Effect of the microscale wall topography on the thermocapillary convection within a heated liquid film

Thin films, which are frequently used for cooling of electronic devices and other components, can be ruptured by thermocapillarity leading to appearance of uncontrolled dry patches that significantly reduce the heat and mass transfer characteristics. Microstructured wall surfaces often improve the performance of such devices. However, the effect of the wall microstructure on the heated film dynamics has not been studied to date. When the temperature of the wall differs from that of ambient gas, the presence of a wall microstructure leads to a temperature gradient along the liquid-gas interface. This is a result of the film thickness inhomogeneity resulting from the microstructure. Thus, a thermocapillary convection develops even in the undisturbed state. In the present paper, the thermocapillary film flow on a horizontal microstructured wall is studied in the framework of the long-wave theory and numerically using the volume of fluid method. The predictions of the liquid velocity fields from the above two methods are compared. It is found that the flow is characterized by a steady roll motion. The gas-liquid interface is found to deform in such a way, that the liquid tends to accumulate within the groove. A film stability analysis is also performed. It is found that the wall microstructure destabilizes the film. (C) 2005 Published by Elsevier Inc.