Flow Structure And Heat Transfer Enhancement In A Narrow Rectangular Channel With Drop Shape Vortex Generator

A kind of drop shaped vortex generator which is set in rectangular channel is designed,and its mechanism of heat transfer enhancement is analyzed.When Re number is 4000-20000,the influence of the different oblique angles of the vortex generator in the single row,and the different attack angles,height,lateral spacing and longitudinal spacing of the vortex generators in the multi rows on the flow and heat transfer characteristics were investigated by numerical simulation and experiment study.The results show that: Oblique angle and attack angle affect the development of tip vortex and the longitudinal vortex respectively.The performance of heat transfer and the flow resistance in the rectangular channel increases with the increasing oblique angle of the vortex generator.And the performance of heat transfer increases firstly and then decreases with the increasing attack angle of the vortex generator,and the flow resistance increases with the increasing attack angle.So considering the two aspects of heat transfer and flow resistance,the comprehensive heat transfer performance of drop shaped vortex generator is more perfect when its oblique angle is0° and its attack angle is between 30° and 45°.In addition,the comprehensive heat transfer performance of drop shaped vortex generator is better when its relative height is 0.125.At low Reynolds number,the smaller relative longitudinal space P~*=P/H and relative horizontal space S~* =S/H(that is the arrangement density of vortex generators is larger),the better of the comprehensive heat transfer performance of drop shaped vortex generator is.And when the Reynolds number is relative higher,the larger P~*and S~*(that is the arrangement density of vortex generators is smaller),the better of the comprehensive heat transfer performance of drop shaped vortex generator is.The enhanced heat transfer capacity of three kinds of different arrangement(gradual expansion arrangement,parallel arrangement,V arrangement)is studied.The results show : After the fluid flows through the vortex generator,it generated horseshoe vortex,backflow vortex,longitudinal vortex,Among them,the horseshoe vortex and the longitudinal vortex have the greatest effect on heat transfer enhancement,There are great differences in the strength and influence area of the longitudinal vortex induced by the drop shaped vortex generators in different configurations.Among them Gradual expansion arrangement have the best effect of heat transfer enhancement,on the hand that the distribution of vortex core and the comprehensive effect of intensity and influence area.The vertical vortex induced by parallel arrangement and V arrangement one is strong and the other is weak,The contribution to the enhancement of heat transfer in the channel is lower than that of the extended arrangement.The heat transfer enhancement factor and resistance factor of three channels(gradual expansion arrangement,parallel arrangement,V arrangement)are discussed and analyzed.The results show that the heat transfer ability of the gradually enlarged channel is the strongest,the average effect increased 4.3% compared with other arrangement,parallel arrangement of the channel have maximum resistance factor,gradual expansion arrangement have the best comprehensive performance on the heat transfer enhancement factor and resistance factor.The comprehensive performance of diffuser layout improves 3.12%-9.26% than the other two kinds of arrangement channel.