Thermodynamics 1 - Test Answers PDF

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THERMODYNAMICS 1 1. A rigid tank contains 50 kg of saturated liquid water at 90°C. Determine the pressure in the tank. A. 70.183 kPa

B. 80.235 kPa

C. 40.616 kPa

D. 80.500 kPa

E. NOTC

D. 1.2111 m3

E. NOTC

2. The volume of the tank for Problem 2 is A. 0.0518 m3

B. 0.9911 m3

C. 0.0303 m3

3. A mass of 200 g of saturated liquid water is completely vaporized at a constant pressure of 100 kPa. Determine the amount of energy transferred to the water in kJ. A. 150

B. 250

C. 350

D. 450

E. NOTC

4. A rigid tank contains 10 kg of water at 90°C. If 8 kg of the water is in the liquid form and the rest is in the vapor form, what is the volume of the tank? A. 2.50 m3

B. 3.67 m3

C. 4.73 m3

D. 5.00 m3

E. NOTC

For Nos. 5 to 8: An 80-L vessel contains 4 kg of refrigerant-134a at a pressure of 160 kPa. 5. Determine the temperature of the refrigerant. A. -15.6°C

B. -10.1 °C

C. -4.00°C

D. 0.00°C

E. 4.00 °C

C. 0.251

D. 1.00

E. NOTC

D. 241.21

E. NOTC

D. 0.0532 m3

E. 0.0775 m3

6. Calculate the quality. A. 0

B. 0.157

7. The enthalpy of the refrigerant in kJ/kg is A. 31.21

B. 64.2

C. 90.0

8. The volume occupied by the vapor phase is A. 0.0223 m3

B. 0.1099 m3

C. 0.2005 m3

9. Determine the temperature of water at a state of P = 0.5 MPa and h = 2890 kJ/kg. A. 210.1°C

B. 213.6°C

C. 216.3°C

D. 231.6°C

E. 261.3°C

10. What is the internal energy of compressed liquid water at 80°C and 5 MPa in kJ/kg?

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A. 335

B. 350

C. 365

D. 370

E. 395

11. A 20-m3 tank contains nitrogen at 23°C and 600 kPa. Some nitrogen is allowed to escape until the pressure in the tank drops to 400 kPa. If the temperature at this point is 20°C, determine the amount of nitrogen that has escaped. A. 35.5 kg

B. 40.1 kg

C. 44.6 kg

D. 49.8 kg

E. 53.7 kg

12. A 10-kg mass of superheated refrigerant-134a at 1.2 MPa and 70°C is cooled at constant pressure until it exists as a compressed liquid at 20°C. Determine the change in volume. A. 0.166 m3

B. -0.166 m3

C. 0.187 m3

D. -0.187 m3

E. NOTC

D. -1984 kJ

D. NOTC

13. The change in total internal energy for No. 12 is A. 1894 kJ

B. -1894 kJ

C. 1984 kJ

14. A piston–cylinder device initially contains 0.4 m3 of air at 100 kPa and 80°C. The air is now compressed to 0.1 m3 in such a way that the temperature inside the cylinder remains constant. Determine the work done during this process in kJ. A. 55.5

B. -55.5

C. 55,500

D. -55,500

E. NOTC

D. Cp

E. AOTC

15. ___ varies with temperature ONLY for ideal gases. A. internal energy

B. enthalpy

C. Cv

For Nos. 16-18: A rigid tank is divided into two equal parts by a partition. Initially, one side of the tank contains 5 kg of water at 200 kPa and 25°C, and the other side is evacuated. The partition is then removed, and the water expands into the entire tank. The water is allowed to exchange heat with its surroundings until the temperature in the tank returns to the initial value of 25°C. 16. Determine the volume of the tank. A. 0.005 m3

B. 0.01 m3

C. 0.05 m3

D. 0.1 m3

E. 1 m3

C. 3.9861 kPa

D. 3.8619 kPa

E. 3.1968 kPa

D. 1.00

2.00

17. What is the final pressure? A. 3.1698 kPa

B. 3.6981 kPa

18. The heat transfer for this process in kJ is A. 0.125

B. 0.250

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C. 0.500

19. Air at 300 K and 200 kPa is heated at constant pressure to 600 K. Determine the change in internal energy in kJ/kg. A. 100

B. 220

C. 335

D. 460

E. 500

20. A piston–cylinder device initially contains air at 150 kPa and 27°C. At this state, the piston is resting on a pair of stops and the enclosed volume is 400 L. The mass of the piston is such that a 350-kPa pressure is required to move it. The air is now heated until its volume has doubled. Determine the total heat transferred to the air in kJ. A. 540

B. 767

C. 325

D. 920

E. 555

21. Two rigid tanks are connected by a valve. Tank A contains 0.2 m3 of water at 400 kPa and 80 percent quality. Tank B contains 0.5 m3 of water at 200 kPa and 250°C. The valve is now opened, and the two tanks eventually come to the same state. Determine the amount of heat transfer when the system reaches thermal equilibrium with the surroundings at 25°C in kJ. A. 1120

B. 1826

C. 3511

D. 4950

E. 2170

For Nos. 22-23: Air at 10°C and 80 kPa enters the diffuser of a jet engine steadily with a velocity of 200 m/s. The inlet area of the diffuser is 0.4 m2. The air leaves the diffuser with a velocity that is very small compared with the inlet velocity. 22. Determine the mass flow rate of the air. A. 50.2 kg/s

B. 35.6 kg/s

C. 78.8 kg/s

D. 80.1 kg/s

E. 90.7 kg/s

D. 350 K

E. 357 K

23. The temperature of air leaving the diffuser. A. 280 K

B. 303 K

C. 313 K

24. Air at 100 kPa and 280 K is compressed steadily to 600 kPa and 400 K. The mass flow rate of the air is 0.02 kg/s, and a heat loss of 16 kJ/kg occurs during the process. Assuming the changes in kinetic and potential energies are negligible, determine the necessary power input to the compressor. A. 2.74 kW

B. 2740 kW

C. 3.90 kW

D. 3900 kW

E. 4.14 kW

25. The power output of an adiabatic steam turbine is 5 MW, and the inlet and the exit conditions of the steam are as indicated below. Calculate the mass flow rate of the steam.

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A. 5.73 kg/s

B. 573 g/s

C. 5730 kg/s

D. 57.3 kg/s

E. NOTC

26. Refrigerant-134a enters the capillary tube of a refrigerator as saturated liquid at 0.8 MPa and is throttled to a pressure of 0.12 MPa. Determine the quality of the refrigerant at the final state. A. 1.00

B. 0.340

C. 0.250

D. 0

NOTC

27. Refrigerant-134a is to be cooled by water in a condenser. The refrigerant enters the condenser with a mass flow rate of 6 kg/min at 1 MPa and 70°C and leaves at 35°C. The cooling water enters at 300 kPa and 15°C and leaves at 25°C. Neglecting any pressure drops, determine the heat transfer rate from the refrigerant to water in kJ/min. A. 1812

B. 1218

C. 1182

D. 1128

E. 1281

28. It is impossible for any device that operates on a cycle to receive heat from a single reservoir and produce a net amount of work. This is the ____ statement of the second law. A. Kelvin

B. Planck

C. KelvinPlanck

D. Clausius

E. Combined

29. A car engine with a power output of 65 hp has a thermal efficiency of 24 percent. Determine the fuel consumption rate of this car if the fuel has a heating value of 19,000 Btu/lbm. A. 41. 5 lb/h

B. 29.9 lb/h

C. 36.3 lb/h

D. 45.0 lb/h

E. 32.2 lb/h

30. The food compartment of a refrigerator is maintained at 4°C by removing heat from it at a rate of 360 kJ/min. If the required power input to the refrigerator is 2 kW, determine the coefficient of performance of the refrigerator. A. 1

B. 2

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C. 3

D. 4

E. 5

31. A perpetual-motion machine of the first kind is a device that violates the first law. A. Sometimes true

B. Always true

C. Never true

D. Always false

E. NOTC

32. A piston–cylinder device contains a liquid–vapor mixture of water at 300 K. During a constant-pressure process, 750 kJ of heat is transferred to the water. As a result, part of the liquid in the cylinder vaporizes. What is the entropy change of the water during this process in kJ/K? A. 1.5

B. 1500

C. 2.5

D. 2500

E. NOTC

33. A rigid tank contains 5 kg of refrigerant-134a initially at 20°C and 140 kPa. The refrigerant is now cooled while being stirred until its pressure drops to 100 kPa. Determine the entropy change of the refrigerant during this process in kJ/K. A. 0.8278

B. -0.8278

C. 1.173

D. -1.173

E. NOTC

34. A piston–cylinder device initially contains 3 lbm of liquid water at 20 psia and 70°F. The water is now heated at constant pressure by the addition of 3450 Btu of heat. Determine the entropy change of the water during this process, in Btu/R. A. 1.776

B. -1.776

C. 5.105

D. -5.105

E. NOTC

35. Steam enters an adiabatic turbine at 5 MPa and 450°C and leaves at a pressure of 1.4 MPa. Determine the work output of the turbine in of steam in kJ/kg if the process is reversible. A. 3317.2

B. 6.8210

C. 2967.4

D. 150.0

E. 349.8

36. Air is compressed from an initial state of 100 kPa and 17°C to a final state of 600 kPa and 57°C. Determine the entropy change of air in kJ/kg-K during this compression process. A. -0.3844

B. -0.3448

C. 0.3844

D. 0.3448

E. -0.3484

37. Air is compressed in a car engine from 22°C and 95 kPa in a reversible and adiabatic manner. If the compression ratio V1/V2 of this engine is 8, determine the final temperature of the air. A. 662.7 K

B. 331.4 K

C. 298.2 K

D. 293.2 K

E. 225.0 K

38. Determine the compressor work input required to compress steam isentropically from 100 kPa to 1 MPa, assuming that the steam exists as saturated liquid. A. 519.5 kJ/kg

B. 0.94

C. 918.3

D. 0.99

39. Repeat Problem 38 if the steam exists as saturated vaport.

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E. 15.66

A. 519.5 kJ/kg

B. 0.94

C. 918.3

D. 0.99

E. 15.66

40. Consider air at 300 K and 0.86 m3/kg. The state of air changes to 302 K and 0.87 m3/kg as a result of some disturbance. A. 0.491

B. -0.491

C. 0.883

D. -0.883

E. NOTC

D. temperature is not a factor

E. NOTC

41. If the Joule-Thomson coefficient is less than zero, A. temperature increases

B. temperature remains constant

C. temperature decreases

42. What is the Joule-Thomson coefficient of an ideal gas? A. 1

B. 0

C. -1

D. 0.5

E. NOTC

43. Consider a steady-flow Carnot cycle with water as the working fluid executed under the saturation dome between the pressure limits of 3 MPa and 10 kPa. Water changes from saturated liquid to saturated vapor during the heat addition process. The net work output of this cycle in kJ/kg is A. 666

B. 975

C. 596

D. 845

E. 1148

44. A simple ideal Rankine cycle operates between the pressure limits of 10 kPa and 3 MPa, with a turbine inlet temperature of 600°C. Disregarding the pump work, the cycle efficiency is A. 24%

B. 37%

C. 52%

D. 63%

E. 71%

45. A simple ideal Rankine cycle operates between the pressure limits of 10 kPa and 5 MPa, with a turbine inlet temperature of 600°C. The mass fraction of steam that condenses at the turbine exit is A. 6%

B. 9%

C. 12%

D. 15%

E. 18%

46. A steam power plant operates on the simple ideal Rankine cycle between the pressure limits of 5 kPa and 10 MPa, with a turbine inlet temperature of 600°C. The rate of heat transfer in the boiler is 300 kJ/s. Disregarding the pump work, the power output of this plant is A. 118 kW

B. 284 kW

C. 508 kW

D. 335 kW

E. 800 kW

47. Consider a simple ideal Rankine cycle. If the condenser pressure is lowered while keeping turbine inlet state the same, A. the turbine work output will decrease B. the amount of heat rejected will decrease

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C. the cycle efficiency will decrease D. the moisture content at turbine exit will decrease E. the pump work input will decrease. 48. Consider a simple ideal Rankine cycle with fixed boiler and condenser pressures. If the steam is superheated to a higher temperature, A. the turbine work output will decrease B. the amount of heat rejected will decrease C. the cycle efficiency will decrease D. the moisture content at turbine exit will decrease E. the amount of heat input will decrease 49. A Van der Waals gas is compressed isothermally from a molar volume of 22.4 L mol-1 to 0.5 L mol-1 at 273.15 K. Find the work done on the gas. a = 2.283 L2 bar mol-2, b = 0.04278 L mol1. Use R = 0.08314 L bar mol-1 K-1 A. 83.9 J/mol

B. -83.9 J/mol

C. 8500 J/mol

-8500 J/mol

D. NOTC

50. What is the pressure of nitrogen gas at T = 175 K and v = 0.00375 m3/kg on the basis of the Beattie-Bridgeman equation of state? A. 13,851 kPa

B. 9471. kPa

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C. 10,110 kPa

D. 10,009 kPA

E. 10,000 kPa...