Interfacial instability of growing drop: Experimental study and conceptual analysis

Capillary pressure experiments were performed at the water/hexane interface including adsorption and mass exchange of hexanol under different conditions. The results from growing drop experiments show that instabilities due to Marangoni convection not only depend on the same parameters as have been reported for quasi-static interfaces, such as direction of mass transfer, distribution coefficient and ratio of diffusion coefficients, but also on the experimental conditions such as dispersed phase flow rate, capillary tip size, size of growing drop and its lifetime. Based on a new flow expansion model for mass transfer, a new approach is presented for data analysis, which includes the various parameters effecting interfacial instabilities. The proposed analysis considers the overall mass transfer coefficient ratio (k1/k2) which includes diffusion and convection effects instead of the pure ratio of diffusivities (D1/D2) under the condition of growing drops. The proposed analysis is verified on the basis of capillary pressure measurements.