**Package with delay models**

This package contains components models for transport delays in piping networks.

The model Buildings.Fluid.Delays.DelayFirstOrder approximates transport delays using a first order differential equation.

For a discretized model of a pipe or duct, see Buildings.Fluid.FixedResistances.Pipe.

Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).

Name | Description |
---|---|

DelayFirstOrder | Delay element, approximated by a first order differential equation |

Examples | Collection of models that illustrate model use and test models |

**Delay element, approximated by a first order differential equation**

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

The model consists of a mixing volume with two ports. The size of the
mixing volume is such that at the nominal mass flow rate
`m_flow_nominal`

,
the time constant of the volume is equal to the parameter `tau`

.

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

Extends from Buildings.Fluid.MixingVolumes.MixingVolume (Mixing volume with inlet and outlet ports (flow reversal is allowed)).

Type | Name | Default | Description |
---|---|---|---|

replaceable package Medium | PartialMedium | Medium in the component | |

Volume | V | V_nominal | Volume [m3] |

Nominal condition | |||

MassFlowRate | m_flow_nominal | Nominal mass flow rate [kg/s] | |

Dynamics | |||

Equations | |||

Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Formulation of energy balance |

Dynamics | massDynamics | energyDynamics | Formulation of mass balance |

Real | mSenFac | 1 | Factor for scaling the sensible thermal mass of the volume |

Nominal condition | |||

Time | tau | 60 | Time constant at nominal flow [s] |

Initialization | |||

AbsolutePressure | p_start | Medium.p_default | Start value of pressure [Pa] |

Temperature | T_start | Medium.T_default | Start value of temperature [K] |

MassFraction | X_start[Medium.nX] | Medium.X_default | Start value of mass fractions m_i/m [kg/kg] |

ExtraProperty | C_start[Medium.nC] | fill(0, Medium.nC) | Start value of trace substances |

ExtraProperty | C_nominal[Medium.nC] | fill(1E-2, Medium.nC) | Nominal value of trace substances. (Set to typical order of magnitude.) |

Advanced | |||

MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |

Assumptions | |||

Boolean | allowFlowReversal | true | = true to allow flow reversal in medium, false restricts to design direction (ports[1] -> ports[2]). Used only if model has two ports. |

Heat transfer | |||

Boolean | prescribedHeatFlowRate | false | Set to true if the model has a prescribed heat flow at its heatPort. If the heat flow rate at the heatPort is only based on temperature difference, then set to false. |

Type | Name | Description |
---|---|---|

VesselFluidPorts_b | ports[nPorts] | Fluid inlets and outlets |

HeatPort_a | heatPort | Heat port for sensible heat input |

model DelayFirstOrder
"Delay element, approximated by a first order differential equation"
extends Buildings.Fluid.MixingVolumes.MixingVolume(final V=V_nominal,
final mSenFac=1);
parameter Modelica.SIunits.Time tau = 60 "Time constant at nominal flow";
protected
parameter Modelica.SIunits.Volume V_nominal = m_flow_nominal*tau/rho_default
"Volume of delay element";
end DelayFirstOrder;

Automatically generated Mon Jul 13 14:24:16 2015.