Research on heat transfer augment of the helical half-pipe jacket by jet longitudinal vortex generator

In order to evaluate the comprehensive performance of enhanced heat transfer by jet more reasonably, considering the increase of additional power consumption caused by jet, the thermal coefficient ratio (TCR) was proposed as the evaluation index to analyze the effect of comprehensive enhanced heat transfer. In this study, the jet vortex generator (JVG) is applied to the half-pipe jacket for obtaining further heat transfer enhancement. The structural parameters of the half-pipe jacket is kept constant. The effect of the jet incidence angle (alpha) and the ratio of jet flow rate to mainstream flow rate (epsilon) on the heat transfer augment has been investigated by numerical simulation. The results showed that the jet action changed the original secondary vortex structure and enhanced the convective heat transfer capacity of the fluid in the helical half-pipe jacket. In the flow region near the jet, a pair of common-flow-down (CFD) longitudinal vortices were generated in the cross section of the half-pipe jacket. With the development of the mainstream, the vortex gradually evolved into a common-flow-up (CFU) vortex. With the increase of epsilon, heat transfer convective heat transfer capacity was enhanced. Moreover the flow resistance was increased. The local Nusselt number (Nulocal) of the heated wall could be enhanced by up to 2.3 times in the investigated range when compared to the corresponding value of the single half-pipe jacket. Within the range of epsilon=0.5-2 and alpha=45 degrees -60 degrees, the jet with alpha=50 degrees had the best comprehensive enhanced heat transfer performance. The TCR was between 0.91 and 1.19.