3. Study of closed systems

One of the applications of thermodynamics is the study of the transformation of thermal energy into mechanical energy (or vice versa) during cyclic transformations of a closed system. In the case of an open transformation of a closed system, the relationships between energy exchanges and variations in state functions are analyzed. In practice, in energy systems, these transformations take place via a compressible or incompressible fluid (or one deemed as such). It is this mass of fluid that constitutes the closed system to be studied.