AME 20231 Thermodynamics Final Exam May 7, 2018 NAME: 1. True or False (10 point

Question

AME 20231 Thermodynamics Final Exam May 7, 2018 NAME: 1. True or False (10 points) One proposition of the 2ad law of thermodynamics states that the change in entropy of a closed system must be greater than or equal to zero. l. Tvul 2. The specific heat ratio k for air is less than 1. 3. When a system undergoes a Carnot cycle, no entropy is generated within the system. A closed system can experience a decrease in entropy only when there is heat transfer from the system to its surroundings during the process. 5. For a Carnot refrigeration cycle 0 is less than or equal to zero. 6. For closed systems undergoing processes involving internal irreversibilities, both change in entropy and entropy generation are positive in value. 7. The change in entropy of a closed system during a process can be greater than, equal to, or less than zero. 8. One statement of the 2nd law of thermodynamics recognizes that the extensive property entropy is generated within systems whenever internal irreversibilities are present. 9. The specific internal energy and enthalpy of an ideal gas are each functions of temperature alone, but its specific entropy depends on two independent intensive properties. 10. For a process to be isentropic it must be reversible and isobaric.

Explanation / Answer

1. True, the change in entropy of a closed system is greater than or equal to zero. It is zero when when the process is completely reversible, and greater than 0 when irreversibility is there in the system.

2. False, it is always greater than or equal to 1 , as Cp is always greater than Cv.

3. True, carnot cycle is a reversible cycle, hence no entropy change occurs in the system.

4. For a cyclic system, the change in entropy is negative when heat is transferred from the system to its surrounding.

5. True, For carnot refrigeration, the cyclic integral of dQ/T will be 0 , because the process is reversible. If irreversibility is taken into account, the integral value must be negative for process to occur.

6. False, change in entropy may be negative but entropy generation is positive during irrversible process.

7. True, the change in entropy for a closed system may be positive, negative or zero.

8. True, entropy generation occurs due to presence of internal irrversibilities.

9. True, the internal enrgy and enthalpy of an ideal gas is a function of temperature alone for an ideal gas, but specific entropy depends on two independent intensive properties.

10. False, for isentropic process, the process must be reversible and adiabatic.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.