modelTwoPortHeatMassExchanger

Partial model transporting one fluid stream with storing mass or energy

Extends from Buildings.Fluid.Interfaces.PartialTwoPortInterface, Buildings.Fluid.Interfaces.TwoPortFlowResistanceParameters.

Information

This component transports one fluid stream. It provides the basic model for implementing dynamic and steady-state models that exchange heat and water vapor with the fluid stream. The model also computes the pressure drop due to the flow resistance. By setting the parameter dp_nominal=0, the computation of the pressure drop can be avoided. The variable vol.heatPort.T always has the value of the temperature of the medium that leaves the component. For the actual temperatures at the port, the variables sta_a.T and sta_b.T can be used. These two variables are provided by the base class Buildings.Fluid.Interfaces.PartialTwoPortInterface.

For models that extend this model, see for example

Implementation

The variable names follow the conventions used in Modelica.Fluid.Examples.HeatExchanger.BaseClasses.BasicHX .

Parameters

TypeNameDefaultDescription
BooleanhomotopyInitializationtrue= true, use homotopy method
Dynamics › Nominal condition
Modelica.Units.SI.Timetau30Time constant at nominal flow (if energyDynamics <> SteadyState)
Dynamics › Conservation equations
Modelica.Fluid.Types.DynamicsenergyDynamicsModelica.Fluid.Types.Dynamics.DynamicFreeInitialType of energy balance: dynamic (3 initialization options) or steady state
Initialization
Medium.AbsolutePressurep_startMedium.p_defaultStart value of pressure
Medium.TemperatureT_startMedium.T_defaultStart value of temperature
Medium.MassFraction[Medium.nX]X_startMedium.X_defaultStart value of mass fractions m_i/m
Medium.ExtraProperty[Medium.nC]C_startfill(0, Medium.nC)Start value of trace substances

Components

TypeNameDefaultDescription
Buildings.Fluid.MixingVolumes.MixingVolumevol
Buildings.Fluid.FixedResistances.PressureDroppreDroFlow resistance

Revisions

  • March 3, 2022, by Michael Wetter:
    Removed massDynamics.
    This is for issue 1542.
  • April 14, 2020, by Michael Wetter:
    Changed homotopyInitialization to a constant.
    This is for IBPSA, #1341.
  • December 1, 2016, by Michael Wetter:
    Updated model as use_dh is no longer a parameter in the pressure drop model.
    This is for #480.
  • January 26, 2016, by Michael Wetter:
    Added final quantity=Medium.substanceNames for X_start.
  • May 6, 2015, by Michael Wetter:
    Added missing propagation of allowFlowReversal to instance vol. This is for issue #412.
  • May 1, 2015, by Marcus Fuchs:
    Fixed links in documentation.
  • October 6, 2014, by Michael Wetter:
    Changed medium declaration in pressure drop element to be final.
  • May 28, 2014, by Michael Wetter:
    Removed annotation(Evaluate=true) for parameter tau. This is needed to allow changing the time constant after translation.
  • November 12, 2013, by Michael Wetter:
    Removed import Modelica.Constants statement.
  • October 8, 2013, by Michael Wetter:
    Removed parameter show_V_flow.
  • December 14, 2012 by Michael Wetter:
    Renamed protected parameters for consistency with the naming conventions.
  • October 17, 2012, by Michael Wetter:
    Fixed broken link in documentation.
  • February 3, 2012, by Michael Wetter:
    Removed assignment of m_flow_small as it is no longer used in the pressure drop model.
  • January 15, 2011, by Michael Wetter:
    Fixed wrong class reference in information section.
  • September 13, 2011, by Michael Wetter:
    Changed assignment of vol(mass/energyDynamics=...) as the previous assignment caused a non-literal start value that was ignored.
  • July 29, 2011, by Michael Wetter:
    Added start value for outflowing enthalpy.
  • July 11, 2011, by Michael Wetter:
    Changed parameterization of fluid volume so that steady-state balance is used when tau = 0.
  • May 25, 2011, by Michael Wetter:
    Removed temperature sensor and changed implementation of fluid volume to allow use of this model for the steady-state and dynamic humidifier Buildings.Fluid.MassExchangers.HumidifierPrescribed.
  • March 25, 2011, by Michael Wetter:
    Added homotopy operator.
  • March 21, 2010 by Michael Wetter:
    Changed pressure start value from system.p_start to Medium.p_default since HVAC models may have water and air, which are typically at different pressures.
  • April 13, 2009, by Michael Wetter:
    Added model to compute flow friction.
  • January 29, 2009 by Michael Wetter:
    First implementation.