WOLFRAM SYSTEMMODELER

ValveCompressible

Valve for compressible fluids, accounts for choked flow conditions

Diagram

Wolfram Language

In[1]:=
SystemModel["Modelica.Fluid.Valves.ValveCompressible"]
Out[1]:=

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, compressible fluid, no phase change, also covering choked-flow conditions.

The parameters of this model are explained in detail in PartialValve (the base model for valves).

This model can be used with gases and vapours, with arbitrary pressure ratio between inlet and outlet.

The product Fk*xt is given by the parameter Fxt_full, and is assumed constant by default. The relative change (per unit) of the xt coefficient with the valve opening can be specified by replacing the xtCharacteristic 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 (21)

allowFlowReversal

Value: system.allowFlowReversal

Type: Boolean

Description: = true to allow flow reversal, false restricts to design direction (port_a -> port_b)

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

p_nominal

Value:

Type: AbsolutePressure (Pa)

Description: Nominal inlet pressure

Fxt_full

Value: 0.5

Type: Real

Description: Fk*xt critical ratio at full opening

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)

port_a

Type: FluidPort_a

Description: Fluid connector a (positive design flow direction is from port_a to port_b)

port_b

Type: FluidPort_b

Description: Fluid connector b (positive design flow direction is from port_a to port_b)

opening

Type: RealInput

Description: Valve position in the range 0..1

opening_filtered

Type: RealOutput

Description: Filtered valve position in the range 0..1

Components (5)

system

Type: System

Description: System wide properties

state_a

Type: ThermodynamicState

Description: state for medium inflowing through port_a

state_b

Type: ThermodynamicState

Description: state for medium inflowing through port_b

filter

Type: Filter

minLimiter

Type: MinLimiter