MCQOPTIONS
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MCQOPTIONS
This section includes 15 Mcqs, each offering curated multiple-choice questions to sharpen your Thermal Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
In a boiler, some part of heat is lost to flue gases. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 2. |
Boiler efficiency doesn’t depend on _____ |
| A. | calorific value of fuel fired |
| B. | specific heat of steam generated |
| C. | boiler design |
| D. | operation time |
| Answer» E. | |
| 3. |
Determine the enthalpy of 1 kg of steam if the boiler efficiency is 79%, the evaporative capacity of the boiler is 9 kg of steam per kg of fuel fired, the feed water temperature is 40°C and the calorific value of coal is 30000 kJ/kg. |
| A. | 2500 kJ/kg |
| B. | 3000 kJ/kg |
| C. | 2800 kJ/kg |
| D. | 2200 kJ/kg |
| Answer» D. 2200 kJ/kg | |
| 4. |
Determine the evaporative capacity of a boiler in kg of steam per kg of fuel fired if the feed water temperature is 40°C, the efficiency of the boiler is 95%, calorific value of the coal fried is 33000 kJ/kg and the steam generated is dry and saturated at 12 bar pressure. |
| A. | 10 kg of steam/kg of fuel |
| B. | 12 kg of steam/kg of fuel |
| C. | 15 kg of steam/kg of fuel |
| D. | 15 kg of steam/kg of fuel |
| Answer» D. 15 kg of steam/kg of fuel | |
| 5. |
A boiler is fired with fuel having calorific value 30000 kJ/kg. It produces steam at 5 bar. The dryness fraction of the steam generated 0.85. The efficiency of the boiler is 77% and the evaporative e capacity of the boiler is 10 kg of steam per kg of fuel. Determine the temperature of feed water. |
| A. | 35°C |
| B. | 29°C |
| C. | 25°C |
| D. | 37°C |
| Answer» C. 25°C | |
| 6. |
A boiler having evaporative capacity 8 kg of steam per kg of fuel produces dry and saturated steam at 13 bar pressure. The feed water temperature is 35°C. Determine the calorific value of coal if the efficiency of the boiler is 70%. |
| A. | 35000 kJ/kg |
| B. | 29560 kJ/kg |
| C. | 31000 kJ/kg |
| D. | 30160 kJ/kg |
| Answer» E. | |
| 7. |
A boiler produces steam at the rate of 1500 kg per hour at 12.5 bar. The water fed to the economizer is at a temperature of 35°C and it is raised to a temperature of 110°C before feeding it to the boiler. Coal is fired at a rate of 200 kg per hour. The dryness fraction of the steam generated is 0.87. If 15% of the coal remains unburnt and the calorific value of the coal being fired is 36200 kJ/kg, determine the overall efficiency. |
| A. | 58% |
| B. | 65% |
| C. | 78% |
| D. | 82% |
| Answer» B. 65% | |
| 8. |
A boiler generates superheated steam having temperature 270°C and pressure 13 bar. The specific heat of the superheated steam 2.1 kJ/kg-K. The temperature of the feed water is 32°C. The evaporative capacity of the boiler is 8 kg of steam per kg of fuel. The calorific value of the coal is 26000 kJ/kg. |
| A. | 86.65% |
| B. | 70.32% |
| C. | 65.87% |
| D. | 90.80% |
| Answer» B. 70.32% | |
| 9. |
A boiler produces 4000 kg of dry and saturated steam in 6 hours. In the same time the mass of coal consumed is 300 kg of coal. The mean pressure of steam generated is 11 bar. The temperature of the feed water is 35°C. Determine the boiler efficiency if the calorific value of the fuel is 30000 kJ/kg. |
| A. | 85.64% |
| B. | 75.65% |
| C. | 95.65% |
| D. | 87.78% |
| Answer» E. | |
| 10. |
Following observations were made after the trial of a boiler for 24 hours.Mass of coal burnt = 1300 kgMass of steam generated = 14000 kgMean effective pressure of steam = 10 barTemperature of the feed water = 40°CCalorific value of coal = 30000 kJ/kgCalculate the boiler efficiency if the dryness fraction of the steam generated is 0.95. |
| A. | 90% |
| B. | 80% |
| C. | 70% |
| D. | 60% |
| Answer» B. 80% | |
| 11. |
Which of the following is not a heat recovery equipment? |
| A. | Economizer |
| B. | Air preheater |
| C. | Feed water heater |
| D. | Steam separator |
| Answer» E. | |
| 12. |
Boiler efficiency is the ratio of heat actually absorbed by water during generation of steam to the heat supplied in by the fuel in the same time period. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 13. |
The following listed are some factors on which boiler efficiency depends. Which of the following is a variable factor? |
| A. | Excess air fluctuations |
| B. | Rated rate of firing |
| C. | Boiler design |
| D. | Heat recovery equipment |
| Answer» B. Rated rate of firing | |
| 14. |
Which of the following is a fixed factor on which boiler efficiency depends? |
| A. | Actual firing rate |
| B. | Humidity of combustion air |
| C. | Condition of heat absorbing surfaces |
| D. | Properties of the fuel burnt |
| Answer» E. | |
| 15. |
Which of the following is the correct formula for calculating boiler efficiency? |
| A. | η = \(\frac{(h-h_{f1})}{C} \) |
| B. | η = \(\frac{m_a (h-h_{f1})}{C} \) |
| C. | η = \(\frac{m_a (h_{f1}-h}{C} \) |
| D. | η = \(\frac{m_a (h-h_{f1})}{2257} \) |
| Answer» C. η = \(\frac{m_a (h_{f1}-h}{C} \) | |