What temp is OC gas?

**Steve** · 21st December 2005, 23:39

The Meg tells me what temperature the water is and what the temperature of the gas I’m breathing is. I can’t think of an application for this info other than it is a bit interesting.

I’m interested to know what temperature OC gas is. Has anyone actually measured the temperature of OC gas? Of course the water temp and the gear in use will affect things but a rough number would be nice to know.

E-man · 22nd December 2005, 01:15

I would assume it would be pretty darn close to the water temp, as the metal tank would give off its heat to it pretty quickly.

**Gill Envy** · 22nd December 2005, 02:35

I think he is asking what temp it is given that it is compressed gas decompressing...endothermic...right? Basically how much colder does the pressure change make the gas? good question, i'd like to know the answere myself.

**nigelh** · 22nd December 2005, 08:40

Quote: (Originally Posted by Gillenvy)

I think he is asking what temp it is given that it is compressed gas decompressing...endothermic...right? Basically how much colder does the pressure change make the gas?

The word you are looking for is Adiabatic. I just played with the numbers and taking the pressure drop as 10bar to 1 bar and gamma for air as 1.4 I get the instantaneous temperature would be 147K (say -126C). Thankfully the specific heat of a lungfull of air is very low.

Naturally dropping 11bar to 2bar at 10m the temperature fall is less.

Compressing air the temperatures are frightening but then we all know what a fill does to 14kilograms of steel tank if you rush it.

divetheworld · 22nd December 2005, 08:46

Quote: (Originally Posted by Steve)

The Meg tells me what temperature the water is and what the temperature of the gas I’m breathing is. I can’t think of an application for this info other than it is a bit interesting.

I’m interested to know what temperature OC gas is. Has anyone actually measured the temperature of OC gas? Of course the water temp and the gear in use will affect things but a rough number would be nice to know.

Just because I'm off work now and bored, I tried it out.
Using a set of Pozzi Xstreams I put a probe in the valve body mouthpeice hole and breathed.

peak instantaneous at -18C

Any surprises there?

abowie · 22nd December 2005, 09:43

Quote: (Originally Posted by divetheworld)

Just because I'm off work now and bored, I tried it out.
Using a set of Pozzi Xstreams I put a probe in the valve body mouthpeice hole and breathed.

peak instantaneous at -18C

Any surprises there?

Yeah I'm amazed it's so cold. I had guessed that it might be maybe a couple of degrees max less than ambient.

Sutty · 22nd December 2005, 18:50

Not surprised its so cold, after all its not just a 10 bar drop across the 2nd stage which is cooling, the drop across the 1st stage is more. I doubt the gas has equalised to water temp in the hose before the 2nd drop, might be nearer to equalising if you did the test in water rather than air of course.
I remember seeing a gadget for "warming" OC gas by having a metal coil after the 1st stage which allowed equalisation of the interstage gas.

Neil

Genesis · 22nd December 2005, 19:29

Its not just the cold - its also the dry.

One thing that I've always hated about OC diving is the cottonmouth. I simply CANNOT use a full-plastic second stage for more than 20 minutes or so - if I try the discomfort becomes extreme. You can "remove, rinse, repeat" but that's not a great solution in water less-than-pristine. A second with a metal air-tube is more tolerable because it condenses some of your expired humidity and then re-evaporates it - a bit better.

I'm very much looking forward to warm, moist gas......

wizbang · 22nd December 2005, 20:19

Guys, not a a fair test to determine the temp of the air.
I thought (think) Steve is asking about what temp is the air that we breathe from the tank.
By putting the Temp probe in the reg and purging you are directly cooling the probe just by pushing lots of expanding air past it.
A fairer test would be to get a garbage bag and put the probe in the end furtherest from the reg and then purge the bag full and then take a reading.

It should be much closer to what we actually breathe.

One of the Docs could chime in here but would it make it warmer and more moist for the lung if we could breath scuba through our nose.?

Oh and Steve, what is the temp of the air in the loop and where does it get its reading from in the loop.?
Thanks Wiz

01RMB · 22nd December 2005, 20:47

Whilst I was demonstrating how to breathe off a free flowing regulator during my Open Water Instructors course in 2000, the rush of cold gas actually cracked one of my back teeth whilst breathing from it

. It was then off to the dentist for a root canal and crown

.

21st December 2005, 23:39	#1 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,041	What temp is OC gas? The Meg tells me what temperature the water is and what the temperature of the gas I’m breathing is. I can’t think of an application for this info other than it is a bit interesting. I’m interested to know what temperature OC gas is. Has anyone actually measured the temperature of OC gas? Of course the water temp and the gear in use will affect things but a rough number would be nice to know. __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
(Offline)

22nd December 2005, 01:15	#2 (permalink)
E-man On the loop! Current Rebreather/s: Inspiration Classic Optima Other Rebreather/s: Titan Join Date: Sep 2005 Location: Eastern Coast ;) Posts: 212	Re: What temp is OC gas? I would assume it would be pretty darn close to the water temp, as the metal tank would give off its heat to it pretty quickly.
(Offline)

22nd December 2005, 02:35	#3 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,209	Re: What temp is OC gas? I think he is asking what temp it is given that it is compressed gas decompressing...endothermic...right? Basically how much colder does the pressure change make the gas? good question, i'd like to know the answere myself. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
(Offline)

22nd December 2005, 08:40	#4 (permalink)
nigelh New Member Current Rebreather/s: Inspiration Vision Other CCR Other Rebreather/s: Inspiration Classic Other CCR Join Date: Mar 2005 Location: Brighton, Sussex, UK Posts: 784	Re: What temp is OC gas? Quote: (Originally Posted by Gillenvy) I think he is asking what temp it is given that it is compressed gas decompressing...endothermic...right? Basically how much colder does the pressure change make the gas? The word you are looking for is Adiabatic. I just played with the numbers and taking the pressure drop as 10bar to 1 bar and gamma for air as 1.4 I get the instantaneous temperature would be 147K (say -126C). Thankfully the specific heat of a lungfull of air is very low. Naturally dropping 11bar to 2bar at 10m the temperature fall is less. Compressing air the temperatures are frightening but then we all know what a fill does to 14kilograms of steel tank if you rush it. __________________ nigelh
(Online)

22nd December 2005, 08:46	#5 (permalink)
divetheworld Dive porn pimp Current Rebreather/s: Inspiration Classic Other CCR Other Rebreather/s: Not Bought Yet Inspiration Classic Inspiration Vision Classic Kiss Other CCR Join Date: Mar 2005 Location: Leeds, England Posts: 1,511	Re: What temp is OC gas? Quote: (Originally Posted by Steve) The Meg tells me what temperature the water is and what the temperature of the gas I’m breathing is. I can’t think of an application for this info other than it is a bit interesting. I’m interested to know what temperature OC gas is. Has anyone actually measured the temperature of OC gas? Of course the water temp and the gear in use will affect things but a rough number would be nice to know. Just because I'm off work now and bored, I tried it out. Using a set of Pozzi Xstreams I put a probe in the valve body mouthpeice hole and breathed. peak instantaneous at -18C Any surprises there? __________________ Self praise is no reccomendation. Dont try to be a great man, just be a man and let history be the judge of you. CHECK OUT OUR INTERWEBS FOR CUSTOM REBREATHER UPGRADES *WWW.NARKEDAT90.CO.UK* *http://www.grpservices.com/pursuit/* Supporting Shearwater Research Products in Europe
(Offline)

22nd December 2005, 09:43	#6 (permalink)
abowie Fighting Girl Current Rebreather/s: Sport Kiss Other Rebreather/s: Join Date: May 2005 Location: Land of Oz Posts: 573	Re: What temp is OC gas? Quote: (Originally Posted by divetheworld) Just because I'm off work now and bored, I tried it out. Using a set of Pozzi Xstreams I put a probe in the valve body mouthpeice hole and breathed. peak instantaneous at -18C Any surprises there? Yeah I'm amazed it's so cold. I had guessed that it might be maybe a couple of degrees max less than ambient. __________________ Andrew Bowie Rebreather-friendly Buddy
(Offline)

22nd December 2005, 18:50	#7 (permalink)
Sutty Classic Kiss diver Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Jun 2005 Location: Glossop, Derbyshire, UK Posts: 763	Re: What temp is OC gas? Not surprised its so cold, after all its not just a 10 bar drop across the 2nd stage which is cooling, the drop across the 1st stage is more. I doubt the gas has equalised to water temp in the hose before the 2nd drop, might be nearer to equalising if you did the test in water rather than air of course. I remember seeing a gadget for "warming" OC gas by having a metal coil after the 1st stage which allowed equalisation of the interstage gas. Neil
(Offline)

22nd December 2005, 19:29	#8 (permalink)
Genesis Bubbless Box of Death Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2005 Location: Sunny Florida Posts: 1,394	Re: What temp is OC gas? Its not just the cold - its also the dry. One thing that I've always hated about OC diving is the cottonmouth. I simply CANNOT use a full-plastic second stage for more than 20 minutes or so - if I try the discomfort becomes extreme. You can "remove, rinse, repeat" but that's not a great solution in water less-than-pristine. A second with a metal air-tube is more tolerable because it condenses some of your expired humidity and then re-evaporates it - a bit better. I'm very much looking forward to warm, moist gas......
(Offline)

22nd December 2005, 20:19	#9 (permalink)
wizbang WEB MERMEN Current Rebreather/s: Inspiration Classic Dolphin Home Build Other Rebreather/s: Not Bought Yet Inspiration Vision Evolution Prism Topaz Sport Kiss Classic Kiss Dolphin Home Build Join Date: Feb 2005 Location: Perth Australia Posts: 379	Re: What temp is OC gas? Guys, not a a fair test to determine the temp of the air. I thought (think) Steve is asking about what temp is the air that we breathe from the tank. By putting the Temp probe in the reg and purging you are directly cooling the probe just by pushing lots of expanding air past it. A fairer test would be to get a garbage bag and put the probe in the end furtherest from the reg and then purge the bag full and then take a reading. It should be much closer to what we actually breathe. One of the Docs could chime in here but would it make it warmer and more moist for the lung if we could breath scuba through our nose.? Oh and Steve, what is the temp of the air in the loop and where does it get its reading from in the loop.? Thanks Wiz
(Offline)

22nd December 2005, 20:47	#10 (permalink)
01RMB Evolving Current Rebreather/s: Evolution Other Rebreather/s: Join Date: May 2005 Location: Brisbane, Australia Posts: 186	Re: What temp is OC gas? Whilst I was demonstrating how to breathe off a free flowing regulator during my Open Water Instructors course in 2000, the rush of cold gas actually cracked one of my back teeth whilst breathing from it . It was then off to the dentist for a root canal and crown . __________________ Cheers Rod
(Offline)

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode