This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Reheat-Regenerative Cycle and Feedwater Heaters”.
1. The reheating of steam is used when the vaporization pressure is ____.
a) low
b) high
c) both when low or high
d) always
View Answer
Explanation: When vaporization pressure is high, the reheating of steam is adopted.
2. 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
View Answer
Explanation: Thus a modern steam power plant has both reheating and regeneration.
3. How many types of feedwater heaters are present?
a) one
b) two
c) three
d) four
View Answer
Explanation: The two types are open heaters and closed heaters.
4. 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
View Answer
Explanation: These are the details of open and closed type heater.
5. The temperature of feedwater leaving a heater is ____ the saturation temperature at steam extraction pressure.
a) less than
b) equal to
c) more than
d) none of the mentioned
View Answer
Explanation: Their difference is known as the terminal temperature difference of heater.
6. Which of the following is true for an open heater?
a) it is simple, has low cost and low heat transfer capacity
b) a pump is required at each heater
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: The open heater has high heat transfer capacity.
7. Deaerator is a type of open heater.
a) true
b) false
View Answer
Explanation: In steam power plants, closed heaters are favoured but one open heater is used for the purpose of feedwater deaeration.
8. Which of the following is true for a closed heater?
a) it requires a single pump regardless of the number of heaters
b) it is costly
c) both of the mentioned
d) none of the mentioned
View Answer
Explanation: Closed heaters may not give as high feedwater temperature as do open heaters.
9. The higher the number of heaters used, the ____ will be the cycle efficiency.
a) lower
b) higher
c) efficiency does not depend on number of heaters
d) none of the mentioned
View Answer
Explanation: The cycle efficiency varies according to the number of heaters.
10. If n heaters are used, the greatest gain in efficiency occurs when overall temperature rise is ____ times the difference between condenser and boiler saturation temperatures.
a) (n-1) / n
b) (n+1) / n
c) n / (n-1)
d) n / (n+1)
View Answer
Explanation: This gives us the greatest gain in efficiency.
11. The efficiency gain follows the law of diminishing return with the increase in the number of heaters.
a) true
b) false
View Answer
Explanation: This is because the cycle efficiency is proportional to the temperature rise of feedwater.
12. Which of the following statement is true?
a) in some cases, an increase in feedwater temperature may reduce the boiler efficiency
b) number of heaters are optimized
c) most often, five points of extraction are used
d) all of the mentioned
View Answer
Explanation: The number of heaters get fixed by the exergy balance of the whole plant.
13. The thermal irreversibility should be ____ to improve the performance.
a) reduced
b) increased
c) kept constant
d) none of the mentioned
View Answer
Explanation: The major exergy destruction due to irreversibility takes place in the steam generation.
Sanfoundry Global Education & Learning Series – Thermodynamics.
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