Since there's more energy in the fluid, I believe that you will have a higher nucleation rate in a hotter (assuming all other relevant variables remain unchanged), is this the case? How can I calculate it?
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asked Dec 8, 2018 at 17:36
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This is hard to calculate, for the following reasons.
Although the solubility of CO2 in water solutions goes down in a predictable way with increasing temperature, it is difficult for CO2 to exsolve on its own: a supersaturated solution of CO2 in water can exist in a metastable state for hours after the pressure urging the CO2 to remain in solution has been released. Prompt equilibration requires the presence of seed nuclei to kickstart the exsolvation process.
These nuclei are most commonly provided by cracks, pits or scratches in the walls of the beer glass which have tiny amounts of air stuck in them. Any model of the rate of bubble nucleation in beer must contain a model of the number and size distribution of the nuclei present, otherwise it will not furnish realistic results.
This effect is so strong that when a beer video is shot for an advertisement and a brand-new beer glass is used, there are very few rising bubble cascades present when the beer is poured into the glass for the camera to capture. The videographer has to drop a handful of ball bearings into the glass first, shake the glass so as to scratch it up with the balls, remove the balls and then pour in the beer in order to get plenty of bubble cascades rising up through the beer.
answered Dec 8, 2018 at 23:01
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$\begingroup$ And it depends on surface tension. And on the diffusion coefficient. $\endgroup$– user137289Dec 8, 2018 at 23:04
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$\begingroup$ to first order, it is nucleation rate-limited. $\endgroup$ Dec 8, 2018 at 23:14
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$\begingroup$ But when nucleation occurs at a surface asperity in a glass, one can see that it takes time for the next bubble to rise from the same spot. The bubble needs to grow to get the buoyancy to go up. That growth depends on diffusion. $\endgroup$– user137289Dec 8, 2018 at 23:28
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1$\begingroup$ I get that, but absent the nucleus, the process has almost no way to get started. I studied this for years when I was designing thermal inkjet printheads for HP. The nucleation properties of the heater resistors had to be understood and controlled in order for the heads to work. $\endgroup$ Dec 9, 2018 at 0:11