Pressure Reducing Valve (TL)

Pressure reducing valve in a thermal liquid network.

blockType: EngeeFluids.ThermalLiquid.Valves.PressureControl.Reducing

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/Physical Modeling/Fluids/Thermal Liquid/Valves & Orifices/Pressure Control Valves/Pressure Reducing Valve (TL)

Description

The Pressure Reducing Valve (TL) unit is a pressure reducing valve in a thermal liquid network. The valve remains open when the pressure at port B is less than the set point. When the pressure at port B reaches or exceeds the set point, the valve closes. The unit is controlled by the difference between the set pressure and the pressure at port B. The unit contains a check valve part that functions identically to the Check Valve (TL) unit when the flow is reversed.

Pressure control

Unit Pressure Reducing Valve (TL) regulates the pressure between the set pressure and the maximum pressure.

The normalised pressure controls the valve cross-sectional area when the parameters Opening parameterization are set to Linear - Area vs. pressure. The normalised pressure represents:

where

- control pressure equal to , where is the atmospheric pressure;
- setting pressure equal to , where is the value of parameters Set pressure (gauge);
- maximum pressure equal to , where is the value of the parameter Pressure regulation range.

Parametrization: area as a function of pressure

If the parameters Opening parameterization are set to Linear - Area vs. pressure or Tabulated data - Area vs. pressure, the mass flow rate through the valve is calculated as follows:

where

- is the flow coefficient, the value of the parameters Discharge coefficient;
- instantaneous valve opening area;
- parameter value Cross-sectional area at ports A and B;
- average density of the liquid;
- pressure difference in the valve .

Critical pressure drop, - pressure drop associated with the value of critical Reynolds number , set by the parameter Critical Reynolds number, which is the point of regime transition between laminar and turbulent flow regimes. The block calculates the critical pressure drop as:

where is the dynamic viscosity of thermal liquid.

The pressure loss takes into account the pressure drop in the valve due to the reduced valve area and is calculated as:

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

If the parameters Opening parameterization is set to . Linear - Area vs. pressure, then the valve cross-sectional area is:

where

- is the value of parameters Leakage area;
- the value of the parameters Maximum opening area.

The figure shows the valve opening characteristics with usage of linear area parameterization.

pressure reducing valve il 1

When the valve is in the nearly open or nearly closed position with linear parameterization, it is possible to maintain numerical stability in the simulation by adjusting the parameter Smoothing factor. If the parameters Smoothing factor is non-zero, a smooth variation of the control pressure and is ensured.

If the parameter Opening parameterization is set to a value of Tabulated data - Area vs. pressure, then the block calculates the opening area as:

where

- control pressure;
;
- is the value of the parameter Pressure at port B (gauge) vector;
- the internal pressure offset at which the valve starts to close when ;
- value of the parameter Opening area vector.

The values and are the first and last elements of the Opening area vector parameters, respectively.

The figure shows the valve opening characteristics with usage of the tabular parameterization.

pressure reducing valve il 2

Parametrization: pressure-dependent volume flow rate

If the parameter Opening parameterization is set to . Tabulated data - Volumetric flow rate vs. pressure, the valve opening is determined according to the user-supplied tabulated volume flow rate and pressure drop between ports A and B. The mass flow rate through the valve is calculated as follows:

where

- volume flow rate;
- average density of the liquid;

The unit calculates the relationship between mass flow rate and pressure using:

where .

Opening dynamics

If the check box Opening dynamics is selected, a delay is introduced in the flow response to the modelled control pressure. The pressure becomes the dynamic control pressure . The instantaneous change in the dynamic control pressure is calculated from the Opening time constant :

By default, the check box Opening dynamics is unchecked.

Energy storage

The energy conservation equation for the valve is as follows:

where

- is the energy flow entering the valve through port A;
- is the energy flow entering the valve through port B.

Ports

Conserving

# A — thermal liquid port
thermal liquid

Details

Thermal liquid port, corresponds to valve inlet A.

Program usage name

inlet

# B — thermal liquid port
thermal liquid

Details

Thermal liquid port, corresponds to valve inlet B.

Program usage name

outlet

Parameters

# Opening parameterization — method of calculating valve opening or closing
Linear - Area vs. pressure | Tabulated data - Area vs. pressure | Tabulated data - Volumetric flow rate vs. pressure

Details

Method for modelling the opening of the valve. Options for selection:

Linear - Area vs. pressure or Tabulated data - Area vs. pressure - valve opening area as a function of the signal pressure.
Tabulated data - Volumetric flow rate vs. pressure - the reference curve of the flow rate and differential pressure of the pressure reducing valve is used.

Values	`Linear - Area vs. pressure` \| `Tabulated data - Area vs. pressure` \| `Tabulated data - Volumetric flow rate vs. pressure`
Default value	`Linear - Area vs. pressure`
Program usage name	`opening_parameterization`
Evaluatable	Yes

# Set pressure (gauge) — overpressure above which the valve is triggered
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

The overpressure above which the valve will actuate. When the pressure in port B reaches this value, the valve begins to close. This parameter shifts the reference curve so that the pressure reducing valve begins to close when the pressure at port B is equal to the set pressure.

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`0.1 MPa`
Program usage name	`p_set_gauge`
Evaluatable	Yes

# Pressure regulation range — pressure control range
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

The operating pressure range of the valve. The pressure control range determines the difference between the parameters Set pressure (gauge) and the maximum operating pressure of the valve.

Dependencies

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

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`0.01 MPa`
Program usage name	`p_regulation_range`
Evaluatable	Yes

# Maximum opening area — fully open valve area
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Cross-sectional area of the valve bore in the fully open position.

Dependencies

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

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`0.0001 m^2`
Program usage name	`max_valve_area`
Evaluatable	Yes

# Leakage area — valve clearance area in fully closed position
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

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 parameter Opening parameterization to the value of Linear - Area vs. pressure.

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`1e-10 m^2`
Program usage name	`leakage_area`
Evaluatable	Yes

# Cross-sectional area at ports A and B — inlet and outlet area of the valve
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

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

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`0.01 m^2`
Program usage name	`port_area`
Evaluatable	Yes

# Discharge coefficient — flow coefficient

Details

Correction factor that takes into account the rarefaction losses in theoretical flows.

Dependencies

To use this parameter, set the parameters Opening parameterization to the value of Linear - Area vs. pressure or Tabulated data - Area vs. pressure.

Default value	`0.64`
Program usage name	`C_d`
Evaluatable	Yes

# Critical Reynolds number — upper limit of Reynolds number for laminar flow

Details

The critical value of the Reynolds number that corresponds to the upper limit of laminar flow through the valve.

Dependencies

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

Default value	`150.0`
Program usage name	`Re_critical`
Evaluatable	Yes

# Smoothing factor — smoothing factor

Details

A continuous smoothing factor that specifies the degree of change in flow response when the valve is 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 parameters Opening parameterization to Linear - Area vs. pressure.

Default value	`0.01`
Program usage name	`smoothing_factor`
Evaluatable	Yes

# Pressure recovery — whether to take into account the pressure increase when the area expands

Details

Whether to take into account the pressure increase when the fluid flows from a region with a smaller cross-sectional area to a region with a larger cross-sectional area.

Dependencies

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

Default value	`false (switched off)`
Program usage name	`pressure_recovery`
Evaluatable	Yes

# Opening dynamics — whether to take into account the flow response to valve opening

Details

Whether to account for transient effects in the fluid system caused by valve opening. Checking Opening dynamics approximates the opening conditions by introducing a first order lag in the flow response. The simulated opening dynamics are controlled by the Opening time constant parameters.

Default value	`false (switched off)`
Program usage name	`opening_dynamics`
Evaluatable	Yes

# Opening time constant — valve opening time constant
d | s | hr | ms | ns | us | min

Details

Time constant by which the delay in the opening dynamics is calculated.

Dependencies

To use this parameter, select the check box Opening dynamics.

Units	`d` \| `s` \| `hr` \| `ms` \| `ns` \| `us` \| `min`
Default value	`0.1 s`
Program usage name	`tau`
Evaluatable	Yes

# Pressure at port B (gauge) vector — vector of overpressure values for the tabular parameterization of the area
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

Overpressure vector for the tabular parameterization of the valve opening area. The elements of the vector must correspond to the elements of the Opening area vector parameters. The elements must be positive and in ascending order. The block uses linear interpolation between data points.

Dependencies

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

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`[0.2, 0.4, 0.6, 0.8, 1.0, 1.2] MPa`
Program usage name	`delta_p_vector`
Evaluatable	Yes

# Opening area vector — vector of opening area values for tabular parameterization
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Valve opening area vector for tabular parameterization of the valve opening area. The elements of the vector must correspond to the elements of the parameter Pressure at Port B (gauge) vector. The elements must be positive and in ascending order. The block uses linear interpolation between data points.

Dependencies

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

Units	`m^2` \| `cm^2` \| `ft^2` \| `in^2` \| `km^2` \| `mi^2` \| `mm^2` \| `um^2` \| `yd^2`
Default value	`[1.0e-5, 8.0e-6, 6.0e-6, 4.0e-6, 2.0e-6, 1.0e-10] m^2`
Program usage name	`valve_area_vector`
Evaluatable	Yes

# Reference pressure at port A (gauge) — port reference pressure A
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

Constant pressure at port A on which the reference curve is based. This value usually corresponds to the maximum operating pressure of the valve. During simulation, the pressure at port A can be any pressure.

Dependencies

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

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`1.5 MPa`
Program usage name	`p_inlet_gauge_reference`
Evaluatable	Yes

# Reference pressure at port B (gauge) vector — port reference pressure B
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

Vector of monotonically decreasing values of pressure at port B on the reference curve as the valve opening area changes. The first element is the reference maximum pressure at which the valve closes completely. The last element is the reference control pressure.

Dependencies

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

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`[1.2, 1.0, 0.8, 0.6, 0.4, 0.2] MPa`
Program usage name	`p_outlet_gauge_reference_vector`
Evaluatable	Yes

# Reference volumetric flow rate vector — vector of volume flow rates for tabular parameterization
m^3/s | m^3/h | cm^3/s | mm^3/s | ft^3/s | lpm | l/s | gpm | gal/s | gal/h

Details

Vector of monotonically increasing reference flow values through the valve. The block uses this curve to calculate the flow coefficient for a varying valve area.

Dependencies

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

Units	`m^3/s` \| `m^3/h` \| `cm^3/s` \| `mm^3/s` \| `ft^3/s` \| `lpm` \| `l/s` \| `gpm` \| `gal/s` \| `gal/h`
Default value	`[1.0e-9, 1.8e-5, 6.6e-5, 0.00013, 0.0002, 0.00028] m^3/s`
Program usage name	`Vdot_reference_vector`
Evaluatable	Yes