1. General

One of the most remarkable properties of electricity as a source of thermal energy is its protean character: it can be mobilized in a wide variety of forms, depending on the way in which the electrical energy is transmitted. Electrothermal processes can be divided into two broad categories:

• indirect heating, where the transmission of energy from the source to the receiver (the body to be heated) obeys the usual thermal laws;

• direct heating, where the receiver, through which an electric current flows, is itself the site of heat release, with subsequent heat exchanges taking place according to the laws of classical thermics.

Table 1 lists the various electrothermal technologies that fall into these two families....