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  1. #1
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    Semi-hermetic compressor and flooded evaporators



    Dear Friends,

    As you know in case of centrifugal compressor by closing or opening IGV or Vane we can control evaporator temperature (by controlling suction gas mass flow).

    At centrifugal compressors route of oil is separate with refrigerant R11/R134a and also there is not any problem for compressor while IGV be in close situation and suction of compressor decreases.

    But I see some chillers with flooded evaporators and semi-hermetic (or screw compressors.

    As you know these compressors are different with centrifugal compressors. Specially at semi-hermetic compressors in air-conditioning chillers when suction decrease a lot we have oil escape and also compressor gets warm.

    Is it true using semi-hermetic compressors with flooded evaporators ?

    Sincerely yours.



  2. #2
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    Re: Semi-hermetic compressor and flooded evaporators

    With proper control of refrigerant flow throughout the system anything is possible.
    Brian - Newton Abbot, Devon, UK
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  3. #3
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    Re: Semi-hermetic compressor and flooded evaporators

    Hi
    in flooded system with F . gas main thing is returning oil from system to compressor
    density of oil is lower than F. gas and oil stay above that
    with different type of compressor we have oil separators
    it separate oil but is not 100% so we have oil run to system and we have to manage to return to compressor or drian it
    in NH3 --oil has high density than NH3
    so we can drain it at the lowest point in system
    Last edited by mbc; 16-02-2018 at 06:09 AM.

  4. #4
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    Re: Semi-hermetic compressor and flooded evaporators

    Flooded systems simply need a good liquid level control, and a decent oil rectifier system set up ,also oil separators can be used to further enhance the oil control.
    Ammonia can be used in both flooded and Dx systems . I have worked on several ammonia direct expansion chillers that use a miscible oil and work well without oil problems
    And as mbc says with flooded ammonia systems you can simply drain oil from the lowest parts of the system.

  5. #5
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    Re: Semi-hermetic compressor and flooded evaporators

    Off the subject a bit, but Danfoss Turbocor compressor is also a good option, as big capacity these days, no oil, reliable etc.
    Also first post suggests overheating & throwing oil over, not really the case as compressor unloads to maintain suction pressure.
    Centrifugas restricts gas flow so different to screw or reciprocating compressor.
    Speed control would be the best in screw, sometimes reciprocating & Turbocor.
    Last edited by RANGER1; 16-02-2018 at 08:53 PM.

  6. #6
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    Re: Semi-hermetic compressor and flooded evaporators

    Dear Friends,
    Thanks for all of your comments.

    Sincerely yours.

  7. #7
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    Re: Semi-hermetic compressor and flooded evaporators

    I dont understand the discussion a centrifugal compressor is in a different league
    Screw compressors restrict gas flow via the slide valve
    Recips restrict gas flow via loading solenoid valves
    Turbocores restrict tge gas flow by an inverter
    Oil managment and migration
    On each system and screw relys on discharge superheat to return oil and centrifugal compressors but lose oil if they do then you have a issue in the igv or the lowspeed shaft seal. Recips the main cause of oil loss is due to liquid flooding back and low load operation

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