ValveVaporizingValve for possibly vaporizing (almost) incompressible fluids, accounts for choked flow conditions |
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Diagram
Information
This information is part of the Modelica Standard Library maintained by the Modelica Association.
Valve model according to the IEC 534/ISA S.75 standards for valve sizing, incompressible fluid at the inlet, and possibly two-phase fluid at the outlet, including choked flow conditions.
The parameters of this model are explained in detail in PartialValve (the base model for valves).
The model operating range includes choked flow operation, which takes place for low outlet pressures due to flashing in the vena contracta; otherwise, non-choking conditions are assumed.
This model requires a two-phase medium model, to describe the liquid and (possible) two-phase conditions.
The default liquid pressure recovery coefficient Fl is constant and given by the parameter Fl_nominal. The relative change (per unit) of the recovery coefficient can be specified as a given function of the valve opening by replacing the FlCharacteristic function.
If checkValve is false, the valve supports reverse flow, with a symmetric flow characteristic curve. Otherwise, reverse flow is stopped (check valve behaviour).
The treatment of parameters Kv and Cv is explained in detail in the User's Guide.
Parameters (20)
| allowFlowReversal |
Value: system.allowFlowReversal Type: Boolean Description: = true to allow flow reversal, false restricts to design direction (port_a -> port_b) |
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| dp_start |
Value: dp_nominal Type: AbsolutePressure (Pa) Description: Guess value of dp = port_a.p - port_b.p |
| m_flow_start |
Value: m_flow_nominal Type: MassFlowRate (kg/s) Description: Guess value of m_flow = port_a.m_flow |
| m_flow_small |
Value: if system.use_eps_Re then system.eps_m_flow * m_flow_nominal else system.m_flow_small Type: MassFlowRate (kg/s) Description: Small mass flow rate for regularization of zero flow |
| show_T |
Value: true Type: Boolean Description: = true, if temperatures at port_a and port_b are computed |
| show_V_flow |
Value: true Type: Boolean Description: = true, if volume flow rate at inflowing port is computed |
| CvData |
Value: Modelica.Fluid.Types.CvTypes.OpPoint Type: CvTypes Description: Selection of flow coefficient |
| Av |
Value: Type: Area (m²) Description: Av (metric) flow coefficient |
| Kv |
Value: 0 Type: Real Description: Kv (metric) flow coefficient [m3/h] |
| Cv |
Value: 0 Type: Real Description: Cv (US) flow coefficient [USG/min] |
| dp_nominal |
Value: Type: Pressure (Pa) Description: Nominal pressure drop |
| m_flow_nominal |
Value: Type: MassFlowRate (kg/s) Description: Nominal mass flowrate |
| rho_nominal |
Value: Medium.density_pTX(Medium.p_default, Medium.T_default, Medium.X_default) Type: Density (kg/m³) Description: Nominal inlet density |
| opening_nominal |
Value: 1 Type: Real Description: Nominal opening |
| filteredOpening |
Value: false Type: Boolean Description: = true, if opening is filtered with a 2nd order CriticalDamping filter |
| riseTime |
Value: 1 Type: Time (s) Description: Rise time of the filter (time to reach 99.6 % of an opening step) |
| leakageOpening |
Value: 1e-3 Type: Real Description: The opening signal is limited by leakageOpening (to improve the numerics) |
| checkValve |
Value: false Type: Boolean Description: Reverse flow stopped |
| Fl_nominal |
Value: 0.9 Type: Real Description: Liquid pressure recovery factor |
| use_Re |
Value: system.use_eps_Re Type: Boolean Description: = true, if turbulent region is defined by Re, otherwise by m_flow_small |
Connectors (4)
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port_a |
Type: FluidPort_a Description: Fluid connector a (positive design flow direction is from port_a to port_b) |
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port_b |
Type: FluidPort_b Description: Fluid connector b (positive design flow direction is from port_a to port_b) |
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opening |
Type: RealInput Description: Valve position in the range 0..1 |
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opening_filtered |
Type: RealOutput Description: Filtered valve position in the range 0..1 |
Components (5)
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system |
Type: System Description: System wide properties |
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state_a |
Type: ThermodynamicState Description: State for medium inflowing through port_a |
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state_b |
Type: ThermodynamicState Description: State for medium inflowing through port_b |
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filter |
Type: Filter |
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minLimiter |
Type: MinLimiter |