Interface (2P-MA)

Two-phase fluid and moist air network interface

• Library:

• Simscape / Fluids / Fluid Network Interfaces

• 

Description

The Interface (2P-MA) block represents a flow connection between a two-phase fluid network and moist air network. Pressure, temperature, and mass flow rate are equal at the interface. The block does not transfer the fluid properties of each fluid network across the interface. When moist air leaves port MA, the block assigns the values of the Interface relative humidity and Interface trace gas mass fraction parameters to the signal. However, when moist air enters port MA, the block retains the upstream values.

You can choose whether to maintain constant moisture and trace gas amounts at the interface or to specify them using the W and TG ports respectively. The fluid at the 2P port must remain superheated. You can use the Two-phase fluid superheated vapor check parameter to choose what action the block performs if the fluid does not meet this condition.

Equations

The block conserves mass such that

$${\dot{m}}_{2P}+{\dot{m}}_{MA}=0,$$

where:

• ṁ_2P is the mass flow rate into port 2P.

• ṁ_MA is the mass flow rate into port MA.

The block maintains equal port pressures and temperatures such that

$$\begin{array}{l}{p}_{2P}=p_{MA}\\ T_{2P}=T_{MA}\end{array}$$

The block calculates the energy balance over the interface as

$${\Phi }_{2P}+{\Phi }_{MA}={\dot{m}}_{2P}\left(h_{2P}+\frac{w_{2P}^2}{2}\right)+{\dot{m}}_{MA}\left(h_{MA}+\frac{w_{MA}^2}{2}\right),$$

where:

• Φ_2P is the energy flow rate into port 2P.

• Φ_MA is the energy flow rate into port MA.

• h_2P is the specific enthalpy at port 2P.

• h_MA is the specific enthalpy at port MA.

• v_2P is the specific volume at port 2P.

• v_MA is the specific volume at port MA.

• w_2P is the flow velocity at port 2P.

• w_MA is the flow velocity at port MA.

For a given cross-sectional area, S, the block defines w_2P as

$$w_{2P}=\frac{{\dot{m}}_{2P}{v}_{2P}}{S}.$$

and w_MA as

$$w_{MA}=\frac{{\dot{m}}_{MA}{v}_{MA}}{S},$$

where

$$v_{MA}=\frac{R_I{T}_{MA}}{p_{MA}}.$$

You specify S using the Cross-sectional area at ports 2P and MA parameter. The block computes the specific gas constant of the interface mixture, R_I, as a function of the fluid on either side such that

$$R_I=f\left(R_A,R_W,R_G,x_{WI},x_{GI}\right),$$

where:

• R_A is the dry air specific gas constant.

• R_W is the water vapor specific gas constant.

• R_G is the trace gas specific gas constant.

• x_WI is the interface specific humidity. When the flow exits port MA, the block assigns this value based on the value of the Interface relative humidity parameter or the input that you supply at port W.

• x_GI is the interface trace gas mass fraction. When the flow exits port MA, the block assigns this value based on the value of the Interface trace gas mass fraction parameter or the input that you supply at port TG.

Ports

Input

W — Moisture, unitless

physical signal

Physical signal port associated with the moisture content at the interface.

Dependencies

To enable this port, set Moisture and trace gas specification to Controlled.

TG — Trace gas, unitless

physical signal

Physical signal port associated with the trace gas at the interface.

Dependencies

To enable this port, set Moisture and trace gas specification to Controlled.

Conserving

2P — Two-phase port

two-phase fluid

Two-phase fluid conserving port associated with the two-phase fluid at the interface.

MA — Moist air port

moist air

Moist air conserving port associated with the moist air at the interface.

Parameters

Moisture and trace gas specification — Interface moisture and trace gas control option

Constant (default) | Controlled

Option to maintain a constant interface or to specify the moisture and trace gas amounts via physical signal ports. When you select Controlled, the block exposes the W and TG ports.

Interface moisture specification — Moisture parameterization option

Relative humidity (default) | Specific humidity | Mole fraction | Humidity ratio

Whether to calculate moisture using relative humidity, specific humidity, mole fraction, or humidity ratio.

Interface relative humidity — Relative humidity at interface

0.5 (default) | positive scalar

Relative humidity at the interface. The block uses this value to calculate the moisture.

Dependencies

To enable this parameter, set Interface type to Constant and Moisture specification to Relative humidity.

Interface specific humidity — Specific humidity at interface

0.01 (default) | positive scalar

Specific humidity at the interface. The block uses this value to calculate the moisture.

Dependencies

To enable this parameter, set Interface type to Constant and Moisture specification to Specific humidity.

Interface water vapor mole fraction — Water vapor mole fraction at interface

0.01 (default) | positive scalar

Water vapor mole fraction at the interface. The block uses this value to calculate the moisture.

Dependencies

To enable this parameter, set Interface type to Constant and Moisture specification to Mole fraction.

Interface humidity ratio — Humidity ratio at interface

0.01 (default) | positive scalar

Humidity ratio at the interface. The block uses this value to calculate the moisture.

Dependencies

To enable this parameter, set Interface type to Constant and Moisture specification to Humidity ratio.

Interface trace gas specification — Trace gas parameterization

Mass fraction (default) | Mole fraction

Whether to parameterize the trace gas at the interface using mass fraction or mole fraction.

Interface trace gas mass fraction — Trace gas mass fraction at interface

0.001 (default) | positive scalar

Mass fraction of trace gas at the interface.

Dependencies

To enable this parameter, set Interface type to Constant and Interface trace gas specification to Mass fraction.

Interface trace gas mole fraction — Trace gas mole fraction at interface

0.001 (default) | positive scalar

Mole fraction of trace gas at the interface.

Dependencies

To enable this parameter, set Interface type to Constant and Interface trace gas specification to Mole fraction.

Relative humidity at saturation — Saturation point relative humidity

1 (default) | positive scalar

Relative humidity at the point of saturation.

Cross-sectional area at ports 2P and MA — Port area

0.01 m^2 (default) | positive scalar

Cross-sectional area of the two-phase fluid and moist air ports.

Two-phase fluid superheated vapor check — Two-phase fluid superheated conditions check

None (default) | Warning | Error

Action to perform when the fluid at the interface does not meet superheated conditions.

Inputs outside valid range — Option to monitor or control invalid inputs

Limit to valid values (default) | Warn and limit to valid values | Error

Monitor or control invalid inputs. When you select Limit to valid values, the block saturates the inputs within the bounds. You can choose to have the block issue a warning when it limits the inputs by selecting Warn and limit to valid values, or you can stop the simulation when the block receives invalid inputs by selecting Error.

Dependencies

To enable this parameter, set Interface type to Controlled.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2022a