The influence of thermocapillarity on the migration of droplets in a liquid possessing a uniform temperature gradient

The influence of thermocapillarity on the migration of water droplets in butylbenzoate and fluorobenzene is investigated at low Reynolds and Marangoni numbers. The two components of both liquid systems are immiscible with one another and have the same density at 32 and 50 C respectively. At temperature gradients of 1 C/cm in stratified butylbenzoate and 4 C/cm in stratified fluorobenzene in equilibrium, gravity is reduced to a hundredth of the interfacial force. Water droplets injected into the test cell are sorted out in the gravity field dependent on their diameters. Under these conditions the smaller droplets migrate to higher temperature than the bigger ones. The final position of a droplet is determined by the balance of Marangoni and gravity forces both of which depend on droplet diameter. The positions of the droplets in the test cell are evaluated photographically. The interface tension gradients are 0.000001 N/cm for both systems.