Gas-Phase Flow and Diffusion Analysis of the Droplet-Train/Flow-Reactor Technique for the Mass-Accommodation Processes

While the droplet-train/flow-reactor method is one of the most powerful experimental techniques to study mass-accommodation kinetics at liquid−vapor interfaces, relatively little is understood about the gas-phase diffusion resistance in the flow tube, an important ingredient to the overall uptake kinetics. In this paper, we theoretically examined the gaseous resistance by numerically solving the coupled-diffusion equation and fluid dynamics in the flow tube. The results indicate that the gaseous resistance for the train of droplets significantly deviates from that for a single spherical droplet because of the interference among the droplets and the flow effect. The dependences of the gaseous transport on varying droplet velocity and orifice frequency are examined and quantitatively elucidated on the basis of the calculated data. This paper suggests that an accurate formula for the gas-phase diffusion resistance is desirable, particularly for the quantitative evaluation of the mass-accommodation coefficients of liquids having substantial vapor pressures.