Buildings.Fluids.Delays

Package with delay models

Package Content

NameDescription
Buildings.Fluids.Delays.DelayFirstOrder DelayFirstOrder Delay element, approximated by a first order differential equation


Buildings.Fluids.Delays.DelayFirstOrder Buildings.Fluids.Delays.DelayFirstOrder

Delay element, approximated by a first order differential equation

Buildings.Fluids.Delays.DelayFirstOrder

Information


This model approximates a transport delay using a first order differential equations.

The model is essentially a mixing volume with two ports and a volume that is such that at the nominal mass flow rate m0_flow the time constant of the volume is equal to the parameter tau.

The heat flux connector is optional, it need not be connnected.


Parameters

TypeNameDefaultDescription
replaceable package MediumPartialMediumMedium in the component
IntegernP2Number of ports
BooleansteadyStatefalseSet to true for steady state model
Nominal condition
Timetau60Time constant at nominal flow [s]
MassFlowRatem0_flow Mass flow rate [kg/s]
Initialization
TempinitTypeTypes.Init.NoInitInitialization option
AbsolutePressurep_startMedium.p_defaultStart value of pressure [Pa]
Booleanuse_T_starttrue= true, use T_start, otherwise h_start
TemperatureT_startif use_T_start then Medium.T...Start value of temperature [K]
SpecificEnthalpyh_startif use_T_start then Medium.s...Start value of specific enthalpy [J/kg]
MassFractionX_start[Medium.nX]Medium.X_defaultStart value of mass fractions m_i/m [kg/kg]

Connectors

TypeNameDescription
FluidPort_aport[nP]Fluid port
HeatPort_athermalPortThermal port

Modelica definition

model DelayFirstOrder 
  "Delay element, approximated by a first order differential equation" 
  extends Buildings.Fluids.MixingVolumes.MixingVolume(final V=m0_flow*tau/rho0, nP=2);
  
  parameter Modelica.SIunits.Time tau = 60 "Time constant at nominal flow";
  parameter Modelica.SIunits.MassFlowRate m0_flow(min=0) "Mass flow rate";
  
protected 
   parameter Medium.ThermodynamicState sta0 = Medium.setState_pTX(T=T_start,
         p=p_start, X=X_start[1:Medium.nXi]);
   parameter Modelica.SIunits.Density rho0=Medium.density(sta0) 
    "Density, used to compute fluid volume";
end DelayFirstOrder;

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