You can choose whether to use the predefined expressions as given, use parts of a predefined set of expressions, or replace expressions entirely. A few short examples highlight the use of the predefined expressions used in the Transport Expressions and Thermodynamic Expressions sections to enter the thermodynamic properties of carbon monoxide. The sections also illustrate the possibility to adapt to different modeling situations.

Carbon monoxide is part of a reacting mixture. You want to do several things: make use of the predefined expressions of species Cp as an input to the heat capacity of the reacting mixture (Equation 2-71); use the predefined expression h for each species to calculate the heat of reaction (Equation 2-72); and use the predefined expression s for each species to calculate the entropy of reaction (Equation 2-73) and subsequently the equilibrium constant of reaction (See Handling of Equilibrium Reactions).

To accomplish this, enter the seven coefficients of the NASA format, a1 to a7, into the appropriate fields, or import a CHEMKIN Import for Species Properties thermo input file.

Carbon monoxide is part of a reacting mixture. You want to make use of the predefined expressions of species Cp to calculate the heat capacity of the reacting mixture (Equation 2-98).

Polynomials for Cp are available in the literature (Ref. 2, Ref. 3, and Ref. 5) in the frequently used form

You can directly use the predefined expression for the species’ heat capacity, Equation 2-71, also given in the Cp field, by supplying coefficients in the a1 to a5 fields.

You also want to use the predefined expressions h for each species to calculate the heat of reaction (Equation 2-72). An option is to make use of the heat of formation at standard state (298.15 K) to calculate the coefficient a6. Identifying the coefficient a6 of Equation 2-72 is straightforward. In the NASA polynomial format, the species molar enthalpy is related to its heat capacity according to

Inserting Equation 2-71 into Equation 2-74, and comparing the result with Equation 2-72, shows that the term a6 Rg is identified as the species enthalpy of formation at 0 K, that is, h(0). Evaluate h(0) from the species enthalpy of formation at standard state temperature, Tstd = 298.15 K, which is given by

Carbon monoxide is again part of a reacting mixture. It is satisfactory to approximate Cp as being constant. Specify the species enthalpy by making use of the heat of formation at 298 K, h(298), according to the well-known expression