GSHP Heat of Extraction/Heat of Rejection
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  1. #1
    Join Date
    Jun 2003
    Location
    Lenexa, KS
    Posts
    433

    Question

    I am looking for a formula to calculate both the Heat of Extraction (HE) and Heat of Rejection (HR) for Ground Source Heat Pumps.

    I have the following variables to plug into the formula:

    Return Air temp
    Supply Air temp
    CFMs
    EWT
    LWT
    GPMs

    The unit is in the HEATING mode.

    If you can help me out I would greatly appreciate it!
    "We are what we repeatedly do.
    Excellence, then, is not an act, but a habit."
    -Aristotle

  2. #2
    Join Date
    Nov 2000
    Location
    Manhattan, Kansas USA
    Posts
    677
    Heat of Extraction/Rejection formaula is:
    HE or HR = Delta T (water) x GPM x brine factor.
    pure water brine factor is 500
    anti-freeze is 485

    From what you have listed, you will still need to know if it is pure water, or a mix to get your brine factor.

    swany



  3. #3
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,024
    Isn't there another formula to figure the gallons per minute involving Delta P (pressure)

  4. #4
    Join Date
    Jun 2003
    Location
    Lenexa, KS
    Posts
    433
    Thanks swanny!
    "We are what we repeatedly do.
    Excellence, then, is not an act, but a habit."
    -Aristotle

  5. #5
    Join Date
    Apr 2002
    Posts
    11,808
    Originally posted by lynn rodenmayer
    Isn't there another formula to figure the gallons per minute involving Delta P (pressure)
    There would be Lynn, but every water to refrigerant heat exchanger would have a different flow vs pressure drop relationship.

    For a particular unit there could be a published table or a chart to get the flow from once you measured the pressure drop.

    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

  6. #6
    Join Date
    Nov 2001
    Location
    east kansas
    Posts
    8,024
    So you can't figure HE/HR without figuring GPM first. And you have to have the manufacture's published data.

  7. #7
    Join Date
    Apr 2002
    Posts
    11,808
    Yes you need to know the flow. You can install a flow meter and read direct or take pressure readings and use the manufactuers data. You could make a formula for each type of heat exchanger to use the pressure readings without looking at a table or a chart.
    The way we build has a greater impact on our comfort, energy consumption and IAQ than any HVAC system we install.

    http://www.ductstrap.com/

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