The entropy balance for this extended system system

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Unformatted text preview: nd the system to include the regions on both sides of the wall that experience a temperature change. Then one side of the system boundary becomes room temperature while the other side becomes the temperature of the outdoors. The entropy balance for this extended system (system immediate surroundings) will be the same as that given above, except the two boundary temperatures will be 300 and 273 K instead of 293 and 278 K, respectively. Then the rate of total entropy generation becomes 1035 W 300 K 1035 W 273 K · Sgen, total 0 · → Sgen, total 0.341 W/K Discussion Note that the entropy change of this extended system is also zero since the state of air does not change at any point during the process. The differences between the two entropy generations is 0.150 W/K, and it represents the entropy generated in the air layers on both sides of the wall. The entropy generation in this case is entirely due to irreversible heat transfer through a finite temperature difference. EXAMPLE 7–18 · Q 27ºC 20ºC 0ºC 30 cm...
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This document was uploaded on 11/28/2012.

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