Numerical Simulation Of The Hygroscopic Process Of Methanol Solution Sprayed Into Moist Air

With the development of science and technology in all countries of the world,people pay more and more attention to the use and exploration of space.In the field of aerospace,the presence of the frost layer in an air pre-cooler increases the heat transfer resistance and reduces heat exchanger efficiency.Therefore,it is of great significance to explore effective methods of anti-frosting.Condensed substance plays an important role in pre-cooler frosting.The distribution of condensed substance,the mass of water vapor absorbed by condensed substance are important factors on the defrosting in the flow channel.In this paper,a model of methanol solution and the water vapor of moist air were developed to predict the mass transfer process,which is combined with the Euler-Lagrange multiphase flow method,using FLUENT software and adding user-defined function(UDF)to simulate the mixed mass transfer process of water vapor and methanol solution,and then the correctness of the model is verified.The mixing process of water vapor and methanol in the flow channel of the pre-cooler at different conditions were numerically studied,such as the ratio of water vapor to methanol is 1:0.4,1:0.5,and 1:0.6,the nozzle injection pressure is 2MPa~10MPa,the spray half angle is 15°~75°,the nozzle size is 0.001~0.002 m,and the number of nozzles is 1~5,the velocity of moist air is 8~16m/s,the temperature is 291.55K~331.55 K and so on,the changes in the parameters example solution distribution,solution absorption rate and relative humidity of moist air were discussed in detail.The results show that the absorption rate of the densely distributed methanol is larger;the smaller the ratio of water vapor to methanol,the later the water vapor is absorbed,and the better the absorption effect of water vapor.From the influence of different nozzle parameters on methanol flow and mass transfer rate we know that the larger the injection pressure,the smaller the methanol absorption rate;the larger the spray half angle,the smaller the methanol absorption rate,but the more uniform distribution of methanol in the flow channel;The larger the diameter of nozzle,the smaller the velocity of the methanol droplets,but the larger the diameter of the methanol droplets.The flow rate of a single nozzle is determined by the ratio of the total flow rate of the methanol solution to the number of nozzles.Therefore,the number of nozzles has a large influence on the flow rate of a single nozzle,and the absorption rate of the methanol droplets is also greatly affected.The spray angle of the nozzle affects the flow state after the methanol droplets are injected.Under the premise that the total flow rate of the required methanol solution is constant,there is a critical value for the nozzle number and angle which has a certain impact on the absorption rate.The velocity of the moist air has an effect on the Re number of the methanol droplets.The greater the velocity of moist air,the greater the Re number of methanol droplets,the greater the absorption rate of methanol droplet.For a given flow channel length,the lower velocity of the moist air,the lower relative humidity of moist air at the exit of the flow channel.The temperature of the moist air also has a large influence on the diffusion coefficient of water vapor.The higher the temperature of the moist air,the larger the water vapor diffusion coefficient,the higher the absorption rate of the methanol droplets and the lower relative humidity of moist air at the exit of the flow channel.