Experimental study of bubble growth by non-condensable dissolved gas diffusion in super-saturated low-pressure water*

Mass diffusion into and out of microbubbles is measured in a specialized facility, where bubbles are suspended and exposed to varying pressures and concentrations of non-condensable dissolved gas. The facility is a closed system with dissolved oxygen probe and pressure transducer measuring the dissolved gas content and pressure in the system over the duration of the experiment. The bubbles are pushed upward into a 2x10mm glass channel test section from an inhouse designed and made monodispersed bubble generator. A stepper motor pushes a syringe to inject downward flow into the test section, where the flow balances the buoyancy force of the rising bubble. Thus, the bubble is trapped in the glass test section and is recorded by time-resolved in-line holography. The holograms are reconstructed to calculate the growth rate of bubbles, which is in term is used to estimate the diffusion coefficient at low pressures. The presentation will cover the inhouse designed and made monodispersed bubble generator and the measured mass diffusion coefficient of non-condensable dissolved gas in water down to 10kPa.