double tank equipment

[jcaplins]

If you took a set of doubles with the isolation manifold closed, and filled one tank with 100% O2, and the other with 100% He. Both tanks to the exact same pressure and temperature....
Unless you have an orifice that is only the diameter of 1 atom, when you open the isolation manifold the 2 tanks will eventually become thoroughly mixed. How long will that take? I don't know, you'll need to break out the slide rule. I believe these are the ideal gas laws dealing with diffusion and Effusion. The gas particles are constantly in motion, and all the O2 molecules are trying to get as far away from each other as possible; same with the He molecules.

 

[nimoh]

If you took a set of doubles with the isolation manifold closed, and filled one tank with 100% O2, and the other with 100% He. Both tanks to the exact same pressure and temperature....
Unless you have an orifice that is only the diameter of 1 atom, when you open the isolation manifold the 2 tanks will eventually become thoroughly mixed. How long will that take? I don't know, you'll need to break out the slide rule. I believe these are the ideal gas laws dealing with diffusion and Effusion. The gas particles are constantly in motion, and all the O2 molecules are trying to get as far away from each other as possible; same with the He molecules.

regardless of how long it takes, if you hooked up a regulator after opening the isolation manifold, and took a breath, would you be breathing:
a. oxygen
b. helium
c. oxygen and helium

If you answered c, then you agree (on at least one point) with agilis in that the gases are being mixed even though both tanks have equal pressure.

 

[PfcAJ]

They won't be mixed equally.

 

[Adobo]

I'm all confused now. I feel like I need an open water refresher.

 

[Lorenzoid]

If you took a set of doubles with the isolation manifold closed, and filled one tank with 100% O2, and the other with 100% He. Both tanks to the exact same pressure and temperature....
Unless you have an orifice that is only the diameter of 1 atom, when you open the isolation manifold the 2 tanks will eventually become thoroughly mixed. How long will that take? I don't know, you'll need to break out the slide rule. I believe these are the ideal gas laws dealing with diffusion and Effusion. The gas particles are constantly in motion, and all the O2 molecules are trying to get as far away from each other as possible; same with the He molecules.

Though I am trying to learn as I follow this thread, that has been my understanding. Is it correct? Doesn't this contradict DivingHoosier in Post 173? It's my understanding that the oxygen and helium molecules will "mix" by diffusion (and, I suppose, effusion through the orifices as you said) and eventually reach some equilibrium mix. Correct?

I do appreciate people trying to correct others--and the others shouldn't take offense--as incorrect information will remain here forever for passersby to see and perhaps be misled.

 

[nimoh]

They won't be mixed equally.

I agree, and it makes filling out the analysis sticker very difficult

 

[jcaplins]

They won't be mixed equally.

Mixed thoroughly and reach an equilibrium. I may do the math later.

Though I am trying to learn as I follow this thread, that has been my understanding. Is it correct? Doesn't this contradict DivingHoosier in Post 173? It's my understanding that the oxygen and helium molecules will "mix" by diffusion (and, I suppose, effusion through the orifices as you said) and eventually reach some equilibrium mix. Correct?

I suppose I am disagreeing with post 173.




(remember: I'm just some guy on the interwebsnets)

---------- Post added June 23rd, 2015 at 04:39 PM ----------

regardless of how long it takes, if you hooked up a regulator after opening the isolation manifold, and took a breath, would you be breathing:
a. oxygen
b. helium
c. oxygen and helium

If you answered c, then you agree (on at least one point) with agilis in that the gases are being mixed even though both tanks have equal pressure.

I would have to go with "c."

 

[Lorenzoid]

They won't be mixed equally.

Please explain. Why do the tanks not eventually reach an equilibrium distribution of oxygen and helium molecules by diffusion through the manifold?

Diffusion, no? https://en.wikipedia.org/wiki/Diffusion

 

[PfcAJ]

It's just not the reality of it. In sure if u have a bajillion years it would even out, but here in real life it doesn't. See tobins comment about the diameter and length of the manifold.

The gases behave more like liquids at scuba pressures.

 

[AfterDark]

regardless of how long it takes, if you hooked up a regulator after opening the isolation manifold, and took a breath, would you be breathing:
a. oxygen
b. helium
c. oxygen and helium

If you answered c, then you agree (on at least one point) with agilis in that the gases are being mixed even though both tanks have equal pressure.

With 2 "equally" filled tanks the mixing would go on in the regulator how much and the % of mix depends on which bottle has the higher pressure the higher pressure gas would have the >%. Higher on 2 equally filled tanks?

Both tanks may read the same on a gauge but since there are tolerances on the gauges, one tank may have a higher pressure small enough not to be read on the gauge but never the less exerts that much more pressure. I would also say the density of the gases involved would have some bearing on the % mixed also. Since the mixing would take place in the regulator which regulator the diver is using may also affect the mixing of the gases. There are a lot of variables involved.