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an applied science that deals with the processes in which electric energy is converted to heat.
In electrical engineering, electrothermics encompasses the design, manufacture, and operation of electrothermal installations; in power engineering it deals with the use of electric power for process heating, smelting, and space heating in industry, transportation, agriculture, medicine, the military and private life. In industry, electrothermics embraces the electrotechnical processes that make use of the heating action of electric energy. For example, in metallurgy it encompasses processes associated with electrometallurgy, in chemistry it embraces processes of plasma chemistry, and in machine building it involves such techniques as high-frequency heating and electrothermic treatment. The following types of heating are distinguished in electrothermics: arc heating, induction heating, dielectric heating, electronic heating, Joule heating, heating in an electrolyte, and heating with laser radiation.
Electrothermal installations or equipment include electric furnaces, plasma reactors, and municipal and household electric heating devices. By using electric power to generate heat, high concentrations of energy can be produced in small volumes; as a result, high temperatures unachievable by other methods of heat generation can be attained. Heating with electric power is rapid, and electrothermal equipment is compact. Since temperature levels and distribution in the heating chamber of a furnace can be regulated, uniform heating of large-volume articles is possible (by direct heating), as is localized heating (for surface hardening and zone melting). Such a capacity for temperature regulation facilitates the automation of heating and industrial processes.
With heat generated by electric power, a vacuum can be created in the heating chamber of a furnace. Thus, pressure can be used as a control factor in an industrial process (in vacuum and pressure-type electric furnaces). Moreover, controlled atmospheres—that is, inert or shielding atmospheres—can be employed to protect the materials and articles being heated from the detrimental effects of air; in particular, melting loss can be reduced. The use of electric heating precludes the formation of exhaust gases that consist of fuel combustion products, thereby increasing the heat utilization factor, that is, the efficiency of the heating unit, and keeping the heating chamber clean. Electric heating units are often portable, and the transmission of electric energy, over power transmission lines, is relatively simple.
The development of electrothermics has been hampered by the drawbacks associated with electrothermic methods of generating heat. The operating costs of electrothermal installations are higher than those of other types of installations. Since the cost of manufacturing, assembling, and operating electrothermal equipment is higher than that of other kinds of heating equipment, capital expenditures are in many cases greater, and production standards are higher. In addition, costly materials in short supply must often be used in the manufacture of electrothermal equipment. Electrothermal equipment is less reliable than other kinds of equipment, has a shorter service life, and is more difficult to maintain; its performance, moreover, is affected by the nature of the power system to which it is linked.
An electrothermal installation is used if an industrial process cannot be performed without the use of electrothermics; the product obtained in the process, however, must be relatively important to the national economy. Electrothermal installations may be employed if their use will result in goods of a quality higher than that of goods produced with other equipment; the economic advisability of the use of electrothermal equipment depends, in this case, on the extent to which the higher quality compensates for the increase in production costs. Electrothermal equipment may also be used if it results in better working conditions and greater safety for service personnel, if production costs are lowered through higher labor productivity, or if capital outlays—including those in related branches of production—are reduced.
Electrothermics accounts for as much as 15 percent of the electric power consumed by industry and has served as the basis for the creation and development of production techniques associated with special steels, ferroalloys, nonferrous and light metals and alloys, hard alloys, rare metals, calcium carbide, and phosphorus. Some forms of pressure shaping and heat treatment of metals are based on electrothermics, which also figures heavily in the electrification of residences and public and private facilities.
REFERENCESEgorov, A. V., and A. F. Morzhin. Elektricheskie pechi dlia proizvodstva stalei. Moscow, 1975.
Svenchanskii, A. D. Elektricheskie promyshlennye pechi, 2nd ed., part 1. Moscow, 1975.
Istoriia energeticheskoi tekhniki SSSR, vol. 2. Moscow-Leningrad, 1957. Pages 460–93.
Paschkis, V., and J. Persson. Industrial Electric Furnaces and Appliances, 2nd ed. New York-London, 1960.
A. V. EGOROV and A. F. MORZHIN