modelPartialFlowMachine

Partial model to interface fan or pump models with the medium

Extends from IBPSA.Fluid.Interfaces.LumpedVolumeDeclarations (Declarations for lumped volumes), IBPSA.Fluid.Interfaces.PartialTwoPortInterface (Partial model transporting fluid between two ports without storing mass or energy).

Information

This is the base model for fans and pumps. It provides an interface between the equations that compute head and power consumption, and the implementation of the energy and pressure balance of the fluid.

Optionally, the fluid volume is computed using a dynamic balance or a steady-state balance.

The parameter addPowerToMedium determines whether any power is added to the fluid. The default is addPowerToMedium=true, and hence the outlet enthalpy is higher than the inlet enthalpy if the flow device is operating. The setting addPowerToMedium=false is physically incorrect (since the flow work, the flow friction and the fan heat do not increase the enthalpy of the medium), but this setting does in some cases lead to simpler equations and more robust simulation, in particular if the mass flow is equal to zero.

Parameters

Type	Name	Default	Description
IBPSA.Fluid.Movers.Data.Generic	per
Boolean	computePowerUsingSimilarityLaws		= true, compute power exactly, using similarity laws. Otherwise approximate.
Boolean	addPowerToMedium	true	Set to false to avoid any power (=heat and flow work) being added to medium (may give simpler equations)
Boolean	nominalValuesDefineDefaultPressureCurve	false	Set to true to avoid warning if m_flow_nominal and dp_nominal are used to construct the default pressure curve
Dynamics › Equations
Modelica.Fluid.Types.Dynamics	energyDynamics (from LumpedVolumeDeclarations)	Modelica.Fluid.Types.Dynamics.DynamicFreeInitial	Type of energy balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	massDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of mass balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	substanceDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of independent mass fraction balance: dynamic (3 initialization options) or steady state
Modelica.Fluid.Types.Dynamics	traceDynamics (from LumpedVolumeDeclarations)	energyDynamics	Type of trace substance balance: dynamic (3 initialization options) or steady state
Initialization
Medium.AbsolutePressure	p_start (from LumpedVolumeDeclarations)	Medium.p_default	Start value of pressure
Medium.Temperature	T_start (from LumpedVolumeDeclarations)	Medium.T_default	Start value of temperature
Medium.MassFraction[Medium.nX]	X_start (from LumpedVolumeDeclarations)	Medium.X_default	Start value of mass fractions m_i/m
Medium.ExtraProperty[Medium.nC]	C_start (from LumpedVolumeDeclarations)	fill(0, Medium.nC)	Start value of trace substances
Medium.ExtraProperty[Medium.nC]	C_nominal (from LumpedVolumeDeclarations)	fill(1E-2, Medium.nC)	Nominal value of trace substances. (Set to typical order of magnitude.)
Dynamics
Real	mSenFac (from LumpedVolumeDeclarations)	1	Factor for scaling the sensible thermal mass of the volume
Assumptions
Boolean	allowFlowReversal (from PartialTwoPort)	true	= false to simplify equations, assuming, but not enforcing, no flow reversal
Nominal condition
Modelica.SIunits.MassFlowRate	m_flow_nominal (from PartialTwoPortInterface)		Nominal mass flow rate
Advanced
Modelica.SIunits.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
Control
IBPSA.Fluid.Types.InputType	inputType	IBPSA.Fluid.Types.InputType.Continuous	Control input type
Real	constInput	0	Constant input set point
Real[:]	stageInputs		Vector of input set points corresponding to stages
Dynamics › Nominal condition
Modelica.SIunits.Time	tau	1	Time constant of fluid volume for nominal flow, used if energy or mass balance is dynamic
Dynamics › Filtered speed
Boolean	use_inputFilter	true	= true, if speed is filtered with a 2nd order CriticalDamping filter
Modelica.SIunits.Time	riseTime	30	Rise time of the filter (time to reach 99.6 % of the speed)
Modelica.Blocks.Types.Init	init	Modelica.Blocks.Types.Init.InitialOutput	Type of initialization (no init/steady state/initial state/initial output)
Real	y_start	0	Initial value of speed

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.IntegerInput	stage	Stage input signal for the pressure head
Modelica.Blocks.Interfaces.RealOutput	y_actual	Actual normalised pump speed that is used for computations
Modelica.Blocks.Interfaces.RealOutput	P	Electrical power consumed
Modelica.Thermal.HeatTransfer.Interfaces.HeatPort_a	heatPort	Heat dissipation to environment

Components

Type	Name	Default	Description
Modelica.SIunits.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.SIunits.PressureDifference	dp (from PartialTwoPortInterface)	port_a.p - port_b.p	Pressure difference between port_a and port_b
Medium.ThermodynamicState	sta_a (from PartialTwoPortInterface)	Medium.setState_phX(port_a.p, noEvent(actualStream(port_a.h_outflow)), noEvent(actualStream(port_a.Xi_outflow)))	Medium properties in port_a
Medium.ThermodynamicState	sta_b (from PartialTwoPortInterface)	Medium.setState_phX(port_b.p, noEvent(actualStream(port_b.h_outflow)), noEvent(actualStream(port_b.Xi_outflow)))	Medium properties in port_b
Modelica.SIunits.VolumeFlowRate	VMachine_flow	eff.V_flow	Volume flow rate
Modelica.SIunits.PressureDifference	dpMachine	-preSou.dp	Pressure difference
Real	eta	eff.eta	Global efficiency
Real	etaHyd	eff.etaHyd	Hydraulic efficiency
Real	etaMot	eff.etaMot	Motor efficiency

Name	Description
Extractorprotected	Extract scalar signal out of signal vector dependent on IntegerRealInput index

Revisions

March 24, 2017, by Michael Wetter:
Renamed filteredSpeed to use_inputFilter.
This is for #665.
December 2, 2016, by Michael Wetter:
Removed min attribute as otherwise numerical noise can cause the assertion on the limit to fail.
This is for #606.
November 3, 2016, by Michael Wetter:
Set start value for VMachine_flow to avoid a warning in IBPSA.Fluid.Movers.Examples.MoverContinuous.
July 29, 2016, by Michael Wetter:
Made Extractor protected so that it can be removed later with a backwards compatible change.
July 19, 2016, by Filip Jorissen:
Created custom implementation for extractor. This is for #498.
June 16, 2016, by Filip Jorissen:
Switched position of mixing volume and mass flow rate sensor. This is to have a consistent operating point tuple of dp and m_flow when having compressible flow. This is for #458.
February 19, 2016, by Michael Wetter and Filip Jorissen:
Refactored model to make implementation clearer. This model now includes code for both speed and flow prescribed models, eliminating the need for an additional level of partial models. This is for #417.
Removed the parameter dynamicBalance. This is for #411.
November 19, 2015, by Michael Wetter:
Removed assignment of parameter showDesignFlowDirection in extends statement. This is for #349. Removed assignment of min and max attributes of the port mass flow rate as this is already done in the base class. Removed import statement.
April 2, 2015, by Filip Jorissen:
Added code for supporting stage input and constant input. Added code for displaying constant set point in symbol.
January 24, 2015, by Michael Wetter:
Propagated m_flow_small of instance vol and made all its parameters final.
May 25, 2011, by Michael Wetter:
Revised implementation of energy balance to avoid having to use conditionally removed models.
July 29, 2010, by Michael Wetter:
Reduced fan time constant from 10 to 1 second.
July 27, 2010, by Michael Wetter:
Redesigned model to fix bug in medium balance.
March 24 2010, by Michael Wetter:
First implementation.