Speaker
Prof.
Angelo Vulpiani
(Dipartimento di Fisica, Universita' Sapienza)
Description
We investigate a kinetic heat engine model constituted by
particles enclosed in a box where one side acts as a
thermostat and the opposite side is a piston exerting a
given pressure. Pressure and temperature are varied in a
cyclical protocol of period $\tau$ and their relative
excursions $\delta$ and $\epsilon$ respectively, constitute
the thermodynamic forces dragging the system out-of-equilibrium.
The analysis of the entropy production of the system allows
to define the conjugated fluxes, which are proportional to
the extracted work and the consumed heat.
The dynamics of the piston can be approximated, through a
coarse-graining procedure, by a Klein-Kramers equation which
- in the linear regime - yields analytic expressions for the
Onsager coefficients and the entropy production. A study of
the efficiency at maximum power shows that the Curzon-
Ahlborn formula is always an upper limit which is approached
at increasing values of the thermodynamic forces, i.e.
outside of the linear regime.
