### 12.6.1. Superheat Region

The superheat region in Figure 12.7: Representation of Superheat Tables Associated with a Material is represented through the following nine tables as functions of temperature and pressure:

1. : Specific enthalpy.

2. : Speed of sound.

3. : Specific volume.

4. : Specific heat at constant volume.

5. : Specific heat at constant pressure.

6. : Partial derivative of pressure with respect to specific volume at constant temperature.

7. : Specific entropy.

8. : Dynamic viscosity.

9. : Thermal conductivity.

All of the tables, with the exception of dynamic viscosity and thermal conductivity are required. Dynamic viscosity and thermal conductivity can also be specified with constant values in the .rgp file header and as constants or CEL expressions in the CCL material definition. Constant values of dynamic viscosity and thermal conductivity are often acceptable in turbulent flows because turbulent diffusion normally dominates molecular diffusion processes.

The superheat tables, in a discrete manner, represent functions dependent on and and are shown in graphic form in Figure 12.7: Representation of Superheat Tables Associated with a Material, where represents any one of the properties , , , , , , , and . As indicated in Figure 12.7: Representation of Superheat Tables Associated with a Material, for a given material, saturation conditions may run through all of the superheat tables. To handle this case, associated 1D tables (for each 2D superheat table) must be included in the .rgp file and represent and , which are shown as graphs in Figure 12.8: Representation of 1D Tables for a Saturation Property in Terms of Pressure. With these 1D tables, property evaluations near saturation can be consistently handled using bilinear interpolation. If the pressure range of the two-dimensional table goes above the critical pressure then the one-dimensional and curves should be set to and , respectively. It is very important to get this right because the flow solver relies on these data being correct in order to accurately interpolate values from your tables.

Figure 12.7: Representation of Superheat Tables Associated with a Material

Figure 12.8: Representation of 1D Tables for a Saturation Property in Terms of Pressure

Figure 12.9: Representation of 1D Tables for Saturation Temperature in Terms of Pressure

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