1. Considerfollowing options for a simple Rankine cycle
i) increasing pressure at exist of turbine
ii) increasing average temperature of heat addition
iii) decreasing pressure at exit of turbine
iv) superheating of steam
v) decreasing pressure during superheating. Which combination of above will increase Rankine efficiency?
Correct : D. ii), iii) & iv)
2. Higher dryness fraction of steam at turbine exit in a Rankine cycle
Correct : C. will protect turbine blading
3. The main purpose of reheat Rankine cycle is
Correct : D. to reduce heat supplied & yet maintain turbine work
4. The temperature of feed water can be increased in following two ways in a regenerative Rankine cycle
i) by passing feed water around turbine casing in direction opposite to flow of steam
ii) by bleeding certain portion of steam at the end of h.p expansion & mixing with condensate to make feed water at the temperature of boiler
Correct : B. ii) is preferred over i) for reduced moisture content of steam in l.p side
5. In a steam power plant which cycle requires two or more feed pumps
Correct : A. regenerative rankine cycle
6. In a regenerative Rankine cycle as compared to simple Rankine cycle
Correct : D. the heat rejected in condenser is smaller
7. A Rankine cycle is less efficient than Carnot cycle because
Correct : B. heat is not added athighest temperature of cycle
8. A regenerative Rankine cycle may approach efficiency of a Carnot cycle between same temperature by
Correct : D. adding heat a highest temp.
9. Average temp.at which heat is supplied is increased in
Correct : C. regenerative rankine cycle
10. A power cycle using steam as working fluid consist of
i) constant pressure heat addition
ii)adiabatic expansion
iii) constant pressure heat rejection &
iv) adiabatic compression. The cycle is
Correct : C. carnot cycle
11. Steam enters the turbine at 5.44 bar with dryness fraction of 0.9 & is expanded adiabatically to a pressure of 0.68 bar. It will enter the condenser with a quality very close to
Correct : B. 0.815
12. A Rankine cycle has efficiency of 19.4%. The steam enters the turbine with enthalpy of 32.85 kJ/Kg while heat of water entering the boiler is 423.6 kJ/Kg.the work of the turbine is 560 kJ/ Kg. the pump work is
Correct : B. 5 kj/kg
13. A steam power plant working on Rankine cycle produces steam in the boiler at a rate of 100 kg/s with enthalpy of 3280 kJ/kg from water whose total heat content is 420 kJ/kg. The plant has Rankine efficiency of 24.65 while pump requires 5 kJ/kg of work. The turbine generates power of
Correct : A. 71 mw
14. In a simple Rankine cycle steam was expanded from 100 bar & 380°C to 1 bar 0.8 dry state. The pump motor consumes 10 kJ/kg of energy. The efficiency of cycle is
Correct : D. 30.6%
15. In a reheat Rankine cycle steam with enthalpy of 3300 kJ/kg is expanded in h.p turbine to a state where enthalpy is 2650 kJ/kg. The steam is further expnaded from a state where enthalpy is 2950 kJ/kg to enthalpy of 2525 kJ/kg & latent heat of 2201 kJ.kg. The work of the cycle & amount of reheat respectively are
Correct : A. 1075 kj/kg,300 kj.kg
16. In above question the heat supplied & efficiency respectively are
Correct : B. 2976 kj/kg, 36.12%
17. Due to which of the following reasons the Carnot cycle cannot be realised in actual practice?
Correct : C. both a & b
18. The flow through turbine on a Mollier chart is represented by
Correct : A. vertical line
19. The latent enthalpy of vapourisation at critical point is
Correct : A. zero
20. Above critical point, a substance exists as
Correct : D. supersaturated fluid
21. Triple point of a pure substance is a point at which
Correct : D. solid, liquid & vapour phases existtogether
22. Which of the following cycles is used in thermal power plants?
Correct : D. rankine
23. In a Carnot engine, when the working substance rejects its heat to sink, the temperature of sink
Correct : A. remains same
24. Which of the following is used as a working substance for a Carnot cycle?
Correct : A. ideal gas
25. ……… is the ratio of actual cycle efficiency to that of the ideal cycle efficiency
Correct : A. efficiency ratio
26. The gas laws can be used with minimum error is case of
Correct : D. superheated steam
27. Mathematically a pure substance can be written as
Correct : D. any of the above
28. A Carnot cycle operates between source & sink temperatures of 250°C & - 15°C. If the system receives 90kJ from the source then the net work transfer equals
Correct : C. 45.54 kj
29. Consider the following statements regarding superheating in Rankine Cycles
1. It reduces the specific steam consumption
2. It increases the dryness fraction of steam at the exhaust for the same value of condenser pressure
3. It reduces the cycle efficiency Of the these statements
Correct : A. 1 & 2 are correct
30. Energy is a
Correct : D. all of the mentioned
31. The specific energy, e=E/m is an extensive property.
Correct : B. false
32. (m*V*V)/2 gives the
Correct : A. macroscopic kinetic energy
33. (m*g*z) gives the
Correct : C. macroscopic potential energy
34. Which of the following types of energy can be present in molecules?
Correct : D. all of the mentioned
35. The total internal energy of the system is given by
Correct : B. u=nɛ
36. In an ideal gas there are no intermolecular forces of attraction and repulsion, and the internal energy is a function of temperature only.
Correct : A. true
37. Which of the following is true in regard to the energy of an isolated system?
Correct : C. e=constant
38. A perpetual motion machine of first kind
Correct : D. all of the mentioned
39. The limitation of the first law is
Correct : A. does not indicate the possibility of a spontaneous process proceeding in a definite direction
40. Integral of dQ/T is independent of reversible path connecting between two points.
Correct : A. true
41. Integral of dQ/T of a reversible path is given by
Correct : B. sf-si
42. Entropy is a
Correct : D. point function, extensive property
43. Specific entropy is given by( where m is the mass)
Correct : C. s/m
44. For any process which is undergone by a system
Correct : B. dq/t<=ds
45. For an irreversible process,
Correct : B. ds>dq/t
46. For two different paths between same two points, entropy change is
Correct : C. same
47. For the general case, we can write
Correct : B. s2-s1>=dq/t for a path
48. A reversible process is performed in such a way that
Correct : D. all of the mentioned
49. A reversible process coincides with a quasi-static process.
Correct : A. true
50. Irreversibility of a process may be due to
Correct : C. both of the mentioned
51. All actual heat transfer processes are
Correct : C. both of the mentioned
52. Free expansion is irreversible.
Correct : A. true
53. Which of the following can be a cause of irreversibility?
Correct : D. all of the mentioned
54. The continual motion of a movable device in the complete absence of friction is known as
Correct : B. pmm3
55. The friction present in moving devices makes a process reversible.
Correct : B. false
56. Which of the following is irreversible?
Correct : D. all of the mentioned
57. A process will be reversible if it has
Correct : A. no dissipative effects
58. Irreversibility can be distinguished in how many types?
Correct : C. 2
59. Internal irreversibility is caused by
Correct : D. all of the mentioned
60. The external irreversibility occurs at the system boundary.
Correct : A. true
61. Which of the following is true?
Correct : D. all of the mentioned
62. The magnitude of mechanical work is the
Correct : B. product of the force and distance travelled parallel to the force
63. Work done by a system is taken to be
Correct : A. positive
64. Work done on a system is taken to be
Correct : B. negative
65. Work is a
Correct : B. path function
66. Thermodynamic properties are
Correct : A. point function
67. In the equation dV=(1/p)dW, (1/p) is known as
Correct : D. integration factor
68. Cyclic integral of a property is always
Correct : A. zero
69. Constant pressure process is also known as
Correct : C. all of the mentioned
70. Work done in a quasi-static process
Correct : A. depends on the path followed
71. A saturation state is a state from which a change of phase may occur
Correct : A. without a change of pressure or temperature
72. In which of the following state does water exist?
Correct : D. all of the mentioned
73. 5 P-V DIAGRAM.
Correct : D. all of the mentioned
74. The triple point is a line on the p-V diagram, where all the three phases, solid, liquid and gas exist.
Correct : A. true
75. At a pressure below the triple point line,
Correct : C. both of the mentioned
76. Which of the following statement is true?
Correct : D. all of the mentioned
77. The greater the temperature, the is the vapour pressure.
Correct : B. higher
78. Phase change occurs at
Correct : C. constant pressure and temperature
79. Which of the following statement is true?
Correct : C. both of the mentioned
80. At absolute zero, an isotherm and an adiabatic are identical.
Correct : A. true
81. When the heat transferred isothermally
Correct : B. exists, cannot, without
82. First law of thermodynamics deals with
Correct : C. conservation of energy
83. During a fluid flow, the temperature is developed due to
Correct : C. translational kinetic energy
84. The equation for the average kinetic energy is
Correct : B. 1.5 kt
85. Entropy occurs due to
Correct : A. change in macroscopic variables
86. What is the equation of entropy?
Correct : A. ratio of reversible transfer of heat to absolute temperature
87. SI unit of enthalpy is
Correct : C. joule/kg
88. Which among this is not an exothermic reaction?
Correct : D. evaporating liquid water
89. What reaction takes place during photosynthesis?
Correct : B. endothermic reaction
90. The first law of thermodynamics doesn’t tell us whether a thermodynamic process is feasible or not.
Correct : A. true
91. According to Joule’s experiments,
Correct : B. work can be completely converted into heat
92. Which of the following is true?
Correct : D. all of the mentioned
93. Boiler, turbine, condenser and pump together constitute a heat engine.
Correct : A. true
94. In a heat engine cycle, which of the following process occurs?
Correct : D. all of the mentioned
95. A thermal energy reservoir is a large body of
Correct : C. infinite heat capacity
96. Processes inside a thermal energy reservoir are quasi-static.
Correct : A. true
97. Carnot cycle is a reversible cycle.
Correct : A. true
98. Which if the following statements are true for a mechanical energy reservoir(MER)?
Correct : D. all of the mentioned
99. The correct sequence of the processes taking place in a carnot cycle is
Correct : D. isothermal -> adiabatic -> isothermal -> adiabatic