Results 1 to 9 of 9
  1. #1
    Join Date
    Dec 2011
    Location
    Australia
    Posts
    7
    Rep Power
    0

    High side float valve and night-time operation



    Hi,

    I am doing some work looking at using more night-time cooling at an industrial facility (refrigeration plant cools a brine solution which is then passed through some tank jackets to cool tanks). The idea is to use cheaper off-peak power and also to take advantage of increased refigeration efficiency at the lower ambient temperatures. The system has an evaporative condenser and refrigerant control is by a high side float.

    I am relatively new to this and I wanted to verify that with this high side float control, I would get lower discharge pressures as the ambient temperature decreased and hence improved refrigeration plant efficiency.

    Thanks for your help. I appreciate it.

    Cheers



  2. #2
    Join Date
    Dec 2007
    Location
    australia
    Posts
    2,418
    Rep Power
    26

    Re: High side float valve and night-time operation

    Hi laudrup,
    From your description the" high side float" usually is for a critically charged system& is connected to main high pressure liquid reciever.
    What condenses & is held in liquid reciever gets dumped straight into lowside of plant ie surge drum,accumulator etc.
    It only passes liquid, not gas if it is operating correctly.
    I can't see it has any bearing on lower condensing pressures, as it only a level control device.

    For efficiency discharge pressure should be as low as possible, but float control has to be big enough to pass enough liquid under lower differential pressures.

    Can you also describe the layout of your plant a bit more, as well as brine temps.
    Do you have plate heat exchangers, surge drums etc etc

  3. #3
    Join Date
    Dec 2011
    Location
    Australia
    Posts
    7
    Rep Power
    0

    Re: High side float valve and night-time operation

    Hi Ranger1,

    The brine is at about -7 deg C.

    The evaporator is a plate heat exchanger with a horizontal surge vessel/accumulator on top of it.

    The high side float is a model HT200MN.

    The compressor is a Hasegawa VML3A (reciprocating I think).

    The refrigerant is ammonia.

    The refrigerant seems to pass from the compressor to the evaporative condenser through the high side float then to the accumulator on top of the plate heat exchanger.

    There was a note on some document that the refrigeration system has a high side float control and a critical ammonia charge to eliminate the need of a liquid receiver.

    Thanks for your help.

    Cheers,
    Laudrup

  4. #4
    Join Date
    Sep 2009
    Location
    Iran
    Age
    60
    Posts
    431
    Rep Power
    11

    Re: High side float valve and night-time operation

    Hi Laudrup

    when we use high float valve in our system after condenser instead of receiver and level controls and solenoid valves . it is cheaper than next one but in efficiency and safety of short gas in system especial in large system and also 2 stage system we need some area to restore our refrigerant liquid during defrosting time our comes on and off time of rooms the second system is better high float valve ,
    but in small system as you have it has sense and it should be good slop from condenser to that with U trap on pipe .

  5. #5
    Join Date
    Dec 2007
    Location
    australia
    Posts
    2,418
    Rep Power
    26

    Re: High side float valve and night-time operation

    laudrup,
    Thanks for description of plant,sounds like a small brewery.

    You are correct in saying that reduced ambient, allowing condensing pressure to decrease,
    increases plant efficiency.
    The high side float does not really assist in reducing discharge pressure.

    In your situation I don't think you can utilize cheaper power at night, but someone else might have a bright idea.
    Usually places like coolstores can run hard a night utilizing cheaper power & cruise through the day at higher suction pressues.

  6. #6
    Join Date
    Sep 2009
    Location
    Iran
    Age
    60
    Posts
    431
    Rep Power
    11

    Re: High side float valve and night-time operation

    in our country we have 3 different prices for power in day
    from 22 t0 6 h (next day) is cheap
    6 t0 18 normal and from 18 to 22 high prices ( 3 times of cheap one)
    normally we use this time (18 - to 22h) for defrosting time and rest time for units ,
    Also I saw some of our customs asked us to up off time for system in this period ( in small system).
    Last edited by mbc; 02-12-2011 at 03:57 PM.

  7. #7
    Join Date
    Dec 2011
    Location
    Australia
    Posts
    7
    Rep Power
    0

    Re: High side float valve and night-time operation

    Thanks for all the replies,

    I have been thinking about it a bit more. If the high-side float valve maintains a certain level of liquid on the high side of the system, there is a given volume for refrigerant gas between the discharge of the compressor and the start of the liquid refrigerant in the condenser. If the ambient temperature is lower, the refrigerant gas will be condensed more easily than when the ambient temperature was warmer, and the pressure resulting from the refrigerant gas in that volume on the discharge side of the compressor should be reduced, such the compressor doesn't have to work so hard to make the refrigerant go around. Therefore it probably should be able to generate more cooling for the amount of electricity that is put in to run the compressor.

    Is my reasoning logical, or am I missing something? (I find a little bit tricky to visualise because of the closed loop nature of the refrigeration cycle).

    Cheers,
    Laudrup

  8. #8
    Join Date
    Dec 2007
    Location
    australia
    Posts
    2,418
    Rep Power
    26

    Re: High side float valve and night-time operation

    Quote Originally Posted by laudrup View Post
    Thanks for all the replies,

    I have been thinking about it a bit more. If the high-side float valve maintains a certain level of liquid on the high side of the system, there is a given volume for refrigerant gas between the discharge of the compressor and the start of the liquid refrigerant in the condenser. If the ambient temperature is lower, the refrigerant gas will be condensed more easily than when the ambient temperature was warmer, and the pressure resulting from the refrigerant gas in that volume on the discharge side of the compressor should be reduced, such the compressor doesn't have to work so hard to make the refrigerant go around. Therefore it probably should be able to generate more cooling for the amount of electricity that is put in to run the compressor.

    Is my reasoning logical, or am I missing something? (I find a little bit tricky to visualise because of the closed loop nature of the refrigeration cycle).

    Cheers,
    Laudrup



    Sounds good to me, so check all sprays & condensor coil for build up to make the most out of it.

  9. #9
    Join Date
    Sep 2009
    Location
    Iran
    Age
    60
    Posts
    431
    Rep Power
    11

    Re: High side float valve and night-time operation

    Dear Laudrup

    as I wrote before in large system we use 2 level controls with solenoid valve ( one level control , controls liquid levels and another one is a high level control for safety side ) or some system has separator float valves with hi level on it.
    In these systems we have pipe between discharge gas pipe and receiver as called equalizing pipe ,
    with this pipe in winter( opening of REG valve on the pipe ) we adjust our discharge gas pressure to get good result in defrost

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •