This model is based on the IEC 534/ISA S.75 standards for valve sizing, compressible fluid.

The model optionally supports reverse flow conditions (assuming symmetrical behaviour) or check valve operation, and has been suitably modified to avoid numerical singularities at zero pressure drop.

The model operating range include choked flow operation, due to sonic conditions in the vena contracta.

The flow characteristic can be customised.

**Modelling options**

The actual gas used in the component is determined by the
replaceable `Medium` package. In the case of multiple
component, variable composition gases, the start composition is
given by `Xstart`,whose default value is
`Medium.reference_X`.

The following options are available to specify the valve flow coefficient in fully open conditions:

`CvData = 0`: the flow coefficient is given by the metric Av coefficient`Av`(m^2).`CvData = 1`: the flow coefficient is given by the metric Kv coefficient`Kv`(m^3/h).`CvData = 2`: the flow coefficient is given by the US Cv coefficient`Cv`(USG/min).`CvData = 3`: the flow coefficient must be specified by an additional initial equation (e.g. w=0.5); the start value given by Av is used to initialise the numerical solution of the equation.

The nominal inlet pressure `pnom` and pressure drop
`dpnom` must always be specified; to avoid numerical
singularities, the flow characteristic is modified for pressure
drops less than `b*dpnom` (the default value is 1% of the
nominal pressure drop). Increase this parameter if numerical
instabilities occur in valves with very low pressure drops.

If `CheckValve` is true, then the flow is stopped when
the outlet pressure is higher than the inlet pressure; otherwise,
reverse flow takes place.

The default flow characteristic `FlowChar` is linear;
this can be replaced by any user-defined function (e.g. equal
percentage, quick opening, etc.).

The product Fk*xt is given by the parameter `Fxtnom`, and
is assumed constant by default. The relative change of the xt
coefficient with the valve opening can be specified by customising
the `xtfun` function.

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

Medium | |

FlowChar | |

xtfun |

*15 Mar 2005*by Francesco Casella:

Rewritten with sqrtReg.*19 Nov 2004*by Francesco Casella:

Adapted to Modelica.Media.

`Avnom`removed,`Av`can now be set directly.`Kvnom`and`Cvnom`renamed to`Kv`and`Cv`.

`CvData=3`no longer uses`dpnom`,`wnom`and`rhonom`, and requires an additional initial equation to set the flow coefficient based on the initial working conditions.*5 Mar 2004*by Francesco Casella:

First release.

Generated at 2020-04-08T01:39:33Z by OpenModelicaOpenModelica 1.16.0~dev-268-gc5be668 using GenerateDoc.mos