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4

An air preheater is installed

A. Before the economiser

B. Before the superheater

C. Between the economiser and chimney

D. None of these

Correct Answer :

C. Between the economiser and chimney


Related Questions

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4

In which of the following boilers, the draught in furnace is increased by utilising exhaust steam from engine

A. Lancashire boiler

B. Locomotive boiler

C. Babcock and Wilcox boiler

D. Benson boiler

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4

The steam enters the nozzle at a

A. High pressure and a low velocity

B. High pressure and a high velocity

C. Low pressure and a low velocity

D. Low pressure and a high velocity

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4

Stoichiometric quantity of air is the

A. Air present in atmosphere at NTP conditions

B. Air required for complete combustion of fuel with no excess air

C. Air required for optimum combustion so as to have reasonable excess air

D. Air required to convert CO into CO₂

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4

When steam after doing work in the cylinder passes into a condenser, the engine is said to be a

A. Slow speed engine

B. Vertical steam engine

C. Condensing steam engine

D. Non-condensing steam engine

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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

The fire tubes in a Cochran boiler usually have _________ diameter.

A. 6.25 mm

B. 62.5 mm

C. 72.5 mm

D. 92.5 mm

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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

Which of the following statement is wrong?

A. The factor of evaporation for all boilers is always greater than unity.

B. The amount of water evaporated in kg per kg of fuel burnt is called equivalent evaporation from and at 100° C.

C. The ratio of heat actually used in producing the steam to the heat liberated in the furnace is called boiler efficiency.

D. None of the above

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4

The specific heat of superheated steam in kcal/kg is generally of the order of

A. 0.1

B. 0.3

C. 0.5

D. 0.8

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4

Natural water circulation, by convection in water tube boilers, with increase in pressure of boiler

A. Increases

B. Decreases

C. Remain unaffected

D. First increases and then decreases

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4

Superheating of steam is done at

A. Constant volume

B. Constant temperature

C. Constant pressure

D. Constant entropy

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4

The length of Cornish boiler is of the order of

A. 24 m

B. 35 m

C. 57.5 m

D. 79 m

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4

In reaction turbines, the axial thrust is due to

A. Pressure drop across the rotor

B. Change in axial velocity

C. Both (A) and (B)

D. None of these

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4

The function of a safety valve is

A. To blow off steam when the pressure of steam inside the boiler exceeds the working pressure

B. To indicate the water level inside the boiler to an observer

C. To measure pressure of steam inside the steam boiler

D. None of the above

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4

The device attached to the steam chest for preventing explosions due to excessive internal pressure of steam is called

A. Safety valve

B. Water level indicator

C. Pressure gauge

D. Fusible plug

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4

The critical pressure ratio for gases is

A. 0.528

B. 0.546

C. 0.577

D. 0.582

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4

The pressure compounded impulse turbine as compared to velocity compounded turbine require __________ number of stages.

A. Same

B. Less

C. More

D. None of these

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4

The radius of a dished head is taken approximately as

A. One fourth

B. Half

C. One

D. Two

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4

In a reaction turbine when the degree of reaction is zero, then there is

A. No heat drop in moving blades

B. No heat drop in fixed blades

C. Maximum heat drop in moving blades

D. Maximum heat drop in fixed blades

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4

Thermal efficiency of well maintained boiler will be of the order

A. 40 %

B. 50 %

C. 75 %

D. 90 %

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4

For maximum discharge through a chimney, the condition is that height of hot gas column producing the draught should be

A. One-half the height of chimney

B. Equal to the height of chimney

C. Two times the height of chimney

D. Four times the height of chimney

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4

For the same diameter and thickness of tube, a water tube boiler has ________ heating surface as compared to fire tube boiler.

A. More

B. Less

C. Equal

D. None of these

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4

A closed vessel made of steel and used for the generation of steam is called a

A. Steam boiler

B. Steam turbine

C. Steam condenser

D. Steam injector

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4

A single stage impulse turbine with a diameter of 1.2 m runs at 3000 r.p.m. If the blade speed ratio is 0.42, then the inlet velocity of steam will be

A. 79 m/s

B. 188 m/s

C. 450 m/s

D. 900 m/s

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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

Cut-off governing of steam engines is a method of controlling the engine output by varying

A. Volume of intake steam

B. Pressure of intake steam

C. Temperature of intake steam

D. All of these

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4

Alkaline pyrogallate is used in Orsat's apparatus for absorption of

A. CO₂

B. CO

C. O₂

D. N₂

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4

Size of boiler tubes is specified by

A. Mean diameter and thickness

B. Inside diameter and thickness

C. Outside diameter and thickness

D. Outside diameter and inside diameter

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4

Which of the following statement is wrong?

A. The critical pressure gives the velocity of steam at the throat equal to the velocity of sound.

B. The flow in the convergent portion of the nozzle is subsonic.

C. The flow in the divergent portion of the nozzle is supersonic.

D. To increase the velocity of steam above sonic velocity (supersonic) by expanding steam below the critical pressure, the divergent portion for the nozzle is not necessary.

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4

Efficiency of Rankine cycle can be increased by

A. Decreasing initial steam pressure and temperature

B. Increasing exhaust pressure

C. Decreasing exhausts pressure

D. Increasing the expansion ratio