Q.1
Minimum work in compressor is possible when the value of adiabatic index ‘n’ is equal to
Q.2
Which of the following cycles has maximum efficiency?
Q.3
No liquid can exist as liquid at
Q.4
The molecular mass expressed in gram (i.e. 1 g - mole) of all gases, at N. T. P., occupies a volume of
Q.5
Otto cycle efficiency is higher than Diesel cycle efficiency for the same compression ratio and heat input because in Otto cycle
Q.6
Which of the following processes is irreversible process?
Q.7
The amount of heat required to raise the temperature of the unit mass of gas through one degree at constant volume, is called
Q.8
A diathermic wall is one which
Q.9
Rankine cycle efficiency of a good steam power plant may be in the range of
  • 15 to 20%
  • 35 to 45%
  • 70 to 80%
  • 90 to 95%
Q.10
The efficiency of an ideal Carnot engine depends on
  • a) working substance
  • b) on the temperature of the source only
  • c) on the temperature of the sink only
  • d) on the temperatures of both the source & the sink
Q.11
Which of the following contributes to the improvement of efficiency of Rankine cycle in a Thermal Power Plant?
  • reheating of steam at intermediate stage
  • regeneration use of steam for heating boiler feed water
  • use of high pressures
  • all of the mentioned
Q.12
A regenerative Rankine cycle may approach efficiency of a Carnot cycle between sametemperature by
  • a) reducing heat to condenser
  • b) reducing volume of steam passed into condenser
  • c) increasing turbine work
  • d) adding heat a highest temp.
Q.13
The temperature of feed water can be increased in following two ways in a regenerative Rankine cyclei) by passing feed water around turbine casing in direction opposite to flow of steamii) 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
  • a) i) is preferred over ii) for higher efficiency
  • b) ii) is preferred over i) for reduced moisture content of steam in l.p side
  • c) only i) is implemented in actual practice
  • d) by preferring ii) overi) significant gain in efficiency results
Q.14
The universal gas constant will be equal to difference between specific heats at constant pressure & constant volume for
  • 1 kg mass of gas
  • 1 molecule of gas
  • 1 kg molecule of gas
  • any mass of gas
Q.15
Air expands from initial condition of pv1 to final condition of 1/2 p2v1.Choose the correct statement
  • a) no work is performed during expansion
  • b) expansion is isothermal
  • c) expansion is polytropic with n= 1.2
  • d) expansion is adiabatic
Q.16
Steam enters the turbine at 5.bar with dryness fraction of 0.9 & is expanded adiabatically to a pressure of 0.bar. It will enter the condenser with a quality very close to
  • a) 0.79
  • b) 0.815
  • c) 0.84
  • d) 0.86
Q.17
A power cycle using steam as working fluid consist ofi) constant pressure heat addition ii)adiabatic expansioniii) constant pressure heat rejection & iv) adiabatic compression. The cycle is
  • simple rankine cycle
  • modified rankine cycle
  • carnot cycle
  • regenerative rankine cycle
Q.18
Which of the following remains constant during an adiabatic expansion
  • a) entropy
  • b) temperature
  • c) internal energy
  • d) none of the above
Q.19
According to Carnot’s theorem, all heat engines operating between a given constant temperature source and sink, none has a higher efficiency than a reversible engine.
  • true
  • false
Q.20
Relative humidity is defined as
  • (saturation pressure of pure water) / pw
  • pw / (saturation pressure of pure water)
  • (saturation pressure of pure water) / p
  • p / (saturation pressure of pure water)
Q.21
The efficiency and work ratio of a simple gas turbine cycle are
  • low
  • very low
  • high
  • very high
Q.22
In a steam power plant which cycle requires two or more feed pumps
  • regenerative rankine cycle
  • reheat rankine cycle
  • simple rankine cycle
  • idealized regenerative rankine cycle
Q.23
The entropy __________ in an irreversible cyclic process.
  • remains constant
  • decreases
  • increases
Q.24
The optimum reheat pressure for most of the power plants is how many times of the initial steam pressure?
  • 0.1-0.15
  • 0.2-0.20
  • 0.2-0.25
  • 0.1-0.10
Q.25
Which of the following cycles is used in thermalpower plants?
  • a) brayton
  • b) carnot
  • c) ericsson
  • d) rankine
Q.26
By reducing the condenser pressure in Rankine power plant
  • a) heat supplied increases & work of cycle decreases
  • b) work of cycle & moisture content of steam in l.p side ofturbine increase
  • c) heat supplied & efficiency of cycle increase
  • d) work of cycle increases but heat supplied decreases
Q.27
Essential parts of a power plant operating on aRankine cycle are
  • a) engine or turbine
  • b) engine or turbine & conderser
  • c) engine or turbine, condenser, pump &boiler
  • d) engine or turbine & boiler
Q.28
Most of the fossil fuelbased power plants operate on
  • a) rankine cycle
  • b) brayton cycle
  • c) carnot cycle
  • d) either rankine or brayton cycle
Q.29
When unsaturated air flows over a sheet of water in an insulated chamber
  • specific humidity of air decreases
  • the water evaporates
  • both air and water are cooled during evaporation
  • all of the mentioned
Q.30
At any dbt, the          the difference of wbt reading below below dbt,          is the amount of water vapour held in mixture.
  • smaller, smaller
  • greater, greater
  • greater, smaller
  • smaller, greater
0 h : 0 m : 1 s