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  1. #1
    Join Date
    Aug 2010
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    Mobjack, VA
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    Aqualogic Delta Star Heat Pump DSHP

    Need info on expected Aualogic Delt Star air to water heat pump evaporator temperature. Presently running below values with new charge of 134a, clear liquid line sight glass and TXV superheat is 15 degrees:
    OAT to air cold condenser 70
    Entering water to chiller 60
    Leaving salt water temp from chiller 58
    Evaporator temperature 36 (22 degree approach looks excessive)
    When unit is set to run with a leaving salt water temperature of 40 degrees the evaporator temperature will be about 18 degrees and I am concerned about potential icing on the evaporator tubes.

    Does anyone have info on what the design approach value should be?

  2. #2
    Join Date
    Dec 2006
    Location
    Vancouver, B.C.
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    Quote Originally Posted by BC_1984pt40 View Post
    Need info on expected Aualogic Delt Star air to water heat pump evaporator temperature. Presently running below values with new charge of 134a, clear liquid line sight glass and TXV superheat is 15 degrees:
    OAT to air cold condenser 70
    Entering water to chiller 60
    Leaving salt water temp from chiller 58
    Evaporator temperature 36 (22 degree approach looks excessive)
    When unit is set to run with a leaving salt water temperature of 40 degrees the evaporator temperature will be about 18 degrees and I am concerned about potential icing on the evaporator tubes.

    Does anyone have info on what the design approach value should be?
    Do you have a model number?

    What is the freeze point of your brine?

    Are you able to increase flow through the evaporator?


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  3. #3
    Join Date
    Aug 2010
    Location
    Mobjack, VA
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    Thread Starter
    thatguy,

    DSHP-9
    Sea Water about 28 degrees
    Already near max flow with 60 inlet and 58 outlet.
    Uses a single pass spiral tube in shell HX.

    Have worked on large chillers for 30 yrs that operated with 10 deg approach
    and above 34 deg evaporator temperatures on straight water.
    Not expecting to seeing such low evaporator temperatures during proper operation.

    Thanks
    BC_1984pt40

  4. #4
    Join Date
    Dec 2006
    Location
    Vancouver, B.C.
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    Aqualogic Delta Star Heat Pump DSHP

    You are only running 2deg F delta through your water coil. With an entering water temp of 40 your exiting temp will only be 38. Unless you have a restriction or lose water flow I would think you should be ok. You could always clip a 32 Deg freeze stat on the water lines if you want to be extra careful. In theory, by the time the ice builds to a sufficient quantity to be of concern your water flow would decrease enough to trigger the freeze stat before the expansion of the ice would cause any damage.


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  5. #5
    Join Date
    Jun 2003
    Location
    Texas
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    something is stopped up. how did you verify water flow through chiller barrel? super heat is too high and evap temp is too low for that water temp or I mis read something

  6. #6
    Join Date
    Aug 2010
    Location
    Mobjack, VA
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    Thread Starter
    Freeze stat on leaving water line is a good idea.

    Outlet 38 deg
    /\
    |
    | | |
    _| | ___________
    |O O O O |___
    | \ / \ / \ /\ /___ Inlet 40 deg
    | \ / \ / \ / \ \
    | O O O O ___
    |_______________|
    Water in the single pass shell may be bypassing the spiral evaporator coil [WWW] and
    Allowing for a warm 38 degree leaving water temp and low 18 deg evaporator temperature.

    Will investigate need for better water distribution and contact with evaporator coil.

    Thanks

  7. #7
    Join Date
    Aug 2010
    Location
    Mobjack, VA
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    Thread Starter
    There is no restriction on the water side. I based water flow on water delta T and as a result I may have overlooked the potential for water bypassing the cooling coil. I miss reported the super heat value and it is actually 10 degrees.

    Diagram to poopa did not maintain formatting. Hope the below diagram looks better.

    Outlet 38 deg
    /\
    |
    | |
    _| | __________
    | O O O O |___
    | \ / \ / \ /\ /___ Inlet 40 deg
    | \ / \ / \ / \ \
    | O O O O ___
    |______________|
    Water in the single pass shell may be bypassing the spiral evaporator coil [WWW] and
    Allowing for a warm 38 degree leaving water temp and low 18 deg evaporator temperature.

    Will investigate need for better water distribution and improved contact with evaporator coil.

    Thanks

  8. #8
    Join Date
    Dec 2006
    Location
    Vancouver, B.C.
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    What are your pressures?


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