In designing air preheaters, the important design consideration is that
Approach temperature should be as low as possible
Handling and maintenance should be easier
Heat transfer area should be optimum
Stack gases should not be cooled to the dew point
Correct Answer :
D. Stack gases should not be cooled to the dew point
Related Questions
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
The ratio of heat actually used in producing the steam to the heat liberated in the furnace, is known as
Equivalent evaporation
Factor of evaporation
Boiler efficiency
Power of a boiler
Water at pressure of 4 kg/cm² and 160°C temperature when exposed to atmosphere will
Boil
Flash i.e. get converted into steam
Remain as it was
Cool down
Expansion ratio is the ratio of
Swept volume to the volume at cut-off
Clearance volume to the swept volume
Volume at cut-off to the swept volume
Swept volume to the clearance volume
Superheating of steam is done at
Constant volume
Constant temperature
Constant pressure
Constant entropy
The ratio of heat equivalent to brake power to the energy supplied in steam is known as
Mechanical efficiency
Overall efficiency
Indicated thermal efficiency
Brake thermal efficiency
The ratio of brake power to the indicated power is known as
Mechanical efficiency
Overall efficiency
Indicated thermal efficiency
Brake thermal efficiency
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
In a boiler, the heat is lost
To dry flue gases
In moisture present in the fuel
To steam formed by combustion of hydrogen per kg of fuel
All of the above
In a De-Laval nozzle expanding superheated steam from 10 bar to 0.1 bar, the pressure at the minimum cross-section (i. e. pressure at throat, p₂) will be
3.3 bar
5.46 bar
8.2 bar
9.9 bar
The ratio of total useful heat drop to the total isentropic heat drop, is called
Stage efficiency
Internal efficiency
Rankine efficiency
None of these
The equivalent evaporation is defined as
The ratio of heat actually used in producing the steam to the heat liberated in the furnace
The amount of water evaporated or steam produced in kg per kg of fuel burnt
The amount of water evaporated from and at 100°C into dry and saturated steam
The evaporation of 15.653 kg of water per hour from and at 100°C
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
The temperature of flue gases at air heater outlet should be
100°C
Above dew point temperature of flue gases
Below dew point temperature of flue gases
Less than wet bulb temperature of flue gases
Degree of reaction is defined as the ratio of
Heat drop in fixed blades to the heat drop in moving blades
Heat drop in moving blades to the heat drop in fixed blades
Heat drop in moving blades to the heat drop in fixed blades plus heat drop in moving blades
Heat drop in fixed blades plus heat drop in moving blades to the heat drop in moving blades
The draught may be produced by a
Mechanical fan
Chimney
A steam jet
All of these
The cylindrical shell of a Lancashire boiler has diameter from
1 to 2 m
1.25 to 2.25 m
1.5 to 2.5 m
1.75 to 2.75 m
In forced circulation steam boilers, the force is applied
To draw water
To circulate water
To drain off the water
All of these
Which of the following varieties of coals is mostly used in steam boilers?
Non-coking bituminous coal
Brown coal
Peat
None of the above
There is always some steam left in the clearance space from the previous stroke. This steam left in the clearance space is called
Wet steam
Saturated steam
Superheated steam
Cushion steam
Duplex feed pumps are used in small steam boilers. These operate on the principle of
Centrifugal pump
Axial flow pump
Gear pump
Reciprocating pump
A condenser where circulating water flows through tubes which are surrounded by steam, in known as
Surface condenser
Jet condenser
Barometric condenser
Evaporative condenser
The balanced draft furnace is one using
Induced draft fan and chimney
Induced draft fan and forced draft fan
Forced draft fan and chimney
Any one of the above
Stoichiometric quantity of air is the
Air present in atmosphere at NTP conditions
Air required for complete combustion of fuel with no excess air
Air required for optimum combustion so as to have reasonable excess air
Air required to convert CO into CO₂
The actual power supplied by the engine crankshaft is called
Indicated power
Brake power
Frictional power
None of these
The fire tubes in a Cochran boiler are
Horizontal
Vertical
Inclined
None of these
The rate of steam produced in Benson boiler is
100 tonnes/h
135 tonnes/h
175 tonnes/h
250 tonnes/h
In an impulse reaction turbine, the pressure drops gradually and continuously over
Fixed blades
Moving blades
Both fixed and moving blades
None of these
Efficiency of Rankine cycle can be increased by
Decreasing initial steam pressure and temperature
Increasing exhaust pressure
Decreasing exhausts pressure
Increasing the expansion ratio
During storage, the heating value of coal
Increases
Decreases
Remain constant
May increase or decrease depending upon the method of storage