modelInjectionTwoWay
Injection circuit with two-way valve
Extends from HydronicConfigurations.Interfaces.PartialHydronicConfiguration.
Information
Summary
This circuit (see schematic hereunder) is used for variable flow primary circuits and either constant flow or variable flow consumer circuits. The fixed bypass prevents the primary pressure differential from being transmitted to the consumer circuit. This allows a proper operation of the terminal control valves on the consumer side when the primary pressure differential is either too low or too high or varying too much. For variable flow consumer circuits, the supply temperature set point must be different from the primary circuit.
The following table presents the main characteristics of this configuration.
| Primary circuit |
Variable flow (See caveats in Buildings.Fluid.HydronicConfigurations.ActiveNetworks.Examples.InjectionTwoWayConstant: control options are critical to achieve a truly variable flow.) |
| Secondary (consumer) circuit | Constant or variable flow |
| Typical applications |
Consumer circuit supply temperature set point different from primary circuit (Otherwise use Buildings.Fluid.HydronicConfigurations.ActiveNetworks.Decoupling) Primary pressure differential either too low or too high or varying too much such as in DHC systems |
| Non-recommended applications |
Variable flow consumer circuit with same supply temperature set point as primary circuit, see
Buildings.Fluid.HydronicConfigurations.ActiveNetworks.Examples.InjectionTwoWayVariable Variable flow consumer circuit with return temperature control, see Buildings.Fluid.HydronicConfigurations.ActiveNetworks.Examples.InjectionTwoWayVariableReturn |
| Built-in valve control options |
Supply temperature (must be different from primary) Return temperature (incompatible with variable secondary) |
|
Control valve selection (See the nomenclature in the schematic.) |
β = ΔpA-B / Δp1 The valve is sized with a pressure drop of Δp1 / 2 which yields an authority of 0.5. |
| Balancing requirement |
dpBal1_nominal=dp1_nominal-dpValve_nominal
for the primary design flow rate
ṁ1, design = ṁ2, design *
(T2, sup, design - T2, ret, design) /
(T1, sup, design - T2, ret, design)
|
|
Lumped flow resistance includes (With the setting use_lumFloRes=true.)
|
Control valve val and primary balancing valve res1
|
Additional comments
The pressure drop through the control valve is compensated by the primary pump, reducing the secondary pump head.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Real | n (from PartialHydronicConfiguration) | 2 | Flow exponent, n1=1 for laminar, n1=2 for turbulent |
| Movers.Data.Generic | perPum (from PartialHydronicConfiguration) | ||
| Configuration | |||
| Boolean | use_siz (from PartialHydronicConfiguration) | true | Set to true for built-in sizing of control valve and optional pump |
| Boolean | use_dp1 (from PartialHydronicConfiguration) | Set to true to enable dp1_nominal | |
| Boolean | use_dp2 (from PartialHydronicConfiguration) | Set to true to enable dp2_nominal | |
| Buildings.Fluid.HydronicConfigurations.Types.Valve | typVal (from PartialHydronicConfiguration) | Type of control valve | |
| Boolean | have_typVar (from PartialHydronicConfiguration) | true | Set to true to enable the choice of the controlled variable |
| Nominal condition | |||
| Modelica.Units.SI.MassFlowRate | m1_flow_nominal (from PartialHydronicConfiguration) | Mass flow rate in primary circuit at design conditions | |
| Modelica.Units.SI.MassFlowRate | m2_flow_nominal (from PartialHydronicConfiguration) | Mass flow rate in consumer circuit at design conditions | |
| Modelica.Units.SI.PressureDifference | dp1_nominal (from PartialHydronicConfiguration) | Primary circuit pressure differential at design conditions | |
| Modelica.Units.SI.PressureDifference | dp2_nominal (from PartialHydronicConfiguration) | Consumer circuit pressure differential at design conditions | |
| Control valve | |||
| Buildings.Fluid.HydronicConfigurations.Types.ValveCharacteristic | typCha (from PartialHydronicConfiguration) | Buildings.Fluid.HydronicConfigurations.Types.ValveCharacteristic.EqualPercentage | Control valve characteristic |
| Modelica.Units.SI.PressureDifference | dpValve_nominal (from PartialHydronicConfiguration) | Control valve pressure drop at design conditions | |
| Actuators.Valves.Data.Generic | flowCharacteristics (from PartialHydronicConfiguration) | Table with flow characteristics | |
| Actuators.Valves.Data.Generic | flowCharacteristics1 (from PartialHydronicConfiguration) | Table with flow characteristics for direct flow path at port_1 | |
| Actuators.Valves.Data.Generic | flowCharacteristics3 (from PartialHydronicConfiguration) | Table with flow characteristics for bypass flow path at port_3 | |
| Pump | |||
| Buildings.Fluid.HydronicConfigurations.Types.Pump | typPum (from PartialHydronicConfiguration) | Buildings.Fluid.HydronicConfigurations.Types.Pump.VariableInput | Type of secondary pump |
| Buildings.Fluid.HydronicConfigurations.Types.PumpModel | typPumMod (from PartialHydronicConfiguration) | Buildings.Fluid.HydronicConfigurations.Types.PumpModel.Speed | Type of pump model |
| Modelica.Units.SI.MassFlowRate | mPum_flow_nominal (from PartialHydronicConfiguration) | m2_flow_nominal | Pump head at design conditions |
| Modelica.Units.SI.PressureDifference | dpPum_nominal (from PartialHydronicConfiguration) | dp2_nominal + dpBal2_nominal | Pump head at design conditions |
| Controls | |||
| Buildings.Fluid.HydronicConfigurations.Types.Control | typCtl (from PartialHydronicConfiguration) | Buildings.Fluid.HydronicConfigurations.Types.Control.None | Type of built-in controls |
| Buildings.Fluid.HydronicConfigurations.Types.ControlVariable | typVar (from PartialHydronicConfiguration) | Buildings.Fluid.HydronicConfigurations.Types.ControlVariable.SupplyTemperature | Controlled variable |
| Buildings.Controls.OBC.CDL.Types.SimpleController | controllerType (from PartialHydronicConfiguration) | Buildings.Controls.OBC.CDL.Types.SimpleController.PI | Type of controller |
| Real | k (from PartialHydronicConfiguration) | 0.1 | Gain of controller |
| Real | Ti (from PartialHydronicConfiguration) | 120 | Time constant of integrator block |
| Assumptions | |||
| Boolean | use_lumFloRes (from PartialHydronicConfiguration) | true | Set to true to use a lumped flow resistance when possible |
| Boolean | allowFlowReversal (from PartialHydronicConfiguration) | true | = false to simplify equations, assuming, but not enforcing, no flow reversal for medium 1 |
| Balancing valves | |||
| Modelica.Units.SI.PressureDifference | dpBal1_nominal (from PartialHydronicConfiguration) | 0 | Primary balancing valve pressure drop at design conditions |
| Modelica.Units.SI.PressureDifference | dpBal2_nominal (from PartialHydronicConfiguration) | 0 | Secondary balancing valve pressure drop at design conditions |
| Modelica.Units.SI.PressureDifference | dpBal3_nominal (from PartialHydronicConfiguration) | 0 | Bypass balancing valve pressure drop at design conditions |
| Dynamics › Conservation equations | |||
| Modelica.Fluid.Types.Dynamics | energyDynamics (from PartialHydronicConfiguration) | Modelica.Fluid.Types.Dynamics.FixedInitial | Type of energy balance: dynamic (3 initialization options) or steady state |
| Advanced › Diagnostics | |||
| Boolean | show_T (from PartialHydronicConfiguration) | false | = true, if actual temperature at port is computed |
Connectors
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Medium.MassFlowRate | m1_flow (from PartialHydronicConfiguration) | port_a1.m_flow | Mass flow rate from port_a1 to port_b1 (m1_flow > 0 is design flow direction) |
| Modelica.Units.SI.PressureDifference | dp1 (from PartialHydronicConfiguration) | port_a1.p - port_b1.p | Pressure difference between port_a1 and port_b1 |
| Medium.MassFlowRate | m2_flow (from PartialHydronicConfiguration) | port_a2.m_flow | Mass flow rate from port_a2 to port_b2 (m2_flow > 0 is design flow direction) |
| Modelica.Units.SI.PressureDifference | dp2 (from PartialHydronicConfiguration) | port_a2.p - port_b2.p | Pressure difference between port_a2 and port_b2 |
| Medium.ThermodynamicState | sta_a1 (from PartialHydronicConfiguration) | if allowFlowReversal then Medium.setState_phX(port_a1.p, noEvent(actualStream(port_a1.h_outflow)), noEvent(actualStream(port_a1.Xi_outflow))) else Medium.setState_phX(port_a1.p, inStream(port_a1.h_outflow), inStream(port_a1.Xi_outflow)) | Medium properties in port_a1 |
| Medium.ThermodynamicState | sta_b1 (from PartialHydronicConfiguration) | if allowFlowReversal then Medium.setState_phX(port_b1.p, noEvent(actualStream(port_b1.h_outflow)), noEvent(actualStream(port_b1.Xi_outflow))) else Medium.setState_phX(port_b1.p, port_b1.h_outflow, port_b1.Xi_outflow) | Medium properties in port_b1 |
| Medium.ThermodynamicState | sta_a2 (from PartialHydronicConfiguration) | if allowFlowReversal then Medium.setState_phX(port_a2.p, noEvent(actualStream(port_a2.h_outflow)), noEvent(actualStream(port_a2.Xi_outflow))) else Medium.setState_phX(port_a2.p, inStream(port_a2.h_outflow), inStream(port_a2.Xi_outflow)) | Medium properties in port_a2 |
| Medium.ThermodynamicState | sta_b2 (from PartialHydronicConfiguration) | if allowFlowReversal then Medium.setState_phX(port_b2.p, noEvent(actualStream(port_b2.h_outflow)), noEvent(actualStream(port_b2.Xi_outflow))) else Medium.setState_phX(port_b2.p, port_b2.h_outflow, port_b2.Xi_outflow) | Medium properties in port_b2 |
| FixedResistances.Junction | junSup | Junction | |
| Components.Pump | pum | Pump | |
| Components.TwoWayValve | val | Control valve | |
| Sensors.TemperatureTwoPort | T2Sup | Consumer circuit supply temperature sensor | |
| FixedResistances.Junction | junRet | Junction | |
| FixedResistances.PressureDrop | res2 | Secondary balancing valve | |
| FixedResistances.PressureDrop | res1 | Primary balancing valve | |
| Sensors.TemperatureTwoPort | T2Ret | Consumer circuit return temperature sensor | |
| Controls.PIDWithOperatingMode | ctl | Controller | |
| Buildings.Controls.OBC.CDL.Integers.GreaterThreshold | isEna | Returns true if enabled | |
| Buildings.Controls.OBC.CDL.Routing.RealExtractor | extIndSig | Select measured signal | |
| FixedResistances.LosslessPipe | res3 | Fluid pass-through that can be replaced by check valve | |
| Buildings.Controls.OBC.CDL.Integers.Sources.Constant | ctlVar | Controlled variable selector |
Revisions
-
June 17, 2026, by Michael Wetter:
Updated implementation to allow a flow coefficientnthat is different from2. This allows use of the model for not fully turbulent flow.
This is for Buildings, #4620. -
June 30, 2022, by Antoine Gautier:
First implementation.