What does 'isentropic' refer to in thermodynamics?

Isentropic refers to a process in thermodynamics that occurs at constant entropy. An isentropic process is characterized by the absence of entropy generation, meaning that it is both adiabatic (no heat exchange with the surroundings) and reversible. This concept is crucial in thermodynamic cycles, such as those in turbines and compressors, because it allows for the analysis of efficiency and performance by assuming ideal conditions.

In practical applications, understanding isentropic processes allows engineers to calculate changes in state variables when systems undergo compressions or expansions while minimizing losses. It's important to use isentropic relations to derive other properties, such as temperature and pressure changes in ideal gas situations.

The other concepts, such as constant temperature, equal pressure, or equal energy levels, do not accurately describe the nature of an isentropic process, as they address different thermodynamic conditions.