Numerical Simulation Of Solutal Marangoni Convection At The Moving Gas-Liquid Interface

Marangoni convection due to mass transfer at the gas-liquid interface tends to enhance the mass transfer process.However,the intensity of Marangoni convection could be generally weakened if it is accompanied by the strong bulk flow or interface movement.In this work,the mass transfer process between gas-liquid interface with bulk flow at the phase interface is numerically simulated by means of the bubble and falling liquid film as research objects.The Volume of Liquid method and the Level Set method are coupled to establish the basic CFD model of the multiphase flow while the error caused by the false flow on simulation are eliminated.On the basis of the CSF method,surface tension gradient is obtained by using the User Define Function,thereby the momentum source term of the Marangoni force is directly obtained.Moreover,a complete multi-component interphase mass transfer and heat transfer model is established,and the phase interface geometry is reconstructed by the User Define Function.Therefore,the mass and energy source terms in the interphase mass transfer process can be accurately calculated.For the single bubble model,the numerical simulation is carried out under the conditions with gravity and without gravity.Quantitative streamline distribution,concentration,velocity and temperature changes indicate the emergence of Marangoni convection.However,due to the small bubble volume,the phase change heat is not large,the influence of temperature effect can be ignored.The Marangoni convection has limited enhancement effect on the whole mass transfer process.The larger the bubble diameter is,the greater the intensity and duration of Marangoni convection are.Under the normal gravity,there are no existence trace of the Marangoni convection.When the gravity is gradually reduced,obvious Marangoni convective cells can be found on the streamline distribution diagram.With rising of the bubble,Marangoni convective cells gradually fall off from the tail,and it is different from the situation under the condition without gravity.In the presence of gravity,the smaller the bubble diameter is,the smaller the rising speed is.The smaller size of the bubble is more conducive to the development of convection of Marangoni.With respect to falling liquid film in the microchannel,the calculation object is CO2-MEA reaction absorption system.In a single channel,the parameter conditions consisting with the experiment are adopted.The gas-liquid mass transfer is carried out in the parallel flowing state.Marangoni convection appears on the section flowing along the liquid film.With the increase of the initial MEA concentration,the enhancement factor of Marangoni convection on mass transfer increases firstly and then decreases slightly.When the initial volume fraction of CO2 is 15%of the industrial condition,the optimal initial MEA concentration value is obtained.Results is beneficial to application of the Marangoni convection on the CO2-MEA reaction absorption in the microchannel system.