4. Homogeneous and heterogeneous thermal runaways

Thermal explosions can behave in two distinct ways: homogeneous or heterogeneous.

The Russian theory of "thermal explosions" takes into account not only reaction kinetics, but also heat transfer conditions with the surrounding environment.

Homogeneous thermal explosions are described by Semenov's theory, which defines the critical conditions leading to loss of temperature control of the reaction system. Semenov's theory is a good representation for a stirred reactor. The data required in this theory are kinetic data.

If the reaction medium is solid or viscous, a non-uniform temperature profile may appear in the medium due to the low conduction of heat in relation to the heat flux produced. The medium in question then exhibits non-homogeneous properties, and is referred to as a heterogeneous thermal explosion. This...