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Originally Posted by jeff88
OK, so the big thing is getting it to a liquid state. The change from liquid to gas is what causes the 'cold' (like a propane tank). It would be nice if the half million webpages devoted to 'how an a/c works' would say that instead of just detailing the refrigerant going from device to device in a loop.  |
It is the compression and expansion which is important. The change of state just makes it more effective and efficient.
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I was trying to find a pressure vs. temperature curve for R134a, but I couldn't find one. Do you know what temperature it has to be at while maintaining atmospheric pressure to turn into a liquid (i.e. without compressing it)?
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Thermodynamic Property Table for saturated R-134a (pressure table), SI units
Refrigerant R134a Properties
http://www2.dupont.com/Refrigerants/...o_prop_eng.pdf
(-15F or -26C)
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I'm wondering if there is a substance that will compress easier than R134a (for efficiency purposes) or if that's the best option.
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Probably not, at least not without other issues. Propane would work (is used sometimes - not anywhere near where I am though
) if you could be 100% certain that it couldn't leak. NH3 (ammonia gas) works but is corrosive and a leak is unpleasant. CO2 works OK and looks to be (one of) the gases used to replace R134a in cars.
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O6, did you mean that you can boil water at less than 100C if you raise the pressure? Hence the reason why Denver has a harder time boiling water and a pressure cooker has an easier time.
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No, definitely reduce. You can boil water when at altitude at a lower temp. The issue is when you're trying to cook something in that water the temp. can be too low and it takes longer to cook things.
It works the other way too. Car cooling systems are kept under pressure to prevent the coolant from boiling.