Experimental study of Marangoni convection around a bubble: Application to the boiling heat transfer under microgravity conditions

Thermocapillary flow induced by a bubble in a liquid layer heated from above is investigated. In this configuration, buoyancy and thermocapillary forces act in opposite way. The three characteristic non dimensional numbers are the Marangoni, Prandtl and Rayleigh numbers. The influence of these parameters on the flow field and the heat transfer is analysed. The velocity field is measured in the meridian plan of the bubble. The law of change of the Reynolds number with the Marangoni and Prandtl numbers is determined. The magnitude of the heat transfer due to Marangoni convection is measured beneath the bubble for various temperature gradients and bubble sizes and a heat exchange law is proposed. The first results obtained with a vapour bubble are presented.