Thought experiment: Diffusion between tanks
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this discussion has me hankering for a "Black & Tan" 
victorzamora
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That might be why i fell into the trap....
Learn something every day
No, I get it. I know gas blending AND I'm an Aerospace Engineer. It's still all too easy for me to fall into those same traps.
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Are you sure? The interfacial tension between pure water and a dilute aqueous solution like milk is very, very, small. I'd be surprised if that played much of a role. And i have a hard time imagining a gas having a measurable surface tension.
I teach to add O2 at 50 to 60 psi / min.
I don't know what you mean by buffer just in case? If you're asking what sort of other safety practices are employed - you use equipment cleaned for oxygen service to remove hydrocarbons and other fuel. You avoid presenting sources of ignition: slowly to avoid compression heating and particle impingement, etc.
Covered in the Bas Blender or Advanced Gas Blender class you can take from a number of agencies.
victorzamora
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That's what I was alluding to...
No "surface tension", but there are attractive forces ("stickiness") between real gas molecules that give rise to viscosity and other non-ideal behavior. Those forces are largely what give rise to "surface tension" in liquids.
The amazing thing to me is that the average (or RMS) velocity of an O2 molecule at room temperature is ca. 500 m/s (yes, that's meters per second), yet at the high pressures in a scuba tank the mixing rate is so slow because of the short mean-free-path (they don't travel very far before bouncing off another molecule) and viscosity effects.
You can easily demonstrate fairly rapid diffusion of gases at 1bar - consider how everyone in the car can smell a fart within 10-20 seconds.
The amazing thing to me is that the average (or RMS) velocity of an O2 molecule at room temperature is ca. 500 m/s (yes, that's meters per second), yet at the high pressures in a scuba tank the mixing rate is so slow because of the short mean-free-path (they don't travel very far before bouncing off another molecule) and viscosity effects.
You can easily demonstrate fairly rapid diffusion of gases at 1bar - consider how everyone in the car can smell a fart within 10-20 seconds.
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Yikes, just checked in.
Predict as in "physical-mathematical explanation" or model as in just get an answer that is supported by testing? Yeah, one could do a proper job if one understood this first: Buckingham π theorem - Wikipedia, the free encyclopedia
I have a fuzzy grasp of it (above) and that is usually enough for me to come up with something that can be twiddled with. Just add gradient factors and it will be OK.
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