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 identical to the primary circuit but a varying set point during operation.
The following table presents the main characteristics of this configuration.
| Primary circuit | Variable flow |
| Secondary (consumer) circuit | Constant or variable flow |
| Typical applications | Widely used in heating applications as it is very simple to achieve. |
| Non-recommended applications | Low-temperature systems that would require the control valve to be operated on a limited opening range: use Buildings.Fluid.HydronicConfigurations.PassiveNetworks.DualMixing instead. |
| Built-in valve control options | Supply temperature |
|
Control valve selection (See the nomenclature in the schematic.) |
β = ΔpA-AB /
(Δp1 + ΔpA-AB) The control valve is sized with a pressure drop equal to the maximum of Δp1 and 3e3 Pa. |
| Balancing requirement | In most cases the bypass balancing valve is not needed. However, it may be needed to counter negative back pressure created by other served circuits, see Buildings.Fluid.HydronicConfigurations.PassiveNetworks.Examples.SingleMixingOpenLoop. |
|
Lumped flow resistance includes (With the setting use_lumFloRes=true.)
|
Control valve val and primary balancing valve res1
|
Additional comments
The parameter dp1_nominal stands for the potential
primary back pressure and must be provided as an absolute value.
By default the secondary pump is parameterized with
a design pressure rise equal to
dp2_nominal + dpBal2_nominal +
max({val.dpValve_nominal + dp1_nominal, val.dp3Valve_nominal + dpBal3_nominal}.
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.