Thermal Engineering

TSadhu Singh, Sukumar Pati

Chapter 4

Steam Power Cycles - all with Video Answers

Educators

Chapter Questions

Problem 1

The efficiency of Rankine cycle can be increased by
(a) decreasing initial steam pressure and temperature
(b) increasing exhaust pressure
(c) increasing expansion ratio
(d) increasing regenerative heaters

Hunza Gilgit

Hunza Gilgit

Numerade Educator

Problem 2

Choose the wrong statement:
(a) bleeding increases the thermodynamic efficiency of turbine
(b) bleeding increases the net power developed by turbine
(c) bleeding decreases the net power developed by turbine
(d) boiler is supplied with hot water due to bleeding.

Hunza Gilgit

Numerade Educator

Problem 3

In the Rankine cycle, with the maximum steam temperature being fixed from metallurgical consideration, as the boiler pressure increases,
(a) the condenser load will increase
(b) the quality of turbine exhaust will decrease
(c) the quality of turbine exhaust will increase
(d) the quality of turbine exhaust will remain unchanged

Hunza Gilgit

Numerade Educator

Problem 4

Rankine cycle comprises
(a) two isentropic and two reversible constant volume processes
(b) two isentropic and two reversible constant pressure processes
(c) two reversible isothermal and two reversible
constant pressure processes
(d) two reversible constant pressure and two reversible constant volume processes.

Hunza Gilgit

Numerade Educator

Problem 5

Regeneration effect on Rankine cycle
(a) decreases thermal efficiency
(b) increases thermal efficiency
(c) has no effect on thermal efficiency
(d) increases or decreases thermal efficiency depending on the point extraction of steam.

Hunza Gilgit

Numerade Educator

Problem 6

Superheating of steam before expansion in a Rankine cycle
(a) decreases thermal efficiency
(b) has no effect on thermal efficiency
(c) increases thermal efficiency
(d) may increase or decrease thermal efficiency.

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Problem 7

Reheating of steam
(a) increases thermal efficiency
(b) increases work output of turbine
(c) decreases work output of turbine
(d) increases thermal efficiency but decreases work output.

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Problem 8

In a binary vapour cycle,
(a) mercury is used in the bottoming cycle
(b) steam is used in the topping cycle
(c) mercury is used in the topping cycle
(d) either mercury or steam may be used in the topping cycle.

Hunza Gilgit

Numerade Educator

Problem 9

In a steam power plant, feed water heater is a heat exchanger to preheat feed water by
(a) live steam from steam generator
(b) hot flue gases coming out of the boiler furnace
(c) hot air from air preheater
(d) extracting steam from turbine

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Numerade Educator

Problem 10

Consider the following statements regarding effects of reheating of steam in a steam turbine:
I. It increases the specific output of the turbine.
II. It decreases cycle efficiency.
III. It increases blade erosion. IV. It improves the quality of exit steam. Which of these statements are correct?
(a) I and II
(b) II and III
(c) III and IV
(d) I and IV

Hunza Gilgit

Numerade Educator

Problem 11

In a steam power plant, what is the outcome of regenerative feed water heating?
I. Increase in specific output
II. Increase in cycle efficiency
III. Improved quality of exhaust steam IV. Reduced condenser load Select the correct answer using the code given below:
(a) I and III only
(b) II only
(c) II and IV
(d) I, II and III

Hunza Gilgit

Numerade Educator

Problem 12

In a regenerative feed heating cycle, the economic number of the stages of regeneration
(a) increases as the initial pressure and temperature increase
(b) decreases as the initial pressure and temperature increase
(c) is independent of the intitial pressure and temperature
(d) depends only on the condenser pressure

Hunza Gilgit

Numerade Educator

Problem 13

Consider the following statements:
The reheat cycle helps to reduce
I. fuel consumption
II. steam flow
III. the condenser size Which of these statements are correct?
(a) I and II
(b) I and III
(c) II and III
(d) I, II, and III

Hunza Gilgit

Numerade Educator

Problem 14

The main advantage of a reheat Rankine cycle is
(a) reduced moisture content in LP side of turbine
(b) increased efficiency
(c) reduced load on condenser
(d) reduced load on pump

Hunza Gilgit

Numerade Educator

Problem 15

Consider the following statement pertaining to the features of regenerative steam cycle plant as compared to a non-regenerative plant:
I. It increases the cycle efficiency.
II. It requires a bigger boiler.
III. It requires a smaller condenser. Which of the statements are correct?
(a) I, II, and III
(b) I and II
(c) II and III
(d) I and III

Hunza Gilgit

Numerade Educator

Problem 16

Which of the following statements is not correct for regenerative steam cycle?
(a) It increase thermodynamic efficiency.
(b) It reduces boiler capacity for a given output.
(c) It reduces temperature stresses in the boiler due to hotter feed.
(d) The efficiency increases with increased number of feed heaters.

Hunza Gilgit

Numerade Educator

Problem 17

Consider the following for a steam turbine power plant:
I. Reduction in blade erosion
II. Increase in turbine speed
III. Increase in specific output
IV. Increase in cycle efficiency Which of these occurs due to reheating of steam?
(a) Only I
(b) $\mathrm{I}$ and II
(c) IIII, and IV
(d) II and III

Hunza Gilgit

Numerade Educator

Problem 18

When is the greatest economy obtained in $\mathrm{a}$ regenerative feed heating cycle?
(a) Steam is extracted from only one suitable point of a steam turbine.
(b) Steam is extracted only from the last stage of steam turbine.
(c) Steam is extracted only from the first stage of a steam turbine.
(d) Steam is extracted from several places in different stages of steam turbines.

Hunza Gilgit

Numerade Educator

Problem 19

Consider the following statements:
The purpose of reheating the steam in a steam turbine power plant is to
$\mathrm{I}$. increase specific output
II. increase turbine efficiency
III. reduce turbine speed IV. reduce specific steam consumption Which of the statements are correct?
(a) II and IV
(b) $\mathrm{I}$ and III
(c) I, II, and IV
(d) I, III, and IV

Hunza Gilgit

Numerade Educator

Problem 20

In the bottoming cycle of cogeneration, low-grade waste heat is used for
(a) processing
(b) power generation
(c) feed water heating
(d) None of these

Hunza Gilgit

Numerade Educator

Problem 21

In steam and other vapour cycles, the process of removing non-condensables is called
(a) scavenging process
(b) deaeration process
(c) exhaust process
(d) condensation process

Hunza Gilgit

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