Which is not the correct statement about moisture in coal?
Inherent moisture and surface moisture are different things
In some coals moisture may be present up to 40%
Some moisture in coal helps in better burning which is not possible with completely dry coal
It increases thermal efficiency
Correct Answer :
D. It increases thermal efficiency
Related Questions
The best suited coal for chain or travelling grate stoker boiler is
Coking coal
Non-coking or free burning coal
Pulverised coal
High sulphur coal
An economiser _________ the steam raising capacity of a boiler.
Increases
Decreases
Has no effect on
None of these
Gusset stays in a boiler are provided to
Prevent the bulging of flat surfaces
Avoid explosion in furnace
Prevent leakage of hot flue gases
Support furnace freely from top
Fire tube boilers are those in which
Flue gases pass through tubes and water around it
Water passes through the tubes and flue gases around it
Forced circulation takes place
Tubes are laid vertically
On Millier chart, the constant pressure lines
Diverge from left to right
Diverge from right to left
Are equally spaced throughout
First rise up and then fall
In forced circulation type boiler
Heating takes place at bottom and the water supplied at bottom gets converted into the mixture of steam bubbles and hot water which rise to drum
Water is supplied in drum and through down comers located in atmospheric condition it passes to the water wall and rises to drum in the form of mixture of water and steam
Feed pump is employed to supplement natural circulation in water wall type furnace
Water is converted into steam in one pass without any recirculation
The draught in locomotive boilers is produced by a
Chimney
Centrifugal fan
Steam jet
None of these
The fusible plug in small boilers is located
In the drum
In the fire tubes
Above steam dome
Over the combustion chamber
The critical pressure at which latent heat of vaporisation is zero is
225.65 kgf/ cm²
273 kgf/ cm²
100 kgf/ cm²
1 kgf/ cm²
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
100% efficiency of a thermal cycle cannot be achieved because of
Frictional losses
It is not possible to achieve 0°K temperature
Leakage
Non availability of ideal substance
In cross compounding, the cylinders are arranged
Side by side and each cylinder has common piston, connecting rod and crank
Side by side and each cylinder has separate piston, connecting rod and crank
At 90° and each cylinder has common piston, connecting rod and crank
At 90° and each cylinder has separate piston, connecting rod and crank
The crown of the fire box is made hemispherical in order to
Give maximum space
Give maximum strength
Withstand pressure inside boiler
Resist intense heat in fire box
Which of the following is a water tube boiler?
Lancashire boiler
Babcock and Wilcox boiler
Locomotive boiler
Cochran boiler
One kg of steam sample contains 0.8 kg dry steam; Its dryness fraction is
0.2
0.8
1.0
0.6
In order to obtain superheated steam, a superheater is added in an existing boiler. As as result, furnace vacuum will
Remain unaffected
Improve
Worsen
May improve/worsen depending on size
By compounding the expansion of steam in two or more cylinders, the length of stroke
Does not change
Increases
Decreases
None of these
The forced circulation of water does not take place in
LaMont boiler
Lancashire boiler
Velox boiler
Benson boiler
The cylinder condensation or missing quantity may be reduced by
The efficient steam jacketing of the cylinder walls
Superheating the steam supplied to the engine cylinder
Keeping the expansion ratio small in each cylinder
All of the above
Parson's turbine is a
Simple impulse turbine
Simple reaction turbine
Impulse-reaction turbine
None of these
A double acting steam engine with a cylinder diameter of 190 mm and a stroke of 300 mm has a cut-off of 0.35. The expansion ratio for this engine is nearly
1.05
2.86
6.65
10.05
The basic job of feed water treatment in boilers is to overcome the problem of
Corrosion
Scale
Carryover
All of the above
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
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
The pressure of feed water has to be raised before its entry into the boiler. The pressure is raised by a device known as
Feed pump
Injector
Feed check valve
Pressure gauge
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 ratio of the useful heat drop to the isentropic heat drop is called
Condenser efficiency
Nozzle efficiency
Boiler efficiency
Vacuum efficiency
The function of injector used in small steam plants is to
Create vacuum in furnace
Create vacuum at turbine exhaust
Pump feed water
Dose chemicals in feed water
Calorific value of coal is of the order of
200-400 kcal/ kg
800-1200 kcal/ kg
2000-4000 kcal/ kg
5000-8000 kcal/ kg
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