modelPartialOneWayFlowElement

Partial model for flow resistance with one-way flow

Extends from Buildings.Fluid.Interfaces.PartialTwoPortInterface (Partial model with two ports and declaration of quantities that are used by many models), Buildings.Airflow.Multizone.BaseClasses.ErrorControl (Interface that defines parameters for error control).

Information

This partial model is used to model one way flow-elements. It holds the conservation equations and should be extended by definition of one of the following variables:

m_flow = mass flow rate trough the component

V_flow = volume flow rate through the component

The flow from A->B is the positive flow. The resulting equation should be in the extends statement, not in the equation section since this model sets both m_flow = V_flow*rho and V_flow = m_flow/rho.

Parameters

Type	Name	Default	Description
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
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
Boolean	forceErrorControlOnFlow (from ErrorControl)	true	Flag to force error control on m_flow. Set to true if interested in flow rate
Boolean	homotopyInitialization	true	= true, use homotopy method
Boolean	useDefaultProperties	true	Set to false to use density and viscosity based on actual medium state, rather than using default values
Modelica.Units.SI.PressureDifference	dp_turbulent	0.1	Pressure difference where laminar and turbulent flow relation coincide. Recommended = 0.1
Advanced › Diagnostics
Boolean	show_T (from PartialTwoPortInterface)	false	= true, if actual temperature at port is computed

Connectors

Type	Name	Default	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)

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
Modelica.Units.SI.VolumeFlowRate	V_flow	m_flow/rho	Volume flow rate through the component
Modelica.Units.SI.Density	rho		Fluid density at port_a

Revisions

September 22, 2025, by Michael Wetter:
Set unbounded=true for mExc_flow. This is to have the same implementation as in Buildings.Airflow.Multizone.BaseClasses.TwoWayFlowElement where this change was done to avoid spikes in port_a.m_flow in Buildings.Airflow.Multizone.Examples.OneOpenDoor.
This is for Buildings, #4360.
September 19, 2025, by Michael Wetter:
Introduced protected parameter sqrt_dp_turbulent, which is needed to improve computing efficiency if flow exponent is 0.5.
This is for IBPSA, #2043.
February 2, 2022, by Michael Wetter:
Revised implementation.
This is for IBPSA, #1436.
Apr 06, 2021, by Klaas De Jonge:
First implementation.