Current methods to determine the thermodynamic energy of explosion are based on the Helmholtz free energy. The Helmholtz free energy represents the maximum work available from a system during a constant temperature process. For many real explosions, the material is initially at a temperature or pressure higher than the ambient environment. Thus, the Helmholtz free energy does not account for all of the energy sources.

The thermodynamic availability provides a general approach to determine the maximum work available from any process. Furthermore, the availability provides a much more formal and structured method for performing the calculations.

This paper provides the formal basis, demonstrates the application of availabilty using a number of examples, and provides a table of availability data.