MEP FS17 EFPLAB2 PDF

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ausgefüllte prüfung von EFPLAB2. Herbst 17, prüfung von Frühling 17. ...

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Final Exam EFPLAB2, HS17, 26.01.2018

________________________________________ Name, First Name

Final Exam EFPLAB2, HS17, 26.01.2018 For an excellent assessment you do not have to solve all tasks entirely. Label all documents at the top with your name!

Part 2: With documents or supporting material. [90 Minutes; 88 Points] You can use a self-prepared summary of 8 pages (4 sheets A4 size) and a calculator. Please write your calculation paths and your solutions on the sheets provided.

Final Exam EFPLAB2, HS17, 26.01.2018

________________________________________ Name, First Name

Final Exam EFPLAB2, HS17, 26.01.2018 For an excellent assessment you do not have to solve all tasks entirely. Label all documents at the top with your name!

Part 2: With documents or supporting material. [90 Minutes; 88 Points] You can use a self-prepared summary of 8 pages (4 sheets A4 size) and a calculator. Please write your calculation paths and your solutions on the sheets provided.

Final Exam EFPLAB2, HS17, 26.01.2018

________________________________________ Name, First Name

Task 1: Expansion

[22.5 Points]

A turbine represents an open thermodynamic system in which we are processing an expansion without heat exchange. The turbine is placed perpendicularly to the gravitational force direction and changes between inlet and exit velocities are negligible. The inlet state is characterized by a pressure of p = 3 bar and a temperature of T = 500 °C. The turbine expands to the atmospheric pressure p = 1 bar. The manufacturer wants to establish the performance of the turbine and he hires two technicians in order to measure the necessary data for performance evaluation. The fluid can be considered as a perfect gas, cp = 1038.8 J/(Kg K) and R = 296.8 J/(kg K) .

a) Sketch the expansion process in the p-v and T-s diagrams. Write a suitable specific energy conservation equation for the thermodynamic system of the turbine. Comment properly. T

s

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Final Exam EFPLAB2, HS17, 26.01.2018

________________________________________ Name, First Name b) Evaluate the specific output of the turbine using the data measured from the: - first technician: Temperature of fluid at the outlet of the turbine Ta = 580 K, ambient temperature on which the turbine is operating is Tair = 25 °C, relative humidity of 90 %, atmospheric pressure of p = 998 mbar (millibar). - second technician: Temperature of fluid at the outlet of the turbine Tb = 540 K, ambient temperature on which the turbine is operating is Tair = 18 °C, relative humidity of 80 %, atmospheric pressure of p = 1013 mbar (millibar). - first technician: Toutlet = 58 K Tambient = 25 °C p = 998 mbar relative humidity of 90 %

-second technician: T outlet = 540 K T ambient = 18 °C p = 1013 mbar relative humidity of 80 %.

c) One of the two technicians did a wrong measurement. Verify which one and justify your answer from theoretical and quantitative point of view.

d) Write down the efficiency of the expansion using the correct measurement.

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Final Exam EFPLAB2, HS17, 26.01.2018

________________________________________ Name, First Name

Task 2: Heating system

[22.5 Points]

A customer needs to heat an industrial oven during the winter period. The options are to use electrical power or to use the heat of a reversible heat pump. The temperature of the oven is T = 550 K and it has to provide 10 kW of heat. The ambient temperature outside varies from winter to summer between -10 °C < Tamb < 30 °C. a) Sketch the thermodynamic system using the heat pump and write a suitable specific energy conservation equation for this system.

b) Evaluate the power used to heat up the oven using the heat pump in both seasons. Compare it to the version using only electrical power.

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Final Exam EFPLAB2, HS17, 26.01.2018

________________________________________ Name, First Name c) The client asks if it’s better to use the oven in winter or in the summer season (minimum and maximum ambient temperature respectively): provide the answer based on power consumption.

d) When using the heat pump, calculate the limit condition for which the client spends only half the amount of money on power supply compared to using electrical power.

e) Evaluate the COP for both winter and summer time.

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Final Exam EFPLAB2, HS17, 26.01.2018

________________________________________ Name, First Name c) The client asks if it’s better to use the oven in winter or in the summer season (minimum and maximum ambient temperature respectively): provide the answer based on power consumption.

d) When using the heat pump, calculate the limit condition for which the client spends only half the amount of money on power supply compared to using electrical power.

e) Evaluate the COP for both winter and summer time.

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