modelDensityTwoPort
Ideal two port density sensor
Extends from Buildings.Fluid.Sensors.BaseClasses.PartialDynamicFlowSensor (Partial component to model sensors that measure flow properties using a dynamic model), Modelica.Icons.RoundSensor (Icon representing a round measurement device).
Information
This model outputs the density of the fluid flowing from
port_a to port_b.
The sensor is ideal, i.e., it does not influence the fluid.
If the parameter tau is non-zero, then its output
is computed using a first order differential equation.
Setting tau=0 is not recommend. See
Buildings.Fluid.Sensors.UsersGuide for an explanation.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.Time | tau (from PartialDynamicFlowSensor) | 1 | Time constant at nominal flow rate (use tau=0 for steady-state sensor, but see user guide for potential problems) |
| 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 PartialFlowSensor) | Nominal mass flow rate, used for regularization near zero flow | |
| Advanced | |||
| Modelica.Units.SI.MassFlowRate | m_flow_small (from PartialFlowSensor) | 1E-4*m_flow_nominal | For bi-directional flow, temperature is regularized in the region |m_flow| < m_flow_small (m_flow_small > 0 required) |
| Initialization | |||
| Modelica.Blocks.Types.Init | initType (from PartialDynamicFlowSensor) | Modelica.Blocks.Types.Init.InitialState | Type of initialization (InitialState and InitialOutput are identical) |
| Medium.Density | d_start | Medium.density(state = Medium.setState_pTX(p = p_start, T = T_start, X = X_start)) | Initial or guess value of output (=state) |
| Modelica.Units.SI.Temperature | T_start | Medium.T_default | Temperature used to compute d_start |
| Modelica.Units.SI.Pressure | p_start | Medium.p_default | Pressure used to compute d_start |
| Modelica.Units.SI.MassFraction[Medium.nX] | X_start | Medium.X_default | Mass fraction used to compute d_start |
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) | |
| Modelica.Blocks.Interfaces.RealOutput | d | Density of the passing fluid |
Revisions
-
June 25, 2026, by Michael Wetter:
Addednominalattribute to state variable.
This is for IBPSA, #2132. -
February 25, 2020, by Michael Wetter:
Changed icon to display its operating state.
This is for #1294. -
January 18, 2016 by Filip Jorissen:
Using parametertauInvsince this now exists in Buildings.Fluid.Sensors.BaseClasses.PartialDynamicFlowSensor. This is for #372. -
June 3, 2011 by Michael Wetter:
Revised implementation to add dynamics in such a way that the time constant increases as the mass flow rate tends to zero. This significantly improves the numerics. -
September 29, 2009, by Michael Wetter:
First implementation, based onModelica.Fluid.