Effect Of Inclination Angle Of Vortex Generator On Fluid Flow And Heat Transfer Characteristics Of Heat Exchanger

Installing vortex generators is a common passive heat transfer enhancement method in heat exchangers.Because the longitudinal vortex generated by the vortex generators will accelerate the efficiency of mixing the fluid between the wall and the main flow area,destroy the boundary layer and improve the wall heat transfer coefficient,so vortex generators can enhance wall heat transfer coefficient.Besides,it not only can achieve great heat transfer enhancement effect with less pressure drop,but also reduce the cost and improve energy efficiency,so it is widely used in a variety of heat exchangers.As the longitudinal vortex are affected by many factors,such as the shape,the vortex generator height,the attack angle and the arrangement of the vortex generators,thus the longitudinal vortex flow is so complicated.Many domestic and foreign scholars have carried out a lot of research work about heat transfer enhancement using vortex generators.At present,the research about longitudinal vortex mainly focuses on the shape,angle of attack,arrangement of the vortex generators and the vortex generators were set normal to the surface.But the relationship between the vortex generator inclination angle and enhanced heat transfer is scarcely studied.In order to improve the performance of heat exchangers,it is of great significant to study the effects of vortex generator inclination angle on fluid flow and heat transfer characteristics.In this paper,the influence of the inclination angle of delta wing vortex generator on the flow and heat transfer characteristics is numerical simulated.Under the condition of constant vortex generator height and projection height of vortex generator,the effects of vortex generator inclination angle on velocity,vorticity,friction factor and heat transfer with different attack angles of vortex generator are carried out.The results show that the inclination angle of the vortex generator has a significant effect on the flow and heat transfer in the channel and there is an optimal inclination angle of vortex generator in terms of the best heat transfer performance.When the height of the delta vortex generator is unchanged,the Nusselt number and the thermal performance factor get maximum values with the inclination angle of the vortex generator equals to-10°.At ?=15°,the maximum differences in the Nusselt number and thermal performance factor with different inclination angles of the vortex generator are 6.4%and 5.4%,respectively;At ?=30°,the maximum differences in the Nusselt number and heat transfer enhancement evaluation factor with different inclination angles of the vortex generator are 8.9% and 5.7%,respectively;At ?=45°,the maximum differences in the Nusselt number and thermal performance factor with different inclination angles of the vortex generator are 11% and 3%,respectively.With the same projection height of vortex generator,the Nusselt number and thermal performance factor are the best at ?=-20°,for both ?=15°and 30°.At ?=15°,the maximum differences in the Nusselt number and thermal performance factor with different inclination angles of the vortex generator are 5.4% and 4.7%,respectively;At ?=30°,the maximum differences in the Nusselt number and thermal performance factor are 5% and 3.7%,respectively.However,when ?=45°,both the Nusselt number and the thermal performance factor get maximum values with the inclination angle of the vortex generator equals to-10°.The maximum differences in the Nusselt number and thermal performance factor with different inclination angles of the vortex generator are 7.6% and 2.2%,respectively.