
69Reviews of Thermodynamics
where states 1 and 2 represent the initial and the nal states of the control
volume, respectively.
3.7 The Second Law of Thermodynamics
The second law of thermodynamics is stated through the Kelvin–Planck state-
ment and the Clausius statement. The Inequality of Clausius is a consequence of
the second law of thermodynamics, and it is stated for a system undergoing
a thermodynamic cycle as
δQ
≤
for a cycle (3.28a)
with
δQ
= 0 for a reversible cycle (3.28b)
and
Q
< 0 for an irreversible cycle. (3.28c)
Application of this statement for a process leads to
dS
Q
T
≥
δ
, (3.29)
where S is the thermodynamic proper ...