The performance of engineering systems is degraded by

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Unformatted text preview: inuously increasing. 3. The performance of engineering systems is degraded by the presence of irreversibilities, and entropy generation is a measure of the magnitudes of the irreversibilities present during that process. The greater the extent of irreversibilities, the greater the entropy generation. Therefore, entropy generation can be used as a quantitative measure of irreversibilities associated with a process. It is also used to establish criteria for the performance of engineering devices. This point is illustrated further in Example 7–2. Source 800 K Source 800 K EXAMPLE 7–2 Entropy Generation during Heat Transfer Processes A heat source at 800 K loses 2000 kJ of heat to a sink at (a) 500 K and (b) 750 K. Determine which heat transfer process is more irreversible. 2000 kJ Sink A 500 K Sink B 750 K (a) (b) FIGURE 7–9 Schematic for Example 7–2. SOLUTION A sketch of the reservoirs is shown in Fig. 7–9. Both cases involve heat transfer through a finite temperature difference, and there...
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This document was uploaded on 11/28/2012.

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