modelPartialTwoPortTransport

Partial element transporting fluid between two ports without storage of mass or energy
Diagram of PartialTwoPortTransportOpen the diagram

Extends from Buildings.Fluid.Interfaces.PartialTwoPort (Partial component with two ports).

Information

This component transports fluid between its two ports, without storing mass or energy. Energy may be exchanged with the environment though, e.g., in the form of work. PartialTwoPortTransport is intended as base class for devices like orifices, valves and simple fluid machines.

Three equations need to be added by an extending class using this component:

  • The momentum balance specifying the relationship between the pressure drop dp and the mass flow rate m_flow,
  • port_b.h_outflow for flow in design direction, and
  • port_a.h_outflow for flow in reverse direction.

Moreover appropriate values shall be assigned to the following parameters:

  • dp_start for a guess of the pressure drop
  • m_flow_small for regularization of zero flow.

Implementation

This is similar to Modelica.Fluid.Interfaces.PartialTwoPortTransport except that it does not use the outer system declaration. This declaration is omitted as in building energy simulation, many models use multiple media, and in practice, users have not used this global definition to assign parameters.

Parameters

TypeNameDefaultDescription
Assumptions
BooleanallowFlowReversal (from PartialTwoPort)true= false to simplify equations, assuming, but not enforcing, no flow reversal
Advanced
Modelica.Units.SI.PressureDifferencedp_start0Guess value of dp = port_a.p - port_b.p
Medium.MassFlowRatem_flow_start0Guess value of m_flow = port_a.m_flow
Medium.MassFlowRatem_flow_smallSmall mass flow rate for regularization of zero flow
Advanced › Diagnostics
Booleanshow_Ttrue= true, if temperatures at port_a and port_b are computed
Booleanshow_V_flowtrue= true, if volume flow rate at inflowing port is computed

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)

Components

TypeNameDefaultDescription
Medium.MassFlowRatem_flowMass flow rate in design flow direction
Modelica.Units.SI.PressureDifferencedpPressure difference between port_a and port_b (= port_a.p - port_b.p)
Modelica.Units.SI.VolumeFlowRateV_flowm_flow/Modelica.Fluid.Utilities.regStep(m_flow, Medium.density(Medium.setState_phX(p = port_a.p, h = inStream(port_a.h_outflow), X = inStream(port_a.Xi_outflow))), Medium.density(Medium.setState_phX(p = port_b.p, h = inStream(port_b.h_outflow), X = inStream(port_b.Xi_outflow))), m_flow_small)Volume flow rate at inflowing port (positive when flow from port_a to port_b)
Medium.Temperatureport_a_TModelica.Fluid.Utilities.regStep(port_a.m_flow, Medium.temperature(Medium.setState_phX(p = port_a.p, h = inStream(port_a.h_outflow), X = inStream(port_a.Xi_outflow))), Medium.temperature(Medium.setState_phX(port_a.p, port_a.h_outflow, port_a.Xi_outflow)), m_flow_small)Temperature close to port_a, if show_T = true
Medium.Temperatureport_b_TModelica.Fluid.Utilities.regStep(port_b.m_flow, Medium.temperature(Medium.setState_phX(p = port_b.p, h = inStream(port_b.h_outflow), X = inStream(port_b.Xi_outflow))), Medium.temperature(Medium.setState_phX(port_b.p, port_b.h_outflow, port_b.Xi_outflow)), m_flow_small)Temperature close to port_b, if show_T = true

Revisions

  • March 30, 2021, by Michael Wetter:
    Added annotation HideResult=true.
    This is for IBPSA, #1459.
  • September 15, 2016, by Michael Wetter:
    Removed wrong annotation, which caused an error in the pedantic model check of Dymola 2017 FD01. This is for #516.
  • January 22, 2016, by Henning Francke:
    Corrected type declaration of pressure. This is for #404.
  • November 19, 2015, by Michael Wetter:
    Removed assignments of parameters port_a_exposesState and port_b_exposesState in base class. This is for #351.
  • August 15, 2015, by Filip Jorissen:
    Implemented more efficient computation of port_a.Xi_outflow and port_a.C_outflow when allowFlowReversal=false. This is for #305.
  • June 6, 2015, by Michael Wetter:
    Removed protected conditional variables state_a and state_b, as they were used outside of a connect statement, which causes an error during pedantic model check in Dymola 2016. This fixes #128.
  • April 1, 2015, by Michael Wetter:
    Made computation of state_a and state_p conditional on show_T or show_V_flow. This avoids computing temperature from enthalpy if temperature is a state of the medium, and the result is not used.
  • October 21, 2014, by Michael Wetter:
    Revised implementation.
  • October 20, 2014, by Filip Jorisson:
    First implementation.