modelEntropyFlowRate

Ideal entropy flow rate sensor
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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 entropy flow rate of the medium in the flow between fluid ports. The sensor is ideal, i.e., it does not influence the fluid.

If the parameter tau is non-zero, then the measured specific entropy sout that is used to compute the entropy flow rate Ṡ = ṁ sout is computed using a first order differential equation. See Buildings.Fluid.Sensors.UsersGuide for an explanation.

Parameters

TypeNameDefaultDescription
Modelica.Units.SI.Timetau (from PartialDynamicFlowSensor)1Time constant at nominal flow rate (use tau=0 for steady-state sensor, but see user guide for potential problems)
Assumptions
BooleanallowFlowReversal (from PartialTwoPort)true= false to simplify equations, assuming, but not enforcing, no flow reversal
Nominal condition
Modelica.Units.SI.MassFlowRatem_flow_nominal (from PartialFlowSensor)Nominal mass flow rate, used for regularization near zero flow
Advanced
Modelica.Units.SI.MassFlowRatem_flow_small (from PartialFlowSensor)1E-4*m_flow_nominalFor bi-directional flow, temperature is regularized in the region |m_flow| < m_flow_small (m_flow_small > 0 required)
Initialization
Modelica.Blocks.Types.InitinitType (from PartialDynamicFlowSensor)Modelica.Blocks.Types.Init.InitialStateType of initialization (InitialState and InitialOutput are identical)
Modelica.Units.SI.SpecificEntropys_out_startMedium.specificEntropy_pTX(p = Medium.p_default, T = Medium.T_default, X = Medium.X_default)Initial or guess value of measured specific entropy

Connectors

TypeNameDefaultDescription
Modelica.Fluid.Interfaces.FluidPort_aport_a (from PartialTwoPort)Fluid connector a (positive design flow direction is from port_a to port_b)
Modelica.Fluid.Interfaces.FluidPort_bport_b (from PartialTwoPort)Fluid connector b (positive design flow direction is from port_a to port_b)
Modelica.Blocks.Interfaces.RealOutputS_flowEntropy flow rate, positive if from port_a to port_b

Revisions

  • June 25, 2026, by Michael Wetter:
    Added nominal attribute to state variable.
    This is for IBPSA, #2132.
  • October 19, 2020, by Antoine Gautier:
    Changed default value for tau from 1 to 0.
    This is for #1406.
  • February 25, 2020, by Michael Wetter:
    Changed icon to display its operating state.
    This is for #1294.
  • July 29, 2016, by Michael Wetter:
    First implementation based on Buildings.Fluid.Sensors.EnthalpyFlowRate.