Deck 15: Rankine Cycle and Properties of Steam

Question 1

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

Answer 1

True

Question 2

Which of the following statement is true?

A)a subcooled liquid is one which is cooled below its saturation temperature at a certain pressure
B)subcooling is the difference between the saturation temperature and the actual liquid temperature
C)both of the mentioned
D)none of the mentioned

Answer 2

both of the mentioned

Question 3

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

A)to control flow rate
B)to control phase change
C)to protect reheat tubes
D)none of the mentioned

Answer 3

to protect reheat tubes

Question 4

Net Work output of the plant   with reheat.

A)decreases
B)increases
C)remains same
D)none of the mentioned

Question 5

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

A)decreases
B)increases
C)remains same
D)none of the mentioned

Question 6

The optimum reheat pressure for most of the power plants is how many times of the initial steam pressure?

A)0.1-0.15
B)0.2-0.20
C)0.2-0.25
D)0.1-0.10

Question 7

What is the most preferable dryness

A)0.99
B)0.77
C)0.66
D)0.88

Question 8

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

A)reheat is used
B)reheat is not used
C)only reheat is used
D)none of the mentioned

Question 9

At critical point, value of Vg-Vf is

A)two
B)one
C)zero
D)infinity

Question 10

Above the critical point, the isotherms are continuous curves.

Question 11

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.

A)0.104 kg
B)0.124 kg
C)0.134 kg
D)0.114 kg

Question 12

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.

A)60.183 kpa
B)70.183 kpa
C)80.183 kpa
D)90.183 kpa

Question 13

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.

A)1.73 m³
B)2.73 m³
C)3.73 m³
D)4.73 m³

Question 14

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

A)0.127
B)0.137
C)0.147
D)0.157

Question 15

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

A)0.022325 m³/kg
B)0.024325 m³/kg
C)0.025325 m³/kg
D)0.026325 m³/kg

Question 16

What is the unit of Heat rate?

A)kj/kw
B)kw/kj
C)kj
D)kw

Question 17

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

A)has higher thermal efficiency than the carnot cycle operating between same pressure limits
B)has lower thermal efficiency than carnot cycle operating between same pressure limits
C)has same thermal efficiency as carnot cycle operating between same pressure limits
D)may be more or less depending upon the magnitudes of p1 and p2

Question 18

Rankine efficiency of a Steam Power Plant

A)improves in summer as compared to that in winter
B)improves in winter as compared to that in summer
C)is unaffected by climatic conditions
D)none of the mentioned

Question 19

Rankine cycle comprises of  

A)two isentropic processes and two constant volume processes
B)two isentropic processes and two constant pressure processes
C)two isothermal processes and two constant pressure processes
D)none of the mentioned

Question 20

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

A)change of internal energy between inlet and outlet
B)change of enthalpy between inlet and outlet
C)change of entropy between inlet and outlet
D)change of temperature between inlet and outlet

Question 21

What is the actual turbine inlet temperature in Rankine cycle?

A)700c
B)800c
C)550c
D)1150c

Question 22

Rankine cycle efficiency of a good Steam Power Plant may be in the range of?

A)15 to 20%
B)35 to 45%
C)70 to 80%
D)90 to 95%

Question 23

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?

A)50
B)60
C)70
D)80

Question 24

Why both reheating and regeneration is used together?

A)the effect of reheat alone on efficiency is very small
B)regeneration has a marked effect on efficiency
C)both of the mentioned
D)none of the mentioned

Question 25

Which of the following statement is true?

A)open heater is also known as contact-type heater
B)in an open type heater the extracted or bled steam is allowed to mix with the feedwater
C)in a closed heater, the fluids are not allowed to mix together
D)all of the mentioned