  A Monte Carlo simulation is performed on a Billiard-type model system, which
has a spontaneously nonequilibrium dimension (SND) in between two ergodic and
chaotic fields. The SND is a nonchaotic transition step, across which two large
areas have different heights in a gravitational field. Elastic particles
randomly move across the SND. The in-plane pressure does work to the lower
'plain' when the plain area varies, and the gravitational force does work to
the upper 'plateau' when the plateau height changes. The local nonchaoticity
comes from the small barrier width, much less than the mean free path of the
particles. The particle density ratio across the SND is spontaneously in a
non-Boltzmann form and therefore, the cross-influence of the two thermally
correlated thermodynamic driving forces becomes asymmetric. As a result, in an
isothermal cycle, the overall produced work is greater than the overall
consumed work. A similar effect may be achieved without changing the plateau
height, if the plateau-plain border is switchable. The SND does not require any
specific knowledge of the system microstate.
