6.5 Useful Work and Action, Which Are What
Distinguishes Reversible-Like Processes
from Spontaneous Natural Processes
The condition for the applicability of Eq. (81) is also internal reversibility. When a
system changes infinitely slowly as a result of an infinitesimal net force, the change
satisfies internal reversibility condition.
However, internal reversibility is not reversibility. Reversibility describes nature
not as it is but as the idealized version it could be. Reversibility could be realized
only if an ideal machine is used to bring about reversible work (corresponding to a
perfectly controlled system change), which is stored in a work reservoir so that this
exact amount of reversible work will be able to return the system and its surroundings to their original “entropy states” [8]. In reversible-like processes (see
below), the external force that balances the internal system force must be used to
produce USEFUL WORK (which can be defined as work that can be gainfully used for a
purpose or stored in work reservoir for later use), which can partially return the
system to its original state. Work, as machines, is necessarily an anthropogenic or
organismic concept. Work is a defining characteristic of organismic existence: what
characterizes life systems are “work cycles in a web of propagating organization of
processes” [19] argued Kauffman.
Having nothing to do with work reservoirs, a quasi-static process in the strict
sense can never be a reversible process. Quasi-static processes and reversible
processes represent two fundamentally different classes of spontaneity-driven
processes [18]: spontaneous natural processes and reversible-like processes (see
below). A quasi-static process is an idealization of a spontaneous natural process.
Recall its definition in Sect. 6.2, “the set consists of a subset-series of infinitely
dense succession of equilibrium states and the corresponding subsets of all the
transient states between each pairs of equilibrium states in the series.” Consider
such an idealized representation of a system undergoing a natural change. The
system, in dividing its change into small steps and representing the system at the
end of each step in terms of its equilibrium states, passes through a series of
equilibrium states (the first quasi-equilibrium subset), and in addition, between each
pair of equilibrium states of the first subset, passes through transient states, which
may be “non-representable, non-equilibrium states” [5:97 and 99] (the second
transient subsets).
We may thus define QUASI-STATICITY as the condition that a process consists of
the set of a series of infinitely dense succession of equilibrium states—i.e., the
erstwhile first subset. Note the difference of this definition from the earlier definition
of quasi-static process repeated above.
Like quasi-staticity, INTERNAL REVERSIBILITY (IR) is not a process operation, but a
condition that a process satisfies: defined as the condition that transient states in
every second-subset of transient states become “at all times infinitesimally near”
148
6 Reversible Processes Versus Quasi-static Processes …
Distinguishes Reversible-Like Processes
from Spontaneous Natural Processes
The condition for the applicability of Eq. (81) is also internal reversibility. When a
system changes infinitely slowly as a result of an infinitesimal net force, the change
satisfies internal reversibility condition.
However, internal reversibility is not reversibility. Reversibility describes nature
not as it is but as the idealized version it could be. Reversibility could be realized
only if an ideal machine is used to bring about reversible work (corresponding to a
perfectly controlled system change), which is stored in a work reservoir so that this
exact amount of reversible work will be able to return the system and its surroundings to their original “entropy states” [8]. In reversible-like processes (see
below), the external force that balances the internal system force must be used to
produce USEFUL WORK (which can be defined as work that can be gainfully used for a
purpose or stored in work reservoir for later use), which can partially return the
system to its original state. Work, as machines, is necessarily an anthropogenic or
organismic concept. Work is a defining characteristic of organismic existence: what
characterizes life systems are “work cycles in a web of propagating organization of
processes” [19] argued Kauffman.
Having nothing to do with work reservoirs, a quasi-static process in the strict
sense can never be a reversible process. Quasi-static processes and reversible
processes represent two fundamentally different classes of spontaneity-driven
processes [18]: spontaneous natural processes and reversible-like processes (see
below). A quasi-static process is an idealization of a spontaneous natural process.
Recall its definition in Sect. 6.2, “the set consists of a subset-series of infinitely
dense succession of equilibrium states and the corresponding subsets of all the
transient states between each pairs of equilibrium states in the series.” Consider
such an idealized representation of a system undergoing a natural change. The
system, in dividing its change into small steps and representing the system at the
end of each step in terms of its equilibrium states, passes through a series of
equilibrium states (the first quasi-equilibrium subset), and in addition, between each
pair of equilibrium states of the first subset, passes through transient states, which
may be “non-representable, non-equilibrium states” [5:97 and 99] (the second
transient subsets).
We may thus define QUASI-STATICITY as the condition that a process consists of
the set of a series of infinitely dense succession of equilibrium states—i.e., the
erstwhile first subset. Note the difference of this definition from the earlier definition
of quasi-static process repeated above.
Like quasi-staticity, INTERNAL REVERSIBILITY (IR) is not a process operation, but a
condition that a process satisfies: defined as the condition that transient states in
every second-subset of transient states become “at all times infinitesimally near”
148
6 Reversible Processes Versus Quasi-static Processes …