Nucleation, growth and detachment of neighboring bubbles over miniature heaters

Abstract

This work investigates how simultaneous CO2 bubbles desorb from water and n-heptane when these liquids become supersaturated with dissolved CO2. Supersaturation is imposed locally by a miniature heater so bubbles grow at adjacent sites across the heater. To suppress buoyancy, experiments are performed at low gravity conditions. The number of nucleation sites and nucleation time delay depend on liquid properties and heating power. Simultaneous bubbles do not grow at exactly the same rate and calculations show that this corresponds to slightly different bubble temperatures. Moreover, they exhibit smaller growth rates than single bubbles at similar conditions, an indication that they compete for dissolved CO2. As bubbles expand into the surrounding cold liquid, the heater's temperature decreases in a fashion implying the inception of Marangoni convection. Simultaneous bubbles detach due to g-jitters but following different ways in the two liquids. However, they always detach together and at smaller sizes than single bubbles do. A temperature triggered destabilization of contact lines is deemed responsible for this. (C) 2008 Published by Elsevier Ltd.