M4D1NV3N70R - 28-11-2004 at 03:05
Hello,
I'm looking for a liquid that expands/vaporizes a great deal when a modest amount of heat is applied to it. I'm not looking for any kind of
combustion, just expansion and/or phase change.
The idea is to generate as much pressure as possible for a given amount of heating.
Would a modern refridgerant such as freon or that R-12 stuff be what I'm looking for?
Thanks!
[Edited on 28-11-2004 by M4D1NV3N70R]
vulture - 28-11-2004 at 06:21
Refrigerants are selected for their heat capacity and evaporation enthalpy, not expansion, so it's doubtful you'll have any luck there.
I don't know if the CRC handbook lists expansion coefficients...
mick - 30-11-2004 at 09:34
you could be talking of water and steam under the right pressure and temperature. If you can find the critical temperature and pressure of the liquid
you are thinking about you could get more power than steam gives. I think they were called phase diagrams. Find the bit where the liquid can not exist
as a liquid but as a gas and then use the ideal gas equation. It could give you a rough idea of how much expansion there could be. CO2 is easily
liquified and sublimed but I think there is a bit where it is always gas.
mick
[Edited on 30-11-2004 by mick]
M4D1NV3N70R - 30-11-2004 at 13:30
Thanks! That helps a lot. I had no idea where to start to figure this out.
HNO3 - 30-11-2004 at 16:53
Umm, butane refiller bottles might work. But the name M4D1NV3N70R sounds a little bit KEI_!$I-I. Ummm, that is kewlish.
neutrino - 30-11-2004 at 18:37
For a liquid, I might suggest mercury. If my lousy memory serves, it was listed in the Guinness Book some year as the liquid with the highest thermal
expansion coefficient. If you want something that will boil, remember that the pressure the boiling liquid will exert is equal to its vapor pressure
at that temperature. If you do want something like this, I would suggest gas dusters. They usually contain fluorinated hydrocarbons with boiling
points around -30*C and vapor pressures of 5-7 atm at room temperature.
S.C. Wack - 30-11-2004 at 19:45
Dalton's law might come in handy here.
mick - 2-12-2004 at 13:17
The only thing I can think of is ammonia. 18g of water could give you 22.14 l of gas at the right temperature. 17g of ammonia could give the same or
more. I think the heat of vapourisation comes into it. The only other thing I can think is boron trihydide, diborane, which could be explosive.
mick
Twospoons - 2-12-2004 at 13:47
Ha! Try liquid Helium 
He
MadHatter - 2-12-2004 at 22:07
Twospoons, I think you nailed it but M4D1NV3N70R might have a hard time getting it.
Probably needs something more available. Liquid nitrogen should be easier to acquire.
M4D1NV3N70R - 3-12-2004 at 06:24
OK, lots of helpful info. Thanks.
But I am kind of looking to avoid cryogenic temperatures. And the materials required to work with them.
S.C. Wack - 3-12-2004 at 10:01
? There are no low temperatures involved, only tanks and an appropriate hose. Turn the tank upside down, liquid whatever comes out, goes through the
hose, into the other tank.
Well fuck, it looks like just about anything will give a high pressure. Why not a solid - CO2? Convenient even with cryogenic handling.
[Edited on 4-12-2004 by S.C. Wack]
Magpie - 3-12-2004 at 19:06
All liquids provide 22.4 liters of volume per gram mole at standard conditions when they form a gas if they behave ideally or close to it. So, from a
theoretical standpoint you are looking for a liquid with a low molar heat of vaporization. A table of compounds listing this should be available in
handbooks such as CRC or Perry's Chem. Engr. You probably want the boiling point to not be too high also.
[Edited on 4-12-2004 by Magpie]