Package with boiler models


This package contains components models for boilers.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Package Content

Buildings.Fluid.Boilers.BoilerPolynomial BoilerPolynomial Boiler with efficiency curve described by a polynomial of the temperature
Buildings.Fluid.Boilers.Examples Examples Collection of models that illustrate model use and test models

Buildings.Fluid.Boilers.BoilerPolynomial Buildings.Fluid.Boilers.BoilerPolynomial

Boiler with efficiency curve described by a polynomial of the temperature



This is a model of a boiler that computes the heat transferred to the medium based on an input control signal. The efficiency of the boiler can be computed using polynomials in the control signal y and the boiler temperature T.

The parameter Q_flow_nominal is the power transferred to the fluid for y=1 and, if the efficiency depends on temperature, for T=T0.

Optionally, the port heatPort can be connected to a heat port outside of this model to impose a boundary condition in order to model heat losses to the ambient. When using this heatPort, make sure that the efficiency curve effCur does not already account for this heat loss.

On the Assumptions tag, the model can be parameterized to compute a transient or steady-state response. The transient response of the boiler is computed using a first order differential equation to compute the boiler's water and metal temperature, which are lumped into one state. The boiler outlet temperature is equal to this water temperature.

Extends from Interfaces.TwoPortHeatMassExchanger (Partial model transporting one fluid stream with storing mass or energy).


replaceable package MediumPartialMediumMedium in the component
MixingVolumevolredeclare Buildings.Fluid.Mi...Volume for fluid stream
PowerQ_flow_nominal Nominal heating power [W]
TemperatureT_nominal353.15Temperature used to compute nominal efficiency (only used if efficiency curve depends on temperature) [K]
EfficiencyCurveseffCurBuildings.Fluid.Types.Effici...Curve used to compute the efficiency
Reala[:]{0.9}Coefficients for efficiency curve
ThermalConductanceUA0.05*Q_flow_nominal/30Overall UA value [W/K]
Nominal condition
MassFlowRatem_flow_nominal Nominal mass flow rate [kg/s]
Pressuredp_nominal Pressure [Pa]
MassFlowRatem_flow.start0Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction) [kg/s]
Pressuredp.start0Pressure difference between port_a and port_b [Pa]
BooleanallowFlowReversalsystem.allowFlowReversal= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
MassFlowRatem_flow_small1E-4*abs(m_flow_nominal)Small mass flow rate for regularization of zero flow [kg/s]
BooleanhomotopyInitializationtrue= true, use homotopy method
Booleanshow_V_flowfalse= true, if volume flow rate at inflowing port is computed
Booleanshow_Ttrue= true, if actual temperature at port is computed (may lead to events)
Flow resistance
Booleanfrom_dpfalse= true, use m_flow = f(dp) else dp = f(m_flow)
BooleanlinearizeFlowResistancefalse= true, use linear relation between m_flow and dp for any flow rate
RealdeltaM0.1Fraction of nominal flow rate where flow transitions to laminar
Nominal condition
TimetauVWat*rho_nominal/m_flow_nomi...Time constant at nominal flow (if energyDynamics <> SteadyState) [s]
DynamicsenergyDynamicsModelica.Fluid.Types.Dynamic...Formulation of energy balance
DynamicsmassDynamicsenergyDynamicsFormulation of mass balance
VolumeVWat1.5E-6*Q_flow_nominalWater volume of boiler [m3]
MassmDry1.5E-3*Q_flow_nominalMass of boiler that will be lumped to water heat capacity [kg]
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
TemperatureT_startMedium.T_defaultStart value of temperature [K]
MassFractionX_start[Medium.nX]Medium.X_defaultStart value of mass fractions m_i/m [kg/kg]
ExtraPropertyC_start[Medium.nC]fill(0, Medium.nC)Start value of trace substances


FluidPort_aport_aFluid connector a (positive design flow direction is from port_a to port_b)
FluidPort_bport_bFluid connector b (positive design flow direction is from port_a to port_b)
input RealInputyPart load ratio
HeatPort_aheatPortHeat port, can be used to connect to ambient
output RealOutputT[K]

Modelica definition

model BoilerPolynomial 
  "Boiler with efficiency curve described by a polynomial of the temperature"
  extends Interfaces.TwoPortHeatMassExchanger(
    show_T = true,
    final tau=VWat*rho_nominal/m_flow_nominal);

  parameter Modelica.SIunits.Power Q_flow_nominal "Nominal heating power";
  parameter Modelica.SIunits.Temperature T_nominal = 353.15 
    "Temperature used to compute nominal efficiency (only used if efficiency curve depends on temperature)";
  // Assumptions
  parameter Buildings.Fluid.Types.EfficiencyCurves effCur=Buildings.Fluid.Types.EfficiencyCurves.Constant 
    "Curve used to compute the efficiency";
  parameter Real a[:] = {0.9} "Coefficients for efficiency curve";
  parameter Modelica.SIunits.ThermalConductance UA=0.05*Q_flow_nominal/30 
    "Overall UA value";
  parameter Modelica.SIunits.Volume VWat = 1.5E-6*Q_flow_nominal 
    "Water volume of boiler";
  parameter Modelica.SIunits.Mass mDry =   1.5E-3*Q_flow_nominal if 
        not (energyDynamics == Modelica.Fluid.Types.Dynamics.SteadyState) 
    "Mass of boiler that will be lumped to water heat capacity";

  Real eta(min=0) "Boiler efficiency";

  Modelica.SIunits.Power QFue_flow "Sensible heat released by fuel";
  Modelica.SIunits.Power QWat_flow "Heat transfer from gas into water";

  Modelica.Blocks.Interfaces.RealInput y(min=0, max=1) "Part load ratio";
  Real eta_nominal "Boiler efficiency at nominal condition";

  parameter Modelica.SIunits.SpecificHeatCapacity cp_nominal=
    "Specific heat capacity of fluid in boiler";

  Modelica.Thermal.HeatTransfer.Components.ThermalConductor UAOve(G=UA) 
    "Overall thermal conductance (if heatPort is connected)";
  Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a heatPort 
    "Heat port, can be used to connect to ambient";
  Modelica.Thermal.HeatTransfer.Components.HeatCapacitor heaCapDry(C=500*mDry,
      T(start=T_start)) if not (energyDynamics == Modelica.Fluid.Types.Dynamics.SteadyState) 
    "heat capacity of boiler metal";
  Modelica.Blocks.Interfaces.RealOutput T(final quantity="Temperature",
                                          final unit = "K", displayUnit = "degC", min=0);
  Buildings.HeatTransfer.Sources.PrescribedHeatFlow preHeaFlo;
  Modelica.Blocks.Sources.RealExpression Q_flow_in(y=QWat_flow);
  Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor temSen 
    "Temperature of fluid";
  if effCur ==Buildings.Fluid.Types.EfficiencyCurves.Constant then
    eta  = a[1];
    eta_nominal = a[1];
  elseif effCur ==Buildings.Fluid.Types.EfficiencyCurves.Polynomial then
    eta  = Buildings.Utilities.Math.Functions.polynomial(
                                                   a=a, x=y);
    eta_nominal = Buildings.Utilities.Math.Functions.polynomial(
                                                          a=a, x=1);
  elseif effCur ==Buildings.Fluid.Types.EfficiencyCurves.QuadraticLinear then
    eta  = Buildings.Utilities.Math.Functions.quadraticLinear(
                                                        a=a, x1=y, x2=T);
    eta_nominal = Buildings.Utilities.Math.Functions.quadraticLinear(
                                                               a=a, x1=1, x2=T_nominal);
    eta  = 0;
    eta_nominal = 999;
  end if;
  assert(eta > 0.001, "Efficiency curve is wrong.");
  // Heat released by fuel
  QFue_flow = y * Q_flow_nominal/eta_nominal;
  // Heat input into water
  QWat_flow = eta * QFue_flow;
  connect(UAOve.port_b, vol.heatPort);
  connect(UAOve.port_a, heatPort);
  connect(heaCapDry.port, vol.heatPort);
  connect(temSen.T, T);
  connect(preHeaFlo.port, vol.heatPort);
  connect(Q_flow_in.y,preHeaFlo. Q_flow);
  connect(vol.heatPort, temSen.port);
end BoilerPolynomial;

Automatically generated Thu Dec 8 16:33:45 2011.