the guy Posted June 23, 2011 Share Posted June 23, 2011 would the 'cooling' section of this page: http://en.wikipedia.org/wiki/Canned_air work with carbon dioxide as the propellant? (i know carbon dioxide is used as an aerosol propellant in cooking spray cans) or does it only work with the chemicals they use? Link to comment Share on other sites More sharing options...
John Cuthber Posted June 24, 2011 Share Posted June 24, 2011 It would work with most gases; CO2 should work quite well. The interesting problem is that the material might freeze to "dry ice". Link to comment Share on other sites More sharing options...
the guy Posted June 24, 2011 Author Share Posted June 24, 2011 so would it work with just compressed air (by air i mean normal atmosphere - nitrogen, oxygen etc.) also, does it have to be liquified in the canister? or can it just be under pressure? Link to comment Share on other sites More sharing options...
John Cuthber Posted June 24, 2011 Share Posted June 24, 2011 Yes, but not nearly so well. The CO2 or freon in a tin of "canned air" is a liquid and when the pressure is released it boils. To do so it takes heat from the surroundings and gets very cold. For air the effect of expanding is much smaller. (And for a few gases like helium and hydrogen, they actually get hotter when you let the compressed gas escape). This page http://en.wikipedia.org/wiki/Joule%E2%80%93Thomson_effect probably tells you more about that than you want to know. Link to comment Share on other sites More sharing options...
the guy Posted June 24, 2011 Author Share Posted June 24, 2011 i thought CO2 didn't have a liquid phase.... oh, never mind, ignore that Link to comment Share on other sites More sharing options...
John Cuthber Posted June 24, 2011 Share Posted June 24, 2011 I take it you realised that it does under pressure. Link to comment Share on other sites More sharing options...
the guy Posted June 24, 2011 Author Share Posted June 24, 2011 yes Link to comment Share on other sites More sharing options...
CaptainPanic Posted July 5, 2011 Share Posted July 5, 2011 i thought CO2 didn't have a liquid phase.... It does, but as soon as the temperature exceeds 31°C, or the pressure exceeds 72.9 atm, it becomes supercritical. Wikipedia shows a picture of the phase diagram. Link to comment Share on other sites More sharing options...
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