Buildings.Fluid.Delays
Package with delay models
Information
This package contains component models for transport delays in piping networks.
The model Buildings.Fluid.Delays.DelayFirstOrder approximates transport delays using a first order differential equation.
Extends from Modelica.Icons.VariantsPackage (Icon for package containing variants).
Package Content
| Name | Description |
|---|---|
 DelayFirstOrder
|
Delay element, approximated by a first order differential equation |
 Examples
|
Collection of models that illustrate model use and test models |
Buildings.Fluid.Delays.DelayFirstOrder
Delay element, approximated by a first order differential equation
Information
This model approximates a transport delay using 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 and need not be connnected.
Extends from Buildings.Fluid.MixingVolumes.MixingVolume (Mixing volume with inlet and outlet ports (flow reversal is allowed)).
Parameters
| 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 | |||
| Conservation equations | |||
| Dynamics | energyDynamics | Modelica.Fluid.Types.Dynamic... | Type of energy balance: dynamic (3 initialization options) or steady state |
| Real | mSenFac | 1 | Factor for scaling the sensible thermal mass of the volume |
| Nominal condition | |||
| Time | tau | 60 | Time constant at nominal flow [s] |
| Advanced | |||
| Dynamics | |||
| Dynamics | massDynamics | energyDynamics | Type of mass balance: dynamic (3 initialization options) or steady state, must be steady state if energyDynamics is steady state |
| MassFlowRate | m_flow_small | 1E-4*abs(m_flow_nominal) | Small mass flow rate for regularization of zero flow [kg/s] |
| Boolean | use_C_flow | false | Set to true to enable input connector for trace substance |
| 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.) |
| Assumptions | |||
| Boolean | allowFlowReversal | true | = false to simplify equations, assuming, but not enforcing, no flow reversal. Used only if model has two ports. |
Connectors
| Type | Name | Description |
|---|---|---|
| VesselFluidPorts_b | ports[nPorts] | Fluid inlets and outlets |
| output RealOutput | U | Internal energy of the component [J] |
| output RealOutput | m | Mass of the component [kg] |
| output RealOutput | mXi[Medium.nXi] | Species mass of the component [kg] |
| output RealOutput | mC[Medium.nC] | Trace substance mass of the component [kg] |
| HeatPort_a | heatPort | Heat port for heat exchange with the control volume |
| input RealInput | C_flow[Medium.nC] | Trace substance mass flow rate added to the medium |