator: A numerical study

Abstract

This paper numerically investigated the effects of incorporating three distinct vortex-based fluidic oscillators on heat transfer and pressure drop within a two-dimensional channel with constant heat flux at different Reynolds numbers ranging from 10,000 to 50,000. These oscillators consist of primary and secondary chambers connected by a throat and a return channel. The dimensions of the base vortex-based fluidic oscillators were halved to design the second oscillator while keeping the inlet and outlet throats unchanged to reduce pressure drop across the oscillator. Finally, a protrusion was incorporated into the wall profile of the second oscillator, intensifying the vortex in the secondary chamber and augmenting the transverse oscillation amplitude to boost heat transfer. The finite volume method with the k–ω shear-stress transport (SST) turbulence model was used to solve the Unsteady Reynolds-Averaged Navier–Stokes (URANS) equations and energy transport. Transient numerical results demonstrated intensified jet oscillations in the channel, enhancing heat transfer, particularly at the inlet zones of the channel owing to vigorous collisions with upper and lower channel walls. The time-averaged numerical results indicated that the first, second, and third oscillators respectively raised the average Nusselt number of the channel by 40%, 21%, and 24% at X/D = 5. Similarly, at X/D = 10, the oscillators led to increases of 22%, 9%, and 11 %, compared to the simple channel without oscillators. The small-size second and third oscillators also increased the performance evaluation criterion (PEC) compared to the base vortex-based fluidic oscillator. The maximum PEC values were 0.95 for the base oscillator, 1 for the second oscillator, and 0.98 for the third oscillator at Re = 10,000. These oscillators can be used as inserts for enhancing heat transfer in channels.