Study And Discussion On Multiphase Flow Resistance In Helical Tube Heat Exchanger

The helical tube exchanger has been widely used in industrial production because of its compact structure and high heat transfer efficiency.The pressure drop has a key influence on the performance of the heat exchanger.Two-phase flow is common in the tube of exchanger,the complexity of two-phase flow,so the research of pressure drop in helical tube is very difficult.In this paper,the helical tube of a helical tube exchanger used in chemical industry is studied,and the frictional resistance characteristic of the tube is numerically simulated,which provides the theoretical basis for developing helical exchanger with good performance.In this thesis,the frictional resistance characteristic of the helical tube is numerically simulated by Fluent,one of the CFD software.In order to study the influence of mass flow rate,dry degree,pressure,heat flux density and helix angle to the resistance characteristic.The main findings are as follows:1.The model of helical tube is established and the parameters are set up and solved.Under the same working conditions,the friction pressure drop of numerical simulation and the pressure drop calculated by the experimental fitting calculation,and the result shows that the model of helical tube is reliable.2.Based on the above model,the numerical simulation of helical tubes with different dryness,mass flow,pressure and heat flux density is carried out to study their influence on frictional resistance characteristics.The conclusions shows that,under the influence of heat flux density,the pressure drop in the tube is basically the same with the change law of dry degree and mass flow rate and without heat flux density.The friction resistance decreases with the increase of the fluid pressure,the exponential increase of the mass flow,and the linear increase with the increase of the dry degree.3.By changing the helix angle and solving the helical tube model,it is found that the frictional resistance characteristic of different helix angle is almost unchanged,which indicates that the helix rise angle has little effect on the frictional resistance of the gas-liquid two-phase flow in the helical tube.4.As the pressure is higher,the friction resistance drop in the helical tube is smaller,so the design of helical tube exchanger should be designed to improve the pipe pressure as high as possible,under the precondition of guaranteeing safety.