[Encyclios]

Types of thermodynamic system

Based on the type and combination of properties of the control surfaces, the following types of thermodynamic system can be distinguished:

• open system: its boundaries are permeable, albeit partially, to the passage of matter;
• closed system: it is delimited by boundaries impermeable to the passage of matter; in other words, a closed system cannot exchange matter with the environment, but only energy;
• isolated system: a system is said to be isolated when, in addition to being closed, it does not exchange energy with the external environment.

The thermodynamic systems listed above are nothing more than a combination of these properties:

• open system: porous, mobile, and diathermic;
  • adiabatic open system: porous, movable and adiabatic;
• closed system: impervious, mobile and diathermic;
  • adiabatic closed system: impervious, movable and adiabatic;
• isolated system: impervious, rigid and adiabatic.

It is clear, from these definitions, that a closed system is characterized by the constancy of its mass, while the opposite is not true, in the sense that a system with constant mass is not necessarily closed: in fact, it could also be an open system in permanent regime, that is a system in which, instant by instant, the incoming mass is perfectly equal to the outgoing one.