Unformatted text preview: ation cycles.
If no irreversibilities occur within the system as well as the reversible cyclic
device, then the cycle undergone by the combined system will be internally
reversible. As such, it can be reversed. In the reversed cycle case, all the quantities will have the same magnitude but the opposite sign. Therefore, the work
WC, which could not be a positive quantity in the regular case, cannot be a
negative quantity in the reversed case. Then it follows that WC, int rev 0 since
it cannot be a positive or negative quantity, and therefore
Q
T 0 (7–2) int rev for internally reversible cycles. Thus, we conclude that the equality in the
Clausius inequality holds for totally or just internally reversible cycles and
the inequality for the irreversible ones.
To develop a relation for the definition of entropy, let us examine Eq. 7–2
more closely. Here we have a quantity whose cyclic integral is zero. Let us
think for a moment what kind of quantities can have this characteristic. We
know that the cyclic integral of wo...
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 Spring '09
 Thermodynamics, Energy, Entropy, entropy change

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