Experimental and conceptual modeling study of CO2 bubble formation on a porous substrate in supersaturated water

• Experiments of supersaturation driven bubble nucleation on a solid substrate were performed • A digital image analysis algorithm to measure the bubble size distribution was developed • The bubble size distribution was measured as a function of time on various substrate types • An initial wave of small bubbles evolves over time into a more flattened and wider size distribution • A nucleation model was able to predict the results qualitatively An experimental study was conducted to investigate and quantify the simultaneous nucleation and growth of multiple bubbles on different substrates following sudden supersaturation. The resulting data support the calibration of parameters of a heterogeneous bubble nucleation model, such as that of Battistella et al. (2018). A custom setup with two interconnected tanks was constructed to control supersaturation of CO2 in water, and capture bubble nucleation and growth dynamics via high-resolution imaging The experiments confirmed model predictions: an initial wave of uniformly sized bubbles evolves over time into a more flattened and wider bubble size distribution as a consequence of detachment, coalescence and nucleation events. The supersaturation ratio resulted in the formation of more bubbles with smaller sizes. The bubble growth follows the same t dependence as described in the analytical solution by Epstein and Plesset (1950), but with a different proportionality, reflecting a reduced mass transfer rate due to surface effects and local depletion. A nucleation model was used to predict qualitatively the experimentally observed bubble size distributions, with a limited effect of surface properties. A distribution in the bubble Sherwood-number was found to be required, to adequately mimic depletion/competition effects, which needs to be studied in more detail in future studies.