This is the base model for the ValveLiq, ValveLiqChoked, and ValveVap valve models. The model is based on the IEC 534 / ISA S.75 standards for valve sizing.

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.

An optional heat loss to the ambient can be included, proportional to the mass flow rate; Qnom specifies the heat loss at nominal flow rate.

Modelling options

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

The nominal 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; it can be replaced by functions taken from Functions.ValveCharacteristics, or by any suitable user-defined function extending Functions.ValveCharacteristics.baseFun.


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