Unique Tool for Chemical Thermodynamic and Energy Release Evaluation Announced

ASTM’s CHETAH program is a unique tool for predicting both thermochemical properties and certain reactive chemicals hazards associated with pure chemical, a mixture of chemicals, or a chemical reaction. This is accomplished through knowledge of only the molecular structure(s) of the components involved by an implementation of Benson's method of group additivity. CHETAH is useful for classifying materials for their ability to decompose with violence, for estimating heats of reaction or combustion, for prediction of chemical equilibrium, and for predicting lower flammable limits.

This most updated version of CHETAH Version 11.0 has an improved interface to enhance ease of use. Various property databases have now been reviewed for consistency and accuracy. Updated thermodynamic values are provided for 20 Benson groups based on latest best values in the literature. The database for ideal gas Benson groups has been expanded and now contains 1,165 groups. It is the largest Benson group database known to exist. In all, 66 new groups have been added. 47 groups have been updated or include additional data. Entropy values were predicted and added to the database for many ideal gas Benson groups that were missing such values. This also enables Gibb’s Free Energy calculations for these groups. Output reports have been improved for clarity of presentation. It is now possible to generate pdf format reports direct from the interface as well as Microsoft Word© documents.

Aside from significant improvements from the previous version, NASA Lewis chemical equilibrium calculations are now available for the first time within CHETAH. This allows the user to predict equilibrium compositions, pressures, and temperatures of a user selected list of reactants. The extensive database of chemicals within the CHETAH databases can be used as reactant chemicals. Also, chemicals not in the databases or even in the published literature can be entered as reactants by making use of the Benson group molecular fragment database. CHETAH 11.0 uses Microsoft Access for database management and to manage the user interface. The calculation details are accomplished in the Visual Basic for Applications structure of Access and in C language. CHETAH 11 is designed to be compatible and seamless with the current versions of the Microsoft Windows operating system.

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