Merged issue290_tabs

lbl-srg · Oct 10, 2014 · 3387ba4 · 3387ba4
1 parent 49bc6ba
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diff --git a/Buildings/Fluid/HeatExchangers/RadiantSlabs/BaseClasses/Functions/heatFlowRate.mo b/Buildings/Fluid/HeatExchangers/RadiantSlabs/BaseClasses/Functions/heatFlowRate.mo
@@ -0,0 +1,59 @@
+within Buildings.Fluid.HeatExchangers.RadiantSlabs.BaseClasses.Functions;
+function heatFlowRate "Heat flow rate for epsilon-NTU model"
+  extends Modelica.Icons.Function;
+  input Modelica.SIunits.Temperature T_a "Temperature at port_a";
+  input Modelica.SIunits.Temperature T_b "Temperature at port_b";
+  input Modelica.SIunits.Temperature T_s "Temperature of solid";
+  input Modelica.SIunits.Temperature T_f "Temperature of fluid control volume";
+
+  input Modelica.SIunits.SpecificHeatCapacity c_p "Specific heat capacity";
+  input Modelica.SIunits.ThermalConductance UA "UA value";
+  input Modelica.SIunits.MassFlowRate m_flow
+    "Mass flow rate from port_a to port_b";
+  input Modelica.SIunits.MassFlowRate m_flow_nominal
+    "Nominal mass flow rate from port_a to port_b";
+
+  output Modelica.SIunits.HeatFlowRate Q_flow "Heat flow rate";
+protected
+  Modelica.SIunits.MassFlowRate m_abs_flow "Absolute value of mass flow rate";
+  Modelica.SIunits.Temperature T_in "Inlet fluid temperature";
+  Real eps "Heat transfer effectiveness";
+
+algorithm
+  m_abs_flow :=noEvent(abs(m_flow));
+  T_in :=smooth(1, noEvent(if m_flow >= 0 then T_a else T_b));
+  if m_abs_flow > 0.15*m_flow_nominal then
+    // High flow rate. Use epsilon-NTU formula.
+    eps := 1-Modelica.Math.exp(-UA/m_abs_flow/c_p);
+    Q_flow :=eps*(T_s-T_in)*m_abs_flow*c_p;
+  elseif (m_abs_flow < 0.05*m_flow_nominal) then
+    // Low flow rate. Use heat conduction to temperature of the control volume.
+    Q_flow :=UA*(T_s-T_f);
+  else
+    // Transition. Use a once continuously differentiable transition between the
+    // above regimes.
+    eps := 1-Modelica.Math.exp(-UA/m_abs_flow/c_p);
+    Q_flow := Buildings.Utilities.Math.Functions.spliceFunction(
+      pos=eps*(T_s-T_in)*m_abs_flow*c_p,
+      neg=UA*(T_s-T_f),
+      x=m_abs_flow/m_flow_nominal-0.1,
+      deltax=0.05);
+  end if;
+
+annotation (
+smoothOrder=1,
+Documentation(info="<html>
+<p>
+fixme
+</p>
+</html>
+",
+revisions="<html>
+<ul>
+<li>
+October 7, 2014, by Michael Wetter:<br/>
+First implementation.
+</li>
+</ul>
+</html>"));
+end heatFlowRate;
diff --git a/Buildings/Fluid/HeatExchangers/RadiantSlabs/BaseClasses/Functions/package.order b/Buildings/Fluid/HeatExchangers/RadiantSlabs/BaseClasses/Functions/package.order
@@ -1 +1,2 @@
 AverageResistance
+heatFlowRate