Bubbly flow and gas-liquid mass transfer in square and circular microchannels for stress-free and rigid interfaces: dissolution model

A model is proposed to describe the dissolution of a chain of spherical pure gas bubbles into a nonvolatile liquid, along square and circular microchannels. The gas-liquid interface is considered stress-free or rigid. This model enables predicting, in each considered case, the evolution along the microchannel of the bubble diameter, the bubble velocity, the separation distance between two successive bubbles, the liquid fraction, the pressure in both the liquid and the gas phases, the concentration of the dissolved gas in the liquid phase and the mass transfer coefficient between the bubble and the liquid phase. The influence on the gas dissolution of the interfacial boundary condition, the microchannel type, the operating conditions and the physicochemical properties of the liquid and gas is analyzed. Existing experimental data for a nearly square microchannel are convincingly reproduced using the model. The validity and the different applications of the model are also discussed.