Two-Phase Mixtures

In the case of two-phase flows, Autodesk® CFD assumes a homogeneous two-phase mixture. The energy equation that is used is written in terms of enthalpy. Temperature is determined using the thermodynamic tables. Both temperature and enthalpy results can be viewed in the Results dialog task (make sure both quantities are enabled on the Output Quantity dialog on the Solve dialog).

Boundary Conditions

Specify the Quality and static Temperature (as well as the appropriate velocity, flow-rate, or pressure) at all inlets. For example, quality is 0 for 100% liquid.

Note: The Quality boundary conditions are necessary to ensure appropriate solver performance.

Materials

Select Steam (Saturated) or other saturated material from the Fluid list on the Material dialog. If the operating state differs from STP, open the Material Environment dialog from the Material branch of the Design Study bar, and modify the Pressure and Temperature. The properties of the material are determined during the analysis using the thermodynamic tables and the specified environment pressure.

Note: You can only use one two-phase table in a single analysis.

Note: You can create your own thermodynamic tables for use with the material you select. See Thermodynamic Table Data for more information.

Solve

On the Physics tab of the Solve dialog, enable Heat Transfer.
Click the Advanced button, and select Quality.
For incompressible flows, only the temperature and reference pressure affect the fluid properties (including the quality).

Note: For proper performance, the phase-change solver requires the presence of solid elements in your model.