Thermodynamic systems
Formalism and principles of thermodynamics

The space outside the thermodynamic system is called the external environment. In any particular study of a thermodynamic system, it is important to define precisely the envelope which, in addition to its role as a boundary, has characteristic properties that enable it to :

• or to totally isolate the thermodynamic system from the rest of the Universe;

• or to authorize certain transfers with the external environment (energy, matter).

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