Analysis of Two Methods for Estimating the Temperature Dependence of the Gas-Phase Chemical Reaction Rate Constants

In this paper, the issues of the structural-parametric identification of kinetic models intended for the mathematical modeling of physical and chemical processes in gas dynamics are discussed. Two methods to estimate the temperature dependence of the rate constants of gas-phase chemical reactions are analyzed: the standard model based on the well-known Arrhenius formula and a new one proposed relatively recently. The focus of the article is on the basic parameter of the temperature dependence of the rate constants, i.e., the activation energy. The values of activation energy for combustion reactions of a mixture of hydrogen and oxygen that are obtained by approximation of the experimental data based on the Arrhenius formula, calculations based on the theory of the transition state, and values of activation energy obtained using a new model are compared. According to this model, the activation energy for exothermic reactions is always zero, while the activation energy for endothermic reactions is determined by the difference between the potential energies of the final and initial states in the given reaction and is numerically equal to its absolute value. The application of this method for estimating the activation energy is shown to produce results that are in good agreement with the empirical data.