Resistance to mass transfer inside droplets

Abstract

AbstractAn experimental investigation of the effects of various physical properties on the dispersedphase mass transfer coefficient was carried out for both nonoscillating and oscillating liquid droplets falling in a single stream through stationary continuous liquid phases. The Colburn and Welsh two‐component technique was used to isolate and measure the disperesed‐phase resistance to mass transfer. This technique limited the experimental study to systems with low interfacial tensions, between 2.5 and 5.8 dynes/cm. Solute was transferred into the droplets, and the droplet concentration was measured after droplet‐fall heights ranging from about 2 cm. to 103 cm. Precautions were taken to minimize end effects.The experimental mass transfer rates on nonoscillating droplets in general were greater than that predicted by the Kronig and Brink model for nonoscillating circulating droplets. Experimental Sherwood numbers for four liquid systems were correlated in terms of a relationship involving the dispersed‐phase Schmidt number, the Weber number, and the time group, 4DLtc/d2e, which allows for the time dependency of the transfer mechanism. The data were correlated with an average absolute deviation of 34%. The Kronig and Brink and Newman relations fitted the experimental data for nonoscillating droplets with an average absolute deviation of 46 and 54%, respectively. The experimental results for the oscillating droplets were correlated by two relationships with an average absolute deviation of 10.5%. The Handlos and Baron model fitted the experimental results for oscillating droplets with an average absolute deviation of 38%.