Name, Surname: Prof. Dr. Nevzat Onur ID No: Dr. Ekin Özgirgin Yapıcı Fall 2016

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Çankaya University

Faculty of Engineering

Mechanical Engineering Department

ME 211 Thermodynamics I

Closed Notes and Bookes

Midterm 1 Exam

Solution

Q-1 Net work of a power cycle shown in the figure is 10000 kJ and the thermal efficiency is 0.64.

Determine the heat transfers Qin and Qout, each in kJ.

Solution:

Name, Surname: Prof. Dr. Nevzat Onur ID No: Dr. Ekin Özgirgin Yapıcı Fall 2016

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Q-2 A piston cylinder arrangement with a linear spring shown in the figure given below contains R-

134a at 16 0C, x = 0.4 and a volume of 0.02 m3. It is heated to 60 0C at which point the pressure is

8 bar. Find; (a) the work, (b) the heat transfer in the process.

Hint: You do not need a spring constant. show the process on a p-v diagram.

Solution:

Name, Surname: Prof. Dr. Nevzat Onur ID No: Dr. Ekin Özgirgin Yapıcı Fall 2016

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Q-3 A piston -cylinder device initially contains 0.3 m3 of nitrogen gas at 350 kPa and 35 ºC. An

electric heater within the device is turned on and is allowed to pass a current of 2 A for 6 min from

a 120 V source. Nitrogen expands at constant pressure, and a heat loss of 3000 J occurs during the

process. Determine the final temperature of the nitrogen. (Average cP for Nitrogen is 1.039 kJ/kgK

and molecular weight of Nitrogen is 28.01 kg/kmol.)

Solution:

V1=0.3 m3

P1=350 kPa

T1= 35ºC

3000 J

Name, Surname: Prof. Dr. Nevzat Onur ID No: Dr. Ekin Özgirgin Yapıcı Fall 2016

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Q-4 A rigid 20 Liter vessel initially contains a mixture of liquid water and vapor at 95 ºC with 0.15

(15%) quality. The mixture is then heated until its temperature is 140 ºC. Calculate the heat

transfer required for this process.

Water

20 L, 95 ºC x=0.15

Qin

Name, Surname: Prof. Dr. Nevzat Onur ID No: Dr. Ekin Özgirgin Yapıcı Fall 2016

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