Effects of circumferential ribs on suppressing cross-flow and enhancing heat transfer in swirl cooling

Abstract

This paper proposed a swirl chamber with circumferential ribs to avoid the impacting of cross-flow to jets, thus enhancing the penetration ability of jet and swirl cooling heat transfer intensity. To reveal the mutual effects between jets and cross-flow, the heat transfer features and flow structures under different Reynolds numbers of smooth swirl chamber and novel rib-roughened swirl chambers were studied and compared using 3D steady numerical analysis. The influence of rib height ratio on flow and heat transfer features was investigated further. The investigation revealed that for smooth swirl chamber, the cross-flow seriously weakened the heat transfer intensity. In contrast, the novel rib-roughened swirl chamber had an excellent suppression effect on cross-flow, thus greatly enhancing the penetration ability of jet and strengthening the swirl cooling heat transfer intensity. Under the Reynolds number of 10,500, for smooth swirl chamber, the peak number of circumferentially-averaged Nusselt number decreased from 80 to 58 from the first pitch to the last pitch. While for the case that rib height ratio is equal to 0.5, it increased from 80 to 120. In addition, the suppression effects of circumferential ribs on cross-flow increased when the rib height ratio increased, likewise the heat transfer enhancement effect. When the rib height ratio is less than 0.5, the Nusselt number ratio was larger than the friction factor ratio, while when the rib height ratio is larger than 0.5, the Nusselt number ratio was less than the friction factor ratio. The best thermal performance can be achieved when the rib height ratio was 0.5. Besides, the heat transfer enhancement effect of circumferential ribs was more significant under a higher Reynolds number in the studying range.