Thermodiffusion effects in a two-phase system with the thermocapillary deformable interface exposed to local heating

Abstract

The non-stationary thermocapillary convection induced by the local thermal load in a two-phase system is studied on the basis of the Navier–Stokes equations in the Boussinesq approximation for the two-dimensional case. The mathematical model for investigating the dynamics and processes of heat and mass transfer in the bilayer system takes into consideration the Dufour and Soret effects in the gas–vapor layer and diffusive-type evaporation at the interface. The temperature regime on the external boundaries of the system is characterized by the presence of heaters with a finite size. The theoretical study of thermocapillary convection under phase changes includes (i) the statement of the problem in terms of the “stream function–vorticity” functions, (ii) the outline of the numerical algorithm allowing one to calculate the main characteristics of the liquid–gas system and position of the interface at any time interval as well as (iii) the investigation results of the impact of thermodiffusion effects on the behavior of the liquid–gas surface and characteristics of the phase transition and vapor content in the gas layer. For the benzine–air system it is found that the specific local concentration patterns in the gas layer are formed under the influence of the Soret effect in the zones of thermal exposures. Depending on the inclusion/exception of the Soret effect, the amplitude of the interface oscillations and evaporative mass flow rate at the interface can be increased/decreased.