Numerical Analysis Of Heat Transfer Enhancement For Channel Arranged With Asymmetric Longitudinal Vortex Generators

The longitudinal vortex generator is a passive and effective method to enhance heat transfer. To further enhance the heat transfer of longitudinal vortex generator. This paper obtains from changing arrangements of the vortex generator to seek a method to enhance heat transfer with reducing flow resistance. The main conclusions are as follows:For the rectangular channels, results show that at Re=500~2000, comparing with the symmetric arrangement of the longitudinal vortex generators(LVGs), the Nusselt number of the asymmetric arrangement of the longitudinal vortex generator only decreased by 4% ~ 6%,while,the friction factor f decreases by 11% ~ 22%,the effect of flow drag reduction is very obvious. The asymmetric arrangement of the longitudinal vortex generators shows the better overall thermal performance with the increase of η by 5% ~ 20%. Proving that asymmetric arrangement of the longitudinal vortex generator is a efficient and low resistivity shape. At the same time, Optimized design of the pitch of the winglet, the height of the winglet, the length of the winglet and the angle of attack for asymmetric arrangement with small winglet.For the fin- circular tube heat exchanger, the heat transfer performance and flow resistance characteristics of the asymmetric arrangement of the rectangular winglet longitudinal vortex generators are numerically studied. Results show that the longitudinal vortex generators play an enhanced heat transfer role for circular tube of back. The LVGs improve the heat transfer of the wake region. At Re=500~2000, comparing with the symmetric arrangement of the longitudinal vortex generator, the Nusselt number of the asymmetric arrangement of the longitudinal vortex generator only decreased by 2.6% ~ 6.3%, while, the friction factor f decreases by 2.8% ~ 18%, The asymmetric arrangement of the longitudinal vortex generators shows the better overall thermal performance with the increase of η by 2.4% ~ 13%. Proving that asymmetric arrangement of the longitudinal vortex generator is an efficient and low resistivity shape again. Meanwhile, Optimized design of the height of the winglet and the angle of attack for asymmetric arrangement with small winglet.The effects of the LVGs arrangements such as symmetric arrangement of LVGs pairs with same sizes, symmetric arrangement of LVGs pairs with different sizes and staggered arrangement of LVGs on heat transfer and flow resistance characteristics were modeled using large eddy simulation method. The results showed that the longitudinal vortices formed in the end of the LVGs. These vortices constant develop and die on the direction of flow and sweeping the heating surface. Comparing the vorticity graph, the section temperature distribution graph and the section pressure profile found that the longitudinal vortex induced by longitudinal vortex generator made near the wall of temperature gradient change and the pressure change significantly place mainly in the longitudinal vortex concentrated area.