solution for Prelim II

solution for Prelim II - Cornell University College of...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Cornell University College of Engineering ENGRD 2210: Thermodynamics Instructors: Stephen Pope, Max Zhang 2 nd Prelim Thursday November 12 th , 2009 - 7:30-9:30pm. You may use a calculator and two pages 8.5” by 11” hand-written note. Answer all parts of all questions. In order to obtain the maximum credit for your solutions, show all steps in your computations. The point value for each problem is given to help you allocate your time. Make sure to include units with your answers. Important: In scoring this exam, we will be looking for your approach to solving each part of the questions. If you get stuck on one part, move on and set up the equations for the other parts to get partial credit. Read each problem thoroughly and make sure you understand what is being asked of you. Make sure to attempt each problem and show what you would have done if you are unable to fully answer the problem or if you run out of time. Exam: 4 problems (10 short answer questions, followed by 3 calculation problems)
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 Problem 1 (30 points) For each of the following statements or equations, say whether it is true or false and provide one sentence of explanation. For example: Statement: For an ideal gas undergoing a process, pv k = constant . Answer: In general this is false. However, it is true for an isentropic process when the specific heats can be considered to be constant. 1) A closed system in communication with a single heat reservoir cannot do work on the surroundings. A) False. It is the case, however, that the system cannot execute a cycle and do work. 2) For a closed system executing a cycle in communication with two heat reservoirs, it is possible to effect a heat transfer Q H > 0 to the high temperature reservoir, while the system receives work W , with W = 1/2Q H . True, for 1 2 / CH TT . The least work possible is for a reversible cycle, for which (1 / ) C H H W T T Q  . 3) A power cycle operating between thermal reservoirs o 800 H TC and o 200 C can have an efficiency of 60%. False. The maximum possible efficiency is 1 / 1 (200 273) / (800 273) 56%   . 4) For a closed system executing a reversible process, the entropy does not change. False. The entropy can change due to heat transfer.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 11

solution for Prelim II - Cornell University College of...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online