Buildings.Fluids.Delays

Package Content

Name	Description
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

Type	Name	Default	Description
replaceable package Medium		PartialMedium	Medium in the component
Integer	nP	2	Number of ports
Boolean	steadyState	false	Set to true for steady state model
Nominal condition
Time	tau	60	Time constant at nominal flow [s]
MassFlowRate	m0_flow		Mass flow rate [kg/s]
Initialization
Temp	initType	Types.Init.NoInit	Initialization option
AbsolutePressure	p_start	Medium.p_default	Start value of pressure [Pa]
Boolean	use_T_start	true	= true, use T_start, otherwise h_start
Temperature	T_start	if use_T_start then Medium.T...	Start value of temperature [K]
SpecificEnthalpy	h_start	if use_T_start then Medium.s...	Start value of specific enthalpy [J/kg]
MassFraction	X_start[Medium.nX]	Medium.X_default	Start value of mass fractions m_i/m [kg/kg]

Connectors

Type	Name	Description
FluidPort_a	port[nP]	Fluid port
HeatPort_a	thermalPort	Thermal 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;