Engee documentation

Translational Mechanical Converter (MA)

The interface between humid air and translational mechanics networks.

blockType: AcausalFoundation.MoistAir.Elements.TranslationalMechanicalConverter

translational mechanical converter (ma)

Path in the library:

/Physical Modeling/Fundamental/Moist Air/Elements/Translational Mechanical Converter (MA)

Description

Block Translational Mechanical Converter (MA) It is an interface (converter) between a humid air network and a mechanical translational network. The unit converts humid air pressure into mechanical force and vice versa. It can be used as a base for translational gas drives.

The converter contains a variable volume of humid air. The pressure and temperature vary depending on the compressibility and heat capacity of the humid air. Liquid water condenses from the volume of moist air when it reaches saturation. Parameter Mechanical orientation allows you to specify whether an increase in the volume of humid air leads to a positive or negative displacement of port R relative to port C.

Port A is the humid air port corresponding to the input of the converter. Port H is a thermal port connected to the temperature of the humid air inside the converter. Ports R and C are mechanical translational ports corresponding to the stem and body of the converter.

The equations

The block’s equations use these symbols:

  • Lower indexes , and They indicate the properties of dry air, water vapor, and impurity gas, respectively.;

  • Lower index indicates the water vapor saturation level;

  • Lower indexes , and specify the appropriate port;

  • Lower index indicates the properties of the internal volume of humid air;

  • — mass consumption;

  • — energy consumption;

  • — heat consumption;

  • — pressure;

  • ρ — density;

  • — universal gas constant;

  • — the volume of moist air inside the converter;

  • — specific heat capacity at constant volume;

  • — specific enthalpy;

  • — specific internal energy;

  • — mass fraction ( — specific humidity, which is a synonym for the mass fraction of water vapor);

  • — molar fraction;

  • φ — relative humidity;

  • — humidity coefficient;

  • — temperature;

  • — the time.

Conservation of mass and energy

The net consumption of moist air in the volume of the converter is equal to:

,

,

,

,

where

  • — condensation consumption;

  • — the rate of energy loss by condensed water;

  • — the level of energy added by sources of moisture and impurity gases;

  • and — the mass consumption of water and gas, respectively, through the port S. Values , and They are determined by sources of moisture and impurity gases connected to the S port of the converter.

The conservation of water vapor mass relates the mass flow of water vapor to the dynamics of the humidity level in the internal volume of humid air:

ρ .

Similarly, the conservation of impurity gas mass relates the mass flow rate of impurity gas to the dynamics of the impurity gas level in the internal volume of humid air.:

ρ .

The conservation of the mass of the mixture relates the mass flow rate of the mixture to the dynamics of pressure, temperature, and mass fractions of the internal volume of moist air.:

ρρ ,

where — volumetric flow rate of the converter.

Finally, energy conservation relates energy consumption to the dynamics of pressure, temperature, and mass fractions of the internal volume of humid air.:

ρ .

The equation of state relates the density of a mixture to pressure and temperature:

ρ .

The universal gas constant of the mixture is:

.

Converter volume:

ε ,

where

  • — the volume of liquid at which the position of the stem is equal to 0;

  • — the cross-sectional area of the rod;

  • — displacement of the stem;

  • ε — the coefficient of mechanical orientation. If the parameter value is Mechanical orientation Pressure at A causes positive displacement of R relative to C Then ε . If Pressure at A causes negative displacement of R relative to C Then ε .

The position of the rod is zero if the volume of moist air inside the transducer is . Then, depending on the value of the parameter Mechanical orientation, the following is true:

  • If the pressure at point A causes a positive displacement of R relative to C, then the displacement of the rod increases when the volume of humid air increases compared to .

  • If the pressure at point A causes a negative displacement of R relative to C, then the displacement of the rod decreases when the volume of moist air increases compared to .

The balance of forces on the mechanical interface is:

ε ,

where

  • — the power transmitted from port R to port C;

  • — ambient pressure.

The gas and thermal resistances in the converter are not modeled:

,

.

When the volume of humid air reaches saturation, condensation of moisture may occur. The specific humidity at saturation is:

φ ,

where

  • φ — relative humidity at saturation (usually 1);

  • — water vapor saturation pressure corresponding to the temperature .

The condensation rate is:

τρ

where τ — parameter value Condensation time constant.

Condensed water is subtracted from the volume of moist air, as shown in the conservation equations. The energy associated with condensed water is:

,

where — specific enthalpy of evaporation, estimated at .

The amounts of moisture and impurity gases are related to each other as follows:

φ ,

,

,

,

.

Assumptions and limitations

  • The converter housing is absolutely rigid.

  • The gas resistance between the input of the transducer and the volume of humid air is not modeled. Connect the block Variable Local Restriction (MA) or a block Flow Resistance (MA) to port A to simulate the pressure loss associated with the inlet.

  • The thermal resistance between the H port and the volume of humid air is not modeled. Use the thermal library blocks to simulate the thermal resistance between the moist air mixture and the environment, including any thermal effects of the chamber walls.

  • The movable rod operates losslessly.

  • The block does not simulate mechanical effects such as mechanical constraints, friction, and inertia.

Ports

Conserving

# A — humid air inlet
humid air

Details

Humid air port, corresponds to the inverter input.

Program usage name

port

# C — hull
translational mechanics

Details

Mechanical progressive port, corresponds to the inverter housing.

Program usage name

case_flange

# H — internal temperature
`heat

Details

Heat port, related to the temperature of the humid air inside the inverter.

Program usage name

thermal_port

# R — stem
translational mechanics

Details

Mechanical progressive port, corresponds to the rod.

Program usage name

rod_flange

# S — addition or removal of moisture and impurity gases
`moist air

Details

Connect this port to the S port of the unit from the library Moist Air: Sources to add or remove moisture and impurity gases.

Program usage name

source_port

Output

# F — information on pressure, temperature, humidity and amount of impurity gases
`vector'

Details

Output port of the signal; a vector with the following elements: pressure, temperature, humidity level and the amount of impurity gases inside the component. The Measurement Selector (MA) block is used to decompress the vector signal.

Data types

Float64.
Complex numbers support

No

# W — condensation rate
scalar

Details

A signal output port that contains the value of the condensation rate in the converter. If the Condensation on wall surface parameters are enabled, this port reports the total water vapour condensation rate, which includes condensation from the saturated humid air volume as well as condensation on the inverter wall.

Data types

Float64.
Complex numbers support

No

Input

# p — is the displacement of port R relative to port C, rad
scalar

Details

Input signal that transmits position information. Connect this port to the position sensor port p.

Dependencies

To use this port, set the parameters Interface displacement to . Provide input signal.

Data types

Float64.
Complex numbers support

No

Parameters

Main

# Mechanical orientation — converter orientation
Pressure at A causes positive displacement of R relative to C | Pressure at A causes negative displacement of R relative to C

Details

Sets the orientation of the movement of the mechanical part in relation to the change in the volume of moist air:

  • Pressure at A causes positive displacement of R relative to C - an increase in the humid air volume results in a positive displacement of the R port relative to the C port.

  • Pressure at A causes negative displacement of R relative to C - an increase in the volume of humid air results in a negative displacement of port R relative to port C.

Values

Pressure at A causes positive displacement of R relative to C | Pressure at A causes negative displacement of R relative to C
Default value

Pressure at A causes positive displacement of R relative to C
Program usage name

orientation
Evaluatable

No

# Initial interface displacement — initial offset of port R with respect to port C
m | um | mm | cm | km | in | ft | yd | mi | nmi

Details

Initial displacement of port R relative to port C. The value 0 corresponds to the initial volume of moist air equal to Dead volume.

  • If Mechanical orientation has a value of Pressure at A causes positive displacement of R relative to C, the parameters value must be greater than or equal to 0.

  • If Mechanical orientation has the value Pressure at A causes negative displacement of R relative to C, the value of the parameters must be less than or equal to 0.

Units

m | um | mm | cm | km | in | ft | yd | mi | nmi
Default value

0.0 m
Program usage name

delta_p_start
Evaluatable

Yes

# Interface cross-sectional area — area pressurised by moist air
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The area pressurised by moist air to produce a translational force.

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

piston_area
Evaluatable

Yes

# Dead volume — Humid air volume at zero stem displacement
m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3

Details

Volume of humid air at stem displacement equal to 0.

Units

m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3
Default value

1.e-5 m^3
Program usage name

dead_volume
Evaluatable

Yes

# Cross-sectional area at port A — area normal to the flow cross-section at the inlet to the transducer
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 transmitter inlet in the direction normal to the wet air flow path.

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

# Environment pressure specification — method of setting the ambient pressure
Atmospheric pressure | Specified pressure

Details

Sets the method for setting the ambient pressure:

  • Atmospheric pressure - atmospheric pressure.

  • Specified pressure - value set by the parameters Environment pressure.

Values

Atmospheric pressure | Specified pressure
Default value

Atmospheric pressure
Program usage name

environment_type
Evaluatable

No

# Environment pressure — outside pressure
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 outside the transmitter that opposes the pressure of the moist air volume inside the transmitter. A value of 0 indicates that the inverter is operating in vacuum.

Dependencies

Available when parameters Environment pressure specification is set to . Specified 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

0.101325 MPa
Program usage name

environment_pressure
Evaluatable

Yes

Moisture and Trace Gas

# Relative humidity at saturation — Relative humidity above which condensation occurs

Details

Relative humidity above which condensation occurs.

Default value

1.0
Program usage name

RH_saturation
Evaluatable

Yes

# Condensation time constant — condensation time constant
s | ns | us | ms | min | hr | d

Details

A time scale factor characterising the time period for the return of the supersaturated volume of moist air to the saturation level due to condensation of excess moisture.

Units

s | ns | us | ms | min | hr | d
Default value

0.001 s
Program usage name

condensation_time_constant
Evaluatable

Yes

# Moisture and trace gas source — source of moisture and impurity gases
None | Constant | Controlled

Details

This parameter controls the usage of the S port and provides the following options for modelling moisture and impurity gas levels within the unit:

  • None - no moisture or impurity gas is introduced into or extracted from the block. The S port is hidden. This value is used by default.

  • Constant - moisture and impurity gas are fed into or extracted from the unit at a constant flow rate. The same parameters as in the Moisture Source (MA) and Trace Gas Source (MA) units are made available in the unit settings. The S port is hidden.

  • Controlled - Moisture and impurity gas are introduced into or removed from the unit at a time-varying flow rate. Port S is available. Units Moisture Source (MA) and Trace Gas Source (MA) are connected to this port.

Values

None | Constant | Controlled
Default value

None
Program usage name

moisture_trace_gas_source
Evaluatable

No

# Moisture added or removed — add or remove moisture in the form of water vapour or water
Vapor | Liquid

Details

Select whether the unit adds or removes moisture as water vapour or water:

  • Vapor - the enthalpy of added or removed moisture corresponds to the enthalpy of water vapour, which is greater than the enthalpy of water.

  • Liquid - the enthalpy of added or removed moisture corresponds to the enthalpy of water, which is less than the enthalpy of water vapour.

Dependencies

To use this parameter, set the parameter Moisture and trace gas source to . Constant.

Values

Vapor | Liquid
Default value

Vapor
Program usage name

moisture_source_phase
Evaluatable

No

# Rate of added moisture — constant mass flow rate through the source
kg/s | kg/hr | kg/min | g/hr | g/min | g/s | t/hr | lbm/hr | lbm/min | lbm/s

Details

Mass flow rate of moisture through the source.

A positive value adds moisture to the connected humid air network. A negative value removes moisture from this network.

Dependencies

To use this parameter, set the parameter Moisture and trace gas source to Constant.

Units

kg/s | kg/hr | kg/min | g/hr | g/min | g/s | t/hr | lbm/hr | lbm/min | lbm/s
Default value

0.0 kg/s
Program usage name

moisture_mass_flow
Evaluatable

Yes

# Added moisture temperature specification — Moisture temperature setting method
Atmospheric temperature | Specified temperature

Details

Selects the method for setting the moisture temperature:

  • Atmospheric temperature - atmospheric temperature is used.

  • Specified temperature - value is set with the parameters Temperature of added moisture.

Dependencies

To use this parameter, set the Moisture and trace gas source parameters to . Constant.

Values

Atmospheric temperature | Specified temperature
Default value

Atmospheric temperature
Program usage name

moisture_temperature_type
Evaluatable

No

# Temperature of added moisture — moisture temperature
K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR

Details

Enter the moisture temperature. This temperature remains constant during the simulation. The unit only uses this value to estimate the specific enthalpy of added moisture. The specific enthalpy of removed moisture is determined based on the temperature of the connected humid air network.

Dependencies

To use this parameter, set the parameters Added moisture temperature specification to Specified temperature.

Units

K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR
Default value

293.15 K
Program usage name

moisture_temperature
Evaluatable

Yes

# Rate of added trace gas — constant mass flow rate through the source
kg/s | kg/hr | kg/min | g/hr | g/min | g/s | t/hr | lbm/hr | lbm/min | lbm/s

Details

Reflects the mass flow rate of impurity gas through the source. A positive value adds impurity gas to the connected humid air volume. A negative value draws impurity gas from that volume.

Dependencies

To use this parameter, set the Moisture and trace gas source parameters to . Constant.

Units

kg/s | kg/hr | kg/min | g/hr | g/min | g/s | t/hr | lbm/hr | lbm/min | lbm/s
Default value

0.0 kg/s
Program usage name

trace_gas_mass_flow
Evaluatable

Yes

# Added trace gas temperature specification — method for setting the impurity gas temperature
Atmospheric temperature | Specified temperature

Details

Selection of the impurity gas temperature setting method:

  • Atmospheric temperature - atmospheric temperature is used.

  • Specified temperature - value is set with the parameters Temperature of added trace gas.

Dependencies

To use this parameter, set the Moisture and trace gas source parameters to . Constant.

Values

Atmospheric temperature | Specified temperature
Default value

Atmospheric temperature
Program usage name

trace_gas_temperature_type
Evaluatable

No

# Temperature of added trace gas — impurity gas temperature
K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR

Details

Enter the desired temperature of the impurity gas to be added. This temperature remains constant during the simulation. The unit only uses this value to estimate the specific enthalpy of the added impurity gas. The specific enthalpy of the removed impurity gas is determined based on the temperature of the connected wet air volume.

Dependencies

To use this parameter, set the parameter Added trace gas temperature specification to . Specified temperature.

Units

K | degC | degF | degR | deltaK | deltadegC | deltadegF | deltadegR
Default value

293.15 K
Program usage name

trace_gas_temperature
Evaluatable

Yes

Examples