Cold air due to pressure of tanks

[Hugh Byrne]

I am doing a college engineering project which involves diving equiptment.

I have found that when the air in a high pressure tank is released it is extremely cold.
I understand the priniciples of why this happens but I was wondering if someone can tell me how diving equiptment gets over this problem?

One would assume the air is at first too cold to breath so there must be a way that it absorbs heat?

Your help is greatly appreciated

Hugh (Ireland)

 

[k ellis]

deleted

 

[jar546]

Under normal operating conditions, the air from the tank is released in a control manner that reduces the chance of freezing. Many 2nd stage regulators then have a built in heat sink to help keep the air temperature from dropping. Some 1st stage regulators are sealed units for use in cold water. In warm, tropical waters, the heat from the water surrounds the regulators, essentially heating them.

Where are the regulator guru folks who can dazzle us with their technical explanation?

 

[bracko]

without going into equations (my text books aren't with me) the change in temperature is dependent on mass/volumetric flow rate. large flowrate, more heat absorbed.

i.e. the air's ability to absorb heat is a property of its mass.


if you hyperventilated into a regulator instead of breathed it would cool down, or more easily (and less likely to make you dizzy) just held down the purge button it should cool down.

I can come back with the equations if you really want, but you should have enough to hunt down the answer you need.

 

[rhwestfall]

(deleted) sorry - just re-read my post anesthesia induced ramblings....

 

[Thalassamania]

PV=nRT

"T" is temperature.

 

[rhwestfall]

and also why I theorize that a "hot rod" first and second stage may not be a good idea in cold water.....

 

[Hugh Byrne]

Thanks all, much appreciated

Ive been experimenting with cylinders in college and the outlet temp has been pretty low. Would I be correct in saying that the lenght of the hose from first stage to second stage is what allows the air to absorb heat from the surroundings?

I will check out the equations and let you know how they go

Hugh

 

[Thalassamania]

No, I would expect that most of the cold is dissipated through the metal body of the first stage, that where the ball of ice forms, it does not coat the IP hose.

 

[spectrum]

The hose does have some heat sink value, the metal fittings even more. A feature of some cold water regulators is the absence of hose protectors on the second stage connections (Sherwood Oasis vs. Blizzard as an example) allows greater conduction to the water which can be relatively warm.

Cold air that has been subjected to severe adiabatic cooling (as in a free flow) while in cold water can result in a seizure of the glottis, the precise term I forget. It addition to gear malfunctions it can be a threat to the body.

Pete