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What kind of air compressors are better?

  1. Sep 12, 2016 #1
    I want to know which kind of compressors are best for compressing very cold air. I mean as cold as they can operate in Antarctica during the winter when the temperature will reach around -50°C. In fact, I am looking for compressors that can withstand lower temperature of around -90°C. But, which kind of compressors can perform better in such conditions and where those can be found.
    One of my friend told me that rotary screw compressors are best and they compress air almost isothermally. But, I want to know whether such compressor can perform similarly even in such cold temperature or not. It may be possible that new kind of problems will arise at such low temperature.
     
  2. jcsd
  3. Sep 13, 2016 #2
    On the surface, someone might suggest a rotary compressor because there is no seal between the vanes and the casing, however selection is more about the trade-off between size and flow/pressure required.
    Most trade tool compressors are reciprocating piston meaning you might get a few for the same cost as one rotary compressor of the same size, if available, but at a certain size the piston design becomes uneconomical and the rotating turbine is applied.
    Regardless of the compressor selected rubbers and oils will be stiffer and more brittle, affecting their longevity, and wear at the mating parts unless replaced by a suitably softer or less viscous alternative.
    So long as your motor will start, there are other considerations that apply depending on the application.
     
  4. Sep 17, 2016 #3
    Actually I want to know what kind of companies can supply such kind of compressors.
     
  5. Sep 17, 2016 #4

    CWatters

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    Not my field but perhaps look at gas turbine engines as used on aircraft. The incoming air is V.cold at altitude.
     
  6. Sep 17, 2016 #5

    Baluncore

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    You need to specify the;
    1. Volume of air input per minute.
    2. Output pressure.
    3. Output air temperature needed.

    Since compression heats the air you might preheat the inlet air with the exhaust air by using an intercooler. That will reduce compression efficiency but will increase the compressor temperature.
     
  7. Sep 17, 2016 #6
    The input pressure will be 1 bara and the output will be 6.4. By volume, the compression ratio will be 1:4. I want to the process to be as close to isothermal as possible. At present, market available compressors used water to keep the temperature of the gas/air during compression as stable as possible. But, as such low temperature, water will be useless and something else has to be used here.
     
  8. Sep 17, 2016 #7

    Baluncore

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    What is the volume of input air, measured in metres3 or feet3 that you need to compress every minute or second?
     
  9. Sep 17, 2016 #8

    Nidum

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  10. Sep 17, 2016 #9
    Amount is not a factor here. I want to know how much scfm (standard Cubic feet per Minute) of compression can be achieved per kW. Scfm is the standard measurement for air/gas compressors.
     
  11. Sep 17, 2016 #10
  12. Sep 17, 2016 #11

    Baluncore

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    Scfm per kW will depend on technology and the scale of the plant.
    I would have thought you required some particular volume for some task.
    You don't seem to know what you want.
     
  13. Sep 17, 2016 #12
    In that case, what kind of technology can give the best scfm/kW?
     
  14. Sep 18, 2016 #13
    At present, performance of compressors has been measured with cfm/hp or cfm/kW. Now, question is whether the cfm is measured before compression or after compression?
     
  15. Sep 29, 2016 #14
    You have gas engine or electric motor compressors for industrial applications or single-stage, piston-type ones for home use. The right tool should always match the level of difficulty of the job. Industrial-grade compressors are characterized or distinguished by their use of storage tanks.
     
  16. Sep 29, 2016 #15
    Just tell me what kind of compressors can give close to isothermal compression. It's for industrial use.
     
  17. Sep 30, 2016 #16

    Mech_Engineer

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  18. Sep 30, 2016 #17

    cjl

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    What are you trying to achieve with isothermal compression?

    EDIT: Hang on, are you still trying to figure out a cycle to make an overunity machine via isothermal compression and adiabatic expansion (as described in your earlier thread here)? It still doesn't work.
     
    Last edited: Sep 30, 2016
  19. Sep 30, 2016 #18
    Do you want to call this an "overunity machine"?
     
  20. Sep 30, 2016 #19

    Mech_Engineer

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    Looks irrelevant to me...
     
  21. Sep 30, 2016 #20
    That's your view. But, this is a proof that atmospheric heat can be extracted and converted into power.
     
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