Implements limit for spray humidifier (not exceeds saturation)

For # 834
RWTH-EBC · Jan 27, 2022 · 9328123 · 9328123 · KremerMartin · Jan 27, 2022
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commit 9328123
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Showing 3 changed files with 36 additions and 3 deletions.
diff --git a/...irflow/AirHandlingUnit/ModularAirHandlingUnit/Components/BaseClasses/PartialHumidifier.mo b/...irflow/AirHandlingUnit/ModularAirHandlingUnit/Components/BaseClasses/PartialHumidifier.mo
@@ -114,7 +114,7 @@ equation
    partialPressureDrop.dp = dp;
 
     // conditional connectors
-   connect(max.y,X_intern);
+   // connect(max.y,X_intern);
    connect(m_wat_flow,m_wat_flow_intern);
 
   connect(X_set, max.u1) annotation (Line(points={{0,110},{0,86},{-48,86},{-48,76},

diff --git a/AixLib/Airflow/AirHandlingUnit/ModularAirHandlingUnit/Components/SprayHumidifier.mo b/AixLib/Airflow/AirHandlingUnit/ModularAirHandlingUnit/Components/SprayHumidifier.mo
@@ -15,9 +15,19 @@ model SprayHumidifier "Idealized model of a spray humidifier"
 
   Modelica.Blocks.Interfaces.RealOutput mWat "mass flow rate water"
     annotation (Placement(transformation(extent={{100,-64},{120,-44}})));
+  Utilities.Psychrometrics.SaturationPressure pSat
+    annotation (Placement(transformation(extent={{-60,30},{-40,50}})));
+  Utilities.Psychrometrics.X_pW humRat(use_p_in=false)
+    annotation (Placement(transformation(extent={{-30,30},{-10,50}})));
 protected
   Real WLN "water to air ratio";
+  Modelica.SIunits.Temperature T_intern "internal outlet temperature";
+  Modelica.Blocks.Sources.RealExpression realExpression(y=T_intern)
+    annotation (Placement(transformation(extent={{-78,-6},{-58,14}})));
+  Modelica.Blocks.Math.Min min
+    annotation (Placement(transformation(extent={{20,46},{40,66}})));
 equation
+  T_intern = T_airOut;
 
   // mass balance
   if simplify_m_wat_flow then
@@ -48,6 +58,21 @@ equation
   // humidification degree
   eta_B = 1 - exp(-k * WLN);
 
+  if use_X_set then
+    assert(min.y > max.y,
+      "saturation exceeded with given set value. Humidification is reduced.",
+      AssertionLevel.warning);
+  end if;
+
+  connect(min.y, X_intern);
+  connect(pSat.pSat, humRat.p_w)
+    annotation (Line(points={{-39,40},{-31,40}}, color={0,0,127}));
+  connect(realExpression.y, pSat.TSat) annotation (Line(points={{-57,4},{-54,4},
+          {-54,22},{-68,22},{-68,40},{-61,40}}, color={0,0,127}));
+  connect(max.y, min.u1) annotation (Line(points={{-19,70},{-2,70},{-2,62},{18,62}},
+        color={0,0,127}));
+  connect(humRat.X_w, min.u2)
+    annotation (Line(points={{-9,40},{4,40},{4,50},{18,50}}, color={0,0,127}));
   annotation (Icon(coordinateSystem(preserveAspectRatio=false), graphics={
         Text(
           extent={{-90,84},{-14,66}},
@@ -95,21 +120,26 @@ equation
           lineThickness=0.5)}),                                  Diagram(
         coordinateSystem(preserveAspectRatio=false)),
     Documentation(info="<html>
-<p>This model provides a idealized spray humidifier. The output air humidity is calculated using the input air humidity and the mass flow rate of water:</P>
+<p>This model provides a idealized spray humidifier. The output air humidity is calculated either using the input air humidity and the mass flow rate of water:</P>
 <p align=\"center\"><i>m<sub>air,in</sub>  X<sub>air,in</sub> + m<sub>wat,in</sub> &eta;<sub>B</sub> = m<sub>air,out</sub> X<sub>air,out</sub> </i></p>
+<p>or it is calculated using a set point for the humidity at the outlet if the parameter <i>use_X_set</i> is set to true. 
+<b>Note:</b> If the relative humidity with the givin set-point would exceed saturation the humidification is reduced to reach saturation as maximum.
+Additionally a warning will be thrown.</p>
 <p>The energy balance is formulated using the enthalpy of the air streams and the enthalpy of the water:</p>
 <p align=\"center\"><i>m<sub>air,in</sub> h<sub>air,in</sub> + m<sub>wat,in</sub> h<sub>wat,in</sub> &eta;<sub>B</sub> = m<sub>air,out</sub> h<sub>air,out</sub> </i></p>
 <p>The humidifying degree <i>&eta;<sub>B</sub></i> is calculated using the water to air ratio <i>E</i>:</p>
 <p align=\"center\"><i>&eta;<sub>B</sub> = 1 - exp(-k E) </i></p>
 <p align=\"center\"><i>E = m<sub>wat,in</sub> &frasl; m<sub>air,in</sub> </i></p>
-<p>If the boolean variable <i>simplify_m_wat_flow</i> is set to true, the mass flow rate of the water is not considered for the mass balance. Moreover the enthalpy of the water is neglected for the energy balance.</p>
+<p>If the boolean variable <i>simplify_m_wat_flow</i> is set to true, the mass flow rate of the water is not considered for the mass balance. 
+Moreover the enthalpy of the water is neglected for the energy balance.</p>
 <p>The equations are based on [1].
 <h4>References</h4>
 <p>[1]: Baumgarth, Hörner, Reeker (Hrsg.): <i>Handbuch der Klimatechnik</i>, Band 2, 5. Auflage, VDE Verlag GmbH, 2011 (pp.304-306)</p>
 </html>", revisions="<html>
 <ul>
 <li>April, 2019, by Martin Kremer:<br>First Implementation.</li>
 <li>April 2020, by Martin Kremer:<br>Extended from PartialHumidifier. </li>
+<li>January 2022, by Martin Kremer:<br>Implemented maximum limit for saturation. </li>
 </ul>
 </html>"));
 end SprayHumidifier;
diff --git a/AixLib/Airflow/AirHandlingUnit/ModularAirHandlingUnit/Components/SteamHumidifier.mo b/AixLib/Airflow/AirHandlingUnit/ModularAirHandlingUnit/Components/SteamHumidifier.mo
@@ -25,6 +25,9 @@ equation
   // specific enthalpies
    assert(T_watIn >= 373.15, "Steam temperature T has to be higher than 100 degC");
    h_steam = cp_water * (373.15 - 273.15) + cp_steam * (T_watIn - 373.15) + r100;
+
+   connect(max.y,X_intern);
+
         annotation (
     preferredView="info",
     Documentation(info="<html>