MARANGONI AND ELECTRIC FIELD EFFECTS UPON MASS TRANSFER TO TRANSLATING DROPS

Interfacial stresses arising from the transfer of an interfacial tension-lowering solute (Marangoni effects) or the presence or an electric field may significantly alter the interfacial velocity or a moving droplet with consequent effects upon the rate of convective mass exchange between the drop and the external medium. The present theoretical study considers separately the Marangoni and electric field effects and delineates the conditions under which mass transfer enhancement should be observed. For Peclet numbers in the range of 10-100, enchancement is predicted for a Marangoni to Peclet number ratio of 100 or for a dimensionless electric velocity of 0.1. As an example, numerical results for a Peclet number of 50 indicate an increase of approximately 20% in the mass transfer coefficient for either a Marangoni number of 5000 or a dimensionless electric velocity of 0.5 for phases of comparable transport properties and solute solubilities.