Argon Bottles

[padiscubapro]

Question on the Thermodynamics -- given the differential compressability of He vs O2 an N2, how does the energy required to raise the temperature of the inspired gas change with depth?

It my just be an illusion, but I sense that the breathing gas is colder when I am diving with a He mixture than a nitrox mixture. Since there are a lot of other factors, including depth and workload, I'm curious as to the science.

For the original question: I use a 6 cu ft tank attached to my backplate. I fill it with air or argon, depending on what is available. So there is often a mixture of the two. I don't notice much difference, but on a cold dive I can sense the denser Ar whenever I add gas to my suit and it has a slightly warmer feel. I can do two 200' dives on the 6 cu ft tank at 2000 psi with gas to spare.

Jerry

at the AMBIENT pressures seen by divers the compressibility differences of the gases is VERY small..
at ~60m/200 fsw air has a compressibilty factor (as used by gas mixers) of ~1.004 while 100% helium would be ~0.997 add to the fact that the helium required for this depth is small, brings the numbers even closer..

Gas compresibilty differences really dont differ much until you start getting to higher pressures..


My guess about the "feeling" the gas is colder is because the energy transfer within the lungs to heat up the gas occurs much faster because of the high thermal conductiivity(there is a temperature gradient to start, but it does reach equilibrium, unlike the gas in a dry suit) , but the net transfer of energy to the breathing mix containing helium is lower..

 

[JS1scuba]

Hey guys,
As I mentioned in another thread I'm looking at doing some tech courses next year, so want to start planning and getting some extra required gear... Could someone please tell me what size of tank is usually used as an Argon bottle? I'd assume something fairly small maybe a 20L. and while I'm being nosey why do you fill a drysuit with argon in tech and not your breathing gas? is it just to conserve breathing gas, or some other reason?

6 cuft @ 3000 psi
14 cuft @2015 psi (easiest to transfill)
13 cuft @3000 psi

All the above work great for open ocean dives and dives shallower than 250 fsw. For deeper dives and longer exposure dives the 19 cuft and 30 cuft luxfer tanks work best.

Keep in mind that Argon gas gets delivers in the 2000-2500 psi range the moment you transfill it you will not beable to get full use of a 3000 psi cylinder unless you have a gas booster or .... top with air (very common)

I take 2 6 cuft bottles with me for most day trips and they are more than sufficent, on longer trips i take the 14s

hope that helps

 

[lamont]

to first order the reason why He has a lower thermal capacity is that when you pump energy into it, it all goes into translational kinetic energy. when you pump energy into a diatomic gas like N2 or O2 some of that energy goes into rotational and vibrational states of the module and less into kinetic (temperature) energy.

 

[jerryn]

at the AMBIENT pressures seen by divers the compressibility differences of the gases is VERY small..
at ~60m/200 fsw air has a compressibilty factor (as used by gas mixers) of ~1.004 while 100% helium would be ~0.997 add to the fact that the helium required for this depth is small, brings the numbers even closer..

Gas compresibilty differences really dont differ much until you start getting to higher pressures..


what you are saying makes sense. At 200f the ambient pressure is just over 100 psi and the compression is only about 1 percent differential. So, I assume that the empirical results show little difference in the energy required to raise the gas temperature at respiration.

I use 18/45 at 200ft. That is almost half of my gas. I don't consider that a small amount of He, but I guess that is a matter of perspective.

Jerry

 

[padiscubapro]

at the AMBIENT pressures seen by divers the compressibility differences of the gases is VERY small..
at ~60m/200 fsw air has a compressibilty factor (as used by gas mixers) of ~1.004 while 100% helium would be ~0.997 add to the fact that the helium required for this depth is small, brings the numbers even closer..

Gas compresibilty differences really dont differ much until you start getting to higher pressures..


what you are saying makes sense. At 200f the ambient pressure is just over 100 psi and the compression is only about 1 percent differential. So, I assume that the empirical results show little difference in the energy required to raise the gas temperature at respiration.

I use 18/45 at 200ft. That is almost half of my gas. I don't consider that a small amount of He, but I guess that is a matter of perspective.

Jerry

I usually use between 25-30% helium for that depth..

 

[jasona111]

Thanks Everyone... I suspect I now know enough to make a decision about argon bottle size

 

[Hoosier]

Are you using an Argon bottle with RB?

If then, what size and valve with what brand first stage?

Thanks in advance,

I usually use between 25-30% helium for that depth..