A New Design Of Fin-tube Heat Exchanger Based On Numerical And Experimental Research

Recently,enhancing the airside heat transfer of fin-tube heat exchangers is the focus of many researchers.Many works have been done on it.However,most of them were about fins,like changing the shape,adding spoilers or vortex generators.What’s more,many techniques bring side effects while enhancing the heat transfer capacity of heat exchangers,including the increase of flow resistance,the manufacturing costs,and cutting off life span of the equipment.Under these circumstances,this thesis studied and proposed a new design of heat exchanger.Main content and results are as follow:1)Studied and proposed a new design of fin-tube heat exchanger,which adopted the design of highway tollgate configuration.The design is meant to cut off flow resistance and enhance heat transfer for heat exchangers.The main idea of this design can be divided into two parts.One is adding flow deflectors between two adjacent finned tube columns,while the other is adding interspace structure between two adjacent finned tube rows by adjusting the vertical and horizontal distances of finned tubes.2)Built up a mathematical model for heat exchanger and conducted numerical simulation based on Computational Fluid Dynamics（CFD）.Simulated the heat transfer and flow process of new heat exchangers（which implied the new design）and the traditional one under different Re numbers.The results show that the heat transfer capacity increased around11.9²4.6%and 38.0⁴6.7%comparing to traditional staggered configuration and traditional in line configuration,respectively,while the flow resistance decreased around 25.5³4.0%and 13.9¹6.2%comparing to traditional staggered configuration and traditional in line configuration,respectively.The JF factor is about 1.31 and 1.48 to traditional staggered configuration and traditional in line configuration,respectively.3)Analyzed the heat transfer and flow process of the new fin-tube heat exchanger based on the results of numerical simulation and the field synergy principle.By analyzing the temperature and velocity field inside the heat exchanger,it is found that the flow deflector contributed mainly to the decrease of flow resistance,while the interspace structure mainly contribute to the enhancement of heat transfer.The synergic angle of the new heat exchanger is smaller than the traditional one,and the distribution is more even,which is consistent with the field synergy principle.4)Optimizing the ratio d_v-h of vertical tube distance to horizontal tube distance under different Re based on numerical simulation.The results show that only within a certain range of d_v-h can the new design improve the overall performance of heat exchangers.The optimal value of d_v-h is2.3.5)Constructed the test bench of fin-tube heat exchangers and conducted experiments under different inlet air volume.The experimental results show that comparing to the traditional staggered fin-tube heat exchanger,the one with the new design increased heat transfer capacity up to 29.9%while cut off flow resistance up to 29.6%.