MEI251 THERMAL ENGINEERING
1. What are the assumptions made on air standard efficiency?
1. Air is the working fluid and it
obeys the perfect gas laws.
2.
The engine operates in a closed cycle.
The cylinder is filled with constant amount of working substance and the
same fluid is used repeatedly and hence mass remains constant.
3.
The working fluid is homogeneous throughout at all times and no chemical
reaction takes place, inside the cylinder.
4.
The compression and expansion processes
are assumed to be adiabatic.
5.
The values of specific heat (Cp and Cv) of the working
fluid remains constant.
6.
All processes are internally reversible and no mechanical or frictional losses
to occur throughout the process.
7.
Combustion is replaced by heat addition process and exhaust is replaced by heat
rejection process.
2. Define compression ratio.
It
is defined as the ratio of the volume of cylinder to the clearance volume.
3. Define mean effective
pressure.
It
is defined as the average pressure acting on the piston during the entire power
stroke that would produce the same amount of net work output during the actual
cycle. It is also defined as the ratio
of work-done per cycle to swept volume.
4. Define Clearance Volume.
It
is the minimum volume occupied by the fluid in the cylinder when the piston
reaches the top dead centre position.
5. What are the conditions for maximum work of an
Otto cycle?
______
T2
= T4 = √(T1XT3)
r k
= (T3/T1)½(γ-1)
6. Define work ratio of gas turbine.
It
is the ratio of network to turbine work.
7. What is the
function of push rod and rocker arm in IC engine?
The function of push rod and rocker arm in IC engine is to transmit
motion of the cam to the valve.
8. What is
scavenging in IC engine?
The process of pushing out of exhaust gases from the cylinder by
admitting the fresh charge into the cylinder is known as scavenging.
9. What is the
function of idling jet in a carburetor?
The function of idling jet in a carburetor is to supply a mixture at
an air fuel ratio of 10:1 for low speed operation.
10. What are the
requirements of a fuel injection system of a diesel engine?
To inject the fuel at correct moment, and quantity at various load conditions
To inject the fuel in a finely atomized condition.
To distribute the fuel uniformly in the combustion chamber.
To control the rate of fuel injection.
11. List the
advantages of electronic ignition system over the conventional system.
Less weight.
Compact
Spark timing can be accurately controlled.
Wiring is simple
12. What is the
purpose of a thermostat in an engine cooling system?
The purpose of thermostat in cooling system is to control the water
flow. It allows the water circulation
only, when the temperature of the radiator is about 75oC.
13. What is
meant by ignition lag?
It is the time interval between the instant of spark and the instant
when there is a noticeable rise in pressure due to combustion.
14.
Differentiate between brake power and indicated power of an IC engine.
Brake Power: It is defined as the
power developed at output crank shaft of an engine for doing external work.
Indicated Power: It is the power
developed by the engine inside the cylinder due to the fuel combustion in the
combustion chamber.
15. What is
Morse test?
Morse test is a performance test conducted on multi cylinder engines
to measure the indicated power without the use of indicator diagram.
16. Which engine will have more cooling requirement
two-stroke engine or four-stroke
engine? Why?
Two stroke-engine will have more cooling requirements since power is
developed for each revolution of crank.
So, for each crank revolution, Combustion occurs and more heat will be
generated inside the cylinder.
17. What is the
function of the carburetor?
To atomize the fuel and mix it
homogeneously with the air.
To run the engine smoothly without
hunting of fuel wastage.
To provide rich mixture during
starting and idling and also for quick acceleration.
To provide a constant air fuel ratio
at various loads.
To start the engine even in cold
weather conditions.
18. List the
requirements of ignition system.
Ignition should takes place at the
end of compression stroke.
There should be no missing cycle due
to the spark failure.
Ignition
must add sufficient energy for starting and sub staining the charge burning
Ignition
system should supply the minimum required energy within a small volume in a
very short time.
19. What are the different types of ignition system
in S.I. engines?
Battery
Ignition system and Magneto ignition system.
20. What are the advantages of Battery
ignition system?
The
initial cost is low (except battery).
It
provides better spark at low speed of engine during starting and idling.
Maintenance
cost is negligible. (expect for battery)
The
spark efficiency remains unaffected by advance and retard positions.
The
simplicity of the distributor drive.
21. What are the disadvantages of Battery
ignition system?
The engine cannot
be started if the battery is weak.
The weight of the
battery is greater than the magneto.
The wiring involved
in the coil ignition is more complicated than magneto.
The sparking
voltage drops with increasing speed of the engine.
22. What is the necessity of cooling in IC engine?
To avoid un even
expansion of the piston in the cylinder.
To reduce the
temperature of piston and cylinder.
To avoid the over
heating of the cylinder.
To avoid the
physical and chemical changes in the lubricating oil which may cause sticking
of piston rings.
23. What are the different types of cooling in IC engines?
Air cooling
Water cooling
system
Thermosyphon
cooling
Forced
circulation cooling
Thermostatic
regulator cooling
Evaporative
cooling
24. What are the purpose of lubrication in IC engines?
To reduce the
friction and wear between the parts having the relative motion.
To cool the
surfaces by carrying away heat generated due to friction.
To seal between two
moving parts.
To clean the
surface by carrying away the carbon particles caused by wear.
To absorb the shock
between bearings and other parts and consequently reduce noise.
25. What is flash point?
Flash point is the
lowest temperature at which the given oil gives sufficient vapour to give a
moment of flash, when a flame is passed across the surface.
26. What is petroil system of lubrication?
A special type of
lubrication system used in two stroke engines in which lubricant (up to 60%) is
thoroughly mixed with fuel and supplied to the engine. It is also known as mist lubrication.
27. What is auto ignition?
A mixture of fuel
and air can react spontaneously and produce heat by chemical reaction without
the uses of flame to initiate the combustion, because the temperature is high
than self-ignition temperature.
28. What is meant by pre-ignition?
At very high
temperature carbon deposits formed inside the combustion chamber ignites the
air fuel mixture much before normal ignition occurred by spark plug. This is called pre-ignition.
29. What are the factors affecting ignition lag?
Compression ratio,
speed of the engine, Chemical nature of fuel and air fuel ration, and Initial
pressure and temperature.
30. What is meant by knocking? How it occurs in diesel engines?
If the delay period
of C.I. engines is long, more fuel is injected and accumulated in the
chamber. When ignition begins, pulsating
pressure rise can be noticed and creates heavy noise. This is known as knocking.
31. What are the effects of knocking?
The engine parts
gets overheated which may cause damage to the piston.
It creates heavy
vibration of engine and hence louder noise and roughness.
Decrease in power
output and efficiency.
More heat is lost
to the coolant as the dissipation rate is rapid.
The auto-ignition
may over heat the spark plug and hence pre-ignition occurs
Carbon deposits.
32. Define specific fuel consumption?
It is the ratio of
fuel consumption per unit time of power developed.
33. Explain an experimental method to determine the frictional power
of an IC engine.
Retardation test
can be carried out to determine the frictional power of an diesel engine. In this method, the engine is started and
made to run at full load conditions at rated speed. After sometimes, the fuel supply is cutoff
and the necessary readings are noted.
Repeat the above procedure for 50% load and calculated the frictional
power of an engine using formulaes.
34. What is the purpose of heat balance sheet in IC engine?
It is the accounts
of heat supplied and heat utilized in various ways in the system.
The heat balance is
generally done by minute basis or percentage basis.
35. What is the use of helical groove in a fuel injection pump used
for CI engine?
To control the
delivery stroke effectively.
To control the
amount of fuel supplied to the engine.
36. Explain the location of sparkplug with respect to knocking in SI
engines.
In order to reduce
the knocking tendency, spark travel distance should be kept as minimum as
possible. Similarly, the distance of the
end charge from the spark plug also should be minimum.
37. What is steam nozzle? How
are they classified?
A steam nozzle is a
device having variable cross-sectional passage in which the potential energy of
steam is converted into kinetic energy at low pressure when a high pressure
steam flows through it. They are classified
as convergent type, divergent type, convergent-divergent type.
38. Define critical pressure ratio.
The pressure which
the area is minimum and discharge per unit area is maximum is called critical
pressure ratio.
Critical pressure
ration = (p2/p1) = (2/(n+1))(n/(n-1))
39. What is the significance of critical pressure ratio?
The critical
pressure gives the velocity of sound.
The flow in the
convergent portion of the nozzle is subsonic and divergent portion is
supersonic
For expanding the
steam below critical pressure, the divergent portion of the nozzle is
necessary.
When p2
approaches the critical value the rate of discharge will be maximum.
40. What is the effect of friction in nozzle?
It reduces the
value of enthalpy drop.
The expansion will
not be isentropic.
It increases the
entropy.
_____________
The exit velocity
will change as C2 = √(2000(h1 – h2)ηn)
If 10% frictional loss ηnozzle = 90%.
Friction increases
the quality of steam.
Final dryness
fraction of steam is increased as the kinetic energy of steam gets converted
into heat due to friction and is absorbed by steam.
41. Explain super saturated flow (or) metastable flow in steam
nozzle.
When super heated
steam is expanded isentropically, it starts condensing at its meet with dry
saturated line. But in nozzles, the
velocity of steam is high and hence the time available is very less (about
0.001 sec). So, the condensation
phenomenon does not start at point '2' for a flow of point 1 to point 5. As a result of this, the steam continues to
expand in dry condition up to point 3.
The steam between state 2 and 3 is said to be supersaturated or
metastable state and the flow of such super saturated steam is known as
supersaturated or metastable flow. A
limit to the super heated state was observed by Wilson
and a line drawn on the chart through the observed points is known as Wilson Wilson
42. What are the effects of super saturation?
The super
saturation increases the specific volume and entropy of the steam.
Super saturation
reduces the heat drop. Thus exit
velocity of the steam is reduced.
Super saturation
increases the dryness fraction of the steam.
The temperature at
which super saturation occurs will be less than the saturation temperature
corresponding to the pressure. Therefore
the density of the super saturated steam will be more than for the equilibrium
condition, which gives the increase in mass of steam discharged.
43. Differentiate super saturated flow and isentropic flow.
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Super saturated flow
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Isentropic flow
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Entropy is not constant
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Entropy remains constant
|
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Super saturation reduces the heat drop
therefore exit velocity is reduced
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No reduction in enthalpy drop.
|
|
Moiller diagrams cannot be used
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Moiller diagrams can be used.
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_________________________
C2=√((2n/(n-1))p1v1(1-(p1/p2)((n-1)/n)))
|
_______________
C2 = √(2000 (h1-h2)
+ C1
|
44. Mention the applications of nozzle.
To
inject feed water into the boiler in steam injectors.
To
maintain, high vacuum in power plant condensers.
To
supply, high velocity jet of steam jet in steam turbines.
To
remove, air in condenser.
45. Define nozzle efficiency.
It
is the ratio of actual enthalpy drop to isentropic enthalpy drop.
46. What are the advantages of convergent
divergent nozzle?
The steam enters the
nozzle at high pressure with negligible velocity and leaves at high velocity
with low pressure.
Convergent-divergent
nozzles are used in back pressure turbine.
47. What is the purpose of divergent portion after the throat
section of nozzle?
It accelerates the
steam leaving the nozzle.
It does not affect
the discharge of steam passing through
the nozzle.
48. Define degree of super saturation.
The ratio of super
saturation pressures corresponding to the temperature between super saturated
region is known as the degree of super saturation.
49. Define blade efficiency or utilization factor.
It is the ratio of
rotor blade work to energy supplied to the rotor.
50. Define degree of reaction.
It is defined as
the ratio of the actual isentropic heat drop to the total heat drop in the
entire stage.
51. What is compounding and explain the purpose of compounding?
Compounding is the
method in which multiple system or rotors are keyed to common shaft in series
and the steam pressure or jet velocity is absorbed in stages as it flows over
the rotor blades.
Purpose of compounding: Reduction of
pressure (from boiler pressure to condenser pressure) in single results in the
very high velocity entering the turbine blades.
Therefore, the turbine rotor will run at a high speed about 30,000 rpm
which is not useful for practical purpose.
In order to reduce the rotor speed up to about 400 m/sec, compounding of
steam turbine are necessary.
52. What are the types of compounding in steam turbines?
Velocity
compounding, Pressure compounding and Pressure velocity compounding.
53. What are the advantages and disadvantages of velocity compounded
turbines?
Advantages:
The cost of turbine
is less because less number of stages.
It occupies less
area.
The system is
reliable and easy to operate.
Turbine casing is
very simple and need not be very strong.
Disadvantages:
The
friction losses are large due to very high steam velocity in the nozzle.
Low
efficiency because blade speed ratio is less than the optimum value.
The power developed
in the later rows is only a fraction of power developed in the first row.
54. What is governing of steam turbine and state the various methods
of governing?
Governing is the
method of maintaining the constant speed of the turbine irrespective of load
variation by varying the flow rate. The
various methods of governing in steam turbines are Throttle governing, Nozzle
control governing, By pass governing, Combinations of throttle and nozzle
governing and Combinations of throttle and by pass governing.
55. Differentiate Impulse and Reaction Turbine.
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Sl. No.
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Impulse Turbine
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Reaction Turbine
|
|
1.
|
Impulse turbines works due to change in
kinetic energy of the fluid flowing through the rotor when the pressure
remains constant.
|
Reaction turbine is one in which the
decreases gradually & Kinetic energy is increased, when the steam flows
over a set of fixed and moving blades
|
|
2.
|
Less number of stages are required for
same output power.
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More number of stages are required for
same out put power.
|
|
3.
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It is suitable for small power
requirements
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It is suitable for medium and high power
requirements.
|
|
4.
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Blade passage is of constant cross
sectional area.
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Blade passage is of converging type.
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5.
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Blades shapes are profile type.
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Blade shapes are aerofoil type.
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6.
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Steam is admitted over the part of the
circumference of the wheel.
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Steam is admitted over the entire
circumference of the wheel.
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7.
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Blade manufacture is easy
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Blade manufacture is difficult.
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8.
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Steam fully expands in nozzle.
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Steam expands in both nozzle and moving
blades.
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9.
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Flow can be regulated without loss
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Flow cannot be regulated without loss
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56. Differentiate between nozzle governing and throttle governing.
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Sl. No.
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Throttle governing
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Nozzle governing
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1.
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More throttling losses occur.
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Throttling losses are negligible
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2.
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Partial admission losses are low
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Partial admission losses are high
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3.
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Less heat drop is available for work
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More heat drop is available for work
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4.
|
Employed for both impulse and reaction
turbines
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Employed only in impulse turbines
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5.
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Less efficient method
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More efficient method
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6.
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Suitable for small turbines
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Suitable for medium and large turbines
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57. What is the fundamental difference between the operation of
impulse and reaction steam turbines?
In impulse turbine,
the steam completely expands in the nozzle and its pressure remain constant
during its flow through the rotor blades.
In reaction
turbine, the steam expands partially in the nozzle and remaining in rotor
blades.
58. Define the term stage efficiency in case of reaction turbines.
It is the ratio of
work done on blades per kg of steam to the enthalpy drop in the nozzle.
59. What is meant by FAD?
Free air delivered
means the actual volume of air delivered by the compressor under normal
temperature and pressure condition.
60. Define Isothermal efficiency.
It is the ratio of
isothermal power to Indicated or actual power.
61. What are the difference between rotary air compressor and
reciprocating air compressor?
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Reciprocating Air compressor
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Rotary Air compressor
|
|
The maximum delivery pressure may be as
high as 1000 bar.
|
The maximum delivery pressure is 10 bar
only.
|
|
They are suitable for low discharge of
air at very high pressure
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They are suitable for large discharge of
air at low pressure.
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The speed of air compressor is low
|
The speed of air compressor is high.
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The air supply is intermittent
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The air supply is continuous.
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The size of the compressor is large for
the given discharge
|
The size of air compressor is small for
the same discharge.
|
|
The balancing is a major problem
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There is no balancing problem
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62. Why
Clearance volume is necessary and explain its importance?
In
actual compressor, the clearance volume is provided to give cushioning effect
otherwise the piston will strike the other end of the cylinder. It is generally expressed as percentage of
piston displacement.
Importance of clearance volume:
To
give cushioning effect to the piston
To
provide space for valve movement.
The
maximum pressure may also be controlled by clearance volume.
The
volumetric efficiency and pressure ratio are depends upo9n clearance
volume. If clearance volume is more, it
reduces the volumetric efficiency.
63. What are the advantages of multi stage
compressor over single stage compressor?
Ø Less work is done by the compressor to deliver the same quantity of
air.
Ø It improves the volumetric efficiency for the given pressure ratio.
Ø The size of the two cylinder may be adjusted to suit the volume and
pressure of the air.
Ø It reduces the leakage losses considerably and provides effective
lubrication.
Ø It provides more uniform torque and thus smaller size of the
flywheel is required.
Ø It reduces the cost by selecting a cheap material for construction.
64. Define volumetric efficiency of the
compressor.
It is the ratio
of actual volume of air drawn in the compressor to the stroke volume of the
compressor.
65. Define mechanical efficiency.
It
is the ratio of indicated power to shaft power or brake power of motor.
66. Define Isentropic efficiency.
It is the ratio of
the isentropic power to the brake power required to drive the compressor.
67. What is the purpose of inter cooling and explain its process?
The purpose of
inter cooling in multistage compression is to reduce the temperature without
reduction in pressure. It is placed
between LP cylinder and HP cylinder.
When air flows through it, the temperature is reduced by maintaining the
water circulation.
68. How the compressors are classified?
According to the number of stages:
Single stage and
Multi stage
According to the number of cylinder:
Single cylinder and
Multi cylinder.
According to the method of cooling:
Air cooled
compressor and Water cooled compressor
According to working:
Reciprocating
compressor and Rotary compressor
According to the action of air:
Single acting
compressor and Double acting compressor
According to the pressure limit:
Low pressure,
Medium pressure and High pressure compressor.
According to the capacity:
Low capacity,
Medium capacity and High capacity compressor.
69. What are the advantages of rotary
compressor over reciprocating compressor?
Maximum
free air delivery is as high as 3000 m3/min.
Air
supply is continuous, more clean.
Small
size is required for the same discharge.
No
balancing problem.
70. What are the difference between
centrifugal and axial flow compressors?
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Centrifugal compressor
|
Axial flow compressor
|
|
The flow of air is perpendicular to the
axis of compressor
|
The flow of air is parallel to the axis
of compressor
|
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It has low manufacturing and running cost
|
It has high manufacturing and running
cost
|
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It requires low starting torque
|
It requires high starting torque
|
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It is not suitable for multi staging
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It is suitable for multi staging.
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It requires large frontal area for a
given rate of flow
|
It requires less frontal area for a given
rate of flow. It makes the compressor
suitable for air crafts.
|
71. Define COP of refrigeration.
The COP of a
refrigeration system is the ratio of net refrigeration effect to the work
required to produce the effect.
72. What is the unit of refrigeration?
The capacity of refrigeration
is expressed in tonnes of refrigeration (TOR).
1 tonnes of
refrigeration = 210 kJ/min (or) = 3.5 kJ/sec (kW)
A tonne of
refrigeration is defined as the quantity of heat to be removed in order to form
one tonne of ice at 0oC in 24 hours.
73. Define refrigeration effect.
The amount of heat
extracted in a given time is known as refrigeration effect.
74. What are the advantage of air refrigeration system?
The refrigeration
used is air, is non poisonous, cheap and easily available.
The system is
highly reliable.
The system is
weight less and less space is required, therefore, air refrigeration is
extremely useful for aircraft refrigeration.
Air is non-flammable
therefore no risk of fire.
75. What are the disadvantages of air refrigeration?
The COP of the air
refrigeration system is low therefore the running cost f the system is high.
Large volume of air
is required to handle, to compare with other system. Therefore it requires large compressor and
expander.
The freezing of
moisture in the air during expansion is liable to choice up the valves.
76. What are the assumptions made for drawing TS diagram of
refrigeration system?
The condition of
the vapour leaving the compressor is dry saturated.
The compression of
vapour in the compressor is isentropic
There is no
pressure loss in the system.
The work required
to drive the system is equal to the difference between the heat rejected in the
condenser and heat absorbed in the avaporator.
77. What re the effects of
under cooling?
It increases the
refrigeration effect therefore the COP increases.
The mass flow rate
of the refrigeration is less than that for the simple saturated cycle.
The reduced mass
flow rate reduces the piston displacement per minute.
Power per tones of
refrigeration losses due to reduction in mass flow rate.
The increased
efficiency may be offer some extent by the rise in the condenser pressure.
Work input almost
remains same.
The heat rejection
capacity of the condenser increases.
78. What are the effects of super heating?
Supper heating
increases the net refrigeration effect, but super heating requires more work
input therefore super heating reduces the COP.
No moisture
contents in the refrigerant therefore no corrosion in the machines part.
79. What re the advantages of vapour absorption system over vapour
compression system?
As there is no
moving part in the system the operation is quiet and there is very little
wearing.
The maintenance
cost is low.
The system does not
depend upon electric power.
It can be built in
capacities well above 1000 tones each.
At reduced loads to
absorption system is almost as efficient as of full load the COP of the
compressor system decrease as the decrease.
Absorption
refrigeration system can operate at reduced evaporator temperature by
increasing the steam which is supplied to generator with little decrease in
capacity. The capacity of its
compression system drops rapidly with lower evaporator temperature.
80. What are the properties of ideal refrigerant?
It should have low
boiling point and low freezing point.
It must have low
specific heat and high latent heat.
It should have high
thermal conductivity to reduce the heat transfer in evaporator and condenser.
It should have low
specific volume to reduce the size of the compressor.
It should be
non-flammable, non-expensive, non-toxic and non-corrosive.
It should have high
critical pressure and temperature to avoid large power requirements.
It should give high
COP to reduce the running cost of the system.
It must be cheap
and must be readily available.
81. What are the advantages of vapour compression system?
The COP is better,
because the cycle using vapour as refrigerant absorbs and rejects heat at
constant temperature.
The expander is
eliminated.
The temperature at
which the heat is to be absorbed can be changed conveniently by altering the
boiling pressure.
The transfer
co-efficiently is high
The same
refrigerant is used over and over again.
82. Differentiate vapour absorption system and vapour compression
system.
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Vapour absorption system
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Vapour compression system
|
|
Due to compressor and fan more wear and
tear
|
Only moving part is liquid pump, less
wear and tear
|
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Electrical power is essential to operate
the system
|
Electrical power is not essential to
operate the system (heat energy is used)
|
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The compressor is used to compress the
refrigerant
|
Compressor is replaced by absorber and
generator.
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|
Freon 12, Freon 22, NH3,
Propane, Isobutane – used as refrigerants
|
NH3 water vapour system,
Lithium Bromide water vapour system is used.
|
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Occupies less space.
|
Occupies more space.
|
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Performance is poor at partial loads.
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Performance is not affected at partial
loads.
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83. List the important industrial and commercial application of
refrigeration.
Food and milk
preservation.
Ice formation
Comfort and
industrial air conditioning
Storage of liquid
fuels used in rockets.
Treatment of metals
and processing in chemical and related industries.
Processing of
beverages and transportation of food below freezing.
Medical and
surgical aids especially in preserving human bloods and tissues.
Oil refining.
84. How does humidity affect human comfort?
Human beings want
to feel comfortable. They want to live
in an environment that is neither hot not cold, neither very humid nor very
dry. The desires of human body could not
be adopted with high or low humidity.
They feels comfortable only when they can freely dissipate their waste
heat to the environment.
85. What do you mean by the "Infiltration" in heat load
calculations?
The amount of heat
load added due the air entering into the A/c system through small opening in
the doors and windows, cracks in the walls etc., are termed as infiltration.
86. Define RSHF.
Room sensible heat
factor is defined as the ratio of
room sensible heat load to
the room total heat load.
87. Define Relative humidity.
It is defined as
the ratio of partial pressure of water vapour (pw) in a mixture to
the saturation pressure (ps) of pure water at the same temperature
of mixture.
88. Define specific humidity.
It is defined as
the ratio of the mass of water vapour (ms) in a given volume to the
mass of dry air in a given volume (ma).
89. Define degree of saturation.
It is the ratio
of the actual specific humidity and the saturated specific humidity at the same
temperature of the mixture.
90. What is dew point temperature?
The temperature
at which the vapour starts condensing is called dew point temperature. It is also equal to the saturation
temperature at the partial pressure of water vapour in the mixture. The dew point temperature is an indication of
specific humidity.
91. Define sensible heat and latent heat.
Sensible heat is
the heat that changes the temperature of the substance when added to it or when
abstracted from it. Latent heat is the
heat that does not affect the temperature but change of state occurred by
adding the heat or by abstracting the heat.
92. What are the important psychrometric
process?
1. Sensible
heating and sensible cooling, 2. Cooling and dehumidification, 3. Heating and humidification, 4. Mixing of
air streams, 5. Chemical dehumidification, 6. Adiabatic evaporative cooling.
93. What is meant by adiabatic mixing?
The process of
mixing two or more stream of air without any heat transfer to the surrounding
is known as adiabatic mixing. It is
happened in air conditioning system.
94. What is meant by dry bulb temperature
(DBT)?
The temperature
recorded by the thermometer with a dry bulb.
The dry bulb thermometer cannot affected by the moisture present in the
air. It is the measure of sensible heat
of the air.
95. What is meant by wet bulb temperature
(WBT)?
It is the
temperature recorded by a thermometer whose bulb is covered with cotton wick
(wet) saturated with water. The wet bulb temperature may be the measure of
enthalpy of air. WBT is the lowest
temperature recorded by moistened bulb.
96. Define dew point depression.
It is the
difference between dry bulb temperature and dew point temperature of air vapour
mixture.
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