伴有Rayleigh对流的气液传质理论

浓度梯度导致的Rayleigh对流会对界面传质产生重要影响。采用格子Boltzmann方法(LBM)对吸收过程伴有Rayleigh对流的气液传质理论进行了分析。针对表面更新理论，提出了将近界面处羽状对流结构的宽度作为特征尺度来求得表面更新时间。结果表明，Rayleigh对流的发生能够有效减小双膜理论中的液膜厚度；液相传质系数的LBM模拟值与表面更新理论预测值吻合较好。

Gas-liquid mass transfer theory accompanied by Rayleigh convection

In an interfacial mass transfer process, the concentration gradient of the transferred component near the interface may generate Rayleigh instability if the concentration gradient leads to a density gradient that directs oppositely to the direction of the gravity, and Rayleigh convection may occur if disturbance exists at the interface. The convection has an important effect on the interfacial mass transfer. In the present study, a 2D time-dependent lattice Boltzmann method (LBM) with a random perturbation model is used to simulate the liquid-phase Rayleigh convection in the CO₂ absorption into solvents process. Gas-liquid mass transfer theory accompanied by Rayleigh convection was analyzed by LBM. The width of plume convection pattern at the interfacial vicinity is considered as characteristic scale, which was used to calculate the surface renewal time for surface renewal theory. The results show that liquid film thickness in two-film theory can be effectively reduced by Rayleigh convection, and the mass transfer coefficients are calculated by the surface renewal theory and agree well with the LBM simulation results.