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Thermodynamics Directory | Heat Transfer Directory
A reversible process for a system
is defined as a process that, once having taken place, can
be reversed, and in so doing leaves no change in either
the system or surroundings. In other words the system and
surroundings are returned to their original condition
before the process took place. In reality, there are no
truly reversible processes; however, for analysis
purposes, one uses reversible to make the analysis
simpler, and to determine maximum theoretical
efficiencies. Therefore, the reversible process is an
appropriate starting point on which to base engineering
study and calculation.
Although the reversible process can be
approximated, it can never be matched by real processes. One
way to make real processes approximate reversible process is
to carry out the process in a series of small or
infinitesimal steps. For example, heat transfer may be
considered reversible if it occurs due to a small temperature
difference between the system and its surroundings. For
example, transferring heat across a temperature difference of
0.00001 °F "appears" to be more reversible than
for transferring heat across a temperature difference of 100
°F. Therefore, by cooling or heating the system in a number
of infinitesimally small steps, we can approximate a
reversible process. Although not practical for real
processes, this method is beneficial for thermodynamic
studies since the rate at which processes occur is not
important.
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