In which branch of thermodynamics would one study irreversible processes?

Studying irreversible processes falls under Non-Equilibrium Thermodynamics. This branch specifically deals with systems that are not in equilibrium, meaning they are subject to changes and processes that do not occur reversibly. Non-Equilibrium Thermodynamics focuses on the transport of energy and matter, and how systems evolve over time when they are driven away from equilibrium conditions.

In contrast, other branches of thermodynamics like Equilibrium Thermodynamics focus on systems that are in a state of balance, where macroscopic properties do not change over time, and reversible processes are the main focus. Statistical Thermodynamics links macroscopic properties to microscopic behaviors but still largely relies on equilibrium concepts. Classical Thermodynamics outlines principles related to work and heat in both non-equilibrium and equilibrium cases but does not specialize in irreversible processes. Therefore, Non-Equilibrium Thermodynamics is essential for understanding the complexities and behaviors of systems undergoing irreversible changes.