Modelica.Fluid.Valves

Information

Package Content

Name	Description
ValveIncompressible	Valve for (almost) incompressible fluids
ValveVaporizing	Valve for possibly vaporizing (almost) incompressible fluids, accounts for choked flow conditions
ValveCompressible	Valve for compressible fluids, accounts for choked flow conditions
ValveLinear	Valve for water/steam flows with linear pressure drop
ValveDiscrete	Valve for water/steam flows with linear pressure drop
BaseClasses	Base classes used in the Valves package (only of interest to build new component models)

Modelica.Fluid.Valves.ValveIncompressible

Information

Valve model according to the IEC 534/ISA S.75 standards for valve sizing, incompressible fluids.< /p>

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

This model assumes that the fluid has a low compressibility, which is always the case for liquids. It can also be used with gases, provided that the pressure drop is lower than 0.2 times the absolute pressure at the inlet, so that the fluid density does not change much inside the valve.

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

Name	Description
replaceable package Medium	Medium in the component
replaceable function valveCharacteristic	Inherent flow characteristic
Flow Coefficient
CvData	Selection of flow coefficient
Av	Av (metric) flow coefficient [m2]
Kv	Kv (metric) flow coefficient [m3/h]
Cv	Cv (US) flow coefficient [USG/min]
Nominal operating point
dp_nominal	Nominal pressure drop [Pa]
m_flow_nominal	Nominal mass flowrate [kg/s]
rho_nominal	Nominal inlet density [kg/m3]
opening_nominal	Nominal opening
Filtered opening
filteredOpening	= true, if opening is filtered with a 2nd order CriticalDamping filter
riseTime	Rise time of the filter (time to reach 99.6 % of an opening step) [s]
leakageOpening	The opening signal is limited by leakageOpening (to improve the numerics)
Assumptions
allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
checkValve	Reverse flow stopped
Advanced
dp_start	Guess value of dp = port_a.p - port_b.p [Pa]
m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
use_Re	= true, if turbulent region is defined by Re, otherwise by m_flow_small
Diagnostics
show_T	= true, if temperatures at port_a and port_b are computed
show_V_flow	= true, if volume flow rate at inflowing port is computed

Connectors

Name	Description
port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
opening	Valve position in the range 0..1
opening_filtered	Filtered valve position in the range 0..1

Modelica.Fluid.Valves.ValveVaporizing

Information

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

Name	Description
replaceable package Medium	Medium in the component
replaceable function valveCharacteristic	Inherent flow characteristic
Fl_nominal	Liquid pressure recovery factor
replaceable function FlCharacteristic	Pressure recovery characteristic
Flow Coefficient
CvData	Selection of flow coefficient
Av	Av (metric) flow coefficient [m2]
Kv	Kv (metric) flow coefficient [m3/h]
Cv	Cv (US) flow coefficient [USG/min]
Nominal operating point
dp_nominal	Nominal pressure drop [Pa]
m_flow_nominal	Nominal mass flowrate [kg/s]
rho_nominal	Nominal inlet density [kg/m3]
opening_nominal	Nominal opening
Filtered opening
filteredOpening	= true, if opening is filtered with a 2nd order CriticalDamping filter
riseTime	Rise time of the filter (time to reach 99.6 % of an opening step) [s]
leakageOpening	The opening signal is limited by leakageOpening (to improve the numerics)
Assumptions
allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
checkValve	Reverse flow stopped
Advanced
dp_start	Guess value of dp = port_a.p - port_b.p [Pa]
m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
use_Re	= true, if turbulent region is defined by Re, otherwise by m_flow_small
Diagnostics
show_T	= true, if temperatures at port_a and port_b are computed
show_V_flow	= true, if volume flow rate at inflowing port is computed

Connectors

Name	Description
replaceable package Medium	Medium in the component
port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
opening	Valve position in the range 0..1
opening_filtered	Filtered valve position in the range 0..1
replaceable function FlCharacteristic	Pressure recovery characteristic

Modelica.Fluid.Valves.ValveCompressible

Information

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

Name	Description
replaceable package Medium	Medium in the component
replaceable function valveCharacteristic	Inherent flow characteristic
Fxt_full	Fk*xt critical ratio at full opening
replaceable function xtCharacteristic	Critical ratio characteristic
Flow Coefficient
CvData	Selection of flow coefficient
Av	Av (metric) flow coefficient [m2]
Kv	Kv (metric) flow coefficient [m3/h]
Cv	Cv (US) flow coefficient [USG/min]
Nominal operating point
dp_nominal	Nominal pressure drop [Pa]
m_flow_nominal	Nominal mass flowrate [kg/s]
rho_nominal	Nominal inlet density [kg/m3]
opening_nominal	Nominal opening
p_nominal	Nominal inlet pressure [Pa]
Filtered opening
filteredOpening	= true, if opening is filtered with a 2nd order CriticalDamping filter
riseTime	Rise time of the filter (time to reach 99.6 % of an opening step) [s]
leakageOpening	The opening signal is limited by leakageOpening (to improve the numerics)
Assumptions
allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
checkValve	Reverse flow stopped
Advanced
dp_start	Guess value of dp = port_a.p - port_b.p [Pa]
m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
use_Re	= true, if turbulent region is defined by Re, otherwise by m_flow_small
Diagnostics
show_T	= true, if temperatures at port_a and port_b are computed
show_V_flow	= true, if volume flow rate at inflowing port is computed

Connectors

Name	Description
port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
opening	Valve position in the range 0..1
opening_filtered	Filtered valve position in the range 0..1
replaceable function xtCharacteristic	Critical ratio characteristic

Modelica.Fluid.Valves.ValveLinear

Information

This very simple model provides a pressure drop which is proportional to the flowrate and to the opening input, without computing any fluid property. It can be used for testing purposes, when a simple model of a variable pressure loss is needed.

A medium model must be nevertheless be specified, so that the fluid ports can be connected to other components using the same medium model.

The model is adiabatic (no heat losses to the ambient) and neglects changes in kinetic energy from the inlet to the outlet.

Parameters

Name	Description
replaceable package Medium	Medium in the component
m_flow_nominal	Nominal mass flowrate at full opening [kg/s]
Nominal operating point
dp_nominal	Nominal pressure drop at full opening [Pa]
Assumptions
allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
dp_start	Guess value of dp = port_a.p - port_b.p [Pa]
m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
show_T	= true, if temperatures at port_a and port_b are computed
show_V_flow	= true, if volume flow rate at inflowing port is computed

Connectors

Name	Description
port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
opening	=1: completely open, =0: completely closed

Modelica.Fluid.Valves.ValveDiscrete

Information

This very simple model provides a (small) pressure drop which is proportional to the flowrate if the Boolean open signal is true. Otherwise, the mass flow rate is zero. If opening_min > 0, a small leakage mass flow rate occurs when open = false.

This model can be used for simplified modelling of on-off valves, when it is not important to accurately describe the pressure loss when the valve is open. Although the medium model is not used to determine the pressure loss, it must be nevertheless be specified, so that the fluid ports can be connected to other components using the same medium model.

The model is adiabatic (no heat losses to the ambient) and neglects changes in kinetic energy from the inlet to the outlet.

In a diagram animation, the valve is shown in "green", when it is open.

Parameters

Name	Description
replaceable package Medium	Medium in the component
m_flow_nominal	Nominal mass flowrate at full opening=1 [kg/s]
opening_min	Remaining opening if closed, causing small leakage flow
Nominal operating point
dp_nominal	Nominal pressure drop at full opening=1 [Pa]
Assumptions
allowFlowReversal	= true to allow flow reversal, false restricts to design direction (port_a -> port_b)
Advanced
dp_start	Guess value of dp = port_a.p - port_b.p [Pa]
m_flow_start	Guess value of m_flow = port_a.m_flow [kg/s]
m_flow_small	Small mass flow rate for regularization of zero flow [kg/s]
Diagnostics
show_T	= true, if temperatures at port_a and port_b are computed
show_V_flow	= true, if volume flow rate at inflowing port is computed

Connectors

Name	Description
port_a	Fluid connector a (positive design flow direction is from port_a to port_b)
port_b	Fluid connector b (positive design flow direction is from port_a to port_b)
open