A Thermocapillary Mechanism for Lateral Motion of Bubbles on a Heated Surface During Subcooled Nucleate Boiling

Abstract

Both thermocapillary flow and the concerted motion of bubbles toward each other in subcooled nucleate boiling have been mentioned in the literature on boiling phenomena, but never associated with each other. Also, it has been shown in previously unrelated contributions that thermocapillary flow around bubbles of sparingly soluble gas can cause those bubbles to aggregate on a warm surface. The conjunction of these observations leads to the hypothesis that mutual entrainment in thermocapillary flow might drive bubbles toward each other during nucleate boiling of a subcooled liquid. An approximate equation for estimating the observability of such motion is presented. The effect would be especially important in cases where the bubble release rate is low such as boiling on horizontal down-facing surfaces and boiling in microgravity.