An experimental study of the temperature field on a film surface of liquid; ranging from highly subcooled up to saturation temperature conditions, flowing freely on a vertical plate with a local heat source in its center, has been made. Direct measurements have shown that an estimation of the temperature gradient on a film surface based on the temperature gradient across the film can cause an incorrect result, since |gardT| across a film is 10-50 times larger than |gradT| on the film surface. The average temperature gradient calculated as a relation of maximal temperature difference on the film surface to a heater length gives a satisfactory estimation of local temperature gradients on an interface for small Reynolds numbers (Re ≤ 6). Film breakdown occurs in several steps: appearance of a large-scale instability with a formation of horseshoe-shaped structures; reorganization of structures; thermocapillary thinning and film breakdown. Two mechanisms of appearance of dry spots have been discovered. They are connected with existence of significant temperature gradients on the film surface near stable structures and with decreasing liquid rate on the heater because of deformation of a horizontal standing wave.
|Журнал||Heat Transfer Research|
|Состояние||Опубликовано - 1998|
ASJC Scopus subject areas
- Fluid Flow and Transfer Processes