Numerical Simulation Of Vortex Generator Intensifying Heat Transfer Efficiency Of Fin-tube Heat Exchanger

As a commonly used heat exchange equipment,finned tube heat exchangers are widely used in aerospace,chemical,refrigeration and other industries.In order to design more efficient finned tube heat exchanger to meet the needs of aero engine heat exchanger,on the basis of the original straight fins,a method of installing a new type of vortex generator is proposed,and the impact on the heat transfer performance of the fin-tube is specifically analyzed.Based on the k-bas turbulence model,the velocity field,temperature field,and pressure field changes of corrugated fins,straight fins and optimized fin-tube heat exchangers are obtained through threedimensional numerical simulation,and the original fins are compared with J and F factors Thermal performance of finned tubes and vortex generator finned tubes.At the same time,the fin structure and the number of vortex generators were studied in depth.The main research contents are as follows:(1)A new type of vortex generator finned tube model is established,and the numerical simulation method is used to compare and analyze the changes of pressure,temperature and convective heat transfer coefficient of smooth straight finned tube and corrugated finned tube.The influence of new vortex generator on the performance of finned tube is studied.(2)By calculating the flow field distribution on the central surface of the heat exchanger,the research results show that the optimized straight fin greatly increases the disturbance ability to the fluid,guides more fluid to scour the wake area behind the tube,improves the average flow rate,and has smaller pressure drop loss than the corrugated fin.By calculating the flow field distribution on the surface of the heat transfer section of the heat exchanger,the results show that the temperature gradient changes significantly near the vortex generator,and its existence delays the separation of the wall boundary layer,further enhances the heat transfer ability,and the average temperature of the fin wall increases after optimization.The change of heat transfer performance and resistance of the heat exchanger was analyzed by changing the inlet flow rate.The results show that the Nusselt number of the optimized vortex generator finned tube is 12 % – 24 % higher than that before optimization.The average pressure drop per unit heat transfer is 1.12 times that before optimization,and the resistance factor increases by4 % – 10 %.(3)The effect of number and height of vortex generator on heat transfer performance of heat exchanger was studied.By calculating the temperature nephogram of fins with 3,6,9,12 vortex generators,the results show that when the number of vortex generators increases from 3to 6,the unit heat transfer pressure drop increases only by 1.21-1.32 times.When the number of vortex generators increases from 9 to 12,the unit heat transfer pressure drop increases by2.01-2.41 times and 2.14-2.43 times,respectively.The flow resistance increases significantly.When the number of vortex generators is 6,the heat transfer ability is significantly improved than that of the three,and the resistance loss is small.The influence of the height of the vortex generator on the fluid heat transfer is analyzed.The results show that with the increase of the height of the vortex generator,the pressure drop increases,and the fluid flow is disturbed.The convective heat transfer efficiency increases with the increase of the height of the vortex generator.However,when the height of the vortex generator exceeds 1.2 mm,the resistance loss is large,and the height of the vortex generator should be less than 1.2 mm.(4)The effects of inlet velocity,transverse tube spacing,fin spacing,fin thickness and outer radius of heat pipe on heat transfer capacity were studied.The results show that when the inlet velocity is within the range of 2m/s,4m/s,6m/s,and 8 m/s,the convective heat transfer coefficient and pressure drop of finned tube decrease with the increase of transverse tube spacing.When the fin spacing varies from 1.6 mm to 1.9 mm,the convective heat transfer coefficient increases by 6.1 %-12.3 % when the fin spacing is 1.8 mm compared with 1.6 mm,the convective heat transfer coefficient decreases by 1.7 %-2.6 % when the fin spacing is 1.9mm compared with 1.8 mm,and the pressure drop decreases by 7.3 %-17.2 % when the fin spacing is 1.9 mm compared with 1.6 mm.The fin spacing should be selected according to the change of pressure drop and convective heat transfer coefficient.When the fin thickness increases from 0.1mm to0.18 mm and the flow rate is 2 m/s,the convective heat transfer coefficient increases by 5 %-9 % and the pressure drop increases by 5.6-9.2 %.When the flow rate is 8m/s,the convective heat transfer coefficient increases by 3.4 %-8.5 % and the pressure drop increases by 7%-18%.When the outer radius of the heat pipe changes within 3.8mm,4mm,4.2mm,4.4 mm,when the flow rate is 1m/s,the convective heat transfer coefficient increases4.2 %-8.4 %,pressure drop increases 2.4 %-6.9 %,when the flow rate is 9 m/s,the convective heat transfer coefficient increases 7.6 %-12.3 %,pressure drop increases 4.2%-7.8%.