Issue1921 organic rankine cycle

IBPSA/Fluid/CHPs/OrganicRankine/BaseClasses/FixedEvaporating.mo

@@ -0,0 +1,213 @@
+within IBPSA.Fluid.CHPs.OrganicRankine.BaseClasses;
+model FixedEvaporating
+  "Thermodynamic computations of the ORC with fixed evaporating temperature"
+  extends IBPSA.Fluid.CHPs.OrganicRankine.BaseClasses.InterpolateStates(
+    TEva=TWorEva,
+    TCon=TWorCon);
+
+  parameter Modelica.Units.SI.TemperatureDifference dTPinEva_set(
+    final min = 0)
+    "Set evaporator pinch point temperature difference"
+    annotation(Dialog(group="Evaporator"));
+  parameter Modelica.Units.SI.SpecificHeatCapacity cpHot
+    "Constant specific heat capacity"
+    annotation(Dialog(group="Evaporator"));
+  parameter Modelica.Units.SI.ThermodynamicTemperature TWorEva
+    "Working fluid evaporator temperature"
+    annotation(Dialog(group="Evaporator"));
+  parameter Modelica.Units.SI.TemperatureDifference dTPinCon
+    "Pinch point temperature difference of condenser"
+    annotation(Dialog(group="Condenser"));
+  parameter Modelica.Units.SI.SpecificHeatCapacity cpCol
+    "Constant specific heat capacity"
+    annotation(Dialog(group="Condenser"));
+  parameter Boolean useLowCondenserPressureWarning = true
+    "If true, issues warning if pCon < 101325 Pa";
+  parameter Modelica.Units.SI.MassFlowRate mWor_flow_max(
+    final min = 0)
+    "Upper bound of working fluid flow rate"
+    annotation(Dialog(group="Cycle"));
+  parameter Modelica.Units.SI.MassFlowRate mWor_flow_min(
+    final min = 0)
+    "Lower bound of working fluid flow rate"
+    annotation(Dialog(group="Cycle"));
+  parameter Modelica.Units.SI.MassFlowRate mWor_flow_hysteresis(
+    final min = 0)
+    "Hysteresis for turning off the cycle when flow too low"
+    annotation(Dialog(group="Cycle"));
+
+  Modelica.Blocks.Interfaces.RealInput THotIn(
+    final quantity="ThermodynamicTemperature",
+    final unit="K",
+    displayUnit="degC") "Incoming temperature of hot fluid in evaporator"
+    annotation (Placement(
+        transformation(extent={{-140,60},{-100,100}}),  iconTransformation(
+          extent={{-120,70},{-100,90}})));
+  Modelica.Blocks.Interfaces.RealInput mHot_flow(
+    final quantity="MassFlowRate",
+    final unit="kg/s") "Evaporator hot fluid flow rate"
+    annotation (Placement(transformation(extent={{-140,20},{-100,60}}),
+        iconTransformation(extent={{-120,30},{-100,50}})));
+  Modelica.Blocks.Interfaces.RealInput TColIn(
+    final quantity="ThermodynamicTemperature",
+    final unit="K",
+    displayUnit="degC") "Incoming temperature of cold fluid in condenser"
+    annotation (Placement(transformation(extent={{-140,-60},{-100,-20}}),
+        iconTransformation(extent={{-120,-50},{-100,-30}})));
+  Modelica.Blocks.Interfaces.RealInput mCol_flow(
+    final quantity="MassFlowRate",
+    final unit="kg/s") "Condenser cold fluid flow rate" annotation (Placement(
+        transformation(extent={{-140,-100},{-100,-60}}), iconTransformation(
+          extent={{-120,-90},{-100,-70}})));
+  Modelica.Blocks.Interfaces.BooleanInput ena
+    "Enable cycle; set false to force working fluid flow to zero"
+    annotation (Placement(transformation(extent={{-140,-20},{-100,20}}),
+        iconTransformation(extent={{-120,-10},{-100,10}})));
+
+  Modelica.Blocks.Interfaces.RealOutput QEva_flow(
+    final quantity="HeatFlowRate",
+    final unit="W") "Evaporator heat flow rate into the cycle"
+    annotation (Placement(transformation(extent={{100,60},{140,100}}),
+                             iconTransformation(extent={{100,70},{120,90}})));
+  Modelica.Blocks.Interfaces.RealOutput QCon_flow(
+    final quantity="HeatFlowRate",
+    final unit="W") "Condenser heat flow rate out of the cycle"
+      annotation (Placement(
+        transformation(extent={{100,-100},{140,-60}}),iconTransformation(extent={{100,-90},
+            {120,-70}})));
+  Modelica.Blocks.Interfaces.RealOutput PExp(
+    final quantity="Power",
+    final unit="W") "Expander power generation"     annotation (Placement(
+        transformation(extent={{100,20},{140,60}}),  iconTransformation(extent={{100,30},
+            {120,50}})));
+  Modelica.Blocks.Interfaces.RealOutput PPum(
+    final quantity="Power",
+    final unit="W")
+    "Electrical power consumption of the pump" annotation (Placement(
+        transformation(extent={{100,-60},{140,-20}}),iconTransformation(extent={
+            {100,-50},{120,-30}})));
+  Modelica.Blocks.Interfaces.BooleanOutput on_actual = ena and hys.y
+    "Actual on off status of the cycle" annotation (Placement(transformation(
+          extent={{100,-20},{140,20}}), iconTransformation(extent={{100,-10},{120,
+            10}})));
+
+  Modelica.Units.SI.ThermodynamicTemperature THotOut(
+    start = TWorEva + dTPinEva_set)
+    "Outgoing temperature of the evaporator hot fluid";
+  Modelica.Units.SI.ThermodynamicTemperature THotPin(
+    start = TWorEva + dTPinEva_set)
+    "Hot fluid temperature at pinch point";
+  Modelica.Units.SI.TemperatureDifference dTPinEva(start = dTPinEva_set)
+    "Pinch point temperature difference of evaporator";
+  Modelica.Units.SI.ThermodynamicTemperature TWorCon
+    "Working fluid condensing temperature";
+  Modelica.Units.SI.ThermodynamicTemperature TColOut
+    "Fluid temperature out of the condenser";
+  Modelica.Units.SI.ThermodynamicTemperature TColPin(
+    start = 300)
+    "Cold fluid temperature at pinch point";
+  Modelica.Units.SI.MassFlowRate mWor_flow
+    "Mass flow rate of the working fluid"
+    annotation (Dialog(group="Cycle"));
+  Modelica.Blocks.Logical.Hysteresis hys(
+    uLow = mWor_flow_min,
+    uHigh = mWor_flow_min + mWor_flow_hysteresis,
+    u = mWor_flow_internal,
+    y(start = false))
+    "Hysteresis for turning off cycle when working fluid flow too low";
+
+protected
+  Modelica.Units.SI.MassFlowRate mWor_flow_internal(
+    start = (mWor_flow_max + mWor_flow_min) / 2)
+    "Working fluid flow rate, intermediate variable";
+  Modelica.Units.SI.ThermodynamicTemperature THotPin_internal
+    "Hot fluid temperature at pinch point, intermedaite variable";
+  Modelica.Units.SI.ThermodynamicTemperature THotOut_internal
+    "Hot fluid outgoing temperature, intermediate variable";
+  Modelica.Units.SI.HeatFlowRate QEva_flow_internal
+    "Evaporator heat flow rate, intermediate variable";
+
+equation
+
+  assert(not (TWorCon > TWorEva - 1 and ena),
+"*** In " + getInstanceName() +
+": Working fluid condensing temperature is too high and close to evaporating temperature.
+This is likely caused by the flow rate of cold fluid in the condenser being too low
+when the ORC is on.");
+
+  assert(not (pCon < 101325 - 1 and ena and useLowCondenserPressureWarning),
+"*** In " + getInstanceName() +
+": Working fluid condensing pressure is lower than 101325 Pa.
+If this is intended, set useLowCondenserPressureWarning = false to turn off this warning.",
+level=AssertionLevel.warning);
+
+  if ena then
+    // Evaporator
+    QEva_flow = mHot_flow * cpHot * (THotOut - THotIn);
+    QEva_flow = mWor_flow * (hPumOut - hExpInl);
+    (THotPin - THotOut) * (hExpInl - hPumOut)
+    = (hPinEva - hPumOut) * (THotIn - THotOut);
+    // Condenser
+    QCon_flow = mCol_flow * cpCol * (TColOut - TColIn);
+    QCon_flow = mWor_flow * (hExpOut - hPumInl);
+    (TColPin - TColIn) * (hExpOut - hPumInl)
+    = (hPinCon - hPumInl) * (TColOut - TColIn);
+  else
+    // Evaporator
+    QEva_flow = 0;
+    THotOut = THotIn;
+    THotPin = THotOut;
+    // Condenser
+    QCon_flow = 0;
+    TColOut = TColIn;
+    TColPin = TColIn;
+  end if;
+  dTPinEva = THotPin - TWorEva; // Evaporator
+  dTPinCon = TWorCon - TColPin; // Condenser
+
+  // Evaporator internal computation
+  QEva_flow_internal = mHot_flow * cpHot * (THotOut_internal - THotIn);
+  QEva_flow_internal = mWor_flow_internal * (hPumOut - hExpInl);
+  (THotPin_internal - THotOut_internal) * (hExpInl - hPumOut)
+  = (hPinEva - hPumOut) * (THotIn - THotOut_internal);
+  dTPinEva_set = THotPin_internal - TWorEva;
+
+  // Other components
+  PExp = mWor_flow * (hExpOut - hExpInl);
+  PPum = mWor_flow * (hPumOut - hPumInl);
+  mWor_flow =
+    if on_actual
+    then
+      IBPSA.Utilities.Math.Functions.smoothMin(
+      x1=mWor_flow_internal,
+      x2=mWor_flow_max,
+      deltaX=mWor_flow_min*1E-2)
+    else 0;
+
+  annotation(defaultComponentName="cyc",
+  Documentation(info="<html>
+<p>
+This model computes the pinch points and the energy exchange,
+and interfaces with the input and output variables.
+The evaporating temperature is fixed as a parameter.
+See the documentation of
+<a href=\"Modelica://IBPSA.Fluid.CHPs.OrganicRankine.ConstantEvaporation\">
+IBPSA.Fluid.CHPs.OrganicRankine.ConstantEvaporation</a>
+for more details.
+</html>", revisions="<html>
+<ul>
+<li>
+January 29, 2024, by Hongxiang Fu:<br/>
+First implementation. This is for
+<a href=\"https://github.com/lbl-srg/modelica-buildings/issues/3433\">#3433</a>.
+</li>
+</ul>
+</html>"),
+    Icon(graphics={Line(
+          points={{-28,20},{66,50}},
+          color={238,46,47},
+          thickness=1), Line(
+          points={{-30,-54},{64,-24}},
+          color={28,108,200},
+          thickness=1)}));
+end FixedEvaporating;