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Current Affairs January 2024

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4

The relative efficiency is defined as the

A. Ratio of thermal efficiency to Rankine efficiency

B. Ratio of brake power to the indicated power

C. Ratio of heat equivalent to indicated power to the energy supplied in steam

D. Product of thermal efficiency and Rankine efficiency

Correct Answer :

A. Ratio of thermal efficiency to Rankine efficiency


Related Questions

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4

Which of the following is correct? (Where pa = Actual mean effective pressure, pm = Theoretical mean effective pressure, and K = Diagram factor)

A. pa = pm/K

B. pa = pm × K

C. pa = K/pm

D. pa = pm + K

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4

O₂ content in atmospheric air on volume basis is

A. 21 %

B. 23 %

C. 30 %

D. 40 %

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4

The draught produced by a steam jet issuing from a nozzle placed in the ash-pit under the fire grate of the furnace is called

A. Induced steam jet draught

B. Chimney draught

C. Forced steam jet draught

D. None of these

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4

The biggest size of thermal power unit operating in India is

A. 30 MW

B. 60 MW

C. 100 MW

D. 500 MW

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4

Reheating of steam in a turbine

A. Increases the workdone through the turbine

B. Increases the efficiency of the turbine

C. Reduces wear on the blades

D. All of these

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4

The critical pressure gives the velocity of steam at the throat

A. Equal to the velocity of sound

B. Less than the velocity of sound

C. More than the velocity of sound

D. None of these

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4

On Mollier chart, flow through turbine is represented by

A. Horizontal straight line

B. Vertical straight line

C. Straight inclined line

D. Curved line

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4

The factor of evaporation for all boilers is always

A. Equal to unity

B. Less than unity

C. Greater than unity

D. None of these

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4

Expanding steam to a very low pressure (high vacuum) in steam engines is

A. Desirable

B. Economical

C. Essential

D. Uneconomical

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4

A nozzle is said to be a divergent nozzle

A. When the cross-section of the nozzle increases continuously from entrance to exit

B. When the cross-section of the nozzle decreases continuously from entrance to exit

C. When the cross-section of the nozzle first decreases from entrance to throat and then increases from its throat to exit

D. None of the above

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4

The effect of friction in the nozzle __________ dryness fraction of steam.

A. Has no effect on

B. Decreases

C. Increases

D. None of these

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4

In designing air preheaters, the important design consideration is that

A. Approach temperature should be as low as possible

B. Handling and maintenance should be easier

C. Heat transfer area should be optimum

D. Stack gases should not be cooled to the dew point

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4

The length of Lancashire boiler varies from

A. 5 to 6 m

B. 6 to 7 m

C. 7.25 to 9 m

D. 9 to 10 m

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4

Duplex feed pumps are used in small steam boilers. These operate on the principle of

A. Centrifugal pump

B. Axial flow pump

C. Gear pump

D. Reciprocating pump

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4

The critical pressure at which latent heat of vaporisation is zero is

A. 225.65 kgf/ cm²

B. 273 kgf/ cm²

C. 100 kgf/ cm²

D. 1 kgf/ cm²

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4

In a nozzle, the effect of super-saturation is to

A. Decrease dryness fraction of steam

B. Decrease specific volume of steam

C. Increase the entropy

D. Increase the heat drop

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4

The high pressure and low pressure cylinders in a receiver type compound engine are regarded as having cranks

A. 180° to each other

B. 90° to each other

C. 0° to each other

D. None of these

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4

In a uniflow engine

A. Steam enters and exhausts through the same port

B. Steam enters at one end and exhausts at the centre

C. Steam enters at the centre and exhausts at the other end

D. None of the above

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4

If partial pressure of air and steam be pa and ps respectively in a condenser, then according to Dalton's law, the pressure in condenser is equal to

A. ps - pa

B. pa - ps

C. pa + ps

D. None of these

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4

Cut-off ratio is the ratio of

A. Swept volume to the volume at cut-off

B. Volume at cut-off to the clearance volume

C. Volume at cut-off to the swept volume

D. Clearance volume to the volume at cut-off

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4

Which of the following gases has the highest calorific value?

A. Producer gas

B. Coal gas

C. Water gas

D. Blast furnace gas

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4

Which device is used in thermal power plants to reduce level of pollution?

A. Induced draft fan

B. Smoke meter

C. Chimney

D. Precipitator

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4

In a steam condenser, the partial pressure of steam and air are 0.06 bar and 0.007 bar respectively. The condenser pressure is

A. 0.007 bar

B. 0.053 bar

C. 0.06 bar

D. 0.067 bar

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4

The clearance in the engine cylinder

A. Increases the mean effective pressure

B. Increases the workdone

C. Decreases the efficiency of the engine

D. All of these

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4

A fusible plug is fitted in small boilers in order to

A. Avoid excessive build up of pressure

B. Avoid explosion

C. Extinguish fire if water level in the boiler falls below alarming limit

D. Control steam dome

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4

In forced circulation steam boilers, the force is applied

A. To draw water

B. To circulate water

C. To drain off the water

D. All of these

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4

The aim of a compound steam engine is

A. To reduce the ratio of expansion in each cylinder

B. To reduce the length of stroke

C. To reduce the temperature range in each cylinder

D. All of the above

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4

When the total heat of steam is h kJ/kg and the sensible heat of feed water is hf1 kJ/kg, then the factor of evaporation is given by

A. (h - hf1)/2257

B. (h + hf1)/2257

C. (h × hf1)/2257

D. None of these

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4

Carbonisation of coal is the process of

A. Pulverising coal in inert atmosphere

B. Heating wood in a limited supply of air at temperatures below 300°C

C. Strongly heating coal continuously for about 48 hours in the absence of air in a closed vessel

D. Binding the pulverised coal into briquettes

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4

When the back pressure of a nozzle is below the designed value of pressure at exit of nozzle, the nozzle is said to be

A. Choked

B. Under-damping

C. Over-damping

D. None of these