### 12.1.1. Using a Real Gas Equation of State

It is recommended that one of the Real Gas equations of state (Aungier Redlich Kwong or Peng Robinson) is used because this is the most flexible option in terms of enabling different temperature and pressure ranges. There is no need to deal with .rgp files (discussed below) because the flow solver automatically calculates properties. The implementation of real gas cubic equations of state are discussed in the flow solver theory documentation. For details, see Real Gas Properties in the CFX-Solver Theory Guide. To use cubic equations of state, the following substance dependent quantities are required:

- Critical Temperature

- Critical Pressure

- Critical Volume

- Boiling Temperature

- Acentric Factor

- Zero pressure (Ideal Gas) specific heat capacity

The default pressure range for this option is 0.01 bar to 10 bar and the default temperature range is 100 K to 1000 K.

Many presupplied materials that use the Real Gas equation of state are contained in the MATERIALS-redkw.ccl and MATERIALS-pengrob.ccl files and are grouped into a few different categories. The materials are suitable for dry gas flows or flows with change of phase.

#### 12.1.1.1. Redlich Kwong Dry Steam

Only water vapor appears in this group. This material is suitable for real gas flows of steam.

#### 12.1.1.2. Redlich Kwong Dry Refrigerants

This group contains several refrigerants including , , , , , , , , , , , , , , , , , and .

is modeled using critical point properties, acentric factor and ideal gas specific heat coefficients obtained from NIST REFPROP V7.0 assuming a fixed composition of 50% and 50% by mass

#### 12.1.1.3. Redlich Kwong Dry Hydrocarbons

This group contains a variety of common hydrocarbons including Methane (), Acetylene (), Ethene (), Ethane (), Ethanol (), Propene (), Propane (), 1-Butyne (), Cyclobutane (), Butane (), Pentane (), Benzene (), Hexane (), Toluene (), Octane (), Nonane (), and Decane ().

#### 12.1.1.4. Dry Redlich Kwong

This group contains various pure fluids that do not appear in any of the other groups and includes Argon, Carbon Monoxide, Carbon Dioxide, Chlorine, Deuterium, Fluorine, Hydrogen, Hydrogen Sulfide, Helium, Nitrogen, Neon, Oxygen, Para-Hydrogen, Sulfur Dioxide, and Ozone.

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