mechanical engineering MCQs – Page 172

Practise multiple-choice questions from mechanical engineering for competitive examinations and subject revision. Review each marked answer and report any item that may be outdated or unclear.

3421. The behaviour of coal in a furnace is determained by_______________________?
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A. the proximate analysis

B. the exact analysis

C. its type

D. the content of ash and heating value

E. the content of sulphur

3422. The capacity of induced draft fan compared to forced draft fan in a boiler is__________________?
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A. less

B. less or more depending on size of boiler

C. more

D. same

E. unpredictable

3423. With increase in load, convection superheater has_______________________?
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A. linear characterisstic

B. none of the above

C. drooping characteristic

D. flat characteristic

E. rising characteristic
3424. Fusible plug for boilers is made of fusible metal containing tin, lead, and___________________?
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A. copper

B. aluminium

C. iron

D. nickel

E. bismuth
3425. The size of a boiler drum in pulverised fuel fired boiler,as its size and capacity, (steam pressure and flow ratings) increase __________________?
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A. remains unchanged

B. increases

C. decreases

D. increases/decreases depending on steam temperature requirements

E. unpredictable

3426. Heating value of fuel used is as on fired basis. If it is reported for dry or moisture free fuel, then latter should be multiplied by the following factor to correct for as fired value ___________________?
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A. 1 + moisture content

B. (1 + moisture content)

C. (1- moisture content)

D. 1 moisture content

3427. Which device is used in thermal power plants to reduce level of pollution___________________?
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A. chimney

B. precipitator

C. induced draft fan

D. smoke meter

E. pulveriser

3428. The function of injector used in small capacity boilers is to____________________?
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A. inject chemical solution in feed pump

B. none of the above

C. pump water, similar to boiler feed pump

D. add make up water in the system

E. create vacuum

3429. The overall efficiency of thermal power plant is________________?
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A. all the three above plus gas cycle efficiency

B. regenerative cycle efficiency

C. boiler efficiency, turhine efficiecny, generator efficiency

D. rankine cycle efficiency

E. carnot cycle efficiency

3430. Gardually increasing temperature of flue gases at inlet to chimney for given steam outputs is an indication of__________________?
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A. high calorific value coal being burnt

B. fouling of heat transfer surfaces

C. raising of steam temperature

D. leakage of air

E. higher effectiveness of boiler

3431. The ratio of heat utilised to produce steam and the heat liberated in furnace is known as___________________?
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A. boiler evaporative capacity

B. boiler effectiveness

C. factor of evaporation

D. equivalent evaporation

E. boiler efficiency
3432. Feed water conditioning in thermal power plants in done to__________________?
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A. increase *heat transfer rate

B. increase efficiency-of thermal power plant

C. reduce hardness and for removal of solids

D. all of the above

E. increase steam parameters

3433. Gusset stays in a boiler are provided to____________________?
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A. avoid explosion in furnace

B. prevent atmospheric air leaking into furnace

C. prevent the bulging of flat surfaces

D. support furnace freely from top

E. prevent leakage of hot flue gases

3434. Sulphur in coal results in___________________?
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A. corroding air heaters

B. all of the above

C. causing clinkering and slagging

D. spontaneous combustion during coal storage

E. facilitating ash precipitation

3435. The latent heat of steam with increase of pressure__________________?
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A. increases

B. none of the above

C. remains same

D. behaves unpredictably

E. decreases
3436. Spontaneous combustion is a phenomenon in which____________________?
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A. all the fuel burns instantaneously producing high energy release

B. none of the above

C. explosion in furnace

D. fuel burns with less air

E. coal bursts into flame without any external ignition source but by itself due to gradual increase in temperature as a result of heat released by combination of oxygen with coal
3437. Which is not correct statement about the function of furnace____________________?
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A. to provide proper conditions for con-tinuous complete combustion

B. separate ash from coal

C. mix fuel with air and ignite

D. maintain heat supply to prepare and ignite the incoming fuel

E. to minimise radiation losses

3438. For combustion of a fuel, following is essential_____________________?
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A. none of the above

B. all the three above

C. proper ignition temperature

D. 02 to support combustion

E. correct fuel air ratio

3439. In forced recirculation type boiler__________________?
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A. feed pump is employed to supplement natural circulation in water wall type furnace

B. water is supplied in drum and through down-comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam

C. heating of water takes place in stages

D. water is converted into steam in one pass without any recirculation

E. heating takes place at bottom and the water supplied at bottom gets converted into the mixture of steam bubbles and hot water which rise to drum

3440. In regenerative air preheater, the heat is transferred _____________________?
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A. from heating an intermediateanaterial and then heating the air from this material

B. none of the above

C. by direct mixing

D. from a metal wall from one medium to another

E. heat is transferred by bleeding some gas from furnace