Natural gas as a refrigerant

  1. I have a large volume of (free) natural gas sitting at 5,000 psi. I'd like to pass the gas through an orifice, give it room to expand on the backside, and use that to chill glycol. I would like to drop the output pressure to 100 psi in the process.

    I wish to use the chilled glycol to cool my home in the summer months, and the lower (output) gas pressure for other purposes. Excess gas will vent to atmosphere.

    Most common refrigerants only need a pressure differential of 150 psi or so to do their work. With my natural gas, will the btu chilling effect be proportional to the 4900 psi pressure drop? In other words, do I gain anything from starting out with such high pressure?

    As it comes from a well, I suspect the temperature of the gas is around 60 degrees F. To equal the equivalent of 6 tons of (conventional) cooling capacity, what am I looking at in terms of orifice/expansion chamber size?

    Thanks for any input.
     
  2. jcsd
  3. SteamKing

    SteamKing 8,846
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    I would be careful about venting unburned natural gas to atmosphere. Instead of cooling your house, you might unintentionally heat it up all at once.
     
  4. Dangers are noted. I can flare it, but I'm hoping it will be a small amount of excess that I have to deal with.
     
  5. I don't think it's much use , gas cools just in the moment when it expands , later on everything goes back to equilibrium in other words it;'s the moment when you let it "free" when stuff cools that is in touch with it after the pressure has dropped everything goes back to normal and the once cooled metal or whatnot gets back his average heat but your left with a expanded gas that is still highly flammable and dangerous.
    I would not do that thing.
    The only way to keep something cooler than the medium in which it is in is to apply a force to a mechanism that does the cooling , well some refrigerator system have used gas as part of their coolant loop but first of all it is or was not natural gas I believe second there was a pump that pumps the coolant around so that it can pick up heat and then extract it through a radiator to the medium ofcourse it's only useful if you have your primary and secondary separated if not again no use.
    We had a discussion about this here on PF just a week or so ago.
     
  6. Natural gas has a critical point of −82.3 °C (190.9 K) and 45.79 atm (4,640 kPa) which means in your case it is close to an ideal gas.

    Venting the gas through an orifice will actually make the gas HOTTER. The reason refrigerators get away is because the latent heat of the phase change during throttling.

    If you want to cool the gas you need to expand it as close to isentropically as possible, e.g. passing it through a turbine. If you do that, then it will come out cold and you can also generate electricity from the pressure difference as a bonus.
     
  7. Thanks for the useful info. Would it work better for me if I drop the pressure to 800 psi or so before I send it through an orifice?

    ---

    I can always power an engine-driven genset with the gas - I just don't have a continuous application for electricity. Plus I didn't want to maintain another piece of machinery. The "hassle factor" needs to be considered.
     
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