Heat Transfer And Flow Resistance Performance Of Double Shellpassshell-and-tube Heat Exchanger Combined With Helical Baffles In The Outer Shell Pass And Louver Baffles In The Inner Shell Pass

The shell-and-tube heat exchanger is widely used in HVAC,energy power and high energy consumption industry,due to its simple structure,convenient processing and manufacturing,reliable operation,and strong adaptability.By improving the performance of the shell-and-tube heat exchanger,the goal of energy conservation and emission reduction can be effectively achieved.Therefore,it is of great significance to optimize the heat exchanger structure and carry out research on the heat transfer and resistance performance of the heat exchanger.The traditional shell-and-tube heat exchanger with segmental baffles has high pressure drop in the shell,large flow dead zone,and high pump power consumption.To solve the above problems,a double shell-pass shell-and-tube structure combined with helical baffles in the outer shell pass and louver baffles in the inner shell pass is proposed.This structure optimize the shell-side flow field,improve the heat transfer efficiency,and reduce pump power consumption.In this paper,a physical model of a double shell-pass shell-and-tube structure combined with helical baffles in the outer shell pass and louver baffles in the inner shell pass is established.Through three-dimensional numerical simulation,the shell-side flow field structure and temperature distribution of the double shell-pass shell-and-tube structure combined with helical baffles in the outer shell pass and louver baffles in the inner shell pass are obtained.Then,the fluid flow and heat transfer characteristics is presented and the mechanism of the high efficiency and low resistance is analyzed.The comparison of the heat transfer,resistance,overall performance between the traditional shell-and-tube heat exchanger with segmental baffles and the new heat exchanger are carried out.The shell side resistance,heat transfer and overall performance of the new heat exchanger are studied under different working conditions,different structural parameters(the helical angle of baffle in the outer shell,the number of louver baffles groups in the inner shell,the oblique angle of louver baffles in the inner shell and the number of louver baffles in the inner shell).The main contents and results are as follows:(1)The flow field and temperature distribution in shell side of the double shell-pass shell-and-tube heat exchanger is obtained by numerical simulation.The results indicated that the flow field distribution is uniform,and the flow dead zone and recirculation zone are small.For the double shell-pass shell-andtube heat exchanger.The heat transfer coefficient per unit pressure drop is 24.4% higher than that of the traditional shell-and-tube heat exchanger with segmental baffles.The overall performance of the double shell-pass tube and shell structure is better than that of the shell-and-tube heat exchanger with segmental baffles.(2)As the helix angle of helical baffle in the outer shell increases,the heat transfer coefficient and the shell side pressure drop decreases.Also,as the helix angle of helical baffle in the outer shell becomes larger,the influence of the change in helix angle on the heat transfer coefficient and the pressure drop in the shell side gradually becomes smaller.When the helix angle of helical baffle in the outer shell is 20°,it has the highest shell-side heat transfer coefficient at the same pressure drop and the best performance.(3)Within the research scope of the number of louver baffles groups in the inner shell,the heat transfer coefficient and the pressure drop of the double shell-pass shell-and-tube heat exchanger increases with the increase of the number of louver baffles groups at the same mass flow rate.When the number of louver baffles groups in the inner shell is 4,the overall performance is optimal.(4)As the oblique angle of louver baffles in the inner shell becomes larger,the heat transfer coefficient and pressure drop of the new heat exchanger decreases.But the change is very small.The change of the oblique angle of louver baffles in the inner shell has little effect on the shell-side performance of the double shell-pass shell-and-tube heat exchanger.(5)With the increase of the number of louver baffles for one group in the inner shell,the heat transfer coefficient and the pressure drop increases in the shell side.When the number of louver baffles for one group in the inner shell is 2,the heat transfer coefficient at the same pressure drop is highest,and the overall performance is the best.(6)When the shell side fluid is oil,the conclusions obtained by changing the parameters are approximately the same as the former.When the shell-side fluid is oil,the new heat exchanger has the best performance as the follow conditions: the helix angle of helical baffle in the outer shell is 20°,the number of louver baffles groups in the inner shell is 4,and the number of louver baffles for one group in the inner shell is 3.