modelLoadTwoWayValve

Model of a load on a hydronic circuit with flow rate modulation by a two-way valve

Extends from Buildings.Fluid.Interfaces.PartialTwoPortInterface (Partial model with two ports and declaration of quantities that are used by many models).

Information

This model represents a thermal load on a hydronic circuit, composed of Buildings.Templates.Components.Loads.Load and a two-way valve component that is used to modulate the flow rate through the load component.

Parameters

Type	Name	Default	Description
Buildings.Fluid.HydronicConfigurations.Types.Control	typ		Load type
Modelica.Units.SI.MassFlowRate	mLiq_flow_nominal	1	Liquid mass flow rate at design conditions
Modelica.Units.SI.PressureDifference	dpTer_nominal	3E4	Liquid pressure drop across terminal unit at design conditions
Modelica.Units.SI.MassFlowRate	mAir_flow_nominal	abs(Q_flow_nominal)/10/1015	Air mass flow rate at design conditions
Modelica.Units.SI.Temperature	TAirEnt_nominal	if typ == Buildings.Fluid.HydronicConfigurations.Types.Control.Heating then 20 + 273.15 else 26 + 273.15	Air entering temperature at design conditions
Modelica.Units.SI.MassFraction	phiAirEnt_nominal	0.5	Air entering relative humidity at design conditions
Modelica.Units.SI.Temperature	TLiqEnt_nominal	if typ == Buildings.Fluid.HydronicConfigurations.Types.Control.Heating then 60 + 273.15 else 7 + 273.15	Liquid entering temperature at design conditions
Modelica.Units.SI.Temperature	TLiqLvg_nominal	TLiqEnt_nominal + (if typ == Buildings.Fluid.HydronicConfigurations.Types.Control.Heating then -10 else +5)	Liquid leaving temperature at design conditions
Modelica.Units.SI.HeatFlowRate	Q_flow_nominal	(MediumLiq.specificEnthalpy_pTX(MediumLiq.p_default, TLiqEnt_nominal, X = MediumLiq.X_default) - MediumLiq.specificEnthalpy_pTX(MediumLiq.p_default, TLiqLvg_nominal, X = MediumLiq.X_default))*mLiq_flow_nominal	Transmitted heat flow rate at design conditions
Real	u_min	0.1	Minimum fan speed
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
Advanced › Diagnostics
Boolean	show_T (from PartialTwoPortInterface)	false	= true, if actual temperature at port is computed
Control valve
Modelica.Units.SI.PressureDifference	dpValve_nominal	dpTer_nominal	Control valve pressure drop at design conditions
Balancing valves
Modelica.Units.SI.PressureDifference	dpBal1_nominal	0	Balancing valve pressure drop at design conditions
Valve controller
Buildings.Controls.OBC.CDL.Types.SimpleController	controllerType	Buildings.Controls.OBC.CDL.Types.SimpleController.PI	Type of controller
Real	k	0.1	Gain of controller
Real	Ti	10	Time constant of integrator block
Real	Td	0.1	Time constant of derivative block
Dynamics › Conservation equations
Modelica.Fluid.Types.Dynamics	energyDynamics	Modelica.Fluid.Types.Dynamics.FixedInitial	Type of energy balance: dynamic (3 initialization options) or steady state

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)
Buildings.Controls.OBC.CDL.Interfaces.RealInput	u	Fraction of design load
Buildings.Controls.OBC.CDL.Interfaces.BooleanInput	u1	System enable
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	yLoa_actual	Actual load fraction met
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	Q_flow	Total heat flow rate transferred to the load
Buildings.Controls.OBC.CDL.Interfaces.RealOutput	yVal_actual	Valve position feedback

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.Templates.Components.Loads.Load	loa		Load
Buildings.Fluid.HydronicConfigurations.ActiveNetworks.Throttle	con		Throttle circuit connection

Name	Description
MediumAir	Medium model for air
MediumLiq	Medium model for liquid (CHW or HHW)

Revisions

December 8, 2025, by Antoine Gautier:
First implementation.