When the circulation of water, in a boiler, is by convection currents which are set up during the heating of water, then the boiler is known as
Internally fired boiler
Externally fired boiler
Natural circulation boiler
Forced circulation boiler
Correct Answer :
C. Natural circulation boiler
Related Questions
Thermal efficiency of well maintained boiler will be of the order
40 %
50 %
75 %
90 %
The friction present between the steam and the nozzle surfaces reduces the heat drop by
10 to 15 %
15 to 25 %
25 to 40 %
40 to 60 %
The specific volume of steam with increase in pressure decreases
Linearly
Slowly first and then rapidly
Rapidly first and then slowly
Inversely
The number of flue tubes in Lancashire boiler is
Zero
One
Two
Four
The density of supersaturated steam is about __________ that of the ordinary saturated vapour at the corresponding pressure.
Same as
2 times
4 times
8 times
Secondary air is the air used to
Provide air around burners for obtaining optimum combustion
Transport and dry the coal
Convert CO (formed in lower zone of furnace) into CO₂ at higher zone
Air delivered by induced draft fan
Cut-off ratio is the ratio of
Swept volume to the volume at cut-off
Volume at cut-off to the clearance volume
Volume at cut-off to the swept volume
Clearance volume to the volume at cut-off
When the nozzle operates with the maximum mass flow, the nozzle is said to be
Choked
Under-damping
Over-damping
None of these
The flow of steam is supersonic
At the entrance to the nozzle
At the throat of the nozzle
In the convergent portion of the nozzle
In the divergent portion of the nozzle
A wet vapour can be completely specified by
Pressure only
Temperature only
Dryness fraction only
Pressure and dryness fraction
The principal function of a stop valve is to
Control the flow of steam from the boiler to the main pipe and to shut off the steam completely when required
Empty the boiler when required and to discharge the mud, scale or sediments which are accumulated at the bottom of the boiler
Put off fire in the furnace of the boiler when the level of water in the boiler falls to an unsafe limit
Increase the temperature of saturated steam without raising its pressure
The maximum discharge through a chimney occurs when the height of chimney is
Infinitely long
Around 200 meters
Equal to the height of the hot gas column producing draught
Outside temperature is very low
The effect of friction on the flow of steam through a nozzle is to
Decrease the mass flow rate and to increase the wetness of steam
Increase the mass flow rate and to increase the exit temperature
Decrease the mass flow rate and to decrease the wetness of steam
Increase the exit temperature without any effect on mass flow rate
The latent heat of steam at pressures greater than atmospheric in comparison to latent heat at atmospheric pressure is
Less
More
Equal
May be less or more depending on temperature
The high steam and low water safety valve is used to blow off steam when the
Steam pressure exceeds the working pressure
Water level in the boiler becomes too low
Both (A) and (B)
None of the above
Which of the following statement is correct?
A horizontal steam engine requires less floor area than a vertical steam engine
The steam pressure in the cylinder is not allowed to fall below the atmospheric pressure
The compound steam engines are generally non-condensing steam engines
All of the above
The maximum steam pressure in a Locomotive boiler is limited to
0.18 MN/m²
1.8 MN/m²
18 MN/m²
180 MN/m²
By compounding the expansion of steam in two or more cylinders, the length of stroke
Does not change
Increases
Decreases
None of these
The ultimate analysis of fuel lists
Various chemical constituents, carbon, hydrogen, oxygen etc, plus ash as percents by volume
Various chemical constituents, carbon, hydrogen, oxygen, etc, plus ash as percents by weight
Fuel constituents as percents by volume of moisture, volatile, fixed carbon and ash
Fuel constituents as percents by weight of moisture, volatile, fixed carbon and ash
In turbines, the fluid undergoes a continuous steady flow process and the speed of flow is
Low
Very low
High
Very high
The actual vacuum in a condenser is equal to
Barometric pressure + actual pressure
Barometric pressure - actual pressure
Gauge pressure + atmospheric pressure
Gauge pressure - atmospheric pressure
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
Superheater
Air-preheater
Economiser
Injector
The maximum discharge of steam through a convergent-divergent nozzle depends upon
Area of nozzle at throat
Initial pressure and volume of steam
Final pressure of steam leaving the nozzle
Both (A) and (B)
During polytropic process
Heat transfer takes place across cylinder walls
Work is done
Steam may be wet, dry or superheated after expansion
All of the above
The efficiency of steam turbines may be improved by
Reheating of steam
Regenerative feed heating
Binary vapour plant
Any one of these
The supersaturated flow of steam through a nozzle as compared to a stable flow, the available heat drop
Remains the same
Increases
Decreases
Is unpredictable
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
79 m/s
188 m/s
450 m/s
900 m/s
While steam expands in turbines, theoretically the entropy
Remains constant
Increases
Decreases
Behaves unpredictably
The latent heat of steam with increase of pressure
Remain same
Increases
Decreases
Behaves unpredictably
The indicated thermal efficiency is defined as the
Ratio of thermal efficiency to the Rankine efficiency
Ratio of brake power to the indicated power
Ratio of heat equivalent to indicated power to the energy supplied in steam
Product of thermal efficiency and Rankine efficiency