| In today’s world,with the profou nd adjustment of t he political and economi c pattern,the relationship between energy supply and demand has undergone significant changes.At present,resource constraints,ecological damage and other problems seriously affect the development of China,adju st the industrial structure,improve energy efficiency,ensure the security of energy supply is an important goal of China’s energy development.As one of the wall heat exchangers,finned tube heat exchanger is more widely used in practice because of its s imple structure,compact arrangement,flexible transformation,strong heat transfer capacity,easy processing and wide adaptability and strong abilit y to remove dirt.Due to the use of finned tube air side is often there will be precipitation,water vapor when the condensed water vapor in the air in the fin,the fin on the droplet formation,and the formation of droplets o f finned tube heat transfer pe rformance has a great influence,at the same time,due to the water vapor in the air in the fin condensatio n,the generation of condensation water can affect the finned tube heat exchanger channels the flow of air in,further influence on the performance o f the finned tube heat exchanger.The fin with reasonable structure can not only guarantee the heat transfe r capacity of the heat exchanger when the condensate is produced,but also reduce the influence on the flow performance of the heat exchanger when the condensate is produced.Therefore,it is necessary to study the influence of fin structure on condensate characteristics.Therefore,this paper carried out numerical simulation analysis on the fin structure’s heat transfer characteristics,condensation char acteristics and flow characteristics under the condition that the condensate was produced:(1)Establish the physical model of the flat fin,simplify the actual situation,establish the mathematical model of wet air condensation,and verify the grid independence and the correctness of the simulation.The temperature field,velocity field and concentration field in the finned tube under wet and dry conditions are obtained.The heat transfer,condensation and flow characteristics of a finned tube heat exchanger were studied when the relative humidity was from 50% to 80% and the inlet velocity was from 1 to 4m/s.(2)Increase the diameter of finned tube base.After calculation,the influence before and after the increase of pipe base diameter was compared.It is found that with the increase of relative humidity and the increase of tube base diameter,the heat transfer capacity of the fin decreases,the amount of condensation increases,but the time-out coefficient decreases.The drag coefficient also increases significantly with increasing pipe diameter.After calculation,the JF factor is between 0.8 and 0.9.(3)Increase the longitudinal spacing of finned tubes.After calculation,it is found that the heat transfer performance and condensation performance are decreased with the increase of fin tube longitudinal spacing,but the drag coefficient is increased.After calculation,the JF factor is between 0.85 and 0.95.(4)Increase the transverse spacing of finned tubes.After calculation and analysis,it is found that the heat transfer and condensation characteristics are slightly decreased with the increase of the transverse distance between finned tubes,while the drag coefficient is slightly increased.After calculation,the JF factor is between 0.98 and 1.04.(5)Add pit structure.When the pit structure is added on the flat fin,the heat transfer capacity of the fin increases greatly,the drag coefficient also increases slightly,but the condensation coefficient decreases slightly.The maximum surface heat transfer coefficient increased by 31%.After calculation,the JF factor is between 1.06 and 1.51. |
