Why no R774A phase change systems?

[ewitte]

I'm looking over boiling point stats and found R774A listed as -89C and no license needed to get it. So how come I've not seen anyone using it? Where I've seen it mentioned said its suitable for use in either single stage or cascade.

[DetroitAC]

I assume you mean R744 (not R744A) There have been a lot of threads on this topic, do a search for R744, or CO2, or carbon dioxide.

The quick answer is the pressures are too high (condensing at 30C will be a pressure of 72 bar abs = 1044 psia) and the compressor must be designed specifically for R744 as the power required to compress the gas per unit suction volume is very much higher.

[ewitte]

I assume you mean R744 (not R744A) There have been a lot of threads on this topic, do a search for R744, or CO2, or carbon dioxide.

The quick answer is the pressures are too high (condensing at 30C will be a pressure of 72 bar abs = 1044 psia) and the compressor must be designed specifically for R744 as the power required to compress the gas per unit suction volume is very much higher.

No. Nitrous Oxide. The search didn't come up with anything but I didn't put R744 but R744A.

[ewitte]

Never mind. I found a thread with NO2. I guess propane would even be a much better option ;)

[trance565]

nitrous oxide is very high pressure also.

[ewitte]

At this point I'm pretty sure my first build will be r134a for wc.

[Brettbeck]

Lots of people use R744/Carbon-Dioxide/Co2 in mainly Auto-Cascades along with normally R290 :). Maybe you could use R290 (Propane) for your first build as a lot of people do. Its really cheap, around £15 or so for a 19Kg refill for the tank I have!

[Big SturL]

Lol, N2O? Isn't the boilingpoint of oxygen like -180C?
(Notice, nitrous oxide is N2O. NO2 is Nitrogendioxide.)

[n00b 0f l337]

And Nitros oxide is an oxidizer, good luck.

[Brettbeck]

Lol, N2O? Isn't the boilingpoint of oxygen like -180C?
(Notice, nitrous oxide is N2O. NO2 is Nitrogendioxide.)

N20 boiling point is -88.5c, but I have never seen anyone use it before.

[LukeXE]

N2O boiling point is -88,6*C :)

Update, Brett was faster :p

[aasmaukr]

I remember an old thread about this. Don't use it if you don't want to blow yourself up aswell as the neighbours children.. That's explosive stuff.

[n00b 0f l337]

Same reason we cant use pure oxygen.

[ak_47_boy]

R774A = Oxygen
Oxygen + Oil + Spark from compressor = Boom

Not to mention it will oxidise everything inside your setup. If it dosent explode right away it will mess with the motor pieces inside your compressor.

Its very unfortunate this happens, it could be a nice refridgerant.

[godmod]

oxygen + oil + no spark from compressor = B0000m anyways ;)

there are at leats two or three threads where that has already benn discussed.

[camouflage]

I remember an old thread about this. Don't use it if you don't want to blow yourself up aswell as the neighbours children.. That's explosive stuff.

:eek: That's the point - and never give it in the hands of terrorists......:eek:

[wdrzal]

Yes Oil and any oxidizer under pressure equal = :caution: :explode2: :caution:


Ps: thats basically how a diesel engine works, Its uses #2 fuel oil and the oxygen in the compressed air provided by the turbine. No spark is required for ignition, just the increased pressure of compression.

[ewitte]

There is one thing that scares me about r290 and thats having a false assumption all the gas has escaped and needing to do some brazing. I know its perfectly safe while inside the compressor.

Eric

[ewitte]

R774A = Oxygen
Oxygen + Oil + Spark from compressor = Boom



Hmm... thats odd. I found this list on three different websites before I posted and you see what it says (nitrous oxide).

http://www.wc101.com/guides/refridgeration/page6.htm

[jinu117]

End of discussion. Further discussion about explosive gas for no good reason will be closed. ewitte, I suggest you listen to people with bit more experiences for your safety.