MCQOPTIONS
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MCQOPTIONS
This section includes 14 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. |
Which of the following is not a heat recovery equipment? |
| A. | Economizer |
| B. | Air preheater |
| C. | Feed water heater |
| D. | Steam separator |
| Answer» E. | |
| 11. |
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 | |
| 12. |
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 | |
| 13. |
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. | |
| 14. |
Which of the following is the correct formula for calculating boiler efficiency? |
| A. | = ( frac{(h-h_{f1})}{C} ) |
| B. | = ( frac{m_a (h-h_{f1})}{C} ) |
| C. | = ( frac{m_a (h_{f1}-h}{C} ) |
| D. | = ( frac{m_a (h-h_{f1})}{2257} ) |
| Answer» C. = ( frac{m_a (h_{f1}-h}{C} ) | |