modelEnthalpyFlowRate

Ideal enthalphy 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 enthalphy 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 enthalpy hout that is used to compute the enthalpy flow rate Ḣ = ṁ hout is computed using a first order differential equation. See Buildings.Fluid.Sensors.UsersGuide for an explanation.

For a sensor that measures the latent enthalpy flow rate, use Buildings.Fluid.Sensors.LatentEnthalpyFlowRate.

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.SpecificEnthalpyh_out_startMedium.specificEnthalpy_pTX(p = Medium.p_default, T = Medium.T_default, X = Medium.X_default)Initial or guess value of measured specific enthalpy

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.RealOutputH_flowEnthalpy 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.
  • January 26, 2016, by Michael Wetter:
    Made unit assignment of output signal final.
  • January 18, 2016 by Filip Jorissen:
    Using parameter tauInv since this now exists in Buildings.Fluid.Sensors.BaseClasses.PartialDynamicFlowSensor. This is for #372.
  • August 31, 2013, by Michael Wetter:
    Removed default value tau=0 as the base class already sets tau=1. This change was made so that all sensors use the same default value.
  • 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 can improve the numerics.
  • April 9, 2008 by Michael Wetter:
    First implementation. Implementation is based on enthalpy sensor of Modelica.Fluid.