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| 1 | |
Air is expanded in a closed system from 1 MPa, 327°C to 100 kPa in an isentropic process. The system surroundings are at 100 kPa, 27°C. How much useful work did this system produce during this process? |
| | A) | 91 kJ/kg |
| | B) | 103 kJ/kg |
| | C) | 135 kJ/kg |
| | D) | 210 kJ/kg |
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| 2 | |
The electrical power supplied to a resistor is dissipated as heat. If the temperature of the resistor is T and the temperature of the surroundings is T0, what is the irreversibility rate of this process? |
| | A) | T0 iΔ V / T |
| | B) | T iΔV / T0 |
| | C) | (1 - T / T0) iΔV |
| | D) | (1 - T0 / T) iΔV |
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| 3 | |
A 1 m3 vessel contains air at 1 MPa, 327°C. Assuming standard conditions for the surroundings, what is the maximum amount of work that can be done by the air in this vessel? |
| | A) | 790 kJ |
| | B) | 826 kJ |
| | C) | 1012 kJ |
| | D) | 1290 kJ |
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| 4 | |
Steam enters a turbine at 3 MPa, 350°C with a velocity of 15 m/s. What is the specific exergy of this steam assuming the surroundings are at standard conditions? |
| | A) | 678 kJ/kg |
| | B) | 827 kJ/kg |
| | C) | 968 kJ/kg |
| | D) | 1116 kJ/kg |
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| 5 | |
Steam at 3 MPa, 350°C is expanded through an adiabatic, steady-flow turbine to a saturated vapor at 100 kPa. The second law efficiency of this turbine is: |
| | A) | 48.2% |
| | B) | 63.7% |
| | C) | 70.7% |
| | D) | 82.1% |
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| 6 | |
Exergy is always |
| | A) | Being produced |
| | B) | Being destroyed |
| | C) | Not changing |
| | D) | None of these |
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| 7 | |
A heat exchanger maintains the air temperature in a room at 25°C by condensing saturated water vapor at 125 kPa to saturated liquid water. The specific exergy destruction associated with this heat exchanger is: |
| | A) | 932 kJ/kg |
| | B) | 958 kJ/kg |
| | C) | 1241 kJ/kg |
| | D) | 1378 kJ/kg |
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| 8 | |
Exergy destruction is a result of: |
| | A) | Heat transfer |
| | B) | Work production |
| | C) | Process irreversibility's |
| | D) | None of these |
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| 9 | |
Air is compressed from 100 kPa, 27°C to 900 kPa, 327°C in an adiabatic piston-cylinder device. What is the irreversibility of this process? |
| | A) | 19.66 kJ/kg |
| | B) | 22.31 kJ/kg |
| | C) | 28.73 kJ/kg |
| | D) | 32.17 kJ/kg |
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| 10 | |
An adiabatic, steady-flow heat exchanger condenses 10,000 kg/hr of saturated steam vapor at 200 kPa to a saturated liquid also at 200 kPa. The condensing steam heats 220,000 kg/hr of air at 100 kPa, 25°C to 100 kPa, 125°C. What is the rate at which exergy is destroyed by this heat exchanger? |
| | A) | 0 MJ/hr |
| | B) | 270 MJ/hr |
| | C) | 1327 MJ/hr |
| | D) | 2295 MJ/hr |
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