  The purpose of this paper is two-fold. First, to make clear (and de-mystify)
the basic concepts of classical thermodynamics, and thus to enable the
integration of thermodynamics within systems modeling and control. Second, to
demonstrate that systems and control theory provides a natural context for the
formulation and understanding of classical thermodynamics. This is not so
surprising since classical thermodynamics, firmly rooted in engineering with
questions such as the maximal efficiency of steam engines, deals from the very
start with systems in interaction with their surrounding (by heat flow,
mechanical work, flow of matter, etc.). In particular, it will be shown that
dissipativity theory is key in the formulation and interpretation of the First
and Second Law of thermodynamics. Also a geometric view on the state properties
and the dynamics of thermodynamic systems will be emphasized, thereby unifying
and simplifying different representations of thermodynamic systems. On the
other hand, I will also argue that thermodynamics motivates paradigm shifts
within systems and control; in particular, the use of non-minimal state space
formulations, and a geometric view on them. Furthermore, while systems and
control theory has been primarily based on linear systems with quadratic cost
criteria, in line with basic system models in electrical and mechanical
engineering (RLC-circuits, mass-spring-damper systems, etc.), thermodynamics
necessitates to go beyond this linear-quadratic paradigm.
