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Are the coefficients of Generator Heat Input Correction Function of Condenser Temperature Curve in ExampleFile IndirectAbsorptionChiller correct?

asked 2018-02-09 04:16:22 -0600

Marc70 gravatar image

updated 2018-02-09 13:50:37 -0600

IndirectAbsorptionChiller ExampleFile - Generator Heat Input Correction Function of Condenser Temperature Curve used in the example file downloaded from EnergyPlus website show a reduction of the generator heat input with increasing of condenser entering water temperature despite I expect a growing trend with increasing of these temperature. The coefficients of the cubic curve are correct? There are any reference database for such curves? Thanking you in advance. All the best

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answered 2018-02-13 03:21:25 -0600

updated 2018-02-13 03:26:28 -0600

The curve in question is SteamFCondTemp (referenced from the Big Chiller here)

  Curve:Cubic,
    SteamFCondTemp,          !- Name
    0.712019,                !- Coefficient1 Constant
    -0.00478,                !- Coefficient2 x
    0.000864,                !- Coefficient3 x**2
    -0.000013,               !- Coefficient4 x**3
    7.0,                     !- Minimum Value of x
    30.0,                    !- Maximum Value of x
    ,                        !- Minimum Curve Output
    ,                        !- Maximum Curve Output
    Temperature,             !- Input Unit Type for X
    Dimensionless; !- Output Unit Type

Go ahead and type that in a google search bar: 0.712019-0.00478*x+0.000864*x**2-0.000013*x**3, see here.

Remember that the range of acceptable values is $x \in [7, 30]$. That doesn't look like a reduction to me. I also plotted the curve with the right limits myself:

SteamFCondTemp


As far as where these are coming from, no clue, I couldn't find any mention of it.

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This is better, except that at temperatures higher than 30C, the curve output will be limited to 1.0. If a user wanted higher generator heat input values new coefficients would be needed and then the max limit could be set higher than 30C. I don't know what the proper curve looks like.

rraustad gravatar imagerraustad ( 2018-02-13 07:40:15 -0600 )edit

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Asked: 2018-02-09 04:16:22 -0600

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Last updated: Feb 13