10 Thermodynamics 232, exam 1 Copyright @Wayne Hacker 2011. All rights reserved.

Question

10 Thermodynamics 232, exam 1 Copyright @Wayne Hacker 2011. All rights reserved. Power and Refrigeration Cycles Problem 23. (refrigeration cycle) For a refrigeration cycle with a steady the coefficient of performance . (s) 5/4 heat flow of -= 400 kJ and Qat-500 k, determine (b) 4/5 (d) 4 (e) None of these Problem 24. A gas in a piston-cylinder assembly undergoes a thermodynamic cycle consisting of three processes: process 1-2: Compression with PV constant and U2-U0 with 1 m3 State 1 : / = 100 kPa, State 2: 1,2 m3 process 2-3: Constant pressure to = 1 process 3-1: Constant volume, Ul-U!-1000 kJ Assumption: We can neglect any change in the system's kinetic and potential energy. In this case, the 1st law of thermodynamics reduces to the equation U-Q-W Find the work done by the system for process 2-3, in kJ. (a) 100 kJ (c) 1100 k.J (e) None of these (b) -100 k (d) -1100 k

Explanation / Answer

23. COP refrigeration = Q2 / (Q1 - Q2)

= 400 / (500 -400)

= 4

Ans(d)

24. W = P2 deltaV = P2 (V3 - V2)

W = (1200 x 10^3 Pa) (1 - 1/2)

W = 100 kJ  

Ans(e)

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