McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 1. |
Rankine cycle efficiency of a good Steam |
| A. | 15 to 20% |
| B. | 35 to 45% |
| C. | 70 to 80% |
| D. | 90 to 95% |
| Answer» B. 35 to 45% | |
| Explanation: efficiency of rankine cycle in actual working condition is found to be between 35 to 45%. | |
| 2. |
A simple Rankine cycle operates the Boiler at 3 MPa with an outlet temperature of 350°C and the Condenser at 50 kPa. Assuming ideal operation and processes, what is the thermal efficiency of this cycle? |
| A. | 7.7 |
| B. | 17.7 |
| C. | 27.7 |
| D. | 37.7 |
| Answer» C. 27.7 | |
| Explanation: fixing the states; h1 = 340.5 kj/kg, h2 = h1 + v1 (p2 – p1) = 343.5 kj/kg, h3 = 3115.3 kj/kg, s3 = 6.7428 kj/kg – k, x4 | |
| 3. |
On what basis are fire and water tube boilers are classified? |
| A. | depending the combustion products formed |
| B. | depending the state of fuel |
| C. | depending on the steam formation rate |
| D. | depending tubular heating surface |
| Answer» D. depending tubular heating surface | |
| Explanation: based on the contents of the tubular heating surface, boilers are primarily classified as fire tube boiler and water tube boiler. fire tube boilers those in which production of combustion pass through the tubes and water tube boilers are those in which the products of combustion surround the water tubes from outside. | |
| 4. |
Cornish boiler is an example of which type of boiler? |
| A. | fire tube boiler |
| B. | water tube boiler |
| C. | vertical tube boiler |
| D. | externally fired boiler |
| Answer» A. fire tube boiler | |
| Explanation: cornish boiler is an example of fire tube boiler and also includes cochran, lancashire, and locomotive and scotch marine boilers. fire tube boilers are those in which the products of combustion pass through the tubes and water lies around the outside of tubes. these boilers operate at moderate pressure (16-20bar) and more suitable to generate 3-8 tons of steam per hour which is used in process heating. | |
| 5. |
Stirling boiler is an example of which type of boiler? |
| A. | inclined tube boilers |
| B. | mobile boiler |
| C. | fire tube boiler |
| D. | water tube boiler |
| Answer» D. water tube boiler | |
| Explanation: water tube boilers are those in which the products of combustion (hot flue gas) surround the water tubes from outside. cold water enters the tubes and leaves hot. these boilers operate at very high pressures and are used for power generation. | |
| 6. |
Which of these is a stationary boiler? |
| A. | locomotive boiler |
| B. | marine boiler |
| C. | mobile boiler |
| D. | babcock-wilcox boiler |
| Answer» D. babcock-wilcox boiler | |
| Explanation: if the boilers are used at one place only they are termed as stationary boilers. these boilers are used for either process heating in industries or for power generation in steam power plants. these are used at central station utility power plants, for plant process etc. ex: babcock-wilcox boiler, fluidized bed combustion (fbc) boiler. | |
| 7. |
Which of these is a mobile boiler? |
| A. | lancashire boiler |
| B. | stirling boiler |
| C. | locomotive boiler |
| D. | cochran boiler |
| Answer» C. locomotive boiler | |
| Explanation: the boilers, if they are portable, i.e., if they can be moved from one place to other place those are known as mobile boilers. such boilers are used in locomotives and ships to get the engine moving. and also small units are used for temporary at working sites. ex: locomotive boiler, marine boiler etc. | |
| 8. |
Are boilers defined on the basis of heat source. |
| A. | yes |
| B. | no |
| Answer» A. yes | |
| Explanation: boilers can be classified based on fuel used for combustion or heat generation source. various heat sources are: heat generated by the combustion of fuel in solid, liquid or gaseous form. heat generated by hot waste gases as byproducts of other chemical processes. heat generated by electrical energy and nuclear energy. | |
| 9. |
What is the steam pressure limit of natural circulation boilers? |
| A. | 650bar |
| B. | 180bar |
| C. | 400bar |
| D. | 550bar |
| Answer» B. 180bar | |
| Explanation: water is purely circulated by density difference with most of the heat from the fuel flame being radiated to the water walls directly. the steam pressure of such boilers is limited to about 180bar, with water and steam being separated in the boiler drum. | |
| 10. |
Which of the given boilers operate above critical pressure? |
| A. | natural circulation boilers |
| B. | forced circulation boilers |
| C. | once-through boilers |
| D. | water tube boilers |
| Answer» C. once-through boilers | |
| Explanation: once-through boilers operate above critical pressure i.e., above 221.2bar. as the density of water and steam are same above the critical pressure there will be no recirculation. these types of boilers are also called as positive forced circulation boilers. | |
| 11. |
Which type of boilers are called drum-less boilers? |
| A. | natural circulation boilers |
| B. | fire tube boilers |
| C. | positive forced circulation boiler |
| D. | forced circulation boiler |
| Answer» C. positive forced circulation boiler | |
| Explanation: in positive forced boilers, water enters the bottom of the tubes and completely transforms into steam as it passes through the tubes and reaches at the top. thus, these boilers do not need a steam drum and hence often referred as drum-less boilers. these boilers work at very high pressures. | |
| 12. |
Chances of sediments depositing inside the water tubes in the shell is less due to? |
| A. | low working pressure |
| B. | natural circulation of water |
| C. | partial circulation of water |
| D. | high working pressure |
| Answer» D. high working pressure | |
| Explanation: due to high working pressure and positive circulation of water, chances of sediments depositing inside water tubes in the shell is less. this high working pressure of boiler in the shell can withstand high temperature or thermal stresses. | |
| 13. |
Out of the given option choose the advantage that supports fire tube boilers? |
| A. | water circulation is cyclic |
| B. | used as a mobile boiler |
| C. | water circulation is limited inside boiler shell |
| D. | bursting of flue tube does not cause any explosion |
| Answer» C. water circulation is limited inside boiler shell | |
| Explanation: water circulation is limited inside the boiler shell. water need not be that much pure and needs minimum treatment like passing through a pressure filter. cleaning | |
| 14. |
Apart from feedheating, what should a plant have to obtain a gain in thermal efficiency? |
| A. | lubrication |
| B. | differential heating |
| C. | reheating cycles |
| D. | regenerative cycles |
| Answer» C. reheating cycles | |
| Explanation: to obtain a gain in thermal cycle efficiency, apart from the feedheating, there should be multiple number of reheats. | |
| 15. |
Which of the following needs to be incorporated to prevent the low pressure turbine exhaust wetness from being excessive? |
| A. | double regeneration |
| B. | double carnotization |
| C. | double reheat |
| D. | double cooling |
| Answer» C. double reheat | |
| Explanation: incorporating double reheat is one way to prevent the low pressure turbine exhaust wetness from being excessive. | |
| 16. |
What is the critical point of steam generation in a “once through” boiler? |
| A. | 221.5 bar |
| B. | 221.4 bar |
| C. | 221.3 bar |
| D. | 221.2 bar |
| Answer» D. 221.2 bar | |
| Explanation: steam generation in a “once through” boiler is at the critical point of 221.2 bar. | |
| 17. |
In a typical layout of a 215MW reheat power plant, the feed in the boiler is at? |
| A. | 280 degree centigrade |
| B. | 230 degree centigrade |
| C. | 238 degree centigrade |
| D. | 250 degree centigrade |
| Answer» C. 238 degree centigrade | |
| Explanation: in a typical layout of a 215mw | |
| 18. |
The input to the low pressure feedwater heater is from? |
| A. | drain heater |
| B. | drain cooler |
| C. | drain pipe |
| D. | none of the mentioned |
| Answer» B. drain cooler | |
| Explanation: the input to the low pressure feedwater heater comes from the drain cooler which goes to the deaerator. | |
| 19. |
The best capable alternative source which can meet the future energy demand is |
| A. | thermal power plant |
| B. | nuclear power plant |
| C. | hydroelectric power plant |
| D. | geothermal power plant |
| Answer» B. nuclear power plant | |
| Explanation: demand of electrical energy is increasing at fast rate owing to booming increase in the population and industrial growth. the reserves of fossil fuel i.e., coal, oil and gas are fast depleting. there are many alternative sources of energy but they are not enough to supply such huge demand, only | |
| 20. |
How much coal is required to generate energy equivalent to the energy generated by 1 kg of uranium? |
| A. | 30000 tonnes of high grade coal |
| B. | 300 tonnes of high grade coal |
| C. | 10000 tonnes of high grade coal |
| D. | 3000 tonnes of high grade coal |
| Answer» D. 3000 tonnes of high grade coal | |
| Explanation: one of the main attention for nuclear fuel is the huge amount of energy that can be released from a small quantity of active nuclear fuel. the energy obtainable by | |
| 21. |
Nuclear fuel in reactor lasts for |
| A. | more than 5 months |
| B. | few weeks |
| C. | few days |
| D. | more than 5 years |
| Answer» D. more than 5 years | |
| Explanation: very small amount of nuclear fuel can produce very high amount of energy. nuclear fuel may remain in a reactor for more than 5 years. | |
| 22. |
Cost of nuclear fuel in nuclear power plant economics is considered as |
| A. | running cost |
| B. | maintenance cost |
| C. | capital cost |
| D. | development cost |
| Answer» C. capital cost | |
| Explanation: nuclear fuel in a nuclear reactor may remain for more than 5 years. so the cost of fuel injected initially is taken as capital cost and may be a few crore rupees. | |
| 23. |
Which of the following are not taken as operation and maintenance cost in economics of nuclear power plant? |
| A. | taxes and insurance |
| B. | salaries and wages of staff |
| C. | cost of waste disposal |
| D. | cost of processing materials |
| Answer» A. taxes and insurance | |
| Explanation: taxes and insurance are taken as fixed costs. salaries and wages of operation and maintenance staff, cost of waste disposal and cost of processing materials are the operation and maintenance cost. | |
| 24. |
What is the overall efficiency of nuclear power plant? |
| A. | 20 to 25% |
| B. | 25 to 30% |
| C. | 30 to 40 % |
| D. | 50 to 70 % |
| Answer» C. 30 to 40 % | |
| Explanation: the overall efficiency of a nuclear power plant is around 30 to 40%. efficiency is higher at high road factors. therefore, a nuclear power plant is always operated as a base load plant. | |
| 25. |
The land area required for installation of nuclear power plant is |
| A. | more than thermal power plant |
| B. | less than thermal power plant |
| C. | equel to thermal power plant |
| D. | depends on type of construction |
| Answer» C. equel to thermal power plant | |
| Explanation: nuclear power plants need less area as compared to any other plant of same generation capacity. a 2000mw nuclear power plant needs about 80 acres whereas the coal fired steam power plant of same generation capacity needs 250 acres of land. | |
| 26. |
All of the nuclear fuel reserve will be ended in about 400 years. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: there are larger deposits of nuclear fuel available all over the world. therefore, such plants can ensure continued supply of electrical energy for thousands of years. | |
| 27. |
With respect to the load centre which location is suitable for stablishment of nuclear power plant? |
| A. | load centre |
| B. | near load centre but at reasonable distance |
| C. | far away from load centre |
| D. | near chemical industries |
| Answer» B. near load centre but at reasonable distance | |
| Explanation: these plants can be located near the load centre because of the negligible | |
| 28. |
Operating cost of nuclear power plant is less than thermal power plant. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: cost of fuel in nuclear power plant is taken as the capital cost. the the total operating cost involves wages and the salaries of operating and maintenance staff only, cost of disposal of waste etc.. the cost of transport and handling of coal for conventional thermal power plant is much higher than the cost of nuclear fuel. | |
| 29. |
What is the role of breaker house in coal feeding? |
| A. | to break the coal into smaller pieces |
| B. | to separate different sizes of coal |
| C. | to separate the light dust from the coal |
| D. | to powder the coal |
| Answer» C. to separate the light dust from the coal | |
| Explanation: because of the brittle nature of the coal, it is a common nature of coal to emit light dust/coal dust during transportation, mining and machine handling. this dust needs to be cleared out and it is performed by coal breaker. | |
| 30. |
Large amount of coal is transported by |
| A. | railway |
| B. | sea or river ways |
| C. | road transportation |
| D. | by airlifting |
| Answer» A. railway | |
| Explanation: the railway is preferred since it is quite economical as well as loading and unloading of coal is easy. and at stretch tons of coal can be transported by goods train from one place to another place. coal is considered as a bulk commodity value which falls in category of minerals and ores. if roadways | |
| 31. |
The coal is fed to the furnace through |
| A. | conveyor belt |
| B. | wagon tipper |
| C. | hopper |
| D. | crane |
| Answer» C. hopper | |
| Explanation: hopper is the conical shaped slow coal dispenser to the furnace. it is placed right above the furnace and a live feeder mechanism is set at end of hopper for a controlled flow. there is no requirement of any external power/force since this works on gravity force. | |
| 32. |
What is the function of cyclone separators in pneumatic ash handling system? |
| A. | to separate the lighter dust particles |
| B. | to force up the movement of ash through pipes or tubes |
| C. | to draw out the dust from furnace |
| D. | to separate minute coal particles |
| Answer» A. to separate the lighter dust particles | |
| Explanation: cyclone separators use air to swirl around the ash that has been dispensed into them. due to centrifugal action heavier ash settles down, where as lighter dust/ash particles is collected in hopper and dumped out. the air flows in helical pattern which makes easy for the heavier dust particle to settle down easily without interrupting the airflow. | |
| 33. |
Which medium is used to carry ash in the pneumatic ash handling system? |
| A. | conveyor belt |
| B. | water trough |
| C. | air |
| D. | chain belt |
| Answer» C. air | |
| Explanation: in pneumatic ash handling system, air is used to carry ash to long distance at a capacity of 5 to 30 tonnes per hour. and the air used for this purpose is easily cleanable and can be exhausted back into atmosphere after the complete filtration processes. | |
| 34. |
Which system is noisy out of all the following ash handling systems? |
| A. | steam jet ash handling system |
| B. | mechanical ash handling system |
| C. | pneumatic ash handling system |
| D. | hydraulic ash handling system |
| Answer» C. pneumatic ash handling system | |
| Explanation: the air is made to pass at very high pressure in order to carry out the ash for long distance. since the air is moving at high speed at high velocity in the conveying pipes, it tends to create a lot of noise by hitting the walls of pipe at swift turns and curves. | |
| 35. |
Which medium is used to carry ash in hydraulic system? |
| A. | air |
| B. | water |
| C. | steam |
| D. | conveyor |
| Answer» B. water | |
| Explanation: water is used as the medium to carry ash at high velocity. depending on water pressure the system is divided as low pressure system and high pressure system. in low pressure system, sloped sumps are used to move the ash at low velocity and in high pressure system nozzle sprays used to ram up the speed of ash flow. | |
| 36. |
What would be the amount of distance that a low pressure system could carry the ash? |
| A. | 25m |
| B. | 500m |
| C. | 150m |
| D. | 800m |
| Answer» B. 500m | |
| Explanation: low pressure system moves the ash mixed in water at a distance of 3 to 5 m/s in a sloped pump made of reinforced constituents and this movement is continuous. so, it has the ability to carry the ash for such long distance. there is no requirement any auxiliary source to move the ash mixed with water. | |
| 37. |
What is the capacity of low pressure hydraulic ash handling system? |
| A. | 80 tonnes/hour |
| B. | 22 tonnes/hour |
| C. | 50 tonnes/hour |
| D. | 10 tonnes/hour |
| Answer» C. 50 tonnes/hour | |
| Explanation: the capacity of low pressure hydraulic ash handling system is 50tonnes/hour at a speed of 3m/s. since the ash produced is mixed in water and dumped, the water has the ability to dissolve and intake more amount of ash. and this mixture is spread throughout the sump. | |
| 38. |
Which of these terms defines the pressure difference in the furnace? |
| A. | draught |
| B. | duct |
| C. | stack |
| D. | chimney |
| Answer» A. draught | |
| Explanation: the term ‘draught’ is used to define the static pressure in the furnace, in the various ducts and the stack. | |
| 39. |
6 DRAUGHT SYSTEM |
| A. | Δp = gh(ρa-ρg) |
| B. | Δp = gh(ρg-ρa) |
| C. | Δp = ghρg |
| D. | Δp = gh(ρa+ρg) |
| Answer» A. Δp = gh(ρa-ρg) | |
| Explanation: the draught produced is given by Δp = gh(ρa-ρg). | |
| 40. |
Which of these is not a type of mechanical draft system for a furnace? |
| A. | balanced draft |
| B. | induced draft |
| C. | forced draft |
| D. | actuated draft |
| Answer» D. actuated draft | |
| Explanation: the three types of mechanical drafts are balanced, induced and forced drafts. | |
| 41. |
Stack heat losses can be minimised by |
| A. | using low c.v. fuels |
| B. | controlling the excess air |
| C. | oxygen enrichment of combustion air |
| D. | maintaining proper draft in the furnace |
| Answer» B. controlling the excess air | |
| Explanation: excess amount of air leads to significant losses in energy due to heat loss through flue gases. | |
| 42. |
Which of these accentuates clinkering trouble on furnace grate burning coal? |
| A. | low reactivity of carbonised residue containing high proportions of iron and sulphur |
| B. | low forced draught and low fuel bed temperature |
| C. | thick fire bed and preheated primary air |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: all these reasons lead to clinkering. | |
| 43. |
In a furnace employing forced draught compared to induced draught |
| A. | the fan operates hot and hence blades are liable to corrosion and erosion |
| B. | positive pressure exists in the furnace |
| C. | air is sucked in, so air leaks are more and hence furnace efficiency is reduced |
| D. | none of the mentioned |
| Answer» C. air is sucked in, so air leaks are more and hence furnace efficiency is reduced | |
| Explanation: a positive pressure exists in the furnace employing forced draught. | |
| 44. |
Which of the following types of the fans has the highest cost? |
| A. | centrifugal fans |
| B. | axial fans |
| C. | primary fans |
| D. | gas recirculation fans |
| Answer» B. axial fans | |
| Explanation: axial fans have the highest cost. | |
| 45. |
Which of these is not a type of drive of variable speed control? |
| A. | variable speed turbine |
| B. | hydraulic coupling |
| C. | multiple speed ac motor |
| D. | electronically adjustable turbine drive |
| Answer» D. electronically adjustable turbine drive | |
| Explanation: except ‘electronically adjustable turbine drive’, all other are a type of drive in variable speed control. | |
| 46. |
Feed water for boiler of thermal power plant is obtained from: |
| A. | natural sources like river and lake |
| B. | partly from condensed steam and natural sources |
| C. | condensed steam and small percentage from natural resources |
| D. | natural sources and small percentage from condensed steam |
| Answer» C. condensed steam and small percentage from natural resources | |
| Explanation: the steam coming out of turbines is condensed and the condenset is fed back to the boiler. some of water losses due | |
| 47. |
Mechanical method of water treatment is done to |
| A. | heat the feed water |
| B. | to remove solid matter and impurities |
| C. | to add some solid materials |
| D. | to remove dissolved gases |
| Answer» B. to remove solid matter and impurities | |
| Explanation: mechanical method of water | |
| 48. |
Which method is used in large modern thermal power plants to heat feed water? |
| A. | open type heatre is used |
| B. | close type heater is used |
| C. | steam is directly taken from main turbine and used to heat it feed water |
| D. | surface type heater is used |
| Answer» C. steam is directly taken from main turbine and used to heat it feed water | |
| Explanation: open and contact type haters are in small power plants. such heaters recives steam from back pressure turbine. in large modern power plants heaters bleed steam from the main turbine and use it for heating of feed water. | |
| 49. |
Thermal treatment methods used to remove impurities like: |
| A. | dissolved carbon dioxide and other gases |
| B. | solid materials |
| C. | carbonate |
| D. | bacterial impurities |
| Answer» A. dissolved carbon dioxide and other gases | |
| Explanation: thermal treatment method involves distillation and derative heating of feed water. during distillation water is evaporated then condensed and collected. during derating heating water is broken up into fine droplets and heated to produced vapour within the deaerator. during these process carbon dioxide and other days of devices separated from feet water. | |
| 50. |
Chemical method of treatment is used for treatment of: |
| A. | diissolve gases |
| B. | carbonate and carbon dioxide |
| C. | bacterial impurities |
| D. | send and suspended materials |
| Answer» B. carbonate and carbon dioxide | |
| Explanation: chemical treatment involvs line treatment, soda treatment, lime and soda treatment. zeolite treatment and demineralisation. iime treatment is done for treatment of carbonate hardness, carbon dioxide in water. soda treatment is done for treatment of water containing non carbonate hardness and line soda treatment is used when both carbonate and none carbonate hardness for feed water. | |
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