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An adiabatic process is one that occurs without transfer of heat or matter between a thermodynamic system and its surroundings. In an adiabatic process, energy is transferred only as work.〔Carathéodory, C. (1909). Untersuchungen über die Grundlagen der Thermodynamik, ''Mathematische Annalen'', 67: 355–386, . A translation may be found (here ). Also a mostly reliable (translation is to be found ) at Kestin, J. (1976). ''The Second Law of Thermodynamics'', Dowden, Hutchinson & Ross, Stroudsburg PA.〕〔Bailyn, M. (1994). ''A Survey of Thermodynamics'', American Institute of Physics Press, New York, ISBN 0-88318-797-3, p. 21.〕 The adiabatic process provides a rigorous conceptual basis for the theory used to expound the first law of thermodynamics, and as such it is a key concept in thermodynamics. Some chemical and physical processes occur so rapidly that they may be conveniently described by the "adiabatic approximation", meaning that there is not enough time for the transfer of energy as heat to take place to or from the system.〔Bailyn, M. (1994), pp. 52–53.〕 In way of example, the adiabatic flame temperature is an idealization that uses the "adiabatic approximation" so as to provide an upper limit calculation of temperatures produced by combustion of a fuel. The adiabatic flame temperature is the temperature that would be achieved by a flame if the process of combustion took place in the absence of heat loss to the surroundings. ==Description== A process that does not involve the transfer of heat or matter into or out of a system, so that ''Q'' = 0, is called an adiabatic process, and such a system is said to be adiabatically isolated.〔Tisza, L. (1966). ''Generalized Thermodynamics'', M.I.T Press, Cambridge MA: "(adiabatic partitions inhibit the transfer of heat and mass)", p. 48.〕 The assumption that a process is adiabatic is a frequently made simplifying assumption. For example, the compression of a gas within a cylinder of an engine is assumed to occur so rapidly that on the time scale of the compression process, little of the system's energy can be transferred out as heat. Even though the cylinders are not insulated and are quite conductive, that process is idealized to be adiabatic. The same can be said to be true for the expansion process of such a system. The assumption of adiabatic isolation of a system is a useful one, and is often combined with others so as to make the calculation of the system's behaviour possible. Such assumptions are idealizations. The behaviour of actual machines deviates from these idealizations, but the assumption of such "perfect" behaviour provide a useful first approximation of how the real world works. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「adiabatic process」の詳細全文を読む スポンサード リンク
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