modelSingleMixing
Single mixing circuit
Extends from BaseClasses.SingleMixing (Single mixing circuit).
Information
Summary
This configuration (see schematic below) is used for variable flow primary circuits and either constant flow or variable flow secondary circuits that have a design supply temperature close or identical to the primary circuit but a varying set point during operation. The control valve should be sized with a pressure drop equal to the primary pressure differential. That pressure drop must be compensated for by the secondary pump which excludes the use of this configuration to applications with a high primary pressure differential.
The following table presents the main characteristics of this configuration.
| Primary circuit | Variable flow |
| Secondary (consumer) circuit | Constant or variable flow |
| Typical applications | Circuits that have a design supply temperature close or identical to the primary circuit but a varying set point during operation. |
| Non-recommended applications | Applications with a high primary pressure differential such as DHC systems due to the constraints on the control valve and secondary pump selection: for those applications use either Buildings.Fluid.HydronicConfigurations.ActiveNetworks.InjectionTwoWay, or Buildings.Fluid.HydronicConfigurations.ActiveNetworks.Decoupling in conjunction with Buildings.Fluid.HydronicConfigurations.PassiveNetworks.SingleMixing. |
| Built-in valve control options | Supply temperature |
| Control valve selection |
β = ΔpA-AB /
(Δp1 + ΔpA-AB) The valve is sized with a pressure drop of Δp1 which yields an authority close to 0.5. |
| Balancing requirement |
The primary balancing valve should compensate for the primary
pressure differential (see additional comments below).
Bypass balancing valve not recommended. |
|
Lumped flow resistances include (With the setting use_lumFloRes=true.)
|
Direct branch: control valve direct branch val.res1
and whole consumer circuit between b2 and a2Bypass branch: control valve bypass branch val.res3
and bypass balancing valve res3
|
Additional comments
The primary pressure differential tends to oppose the bypass flow rate.
It is possible to reach zero bypass flow at partial valve opening and
a negative bypass flow for even lower opening values.
Therefore, a balancing valve in the bypass is not recommended as it
would further reduce the bypass flow rate.
When using that model, one should keep the default setting
dpBal3_nominal=0 Pa.
The balancing procedure should ensure that the primary pressure differential is compensated for by the primary balancing valve. Otherwise, the flow may reverse in the bypass branch and the mixing function of the three-way valve cannot be achieved. The control valve pressure drop must be compensated for by the secondary pump.
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 |
| Buildings.Fluid.HydronicConfigurations.Components.ThreeWayValve | val (from SingleMixing) | Control valve | |
| FixedResistances.Junction | jun (from SingleMixing) | Junction | |
| FixedResistances.PressureDrop | res1 (from SingleMixing) | Primary balancing valve | |
| FixedResistances.PressureDrop | res2 (from SingleMixing) | Secondary balancing valve | |
| Buildings.Fluid.HydronicConfigurations.Components.Pump | pum (from SingleMixing) | Pump | |
| Sensors.TemperatureTwoPort | T2Sup (from SingleMixing) | Consumer circuit supply temperature sensor | |
| Controls.PIDWithOperatingMode | ctl (from SingleMixing) | Controller | |
| Buildings.Controls.OBC.CDL.Integers.GreaterThreshold | isEna (from SingleMixing) | Returns true if enabled | |
| Sensors.TemperatureTwoPort | T2Ret (from SingleMixing) | Consumer circuit return temperature sensor | |
| FixedResistances.PressureDrop | res3 (from SingleMixing) | Bypass balancing valve |
Revisions
-
June 30, 2022, by Antoine Gautier:
First implementation.