Effect Of Vortex Generator And Longitudinal Corrugation On Flow And Heat Transfer Performance Of Fin-and-tube Heat Exchanger

The fin-and-tube heat exchanger is a kind of heat transfer equipment which is widely used in various fields such as machinery,chemical industry,air conditioning.Improving its heat transfer efficiency has a significant impact on the energy utilization rate in industrial production.There are several technologies available for enhancing heat transfer,including slotting the heat transfer channel,coating and installing spoiler elements.These techniques have been widely implemented in various types of heat transfer equipment,such as tube-and-fin heat exchangers and plate heat exchangers.The vortex generator can produce secondary flow and promote heat exchange between fluids.The use of vortex generator has become a primary technology for improving heat transfer of heat exchangers.Therefore,this paper numerically studied the combination of longitudinal corrugation and vortex generators for a fin-and-tube heat exchanger.The effects of the placement,position,angle of attack of the vortex generators and corrugation height on the distributions of Nu_local,Nu_s-ave,the average Nu,the friction factor f and the comprehensive evaluation factor JF were analyzed.The main conclusions are as follows:Compared with the smooth fins,the longitudinal corrugated fins can increase the fluid disturbance in the heat exchange channel.Due to the installation of vortex generators into the longitudinal corrugated channel,the longitudinal vortex generated by the longitudinal corrugation and the vortex generators interact with each other,which enhances the heat transfer and increases the fluid flow resistance meanwhile.The average Nu in the channel is higher compared with the values in the channel with vortex generator,the smooth corrugated channel and the smooth fin channel.The average Nu increases by 18.1%,30.2%and 56.2%in these channels,while f increases by 42.1%,39.4%and 105.1%,respectively.In contrast to the influence of The vortex generator arrangements are marked as up-type and down-type according to the distance between the windward vertices of the vortex generator and the distance between the tail ends.The up-type produces a counterclockwise longitudinal vortex,which has the same direction as the longitudinal vortex generated by the longitudinal corrugation.The down-type vortex generator generates a clockwise longitudinal vortex that has the opposite direction as the longitudinal vortex generated by the longitudinal corrugation.The interaction between co-directional longitudinal vortices can enhance the secondary flow intensity.Compared with the down-type arrangement,the up-type arrangement of the vortex generator is more conducive to heat transfer enhancement in the longitudinal corrugated channel.The average Nu and JF of the model with vortex generator installed on the outer side of the corrugation are consistently better than that with vortex generator installed on the inner side.The longitudinal vortex generated by the vortex generator on the outer side of the corrugation interacts with the longitudinal vortex generated by the longitudinal corrugation,resulting in better heat transfer.Installing vortex generators on the outside of longitudinal corrugations can significantly enhance the mixing of hot and cold fluids,resulting in improved heat exchange within the channel.As the angle of attack of the vortex generator increases from 10°to 40°,the strength of the longitudinal vortex gradually increases,and the fluid scouring of the wall becomes stronger.The average Nu,friction factor f and comprehensive evaluation factor JF increase gradually.The average Nu forα=40°increases by a maximum of 17.6%compared withα=10°,while f increases by 43.5%.The maximum JF could reach 1.25,which is 18.2%higher than the corrugated fin,and 6.1%higher than the fin model withα=10°.When the longitudinal corrugation height k increases from 1.2 mm to 2.7 mm,the longitudinal vortex strength first increases and then decreases.And the average Nu and friction factor f both gradually increase with the increase of corrugation height.When k=2.7mm,the average Nu and friction factor f are always the largest,the maximum increases in Nu and f are 12.2%and 35.4%compared with k=1.2 mm,respectively.JF first increases and then decreases with the increase of Re.JF reaches the maximum 1.23 when Re=400 and k=2.4mm,which is 2.1%higher than that of k=1.2 mm.