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
41 ●2

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

__AmirRoth__

4436 ●5 ●17 http://bleedinggreenna...

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

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

Julien Marrec

29706 ●94 ●76 http://www.effibem.com/

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.