EU Regional School - Struchtrup Seminar

Location: AICES Seminar Room 115, 1st floor, Schinkelstr. 2, 52062 Aachen

Prof. Dr. Struchtrup - Entropy, Equilibrium, Irreversibility: The 2nd Law of Thermodynamics and its Numerous Consequences

Department of Mechanical Engineering
University of Victoria


Put in simple words, the 2nd Law of Thermodynamics describes the trend of any system left to itself towards a unique and stable equilibrium state. Indeed, the second law can be deduced from rather simple arguments on equilibration processes seen in daily life, including the experience that heat by itself will only go from warm to cold, while there is no restriction on the direction of work transfer. The 2nd Law is a balance equation for entropy, with a non-negative production term, and often is written as an inequality. With this, it differs from most other laws of physics, which typically are conservation laws (e.g., mass, energy, momentum). The non-negativity of entropy generation has far reaching consequences for technical processes and for the description of nature which will be explored through a large number of examples. We will look at modifications of technical processes that reduce entropy generation and thus improve efficiency. Then we discuss the approach to equilibrium, and the final equilibrium states, which often are a result of a competition between entropy and energy. We will identify thermodynamic forces in non-equilibrium states that induce thermodynamics fluxes which drive the system towards equilibrium. Along the way, we make an excursion to Kinetic Theory of Gases which provides the microscopic interpretation of entropy. The 2nd law is often perceived to be difficult to understand—this lecture aims at making it accessible by clear explanations and a multitude of examples. 

Lecture Material