Engineering Thermodynamics Set 15 MCQs

Q1 | The superheat or degree of superheat is given by

difference between the temperature of saturated liquid and saturation temperature

difference between the temperature of superheated vapour and saturation temperature

sum of the temperature of superheated vapour and saturation temperature

none of the mentioned

Q2 | When the temperature of a liquid is less than the saturation temperature at the given pressure, the liquid is called compressed liquid.

true

false

Q3 | Which of the following statement is true?

a subcooled liquid is one which is cooled below its saturation temperature at a certain pressure

subcooling is the difference between the saturation temperature and the actual liquid temperature

both of the mentioned

none of the mentioned

Q4 | Why is the steam not allowed to expand deep into the two phase region before it is taken to reheating?

to control flow rate

to control phase change

to protect reheat tubes

none of the mentioned

Q5 | Net Work output of the plant with reheat.

decreases

increases

remains same

none of the mentioned

Q6 | What is the effect of decrease of reheat pressure on the quality of steam at turbine exhaust?

decreases

increases

remains same

none of the mentioned

Q7 | 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

Q8 | What is the most preferable dryness

0.99

0.77

0.66

0.88

Q9 | For pressure ratio = 1, efficiency = 0, then?

reheat is used

reheat is not used

only reheat is used

none of the mentioned

Q10 | At critical point, value of Vg-Vf is

two

one

zero

infinity

Q11 | Above the critical point, the isotherms are continuous curves.

true

false

Q12 | A piston –cylinder device contains 0.06m3 of saturated water vapour at 350 kPa pressure. Determine the temperature and mass of the vapour inside the cylinder.

0.104 kg

0.124 kg

0.134 kg

0.114 kg

Q13 | 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 vapour form, determine the pressure in the tank.

60.183 kpa

70.183 kpa

80.183 kpa

90.183 kpa

Q14 | 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 vapour form, determine the volume of the tank.

1.73 m3

2.73 m3

3.73 m3

4.73 m3

Q15 | An 80 litre vessel contains 4 kg of R-134a at a pressure of 160 kPa. Determine the quality.

0.127

0.137

0.147

0.157

Q16 | Determine the specific volume of R-134a at 1 MPa and 50°C, using ideal gas equation of state.

0.022325 m3/kg

0.024325 m3/kg

0.025325 m3/kg

0.026325 m3/kg

Q17 | What is the unit of Heat rate?

kj/kw

kw/kj

kj

kw

Q18 | Rankine cycle operating on low pressure limit of p1 and high pressure limit of p2

has higher thermal efficiency than the carnot cycle operating between same pressure limits

has lower thermal efficiency than carnot cycle operating between same pressure limits

has same thermal efficiency as carnot cycle operating between same pressure limits

may be more or less depending upon the magnitudes of p1 and p2

Q19 | Rankine efficiency of a Steam Power Plant

improves in summer as compared to that in winter

improves in winter as compared to that in summer

is unaffected by climatic conditions

none of the mentioned

Q20 | Rankine cycle comprises of

two isentropic processes and two constant volume processes

two isentropic processes and two constant pressure processes

two isothermal processes and two constant pressure processes

none of the mentioned

Q21 | In Rankine cycle, the work output from the turbine is given by

change of internal energy between inlet and outlet

change of enthalpy between inlet and outlet

change of entropy between inlet and outlet

change of temperature between inlet and outlet

Q22 | What is the actual turbine inlet temperature in Rankine cycle?

700c

800c

550c

1150c

Q23 | 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%

Q24 | A simple Rankine cycle produces 40 MW of power, 50 MW of process heat and rejects 60 MW of heat to the surroundings. What is the utilization factor of this co generation cycle neglecting the pump work?

50

60

70

80

Q25 | Why both reheating and regeneration is used together?

the effect of reheat alone on efficiency is very small

regeneration has a marked effect on efficiency

both of the mentioned

none of the mentioned