Calculating high-temperature thermodynamic properties of diatomics in air: Evaluation and accuracy assessment

Construction of a set of thermodynamic properties for air at high temperature is required for accurate modeling of hypersonic flow phenomena. Here we concentrate on the main diatomic species in air: N2, O2 and NO, and we use both state-sum and virial coefficient methods to calculate thermodynamic properties from 200K to 14,000K. We examine the results of these calculations and compare and contrast both methods, and also compare our results with those of other workers. Finally, we assess the accuracy one can realistically expect to obtain for these diatomic properties as the temperature increases to 14,000K and beyond, and the practical implications of these accuracy limitations.