transformation of pure spontaneity in the system into work by extracting heat from
the reservoir. This is explained in the example below as described in Fig. 8.6, where
the problem is treated in conformity to Eq. (130).
T 0 and p 0 reservoir
Thermal
composite
system
Thermal
composite
system
Heat Q body from
the composite
system is
− Q spon
Necessary rejected
heat is 0 kJ
Useful work is
100% of heat
from the body of
the composite
Fig. 8.5 Thermal composite system. The system undergoes a spontaneous event on left; the
system undergoes a reversible event on right as managed by a Carnot micro-cycle machine
Fig. 8.6 Schematics of an isolated thermal system with pure spontaneity: Top depicts the
spontaneous event and bottom depicts three reversible events with the thermal system in
interaction with three different heat reservoirs
8.4 Entropic Drive Corollary for Isolated Systems: Pure Spontaneity
207