Heating-induced release of trapped bubbles from dead-end pore throats filled with nonvolatile liquid

Abstract

The release of trapped bubbles from dead-end pore throats filled with nonvolatile liquid has widespread applications in gas–liquid reactors, radiators, foam flooding, ceramic sintering, and droplet microcarriers. As conventional pressure-driven flow cannot induce the transport of bubbles in dead-end pores, this paper explores the possibility of using heating to control the release of bubbles from dead-end pore throats. Visualization experiments of the microfluidics within a dead-end pore throat structure are conducted to address the release process of bubbles during heating. An increase in temperature causes dissolved gas in the solution to be transferred to the bubble, which enhances the bubble pressure and enables the bubble to pass through the pore throat. We analyze the effects of the initial bubble radius and initial temperature on the critical temperature Tcr at which the bubble passes through the pore throat. A larger initial radius does not necessarily make it more difficult for the bubble to pass through the throat, but there is a critical radius above which any increase in radius produces a lower value of Tcr. A theoretical model considering diffusion mass transfer, capillary forces, and corner film flows is developed, and this model is found to be in good agreement with the experimental results. Finally, we obtain three dimensionless numbers that can be used to predict Tcr. Our work provides guidance for the effective regulation of diffusive growth and the heating-induced release of bubbles from dead-end pore throats.