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15-6 Refrigerators, Air Conditioners, and Heat Pumps

15-6 Refrigerators, Air Conditioners, and Heat Pumps. Clausius statement of the 2 nd Law of T…. …A perfect refrigerator, that requires no work from the low temp. region to the high temp. region is not possible. The coefficient of performance (CP), of a refrigerator is defined as …CP= Q L /W.

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15-6 Refrigerators, Air Conditioners, and Heat Pumps

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  1. 15-6 Refrigerators, Air Conditioners, and Heat Pumps Clausius statement of the 2nd Law of T…. …A perfect refrigerator, that requires no work from the low temp. region to the high temp. region is not possible. The coefficient of performance (CP), of a refrigerator is defined as …CP= QL/W. CP= QL/W= QL/(QH-QL) The best you can do is the CPideal=TL/(TH-TL) Heat pumps take QL and bringing it in to QH… so CPheat pump = QH/W

  2. 15-6 (cont’d) • See figure 15-6 p 457 • See Example 15-11 p458

  3. 15-7 Entropy and the 2nd Law of T • Entropy is a measure of disorder. • Entropy naturally increases in a closed system, in our universe…or the entropy of any system, plus the universe, increases. • DS= Q/T • See Examples 15-12 and 15-13 p459

  4. 15-8 Order to Disorder • Natural systems tend to move toward more disorder…eg. Your room? • Energy can be expended to decrease entropy. • Information theory…more information…less entropy

  5. 15-10 Unavailability of Energy; Heat Death • Because of the second law of thermodynamics, some energy becomes unavailable to do work….energy is degraded…the extreme case of this would result in heat death.

  6. 15-10 Evolution and Growth • entropy…time’s arrow

  7. 15-11 Statistical Interpretation of Entropy • The microstate would be the position and velocity of every particle…the macrostate is the larger view of temperature, pressure, number of moles, etc…. • See pg 463 penny example. • (Ludwig Boltzman [1844-1906])

  8. 15-12 Energy Resources: Thermal Pollution • Greenhouse effect… • Thermal pollution… • Fossil-fuel steam plants… • Nuclear energy… • Geothermal energy… • Hydroelectric power plants… • Tidal energy… • Wind power…. • Solar energy…. Photoelectric effect, solar cell

  9. HOMEWORK… • Page 473 21, 28-31, 34-37, 42, 46-47

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