Physics for Scientists and Engineers
10th Edition
ISBN: 9781337553278
Author: Raymond A. Serway, John W. Jewett
Publisher: Cengage Learning
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Chapter 21, Problem 42AP
You are working as an expert witness for an environmental agency. A utility in a neighboring town has proposed a new power plant that produces electrical power P from turbines. The utility claims that the plant will take in steam at temperature Th and reject water at temperature Tc into a flowing cold-water river. The flow rate of the river is Δm/Δt. The agency supervisor is concerned about the effect of dumping warm water on the fish in the river. (a) The utility claims that the power plant operates with Carnot efficiency. With that assumption, you need to determine for a trial presentation by how much the temperature of the water downstream from the power plant will rise due to the rejected energy from the power plant. (b) If you abandon the utility’s claim that the power plant operates at Carnot efficiency and assume a more realistic efficiency e, you need to determine the increase in water temperature in the stream. (c) Finally, you need to testify whether the increase in water temperature in part (b) will be higher or lower than that found in part (a).
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A Carnot heat engine delivers P = 5 x 105 Btu / hr of power while operating between reservoirs at Tc = 470 °F and Th = 1680 °F.
a) Write an expression for how much energy it receives per hour from the high temperature thermal reservoir in terms of the absolute temperatures Tc and Th.
b) Solve numerically for the amount of energy, in BTUs, that is rejected per hour to the low temperature thermal reservoir.
Chapter 21 Solutions
Physics for Scientists and Engineers
Ch. 21.1 - The energy input to an engine is 4.00 times...Ch. 21.2 - The energy entering an electric heater by...Ch. 21.4 - Three engines operate between reservoirs separated...Ch. 21.6 - (a) Suppose you select four cards at random from a...Ch. 21.7 - An ideal gas is taken from an initial temperature...Ch. 21.7 - True or False: The entropy change in an adiabatic...Ch. 21 - A particular heat engine has a mechanical power...Ch. 21 - The work done by an engine equals one-fourth the...Ch. 21 - Suppose a heat engine is connected to two energy...Ch. 21 - During each cycle, a refrigerator ejects 625 kJ of...
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