In a boiler, feed water supplied per hour is 205 kg while coal fired per hour is 23 kg. The net enthalpy rise per kg of water is 145 kJ. If the calorific valve of the coal is 2050 kJ/kg, then the boiler efficiency will be
56 %
63 %
74 %
78 %
Correct Answer :
B. 63 %
Related Questions
The diameter of internal flue tubes in a Lancashire boiler compared to its shell is
One-half
One-third
Two-fourth
Two-fifth
A regenerative steam cycle renders
Increased work output per unit mass of steam
Decreased work output per unit mass of steam
Increased thermal efficiency
Decreased work output per unit mass of steam as well as increased thermal efficiency
Incomplete combustion can be best judged by
Smoky chimney exit
Excess air in flue gases
Measuring carbon monoxide in flue gases
Measuring temperature of flue gases at exit of furnace
Which of the following boilers is best suited to meet fluctuating demands?
Babcock and Wilcox
Locomotive
Lancashire
Cochran
The fire tubes in a Scotch marine boiler are
Horizontal
Vertical
Inclined
None of these
The flow through a nozzle is regarded as
Constant volume flow
Constant pressure flow
Isothermal flow
Isentropic flow
The feed check valve is used in order to
Regulate flow of boiler water
Check level of water in boiler drum
Recirculate unwanted feed water
Allow high pressure feed water to flow to drum and not allow reverse flow to take place
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
Sulphur content of fuels is very important to the plant operators because it
Has high heating value
Retards electric precipitation
Promotes complete combustion
Has highly corrosive effect
The safety valve at superheater as compared to drum safety valve setting is set at
Higher value
Lower value
Same value
Any value
In turbines, the fluid undergoes a continuous steady flow process and the speed of flow is
Low
Very low
High
Very high
The overall efficiency of thermal power plant is
Boiler efficiency, turbine efficiency, generator efficiency
All the three above plus gas cycle efficiency
Carnot cycle efficiency
Regenerative cycle efficiency
Willians line follows the law (where b = A constant representing the shape of the Willians line, a = Another constant i.e. no load consumption per hour, I.P. = Indicated power, and m = Steam consumption per hour)
I.P. = a × m + b
m = a + b × I.P.
I.P. = b × m + a
m = (b/I.P.) - a
A nozzle is said to be a divergent nozzle
When the cross-section of the nozzle increases continuously from entrance to exit
When the cross-section of the nozzle decreases continuously from entrance to exit
When the cross-section of the nozzle first decreases from entrance to throat and then increases from its throat to exit
None of the above
Which of the following is a water tube boiler?
Locomotive boiler
Cochran boiler
Cornish boiler
Babcock and Wilcox boiler
Feed water conditioning in thermal power plants in done to
Reduce hardness and for removal of solids
Increase efficiency of thermal power plant
Increase heat transfer rate
Increase steam parameters
A packaged boiler is one in which various parts like firing equipment, fans, feed pumps and automatic controls are
Supplied by same manufacturer loose and assembled at site
Supplied mounted on a single base
Purchased from several parties and packed together at site
Packaged boiler does not exist
Efficiency of Rankine cycle can be increased by
Decreasing initial steam pressure and temperature
Increasing exhaust pressure
Decreasing exhausts pressure
Increasing the expansion ratio
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
All steam engines work on
Zeroth law of thermodynamics
First law of thermodynamics
Second law of thermodynamics
None of these
1 kg.m is equal to
9.81 Joules
102 Joules
427 Joules
None of these
The fittings mounted on the boiler for its proper and safe functioning is a
Water level indicator
Pressure gauge
Safety valve
All of these
Which of the following boiler is best suited to meet the fluctuating demand of steam?
Locomotive boiler
Lancashire boiler
Cornish boiler
Babcock and Wilcox boiler
The length of Cornish boiler varies from
2 to 4.5 m
3 to 5 m
5 to 7.5 m
7 to 9 m
A compound steam engine in which the high pressure and low pressure cylinders have common piston rod, is called
Receiver type compound engine
Tandem type compound engine
Woolf type compound engine
None of these
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
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
The factor of evaporation for all boilers is always
Equal to unity
Less than unity
Greater than unity
None of these
For a Parson's reaction turbine, if α₁ and α₂ are fixed blade angles at inlet and exit respectively and β₁ and β₂ are the moving blade angles at entrance and exit respectively, then
α₁ = α₂ and β₁ = β₂
α₁ = β₁ and α₂= β₂
α₁ < β₁ and α₂ > β₂
α₁ = β₂ and β₁ = α₂
The diagram efficiency is the ratio of
Workdone on the blades to the energy supplied to the blades
Workdone on the blades per kg of steam to the total energy supplied per stage per kg of steam
Energy supplied to the blades per kg of steam to the total energy supplied per stage per kg of steam
None of the above