A device used to heat feed water by utilizing the heat in me exhaust flue gases before leaving through the chimney, is known as

Draught produced by a tall chimney due to density difference between hot flue gas inside the Chimney and atmospheric air outside the chimney is more appropriately known as the __________ draught.

A

Natural

B

Induced

C

Forced

D

Chimney

Thermal conductivity based continuous flue gas analyser makes use of varying thermal conductivity of the constituents of flue gases. Which of the following constituents of flue gases has the maximum thermal conductivity?

A

CO₂

B

N₂

C

O₂

D

CO

The velocity of flue gases (V) through the chimney under a static draught of (H') metres is given by

A

$${\text{V}} = \sqrt {2{\text{gH}}'} $$

B

$${\text{V}} = \sqrt {\frac{{2{\text{g}}}}{{{\text{H}}'}}} $$

C

$${\text{V}} = \frac{{{\text{H}}'}}{{\sqrt {2{\text{g}}} }}$$

D

$${\text{V}} = 2{\text{g}}\sqrt {{\text{H}}'} $$

The ratio of the energy required to produce the artificial draught (expressed in meters head or J/kg of flue gas) to the mechanical equivalent of extra heat carried away per kg of flue gases due to natural draught, is known as

A

Efficiency of the boiler

B

Efficiency of the chimney

C

Efficiency of the fan

D

Power of the boiler

The draught produced, for a given height of the chimney and given mean temperature of chimney gases

A

decreases with increase in outside air temperature

B

increases with increase in outside air temperature

C

remains the same irrespective of outside air temperature

D

may increase or decrease with increase in outside air temperature

A device in which some portion of waste heat of flue gases is recovered to heat the air before it passes to the furnace for combustion purpose, is known as

A

Superheater

B

Air-preheater

C

Economizer

D

Injector

Gradually increasing temperature of flue gases at inlet to chimney for given steam outputs is an indication of

A

Higher effectiveness of boiler

B

High calorific value coal being burnt

C

Fouling of heat transfer surfaces

D

Raising of steam temperature

The maximum discharge through a chimney occurs when the height of chimney is

A

Infinitely long

B

Around 200 meters

C

Equal to the height of the hot gas column producing draught

D

Outside temperature is very low

Sulphur dioxide present in the industrial chimney exhaust gases causes

A

Respiratory & lung disease

B

Reduction in plant's productivity owing to acid rain

C

Corrosion of building materials

D

All of the above

Flue gas discharge velocity through chimney of a big thermal power plant may be around __________ m/sec.

A

0.5

B

500

C

10

D

50

A device used to heat feed water by utilizing the heat in me exhaust flue gases before leaving through the chimney, is known as

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