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Unformatted text preview: e Ssink ( 2.5 4.0) kJ/K 1.5 kJ/K Therefore, 1.5 kJ/K of entropy is generated during this process. Noting that
both reservoirs have undergone internally reversible processes, the entire entropy generation took place in the partition.
(b) Repeating the calculations in part (a) for a sink temperature of 750 K, we
Ssink 2.5 kJ/K
2.7 kJ/K and Sgen Stotal ( 2.5 2.7) kJ/K 0.2 kJ/K The total entropy change for the process in part (b) is smaller, and therefore it
is less irreversible. This is expected since the process in (b) involves a smaller
temperature difference and thus a smaller irreversibility.
Discussion The irreversibilities associated with both processes could be eliminated by operating a Carnot heat engine between the source and the sink. For
this case it can be shown that Stotal 0. 7–3 I ENTROPY CHANGE OF PURE SUBSTANCES Entropy is a property, and thus the value of entropy of a system is fixed once
the state of the system is fixed. Specifying two intensive independent properties fixes the state of a simple compressible system, and thus the value of
entropy, as well as the values of other properties at that st...
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This document was uploaded on 11/28/2012.
- Spring '09