.TAeZoSysPro.FluidDynamics.Components.Valves.BaseClasses.PartialDamper

Information

This is the base model for Damper_parallelBlades and Damper_opposedBlades strongly inspired from the PartialValve of Modelica Standard Library (MSL). The model is based on the IEC 534 / ISA-75.01.01-2007 standard for valve sizing.

The model optionally supports reverse flow conditions (assuming symmetrical behaviour) or check valve operation, and has been suitably regularized, compared to the equations in the standard, in order to avoid numerical singularities around zero pressure drop operating conditions.

The model assumes adiabatic operation (no heat losses to the ambient); changes in kinetic energy from inlet to outlet are neglected in the energy balance.

Modelling options

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

• CvData = Modelica.Fluid.Types.CvTypes.Av: The cross section surface area is given by the metric A coefficient (m^2).
• CvData = Modelica.Fluid.Types.CvTypes.Kv: the flow coefficient is given by the metric Kv coefficient (m^3/h).
• CvData = Modelica.Fluid.Types.CvTypes.Cv: the flow coefficient is given by the US Cv coefficient (USG/min).
• CvData = Modelica.Fluid.Types.CvTypes.OpPoint: the flow is computed from the nominal operating point specified by p_nominal, dp_nominal, m_flow_nominal, rho_nominal, opening_nominal.

The nominal conditions (mainly pressure drop dp_nominal and mass flow rate m_flow_nominal) must always be specified;

• To avoid numerical singularities, the flow characteristic is modified for pressure drops less than dp_small. The default value for dp_small is 1% of the nominal pressure drop dp_nominal. Increase dp_small if numerical problems occur in dampers with very low pressure drops
• To be used a guess values. Moreover the homotopy operator used dp_nominal and m_flow_nominal to compute the flow with the 'simplified' solution.

If checkValve is true, then the flow is stopped when the outlet pressure is higher than the inlet pressure; otherwise, reverse flow takes place. Use this option only when needed, as it increases the numerical complexity of the problem.

The valve opening characteristic valveCharacteristic, linear by default, can be replaced by any user-defined function available in the ValveCharacteristics package. Functions provides by the Modelica Standard Library (MSL) are compatible. The characteristics for constant port_a.p and port_b.p pressures with continuously changing opening are shown in the next two figures:

The treatment of parameters Kv and Cv slightly differs from the explaination detailled in the User's Guide and derives more from the standard.

In the above equation, m_flow and p unit are respectively in m3/h and bar.

Where:

• m_flow is the mass flow rate in m3/h
• Y is the expansion factor as defined in the standard
• x is the ratio of pressure differential to upstream absolute pressure (dp /p)
• Fγ is the Specific heat ratio factor (γ/1.4)
• d is the upstream density
• N6 is a constant depending of the chosen coefficient Kv or Cv

Contents

Name	Description
valveCharacteristic	Inherent flow characteristic
Medium	Medium in the component