modelBoilerPolynomial

Boiler with efficiency curve described by a polynomial of the control signal and (optional) temperature

Extends from Buildings.Fluid.Boilers.BaseClasses.PartialBoiler (Boiler base class with efficiency unspecified).

Information

This is a model of a boiler whose efficiency is described by a polynomial. See Buildings.Fluid.Boilers.UsersGuide for details.

The parameter effCur determines what polynomial is used to compute the efficiency with the following selections:

Parameter effCur	Efficiency curve
Buildings.Fluid.Types.EfficiencyCurves.Constant	η = a₁
Buildings.Fluid.Types.EfficiencyCurves.Polynomial	η = a₁ + a₂ y + a₃ y² + ...
Buildings.Fluid.Types.EfficiencyCurves.QuadraticLinear	η = a₁ + a₂ y + a₃ y² + (a₄ + a₅ y + a₆ y²) T

where T is the boiler outlet temperature in Kelvin. For effCur = Buildings.Fluid.Types.EfficiencyCurves.Polynomial, an arbitrary number of polynomial coefficients can be specified.

Parameters

Type	Name	Default	Description
Boolean	homotopyInitialization (from TwoPortHeatMassExchanger)	true	= true, use homotopy method
Buildings.Fluid.Data.Fuels.Generic	fue (from PartialBoiler)		Fuel type
Modelica.Units.SI.HeatFlowRate	Q_flow_nominal (from PartialBoiler)		Nominal heating power (useful heat)
Modelica.Units.SI.Efficiency	eta_nominal (from PartialBoiler)		Boiler efficiency at nominal condition, useful heat divided by fuel use
Modelica.Units.SI.HeatFlowRate	QFue_flow_nominal (from PartialBoiler)	Q_flow_nominal/eta_nominal	Fuel use at nominal conditions
Buildings.Fluid.Types.EfficiencyCurves	effCur	Buildings.Fluid.Types.EfficiencyCurves.Constant	Curve used to compute the efficiency
Real[:]	a	{0.9}	Coefficients for efficiency curve
Modelica.Units.SI.Temperature	T_nominal	353.15	Temperature used to compute nominal efficiency (only used if efficiency curve depends on temperature)
Assumptions
Boolean	allowFlowReversal (from PartialTwoPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Nominal condition
Modelica.Units.SI.MassFlowRate	m_flow_nominal (from PartialTwoPortInterface)		Nominal mass flow rate
Modelica.Units.SI.PressureDifference	dp_nominal (from TwoPortFlowResistanceParameters)		Pressure difference
Advanced
Modelica.Units.SI.MassFlowRate	m_flow_small (from PartialTwoPortInterface)	1E-4*abs(m_flow_nominal)	Small mass flow rate for regularization of zero flow
Advanced › Diagnostics
Boolean	show_T (from PartialTwoPortInterface)	false	= true, if actual temperature at port is computed
Flow resistance
Boolean	computeFlowResistance (from TwoPortFlowResistanceParameters)	true	=true, compute flow resistance. Set to false to assume no friction
Boolean	from_dp (from TwoPortFlowResistanceParameters)	false	= true, use m_flow = f(dp) else dp = f(m_flow)
Real	n (from TwoPortFlowResistanceParameters)	2	Flow exponent, n=1 for laminar, n=2 for turbulent
Boolean	linearizeFlowResistance (from TwoPortFlowResistanceParameters)	false	= true, use linear relation between m_flow and dp for any flow rate
Real	deltaM (from TwoPortFlowResistanceParameters)	0.1	Fraction of nominal flow rate where flow transitions to laminar
Dynamics › Nominal condition
Modelica.Units.SI.Time	tau (from TwoPortHeatMassExchanger)	30	Time constant at nominal flow (if energyDynamics <> SteadyState)
Dynamics › Conservation equations
Modelica.Fluid.Types.Dynamics	energyDynamics (from TwoPortHeatMassExchanger)	Modelica.Fluid.Types.Dynamics.DynamicFreeInitial	Type of energy balance: dynamic (3 initialization options) or steady state
Initialization
Medium.AbsolutePressure	p_start (from TwoPortHeatMassExchanger)	Medium.p_default	Start value of pressure
Medium.Temperature	T_start (from TwoPortHeatMassExchanger)	Medium.T_default	Start value of temperature
Medium.MassFraction[Medium.nX]	X_start (from TwoPortHeatMassExchanger)	Medium.X_default	Start value of mass fractions m_i/m
Medium.ExtraProperty[Medium.nC]	C_start (from TwoPortHeatMassExchanger)	fill(0, Medium.nC)	Start value of trace substances
Heat loss to ambient
Modelica.Units.SI.ThermalConductance	UA (from PartialBoiler)	0.05*Q_flow_nominal/30	Overall UA value
Dynamics
Modelica.Units.SI.Volume	VWat (from PartialBoiler)	1.5E-6*Q_flow_nominal	Water volume of boiler
Modelica.Units.SI.Mass	mDry (from PartialBoiler)	1.5E-3*Q_flow_nominal	Mass of boiler that will be lumped to water heat capacity

Connectors

Type	Name	Description
Modelica.Fluid.Interfaces.FluidPort_a	port_a (from PartialTwoPort)	Fluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_b	port_b (from PartialTwoPort)	Fluid connector b (positive design flow direction is from port_a to port_b)
Modelica.Blocks.Interfaces.RealInput	y (from PartialBoiler)	Part load ratio
Modelica.Blocks.Interfaces.RealOutput	T (from PartialBoiler)	Temperature of the fluid
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a	heatPort (from PartialBoiler)	Heat port, can be used to connect to ambient

Components

Type	Name	Default	Description
Modelica.Units.SI.MassFlowRate	m_flow (from PartialTwoPortInterface)	port_a.m_flow	Mass flow rate from port_a to port_b (m_flow > 0 is design flow direction)
Modelica.Units.SI.PressureDifference	dp (from PartialTwoPortInterface)	port_a.p - port_b.p	Pressure difference between port_a and port_b
Medium.ThermodynamicState	sta_a (from PartialTwoPortInterface)	if allowFlowReversal then Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow))) else Medium.setState_phX(port_a.p, noEvent(inStream(port_a.h_outflow)), noEvent(inStream(port_a.Xi_outflow)))	Medium properties in port_a
Medium.ThermodynamicState	sta_b (from PartialTwoPortInterface)	if allowFlowReversal then Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow))) else Medium.setState_phX(port_b.p, noEvent(port_b.h_outflow), noEvent(port_b.Xi_outflow))	Medium properties in port_b
Buildings.Fluid.MixingVolumes.MixingVolume	vol (from TwoPortHeatMassExchanger)
Buildings.Fluid.FixedResistances.PressureDrop	preDro (from TwoPortHeatMassExchanger)		Flow resistance
Modelica.Units.SI.Efficiency	eta (from PartialBoiler)		Boiler efficiency, useful heat divided by fuel use
Modelica.Units.SI.HeatFlowRate	QFue_flow (from PartialBoiler)	y*QFue_flow_nominal	Heat released by fuel
Modelica.Units.SI.HeatFlowRate	QUse_flow (from PartialBoiler)	eta*QFue_flow	Useful heat for exchange with fluid ports
Modelica.Units.SI.HeatFlowRate	QExh_flow (from PartialBoiler)	-QFue_flow + QWat_flow	Heat exhausted by flu gas (negative)
Modelica.Units.SI.Power	QAmb_flow (from PartialBoiler)	heatPort.Q_flow	Heat loss to ambient (negative)
Modelica.Units.SI.Power	QWat_flow (from PartialBoiler)	QUse_flow - QAmb_flow	Heat transfer from gas into water (from where some heat is lost to ambient)
Modelica.Units.SI.MassFlowRate	mFue_flow (from PartialBoiler)	QFue_flow/fue.h	Fuel mass flow rate
Modelica.Units.SI.VolumeFlowRate	VFue_flow (from PartialBoiler)	mFue_flow/fue.d	Fuel volume flow rate
Modelica.Thermal.HeatTransfer.Components.HeatCapacitor	heaCapDry (from PartialBoiler)		Heat capacity of boiler metal
Buildings.HeatTransfer.Sources.PrescribedHeatFlow	preHeaFlo (from PartialBoiler)		Prescribed heat flow
Modelica.Blocks.Sources.RealExpression	Q_flow_in (from PartialBoiler)		Heat transfer from gas into water
Modelica.Thermal.HeatTransfer.Sensors.TemperatureSensor	temSen (from PartialBoiler)		Temperature of fluid
Modelica.Thermal.HeatTransfer.Components.ThermalConductor	UAOve (from PartialBoiler)		Overall thermal conductance (if heatPort is connected)

Revisions

October 11, 2026, by Michael Wetter:
Corrected bug in base class that led to heat loss of boiler to be accounted twice in the energy balance. With this change, the heatPort must be connected, as otherwise, the heat loss is not properly calculated. The translation will stop with an error message if the heatPort is unconnected.
This is for #4775.
March 7, 2022, by Michael Wetter:
Set final massDynamics=energyDynamics.
This is for #1542.
October 13, 2021, by Hongxiang Fu:
For the implementation of Buildings.Fluid.Boilers.BoilerTable, moved most of the code to the base model Buildings.Fluid.Boilers.BaseClasses.PartialBoiler. This is for #2651.
May 27, 2016, by Michael Wetter:
Corrected size of input argument to Buildings.Utilities.Math.Functions.quadraticLinear for JModelica compliance check.
May 30, 2014, by Michael Wetter:
Removed undesirable annotation Evaluate=true.
October 9, 2013 by Michael Wetter:
Removed conditional declaration of mDry as the use of a conditional parameter in an instance declaration is not correct Modelica syntax.
December 14, 2012 by Michael Wetter:
Renamed protected parameters for consistency with the naming conventions.
December 22, 2011 by Michael Wetter:
Added computation of fuel usage and improved the documentation.
May 25, 2011 by Michael Wetter:
- Removed parameter dT_nominal, and require instead the parameter m_flow_nominal to be set by the user. This was needed to avoid a non-literal value for the nominal attribute of the pressure drop model.
- Changed assignment of parameters in model instantiation, and updated model for the new base class that does not have a temperature sensor.
January 29, 2009 by Michael Wetter:
First implementation.