| As the cornerstone of social progress and economic development,energy consumption and demand are very large,especially fossil energy accounts for the majority of energy consumption.However,the environmental problems caused by the extensive use of fossil energy have become increasingly prominent,so ene rgy saving has been the focus of human attention.As a heat transfer device,heat exchanger widely exists in all kinds of energy utilization equipment.Through the use of enhanced heat transfer technology,the development of efficient heat exchanger can effectively improve the heat transfer efficiency,which is of great significance for saving energy consumption.Based on the enhanced heat transfer technology,three kinds of ring-shaped inner fin heat transfer tubes with triangular,rectangular and fan-shaped fins are proposed.The fluid flow and heat transfer characteristics of three kinds of inner finned tubes were studied by numerical simulation technology.The heat transfer performance,resistance performance and comprehensive heat transfer performance of three kinds of inner finned tubes were compared.Then the fin structure was optimized.The resistance and heat transfer performance of inner finned tubes with different fin spacing and fin height were analyzed,and the mechanism of heat transfer enhancement was discussed,The comprehensive performance evaluation results of heat exchange tubes with different fin structures are obtained.Firstly,the temperature field,velocity field,pressure field and turbulent kinetic energy characteristics of triangular,rectangular and fan-shaped inner finned tubes are studied,and then the Nusselt number Nu,resistance coefficient f and comprehensive performance evaluation factor η of the inner finned tubes are calculated at Re=10000～30000.The results show that the fin can enhance the mixing degree of the wall fluid and the central fluid,and accelerate the heat diffusion of the fluid.At the same time,when the wall fluid is disturbed by the fin,the boundary layer will be destroyed,the heat transfer will be strength ened,and the resistance loss will increase greatly.Compared with the smooth tube,the Nu and f of the inner rib tube are increased by 167.6～205.8% and 2623.52～ 5998.8%respectively.From high to low,Nu and f of three kinds of inner fin heat exchanger tubes are triangular,rectangular and fan-shaped;η of fan-shaped inner rib tube is best.The structure parameters of fin spacing and height were optimized,and the resistance and heat transfer characteristics of three kinds of inner fin tubes with different fin parameters were analyzed.When the rib spacing is too large,the fluid disturbance is weakened,and the heat transfer intensity and pressure loss are decreased;When the rib spacing is too small,it is difficult for the mainstream to enter into the ribs and disturb the wall fluid,and the heat transfer intens ity and pressure loss decrease.The Nu and f of the three kinds of inner rib tubes first increase and then decrease continuously,and the rectangular inner rib tube is most affected by the rib spacing.With the increase of rib height,the fluid disturbance increases,the pressure drop and the heat transfer effect of the inner rib tube increase greatly,and the Nu of the three kinds of inner rib tubes increases linearly.Among them,the triangular inner rib tube is most affected by the rib height,and the Nu growth rate is higher than that of rectangular and fan-shaped inner rib tubes.The f values of three kinds of inner rib tubes increase exponentially with rib height.With the increase of rib spacing,the η of three kinds of inner rib tube first increases and then decreases.The optimum rib spacing of triangular,rectangular and fan-shaped inner rib tubes is 48,56 and 48 mm respectively;With the increase of rib height,the η of three kinds of inner rib tube have a significant decrease and the triangular inner ribbed tube decrease range is the smallest,The numerical valueη is 0.78～1.04,and the η of rectangular and fan-shaped tubes is 0.76～1.06 and0.83～1.17 respectively. |
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