8th Edition

ISBN: 8220100257056

Author: CENGEL

Publisher: YUZU

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In physics, entropy means the amount of disorder or the degree of randomness associated with a thermodynamic system. The system is not self-organized when the entropy of the system is high. For instance, when a system is at an elevated temperature, its m…

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Textbook Question

Chapter 8.8, Problem 142FEP

Keeping the limitations imposed by the second law of thermodynamics in mind, choose the wrong statement below:

(a) A heat engine cannot have a thermal efficiency of 100 percent.
(b) For all reversible processes, the second-law efficiency is 100 percent.
(c) The second-law efficiency of a heat engine cannot be greater than its thermal efficiency.
(d) The second-law efficiency of a process is 100 percent if no entropy is generated during that process.
(e) The coefficient of performance of a refrigerator can be greater than 1.

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Chapter 8.8, Problem 141FEP

Chapter 8.8, Problem 143FEP

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Answer the following true or false. Explain. (a) A process that violates the second law of thermodynamics violates the first law of thermidynamics. (b) When a net amount of work is done on a closed system undergoing an internally reversible process, a net heat transfer of energy from the system also occurs. (c) One corollary of the second law of thermodynamics states that the change in entropy of a closed system must be greater than zero or equal to zero. (d) A closed system can experience an increase in entropy only when irreversibilities are present within the system during the process. (e) Entropy is produced in every internally reversible process of a closed system. (f) In an adiabatic and internally reversible process of a closed system, the entropy remains constant. (g) The energy of an isolated system must remain constant, but the entropy can only decrease.

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Chapter 8 Solutions

EBK THERMODYNAMICS: AN ENGINEERING APPR

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Solution Summary: The author explains that the second-law efficiency of a heat engine cannot be greater than its thermal efficiency.

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