Numerical Study On Flow And Heat Transfer Characteristics Of A Channel Formed By Round Tube Bank Fins Stamped With Combined Vortex Generators

As a kind of general industrial equipment for heat exchange,heat exchanger is widely used in the national production fields or living facilities closely related to people’s heating,power,refrigeration,air conditioning and people’s production and life.The improvement of its performance is of great significance for energy utilization,energy conservation and emission reduction.For the pipe wing type heat exchanger with the working medium of air and water,the heat transfer capacity is mainly limited by the surface heat transfer coefficient of the fin surface,and the energy consumption mainly comes from the energy consumed when the tissue airflow flows through the heat exchanger.Due to the limitation of economy and size,the area of the fin can not be increased at will.In order to further improve the heat transfer performance of the round tube fin,setting the vortex generator on the surface of the fin is an effective measure to improve the heat transfer.The vortex generator stamping out on the surface of the fin can make the secondary flow of the fluid and promote the rapid mixing between the hot and cold fluid,which can effectively strengthen the heat transfer performance of the fin surface.This paper proposes a side combination vortex generator fin heat exchanger on the front of the round tube fin fin fin vortex generator.First,the calculation domain of the side combined vortex generator is divided by ANSYS ICEM software,and then FLUENT is used for numerical simulation;For the physical models and working conditions,The selected turbulence model and the numerical method are verified;The average and local characteristics of flow and heat transfer in the channel of curved trapezoidal vortex generator fin and side composite vortex generator fin are analyzed,The advantages of side combination vortex generator are expounded;The influence of the structural parameters of the fin and vortex generator on the flow and heat transfer characteristics of the fluid in the channel,Multiple linear regression is used to obtain the mean Nuuser number,resistance coefficient and the fit correlation of the quadratic flow intensity with each structure parameter,The intensity of the secondary flow in the fluid channel is discussed.The main conclusions obtained are as follows.（1）Compared with curved trapezoidal vortex generator fin,side combination vortex generator has a stronger disturbance to fluid,the channel of secondary fluid intensity is improved significantly,fluid velocity boundary layer destroyed,speed distribution more uniform,this can make different speed of cold and hot fluid fully mixed,thus effectively improve the heat transfer performance of the heat exchanger.When the Reynold number Re=1200,the structure parameters areα=10°and T_p=2.0mm,D₀=9mm,L₀=1.35mm,H₂=0.8415mm,the best comprehensive heat transfer performance,and the comprehensive enhanced heat transfer evaluation factor JF=1.333.（2）The structural parameters of side combined vortex generator have obvious influence on the flow and heat transfer characteristics.The decrease of the fin spacing makes the flow space of the fluid relatively narrow,resulting in a large pressure drop loss,but also effectively improves the heat transfer performance of the fin surface.At T_p=2.0mm,the heat exchanger has the best heat transfer performance.The increase of pipe diameter will narrow the flow space of the fluid,increase the pressure drop loss,and its improvement of heat transfer effect is limited.Therefore,the smaller the pipe diameter,the better the comprehensive enhanced heat transfer effect is better.When D₀=8mm,the highest evaluation factor of comprehensive enhanced heat transfer.（3）The Angle of attack,intermittent distance and short side height of side combination vortex generator have important influence on enhanced heat exchange.When the angle of attack is positive,the side combined vortex generator can disturb more high-speed fluid,and the enhanced heat transfer effect is higher than the negative value;when the angle of attack isα=10°,the side combined vortex generator can obtain considerable heat transfer performance with small pressure drop loss,and the comprehensive heat transfer performance is best.The smaller the discontinuity distance of the side combination vortex generator,the better the enhanced heat exchange effect.The average number is significantly higher than L₀/L₁=0.2and L₀/L₁=0.4,and the pressure drop loss is the largest;the resistance coefficient of L composite vortex generator is L₀/L ₁=0.2.The size of the short side height H₂has little effect on the average user number and the secondary flow strength,but the increase of the short side height will increase the resistance coefficient,which leads to the decrease of the comprehensive heat transfer performance.When H₂/H₁=0.5,the highest comprehensive enhanced heat transfer evaluation factor.（4）By multivariate linear regression,the average Nu,resistance coefficient f and the secondary flow intensity Se and the fin spacing T_p,tube diameter D₀,the side composite vortex generatorα,the intermittent distance H₂and the power index relation of the average Nu Nu and the secondary flow strength Se.