Hess Law Applicability to Heterogeneous Combustion Reactions Resulting to Non-Monotonicity of Enthalpy Distribution in Them

Authors

  • I. A. Filimonov Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Academician Osipyan str., 8, Chernogolovka, Moscow Region, 142432, Russia
  • I. I. Filimonova Gubkin Russian State University of Oil and Gas (National Research University), Leninskii av. 65, build 1, Moscow, 119991, Russia

DOI:

https://doi.org/10.37256/est.3220221301

Keywords:

potential enthalpy, independence on reaction way, diffusion coefficients, Lewis numbers

Abstract

The definition of reaction irreversibility (reversibility) available now in literature does not allow for determining this reaction peculiarity before a practice. Moreover, in mathematical terms, such a definition is not universal and leads actually to the denial of any similarity in physicochemical processes, in particular in combustion waves. We have considered the irreversibility of reactions from the mathematical viewpoint as independence of a reaction rate on the concentration of products directly. As a result, in terms of Lei numbers, we have formulated conditions sufficient for the enthalpy of reagents to be a complete differential (or a thermodynamic potential) and independent of the reaction path. And conversely, the conditions necessary for that enthalpy of reagents are significantly dependent on the reaction path (Le ≌ 1). A comparison of the conclusions we obtained with the data from experiments available in the literature showed a good agreement with them and put an edge on the question of determining the irreversibility (reversibility) of reactions in the scientific community. We have shown that the small values of the diffusion coefficients of reagents Di compared to the thermal diffusivity coefficient κ, and with them, the corresponding small Lewis numbers (Lei = Di/κ << 1) for the most heterogeneous combustion synthesis systems, are the sufficient conditions for the enthalpy of reactions (H) to be a complete differential of the systems states and, vice versa, a strong similarity appears between the enthalpy and concentration fields at Le ≌ 1.

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Published

2022-05-23

How to Cite

[1]
I. A. Filimonov and I. I. Filimonova, “Hess Law Applicability to Heterogeneous Combustion Reactions Resulting to Non-Monotonicity of Enthalpy Distribution in Them”, Engineering Science &amp; Technology, vol. 3, no. 2, pp. 188–193, May 2022.