Pressure Relief Valve (TL)

Safety valve in the heat-conducting liquid network.

blockType: EngeeFluids.ThermalLiquid.Valves.PressureControl.Relief

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

Description

Block Pressure Relief Valve (TL) It is a pressure relief safety valve in a heat-conducting liquid network. The valve is closed when the pressure is less than the set value. When the pressure reaches or exceeds the set pressure value, the valve opens. The installation pressure is either the threshold pressure difference on the valve between ports A and B, or between port A and atmospheric pressure. The control pressure exceeding the set pressure causes the valve to open gradually, which relieves the excess pressure in the fluid network.

Pressure regulation

If for the parameter Opening parameterization the value is set Linear - Area vs. pressure, then the normalized pressure determines the opening area. The normalized pressure is defined as:

where

— control pressure. If for the parameter Pressure control specification the value is set Pressure differential, then the control pressure is . If for the parameter Pressure control specification the value is set Pressure at port A The control pressure is the difference between the pressure at port A and atmospheric pressure;
— installation pressure. If for the parameter Pressure control specification the value is set Pressure differential Then — the value of the Set pressure differential parameter. If for the parameter Pressure control specification the value is set Pressure at port A Then — parameter value Set pressure (gauge);
— the maximum of the pressure control range, defined as , where — parameter value Pressure regulation range.

Parameterization: area depending on pressure

If for the parameter Opening parameterization the value is set Linear - Area vs. pressure or Tabulated data - Area vs. pressure, then the mass flow rate is

where

— flow coefficient, the value of the parameter Discharge coefficient;
— instant opening area of the valve;
— parameter value Cross-sectional area at ports A and B;
— the average density of the liquid;
— pressure drop.

Critical pressure drop — this is the pressure drop determined from the value of the critical Reynolds number , set by the parameter Critical Reynolds number, the transition point of the regime between laminar and turbulent flow. The unit calculates the critical pressure drop as:

where — dynamic viscosity of a thermally conductive liquid.

Pressure loss describes a decrease in pressure in the valve due to a decrease in its area and is calculated as:

Restoring the pressure allows you to account for the positive pressure change in the valve due to the increased area. To ignore pressure recovery, uncheck the box. Pressure recovery. In this case, the pressure loss is .

If for the parameter Opening parameterization the value is set Linear - Area vs. pressure, then the opening area is:

where

— parameter value Leakage area;
— parameter value Maximum opening area.

This figure shows how the unit controls the valve opening area using linear parameterization.

pressure compensator valve il 2

When the valve is in an almost open or almost closed position in linear parameterization, numerical stability can be maintained in the simulation by adjusting the parameter Smoothing factor. If the parameter Smoothing factor is not equal to zero, provides a smooth change in the control pressure between and .

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

where

;
— the value of the parameter Pressure differential vector or Opening pressure (gauge) vector, depending on the value of the parameter Pressure control specification;
— the change in internal pressure at which the valve starts to close when ;
— the value of the Opening area vector parameter.

This figure shows how the unit controls the valve opening area using tabular parameterization.

pressure compensator valve il 4

Parameterization: volumetric flow rate depending on pressure

If for the parameter Opening parameterization the value is set Tabulated data - Volumetric flow rate vs. pressure, then the valve opens in accordance with the tabular data of the volume flow and pressure drop between ports A and B provided by the user.

The mass flow rate is defined as

where

— volume consumption;
— the average density of the liquid.

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

where

Dynamics of the opening

If the check box is selected Opening dynamics, then a delay is introduced into the flow response to the simulated control pressure. Pressure It becomes a dynamic control pressure . The instantaneous change in dynamic control pressure is calculated based on the time constant Opening time constant :

By default, the checkbox Opening dynamics removed.

Energy conservation

The energy conservation equation in the valve has the form:

where

— energy flow entering the valve through port A;
— the flow of energy entering the valve through port B.

Ports

Conserving

# A — thermal liquid port
thermal liquid

Details

Thermal liquid port, corresponds to the valve inlet.

Program usage name

inlet

# B — thermal liquid port
thermal liquid

Details

Thermal liquid port, corresponds to the valve outlet.

Program usage name

outlet

Parameters

# Opening parameterization — valve opening calculation method
Linear - Area vs. pressure | Tabulated data - Area vs. pressure | Tabulated data - Volumetric flow rate vs. pressure

Details

The method of modeling the valve opening. The valve opening is parameterized either linearly or using a table of values that relate the area to the pressure drop.

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	No

# Pressure control specification — the pressure drop used to control the valve
Pressure differential | Pressure at port A

Details

The method of setting the control pressure of the valve. If this parameter is set to Pressure at port A, then the unit uses only the pressure at port A to determine if the flow pressure exceeds the parameter value Set pressure (gauge). If this parameter is set to Pressure differential, then the block uses the parameter value Set pressure differential to determine whether the pressure drop from port A to port B is out of range.

Dependencies

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

Values	`Pressure differential` \| `Pressure at port A`
Default value	`Pressure at port A`
Program usage name	`opening_pressure_type`
Evaluatable	No

# Set pressure (gauge) — excessive pressure at which the opening mechanism is triggered
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The pressure at which the opening mechanism is triggered. The opening area remains variable over the entire valve pressure control range.

Dependencies

To use this parameter, set for the parameter Opening parameterization meaning Linear - Area vs. pressure, and for the parameter Pressure control specification meaning Pressure at port A or set for the parameter Opening parameterization meaning Tabulated data - Volumetric flow rate vs. pressure.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.1 MPa`
Program usage name	`p_set_gauge`
Evaluatable	Yes

# Pressure regulation range — valve operating pressure range
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

Operating pressure range of the valve. The valve starts to open at the set pressure value and fully opens at the maximum operating range. , where .

Dependencies

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

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.15 MPa`
Program usage name	`p_regulation_range`
Evaluatable	Yes

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

Details

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

Dependencies

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

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
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 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

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

Dependencies

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

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`1.0e-10 m^2`
Program usage name	`leakage_area`
Evaluatable	Yes

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

Details

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

Dependencies

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

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

# Discharge coefficient — expense ratio

Details

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

Dependencies

To use this parameter, set for the parameter Opening parameterization meaning 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 the Reynolds number for laminar flow

Details

The upper limit of the Reynolds number for laminar flow through the valve.

Dependencies

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

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

# Smoothing factor — numerical smoothing factor

Details

The continuous smoothing coefficient ensures smooth opening by correcting for the valve characteristics in the almost open and almost 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 for the parameter Opening parameterization meaning Linear - Area vs. pressure or Tabulated data - Area vs. pressure.

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

# Pressure recovery — accounting for increased pressure during expansion of the area

Details

Determines whether an increase in pressure will be taken into account when liquid flows from an area with a smaller cross-sectional area to an area with a larger cross-sectional area.

Dependencies

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

Default value	`false (switched off)`
Program usage name	`pressure_recovery`
Evaluatable	No

# Opening dynamics — consideration of valve opening dynamics

Details

Determines whether to take into account the transient effects in the fluid system caused by the opening of the valve. Check the box Opening dynamics introduces a first-order delay to the valve control pressure. The Opening time constant parameter determines the dynamics of the opening.

Dependencies

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

Default value	`false (switched off)`
Program usage name	`opening_dynamics`
Evaluatable	No

# Set pressure differential — minimum pressure drop
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The minimum pressure difference between ports A and B required to open the valve. If the pressure drop exceeds this value, the valve gradually opens until it reaches a fully open state.

Dependencies

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.0 MPa`
Program usage name	`delta_p_set`
Evaluatable	Yes

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

Details

The time constant used to calculate the delay in the opening dynamics.

Dependencies

To use this option, check the box Opening dynamics.

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

# Pressure differential vector — differential pressure values for tabular parameterization
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

A 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 the parameter Opening area vector or from the Volumetric flow rate vector parameter, depending on the selected parameterization type. The items are listed in ascending order and must be larger. 0. Linear interpolation is used between the points of the tabular data.

The first element of this parameter is the pressure value at which the valve starts to open. The last element is the maximum pressure at which the valve is fully open. The difference between these two values is the valve pressure control range.

Dependencies

To use this parameter:

set for the parameter Opening parameterization meaning Tabulated data - Area vs. pressure, and for the parameter Pressure control specification meaning Pressure differential;
set for the parameter Opening parameterization meaning Tabulated data - Volumetric flow rate vs. pressure.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
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 valve opening area values for tabular parameterization
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

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

Dependencies

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

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

# Opening pressure (gauge) vector — overpressure values for tabular parameterization
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

A vector of overpressure values for tabular parameterization of the valve opening area. The elements of the vector correspond to the elements of the vector from the parameter Opening area vector. The items are listed in ascending order and must be larger. 0. Linear interpolation is used between the points of the tabular data.

Dependencies

To use this parameter, set for the parameter Opening parameterization meaning Tabulated data - Area vs. pressure, and for the parameter Pressure control specification meaning Pressure at port A.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`[0.2, 0.4, 0.6, 0.8, 1.0, 1.2] MPa`
Program usage name	`p_gauge_vector`
Evaluatable	Yes

# Volumetric flow rate vector — vector of volume flow values for tabular parameterization
m^3/s | mm^3/s | cm^3/s | m^3/hr | m^3/min | l/hr | l/min | l/s | gal/hr | gal/min | gal/s | ft^3/hr | ft^3/min | ft^3/s

Details

Vector of volume flow values for tabular parameterization. The values in this vector correspond to the elements of the vector from the parameter Pressure differential vector. The items are listed in ascending order.

Dependencies

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

Units	`m^3/s` \| `mm^3/s` \| `cm^3/s` \| `m^3/hr` \| `m^3/min` \| `l/hr` \| `l/min` \| `l/s` \| `gal/hr` \| `gal/min` \| `gal/s` \| `ft^3/hr` \| `ft^3/min` \| `ft^3/s`
Default value	`[1.0e-9, 3.6e-5, 8.9e-5, 0.00015, 0.00023, 0.00031] m^3/s`
Program usage name	`Vdot_vector`
Evaluatable	Yes

Examples

Recirculating drive with differential cylinders