Pressure Difference Source (MA)

Source of differential pressure.

blockType: AcausalFoundation.MoistAir.Sources.PressureDifference

Controlled Pressure Difference Source (MA)

Path in the library:

/Physical Modeling/Fundamental/Moist Air/Sources/Controlled Pressure Difference Source (MA)

Pressure Difference Source (MA)

Path in the library:

/Physical Modeling/Fundamental/Moist Air/Sources/Pressure Difference Source (MA)

Description

The Pressure Difference Source (MA) unit is an ideal source of mechanical energy in a wet air network. The source can maintain a constant or variable differential pressure at its ports regardless of the mass flow rate through the source. There is no gas resistance and no heat exchange with the environment. A positive value of the differential pressure causes the pressure at port B to be greater than the pressure at port A.

Conservation of mass

where

- mass flow rate;
The lower indices and indicate ports A and B respectively;
Lower indices and indicate water vapour and gas impurity properties respectively;

Energy balance

where and are the energy flow through ports A and B respectively.

If the source does not perform any work (for the parameter Isentropic power added) switched off, then .

If the source is isoentropic (for the parameter Isentropic power added) turned on, then:

where

The enthalpies of the mixtures, and , are bounded by isoentropic dependence, i.e., there is no entropy change:

The value given by the parameters Pressure differential or the input signal P of the source is of the form:

Assumptions and limitations

There are no irreversible losses.
No heat exchange with the environment.

Ports

Conserving

# A — source input
moist air

Details

Wet air port. Positive pressure drop causes the pressure at port B to be greater than the pressure at port A.

Program usage name

inlet

# B — source input
moist air

Details

Wet air port. Positive pressure drop causes the pressure at port B to be greater than the pressure at port A.

Program usage name

outlet

Input

# P — differential pressure setting signal, Pa
scalar

Details

An input port that determines the wet air pressure differential at the source. A positive signal at port P causes the pressure at port B to be greater than the pressure at port A.

Dependencies

To use this port, select the checkbox Controlled source.

Data types	`Float64`.
Complex numbers support	No

Parameters

# Controlled source — whether the differential pressure is set by the input signal

Details

Defines how the differential pressure is set:

If the checkbox is selected, the differential pressure is set by the input signal P.
If unchecked, the constant differential pressure is set by the parameters Pressure differential.

Default value	`—`
Program usage name	`controlled`
Evaluatable	No

# Pressure differential — constant pressure drop
Pa | GPa | MPa | atm | bar | kPa | ksi | psi | uPa | kbar

Details

The pressure drop of the moist air mixture at the source ports.

Dependencies

To use this parameter, uncheck Controlled source.

Units	`Pa` \| `GPa` \| `MPa` \| `atm` \| `bar` \| `kPa` \| `ksi` \| `psi` \| `uPa` \| `kbar`
Default value	`0.0 MPa`
Program usage name	`delta_p_const`
Evaluatable	Yes

# Isentropic power added — whether the source is doing isoentropic work

Details

Sets whether the source performs isoentropic work with moist air flow:

If checked, the source performs isoentropic work with moist air to maintain the specified differential pressure. Use this parameter to represent an ideal pump or compressor and to properly account for energy input and output, especially in closed loop systems.
If unchecked, the source does not perform any work on the flow, either adding or removing power, regardless of the pressure differential created by the source. Use this option to set the desired flow condition upstream of the system without affecting the flow temperature.

Default value	`true (switched on)`
Program usage name	`isentropic`
Evaluatable	No

# Cross-sectional area at port A — cross-sectional area normal to the flow path at the port A
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Cross-sectional area normal to the flow path at port A.

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	`inlet_area`
Evaluatable	Yes

# Cross-sectional area at port B — cross-sectional area normal to the flow path at the port B
m^2 | cm^2 | ft^2 | in^2 | km^2 | mi^2 | mm^2 | um^2 | yd^2

Details

Cross-sectional area normal to the flow path at port B.

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	`outlet_area`
Evaluatable	Yes