Engee documentation

Check Valve (IL)

A check valve in an isothermal liquid network.

check valve il

Description

The Check Valve (IL) unit is a check valve with free flow from port A to port B and restricted flow from port B to port A. When the overpressure at port A or the differential pressure reaches or exceeds the set pressure threshold, the valve starts to open.

Opening parameterization

When the Opening parameterization is set to Linear - Area vs. pressure, the valve opening area is linearly dependent on the opening differential pressure.

*Opening pressure

There are two options for controlling the valve:

  • If the Opening pressure specification is set to Pressure differential, the control pressure is the pressure differential between ports A and B. The valve starts to open when reaches or exceeds the value of Cracking pressure differential.

  • If the Opening pressure specification is set to Pressure at port A, the control pressure is the pressure differential between port A and atmospheric pressure. The valve starts to open when reaches or exceeds the Cracking pressure (gauge) value.

*Opening area and pressure

The linear parameterization of the valve cross-section is as follows

where the normalised pressure is

When the valve is in the nearly open or nearly closed position in the linear parameterization, it is possible to maintain numerical stability in the simulation by adjusting the Smoothing factor parameter. If the Smoothing factor is not zero, a smooth variation of the control pressure between and is ensured.

If the Opening parameterization is set to Tabulated data - Volumetric flow rate vs. pressure, then is the linearly interpolated value of the Opening area vector parameter from the Pressure differential vector parameter and the calculated differential pressure.

*Mass flow equation

Mass conservation equation:

The mass flow rate through the valve is calculated as follows:

where

  • - flow coefficient, the value of the Discharge coefficient parameter;

  • - is the instantaneous opening area of the valve;

  • - Cross-sectional area at ports A and B;

  • - is the average density of the fluid;

  • - pressure difference in the valve .

Critical pressure drop, - pressure drop determined from the value of the critical Reynolds number , given by the Critical Reynolds number parameter, which is the transition point between laminar and turbulent flow:

Pressure loss to account for the pressure drop in the valve due to the reduction in valve area and is calculated as:

Pressure recovery describes the positive change in valve pressure due to an increase in area. To disregard pressure recovery, uncheck the Pressure recovery box. In this case the pressure loss .

Tabular parameterization of the volume flow rate

If the Opening parameterization is set to Tabulated data - Volumetric flow rate vs. pressure, the valve opens according to the user provided tabulated volumetric flow rate and differential pressure data between ports A and B.

The mass flow rate is

where

  • - is the average density of the liquid;

  • - pressure drop in the valve ;

  • where

    • - flow coefficient;

    • - critical Reynolds number;

    • - kinematic viscosity.

In this parameterization and have fixed values of 0.64 and 150 respectively.

With differential pressure values within the tabulated data:

where

  • - is the value of parameter Pressure differential vector;

  • where is the value of the Volumetric flow rate vector parameter.

If during the simulation the value of the pressure drop becomes less than the first element of the Pressure differential vector parameter :

where is the first element of the Volumetric flow rate vector.

If during the simulation the differential pressure becomes greater than the last element of the Pressure differential vector :

where is the last element of the Volumetric flow rate vector parameter.

Opening dynamics

With linear parameterization it is possible to model the opening and closing dynamics of the valve. If this is modelled, a lag is added to the signal pressure value. Then the dynamic signal pressure is used instead of , otherwise is the steady-state pressure. The derivative of the dynamic signal pressure is calculated from the Opening time constant :

By default, the Opening dynamics checkbox is unchecked.

Ports

Non-directional

A - isothermal liquid port
isothermal liquid

Isothermal liquid port, corresponds to the valve inlet.

B - isothermal liquid port
isothermal liquid

Isothermal liquid port, corresponds to the valve outlet.

Parameters

Opening parameterization - method for calculating valve opening
Linear - Area vs. pressure (by default) | Tabulated data - Area vs. pressure | Tabulated data - Volumetric flow rate vs. pressure

Method for calculating valve opening. Options for selection:

  • `Linear - Area vs. pressure' - the valve opening area is linearly dependent on the differential pressure.

  • Tabulated data - Area vs. pressure' - the mass flow rate through the valve is calculated using a table of area values as a function of differential pressure.

  • Tabulated data - Volumetric flow rate vs. pressure - The mass flow rate through the valve is calculated using a table of volumetric flow rates as a function of differential pressure.

Opening pressure specification - differential pressure used as control pressure
`Pressure differential (by default) | Pressure at port A.

Defines the control pressure. The Pressure differential value defines the control pressure as the pressure difference between ports A and B. The `Pressure at port A' value defines the control pressure as the difference between the pressure at port A and the atmospheric pressure.

Dependencies

To use this parameter, set the Opening parameterization parameter to Linear - Area vs. pressure.

Cracking pressure differential - trigger pressure
0.01 MPa (by default) | `positive scalar'.

The pressure above which the valve is actuated. This pressure is set when the control pressure is the differential pressure between ports A and B.

Dependencies

To use this parameter, set the Opening pressure specification parameter to `Pressure differential' and the Opening parameterization parameter to `Linear - Area vs. pressure'.

Cracking pressure (gauge) - tripping pressure
0.1 MPa (by default) | positive scalar.

The overpressure above which the valve is actuated. This pressure is set when the control pressure is the differential pressure between port A and atmospheric pressure.

Dependencies

To use this parameter, set Opening pressure specification to `Pressure at port A' and Opening parameterization to `Linear - Area vs. pressure'.

Maximum opening pressure differential - pressure differential at open valve
0.1 MPa (by default) | positive scalar

Pressure drop at fully open valve.

Dependencies

To use this parameter, set Opening pressure specification to `Pressure differential' and Opening parameterization to `Linear - Area vs. pressure'.

Maximum opening pressure (gauge) - overpressure at open valve
0.2 MPa (by default) | positive scalar

Overpressure when the valve is fully open.

Dependencies

To use this parameter, set Opening pressure specification to `Pressure at port A' and Opening parameterization to `Linear - Area vs. pressure'.

Maximum opening area is the area of the valve fully open
1e-4 m² (by default) | positive scalar

The cross-sectional area of the valve opening in the fully open position.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Linear - Area vs. pressure'.

Leakage area is the clearance area of the valve in the fully closed position
1e-10 m² (by default) | positive scalar.

The sum of all clearances when the valve is in the fully closed position. Any area less than this value equates to the specified leakage area. This parameter contributes to the stability of the numerical solution by maintaining flow continuity.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Linear - Area vs. pressure'.

Pressure differential vector - differential pressure values for tabular parameterization
[0.01:0.01:0.01:0.1…​] MPa (by default) | `vector'.

Vector of differential pressure values for tabular parameterization of the valve opening area. The elements of the vector correspond to the elements of the vector from parameter Opening area vector or from parameter Volumetric flow rate vector, depending on the selected parameterization type. The elements are listed in ascending order and must be greater than 0. Linear interpolation is used between tabulated data points.

Dependencies

To use this parameter, set Opening parameterization to `Tabulated data - Area vs. pressure' or `Tabulated data - Volumetric flow rate vs. pressure'.

Opening area vector - vector of valve opening area values for tabulated parameterization
[1e-10, 1e-05, 2e-05, 3e-05, 4e-05, 5e-05, 6e-05, 7.5e-05, 8.5e-05, 0.0001] m² (by default) | `vector'.

Vector of valve opening area values for tabular parameterization. The values in this vector correspond to the elements of the vector from the Pressure differential vector parameter. The elements are listed in ascending order and must be greater than 0. Linear interpolation is used between the tabular data points.

Dependencies

To use this parameter, set the Opening parameterization parameter to Tabulated data - Area vs. pressure.

Cross-sectional area at ports A and B - area at inlet or outlet of the valve
Inf (By default) | `positive scalar'.

The cross-sectional area at ports A and B inlet and outlet. This area is used when calculating the mass flow rate through the valve.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Linear - Area vs. pressure' or `Tabulated data - Area vs. pressure'.

Discharge coefficient - flow coefficient
0.64 (By default) | positive scalar

The correction factor is the ratio of the actual mass flow rate to the theoretical mass flow rate through the valve.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Linear - Area vs. pressure' or `Tabulated data - Area vs. pressure'.

Critical Reynolds number - upper limit of the Reynolds number for laminar flow
150 (By default) | `positive scalar'.

Upper Reynolds number limit for laminar flow through the valve.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Linear - Area vs. pressure' or `Tabulated data - Area vs. pressure'.

Smoothing factor - numerical smoothing factor
0.01 (by default) | `positive scalar'.

Continuous smoothing factor that provides smooth opening by correcting the valve characteristic in the nearly open and nearly closed positions. Set a non-zero value less than one to increase the stability of the simulation in these modes.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Linear - Area vs. pressure'.

Pressure recovery - account for pressure rise during area expansion
off (By default) | `on

Determines whether pressure rise is taken into account when fluid flows from a smaller cross-sectional area to a larger cross-sectional area.

Dependencies

To use this parameter, set Opening parameterization to `Linear - Area vs. pressure' or `Tabulated data - Area vs. pressure'.

Opening dynamics - take into account the valve opening dynamics
off (By default) | `on

Determines whether the transient effects in the fluid system caused by valve opening should be taken into account. Checking Opening dynamics introduces a first order lag to the valve signal pressure. The Opening time constant parameter determines the opening dynamics.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Linear - Area vs. pressure' or `Tabulated data - Area vs. pressure'.

Opening time constant - valve opening time constant
0.1 s (By default) | on.

A constant that defines the time required for the fluid to reach a steady state when the valve is opened or closed. This parameter defines the opening dynamics.

Dependencies

To use this parameter, set the Opening parameterization parameter to Linear - Area vs. pressure or Tabulated data - Area vs. pressure and check the Opening dynamics checkbox.

Volumetric flow rate vector - vector of volumetric flow rate values for tabular parameterization
[.000358, .045, .11, .191, .284, .39, .505, .63, .764, .905] m3/s (by default) | vector.

Vector of volumetric flow rate values for tabular parameterization. The values in this vector correspond to the elements of the vector from the Pressure differential vector parameter. The elements must be specified in ascending order.

Dependencies

To use this parameter, set the Opening parameterization parameter to `Tabulated data - Volumetric flow rate vs. pressure'.