Buildings.HeatExchangers.CoolingTowers.Correlations.BaseClasses

Package Content

Name	Description
Bounds	Coefficient data record for properties of perfect gases
der_yorkCalc	Derivative of cooling tower performance correlation for YorkCalc model

Buildings.HeatExchangers.CoolingTowers.Correlations.BaseClasses.Bounds

Information

This data record contains the bounds for the cooling tower correlations.

Modelica definition

record Bounds 
  "Coefficient data record for properties of perfect gases" 
  extends Modelica.Icons.Record;
  Modelica.SIunits.Temperature TAirInWB_min 
    "Minimum air inlet wet bulb temperature";
  Modelica.SIunits.Temperature TAirInWB_max 
    "Maximum air inlet wet bulb temperature";
  Modelica.SIunits.Temperature TRan_min "Minimum range temperature";
  Modelica.SIunits.Temperature TRan_max "Minimum range temperature";
  Modelica.SIunits.Temperature TApp_min "Minimum approach temperature";
  Modelica.SIunits.Temperature TApp_max "Minimum approach temperature";
  Modelica.SIunits.MassFraction FRWat_min "Minimum water flow ratio";
  Modelica.SIunits.MassFraction FRWat_max "Maximum water flow ratio";
  Modelica.SIunits.MassFraction liqGasRat_max "Maximum liquid to gas ratio";
  
end Bounds;

Buildings.HeatExchangers.CoolingTowers.Correlations.BaseClasses.der_yorkCalc

Information

Derivative of correlation for approach temperature for YorkCalc cooling tower model with respect to FRWat.

During the initialization of the YorkCalc cooling tower model, FRWat is the independent variable. Providing this derivative avoids Dymola from having to compute the Jacobian numerically.

Parameters

Type	Name	Default	Description
Nominal condition
Temperature	TRan		Range temperature (water in - water out) [K]

Inputs

Type	Name	Default	Description
Temperature	TWB		Air wet-bulb inlet temperature [K]
MassFraction	FRWat		Ratio actual over design water mass flow ratio [1]
MassFraction	FRAir		Ratio actual over design air mass flow ratio [1]
Real	der_FRWat		Derivative of ratio actual over design air mass flow ratio
Nominal condition
Temperature	TRan		Range temperature (water in - water out) [K]

Outputs

Type	Name	Description
Temperature	der_TApp	Derivative of approach temperature with respect to FRWat [K]

Modelica definition

function der_yorkCalc 
  "Derivative of cooling tower performance correlation for YorkCalc model" 
  
  
  input Modelica.SIunits.Temperature TRan 
    "Range temperature (water in - water out)";
  input Modelica.SIunits.Temperature TWB "Air wet-bulb inlet temperature";
  input Modelica.SIunits.MassFraction FRWat 
    "Ratio actual over design water mass flow ratio";
  input Modelica.SIunits.MassFraction FRAir 
    "Ratio actual over design air mass flow ratio";
  input Real der_FRWat 
    "Derivative of ratio actual over design air mass flow ratio";
  
  output Modelica.SIunits.Temperature der_TApp 
    "Derivative of approach temperature with respect to FRWat";
  
protected 
  Modelica.SIunits.CelsiusTemperature TWB_degC "Air wet-bulb inlet temperature";
  Modelica.SIunits.MassFraction liqGasRat "Liquid to gas mass flow ratio";
  constant Real c[:] = {-0.359741205, -0.055053608,  0.0023850432,
                      0.173926877, -0.0248473764,  0.00048430224,
                      -0.005589849456,  0.0005770079712, -0.00001342427256,
                      2.84765801111111, -0.121765149,  0.0014599242,
                      1.680428651, -0.0166920786, -0.0007190532,
                     -0.025485194448,  0.0000487491696,  0.00002719234152,
                     -0.0653766255555556, -0.002278167,  0.0002500254,
                     -0.0910565458,  0.00318176316,  0.000038621772,
                     -0.0034285382352,  0.00000856589904, -0.000001516821552} 
    "Polynomial coefficients";
  
algorithm 
  TWB_degC :=Modelica.SIunits.Conversions.to_degC(TWB);
  liqGasRat := FRWat/FRAir;
  // first term due to chain rule
  der_TApp := 1/FRAir * (
       c[10]  +
       c[11] * TWB_degC +
       c[12] * TWB_degC * TWB_degC +
       c[13] * TRan +
       c[14] * TWB_degC * TRan +
       c[15] * TWB_degC * TWB_degC * TRan +
       c[16] * TRan * TRan +
       c[17] * TWB_degC * TRan * TRan +
       c[18] * TWB_degC * TWB_degC * TRan * TRan +
       c[19] * 2 * liqGasRat +
       c[20] * TWB_degC * 2 * liqGasRat +
       c[21] * TWB_degC * TWB_degC * 2 * liqGasRat +
       c[22] * TRan * 2 * liqGasRat +
       c[23] * TWB_degC * TRan * 2 * liqGasRat +
       c[24] * TWB_degC * TWB_degC * TRan * 2 * liqGasRat +
       c[25] * TRan * TRan * 2 * liqGasRat +
       c[26] * TWB_degC * TRan * TRan * 2 * liqGasRat +
       c[27] * TWB_degC * TWB_degC * TRan * TRan * 2 * liqGasRat);
end der_yorkCalc;