modelPressureVacuumValve
Extends from FreeFluids.Interfaces.TwoFluidPorts (To be used by equipment with two fluid ports.).
Information
The model is for a pressure/vacuum relief valve for tanks. The model performs no calculation from the media defined, and the supplied density is only used to convert from volumetric flow to mass flow. This can produce innexact results if the pressure (and so the density)is too diferent from the one used for the rating. This could be the case if the pressure in the tank is too high. For vacuum no problem should be expected, as normally we will be taking the gas from the atmosphere.Elevation and specific enthalpy are passed from Port A to Port B, also when the flow is from PortB to PortA. So normally Port A should be connected to the tank, mainly for getting the correct elevation of the port, because specific enthalpy is not usable when the flow is from PortB to A.
If a more flexible model is needed, we can use separate valves, attached to separate ports of the tank. In this case the pressure correction can be applied and the specific enthalpy used.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.AbsolutePressure | pressureSet | 102325 | |
| Fraction | overPressure | 0.1 | as fraction of set pressure |
| Modelica.Units.SI.AbsolutePressure | pressureHysteresis | 500 | hysteresis for revert overpressure valve opening |
| Modelica.Units.SI.VolumeFlowRate | pressureFlow | air flow at the given overpressure | |
| Modelica.Units.SI.AbsolutePressure | vacuumSet | 100325 | |
| Fraction | underPressure | 0.1 | as fraction of set vacuum |
| Modelica.Units.SI.AbsolutePressure | vacuumHysteresis | 500 | hysteresis for revert underpressure valve opening |
| Modelica.Units.SI.VolumeFlowRate | vacuumFlow | air flow at the given underpressure | |
| Modelica.Units.SI.Density | rho | 1.2 | density used for rating |
| Ports links | |||
| Boolean | useElevDifference (from TwoFluidPorts) | true | introduces, or not, an equation for the ports elevation. Use only in one connector |
| FreeFluids.Types.ElevationOption | elevCalcMethod (from TwoFluidPorts) | FreeFluids.Types.ElevationOption.differential | if useElevDifference==true, selects the equation to use: differential, or absolute for PortB |
| Modelica.Units.SI.Length | elevDifference (from TwoFluidPorts) | 0.0 | used only if previously selected. Positive if PortB higher than PortA |
| Modelica.Units.SI.Length | portBelevation (from TwoFluidPorts) | 0.0 | used only if previously selected. |
| Boolean | calcEnthalpyDifference (from TwoFluidPorts) | true | if true, will calculate the enthalpy difference between ports. Use only in one connector |
| Boolean | passComposition (from TwoFluidPorts) | true | if true, the equation PortA.X=PortB.X will be activated |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| FreeFluids.Interfaces.FluidPortA | PortA (from TwoFluidPorts) | ||
| FreeFluids.Interfaces.FluidPortB | PortB (from TwoFluidPorts) |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Modelica.Units.SI.SpecificEnthalpy | Hdiff (from TwoFluidPorts) | specific enthalpy difference: Port B - Port A | |
| Modelica.Units.SI.PressureDifference | Pdiff (from TwoFluidPorts) | pressure difference: Port B - Port A | |
| Boolean | p | ||
| Boolean | v |