Numerical Simulation Study On Structural Optimization And Heat Transfer Performance Of Finned Tube Heat Exchangers

The finned tube heat exchanger has high heat exchange performance and has been widely used in aerospace,chemical,refrigeration and other industries.In the application of heat exchanger,it is necessary to be optimized on the basis of the original heat exchanger to enhance heat transfer performance and improve energy utilization effectiveness.The heat exchanger model was established by Gambit software.The heat transfer process was numerically simulated by FLUENT software,in which the air-cooled flat finned tube heat exchanger was selected as the research object in this paper.The heat transfer characteristics and resistance characteristics of the optimized heat exchanger were analyzed.And the influences of factors such as the number of eddy current generators,the height of the vortex generator,the fin thickness,the outer diameter of the finned tube,the fin spacing,the distance between and the transverse tubes of the finned tubes on the heat transfer performance.The main research contents are as follows:(1)The model of a fin-and-tube heat exchanger was established.The initial flat fins and corrugated fins are compared,the changing rules of temperature field,pressure field and convective heat transfer coefficient after optimization of straight fins were studied.The enhanced heat transfer mechanism of the optimized method of adding eddy current generator was analyzed.(2)The change of heat transfer performance of finned tube heat exchanger before and after optimization was studied by changing the flow velocity of inlet medium.After optimization,the average pressure drop per unit heat transfer of flat fin was 1.09 times of that before optimization,the nusselt number increased by 11%-23%,the resistance factor increased by 5%-12% and finned tube heat exchanger has better comprehensive heat transfer performance.(3)Based on the optimized flat fins,the influences of the flow rate of the heat exchange medium,the number and height of the vortex generator on the heat transfer capacity and resistance loss of the heat exchanger were studied.With the increase of the flow rate of the heat exchange medium,pressure drop and heat transfer capacity increase.Under the condition that the flow rate of the heat exchange medium is constant,the convective heat transfer coefficient and pressure drop increase with the increase of the number of installed vortex generator.When the number of vortex generator increases to more than 6,the increase of the convective heat transfer coefficient decreases and the pressure drop increases.Under the condition that the flow rate of the heat exchange medium and the number of vortex generators are constant,with the increase of the height of vortex generator,the convective heat transfer coefficient and pressure drop increase.When the height increases to 1.2 mm,the increase of the convective heat transfer coefficient decreases and the pressure drop continues to increase.(4)The influences of the flow rate of heat exchange medium,fin thickness,fin tube outer diameter,fin spacing,and fin tube lateral tube spacing on heat transfer performance of the optimized finned tube heat exchanger.The results show that when the thickness of the fin increases from 0.1mm to 0.18 mm,the convective heat transfer coefficient increases slightly,the flow resistance increases,the heat transfer performance has less improved.When the outer diameter of finned tube increased from 3.8mm to 4.4mm,the convection heat transfer coefficient and pressure drop increased significantly.When the fin spacing increases from 1.6mm to 1.8mm,the convection heat transfer coefficient increases and the pressure drop decreases.When it continues to increase to 1.9mm,the convection heat transfer coefficient decreases,the pressure drop decreases and the flow resistance decreases.The transverse tube spacing increased from 16.8mm to 32.8mm,the convection heat transfer coefficient and pressure drop decreased.The heat transfer performance of the optimized parallel finned tube heat exchanger can be further improved by selecting appropriate fin spacing,finned tube outer diameter and transverse fin tube spacing.