908- KUMARAN
POLYTECHNIC COLLEGE
22042- THERMAL
ENGINEERING-1
UNIT-I
BASICS
OF THERMODYNAMICS AND THERMODYNAMIC PROCESS OF PERFECT GASES
1. Define
Pressure
Pressure:
* Force per unit
area is called pressure.
* It is denoted
by (P).
Pressure=Force/area.
Unit of pressure is N/mm2.
2. Define density and specific volume
Density:
Mass per unit volume
is known as density (or) specific mass.
Density is denoted by
(ℓ).
Unit of density is Kg/m2.
Specific volume:
The volume occupied by
unit mass substance is known as specific volume.
Specific volume (V) = volume/mass=1/density.
Unit of specific volume
is m3/kg.
3. Define temperature
Temperature of substance
may be defined as measure of intensity of heat (or) degree of hotness
(coldness) in a body.
4. Define absolute zero
temperature
Temperature measured from
the absolute zero temperature is called as absolute temperature. (Kelvin
temperature is 0K).
5. What do you mean by thermodynamics
system?
Thermodynamics system is defined
area (or) a space which some thermodynamic process is taking place.
6. Define closed system
In a closed system, heat
and work transfer places, but there is no mass transfer, mass of the system
remain constant.
Example: Steam
power plant.
7. Define open system
*Mass transfer takes place.
* Heat and work also takes
place.
Example: Boiler, air compressor.
8. How thermodynamic properties
are classified?
1. Intensive (or)
intrinsic properties.
2. Extensive (or)
Extrinsic properties.
9. What are intrinsic properties?
The properties which do
not depend on the mass of system are known as intensive properties.
Ex: Pressure,
temperature, density.
10. What is an extrinsic property with one
example?
The properties which
depends on the mass of the system is known as extrinsic properties.
Ex: Volume,
energy.
11. State the thermal equilibrium of a
system.
If a system has same
temperature at all points of the system, then the system is said to be in
thermal equilibrium.
12. What are the laws of
thermodynamics?
* Zeroth law of
thermodynamics
*First law of
thermodynamics
* Second law of
thermodynamics
13. State Zeroth law of thermodynamics
When two bodies are
separately in thermal equilibrium with a third body, then they are in thermal
equilibrium with each other.
14. State the first law of
thermodynamics.
When a system undergoes a
cycle, net work transfer is equal to the net heat transfers.
15. State the second law of
thermodynamics.
Clausis
statement:
The heat can be transferred
from hot body to cold body.
Heat cannot be transfer
from cold body to hot body.
Kelvin plank
statement:
It is impossible to construct a heat engine in which all heat energy is
converted into mechanical work
16. Write down the characteristic
as equation for perfect gas?
P= Pressure.
V=Volume.
M=Mass.
R=Gas Constant.
T=Temperature.
17. What is perfect gas?
A perfect gases is one in
which it obeys all the gas laws at all range of pressure and temperature.
18. What are the laws of gases?
* Boyles law.
* Charles law.
* Renaults’ law.
* Joules law
* Avogadro’s law.
19. State Boyle’s law
When a gas is heated (or) cooled at
constant temperature the volume of a given mass of gas varies inversely
proportional to the absolute pressure.
P1V1
= P2V2=constant.
20. Write Renaults law?
Specific heat Cp& CV
are always constant. It cannot be depends upon the pressure and
temperature.
Cp& CV = constant
Cp / CV = constant
21. Write Charles law
It state that, at
constant pressure volume of gas directly proposition to temperature.
22. Define Avogadro’s law
Equal volume of
all gases contains equal number of molecules.
23. Write joule law?
It states that internal
energy of gas is function of temperature only
24. Define the term enthalpy
Enthalpy: (h)
Sum of the internal energy and flow energy
(pressure × volume) is called enthalpy.
25. Define Entropy?
Entropy is defined as heat
energy with respect to temperature.
26. Define the gas and Vapor?
Gas:
Fully or completely evaporated
liquid is called gas.
Example: O2, H2,
N2.
Vapor:
Partially
(or) incompletely evaporated liquid is called as vapor.
Example: Steam,
CO2 SO2, NH3.
27. What do you meant by
thermodynamics process?
The change in the state of a
gases (or) vapor due to flow of energy is known as thermodynamics process.
28. Identify the thermodynamics
process?
1. Constant volume
process. (Isochoric)
2. Constant pressure
process. (Isobaric)
3. Constant
temperature process. (Isothermal)
4. Hyperbolic
process.
5. Adiabatic process.
6. Polytrophic process.
UNIT-II
THERMODYNAMICS AIR CYCLES AND STEADY FLOW ENERGY
EQUATION
1.
What is control volume?
The space enclosed
by these boundaries is called control volume.
A certain region (or) space through
which the fluid flows at a steady rate is called control volume.
2. Define air standard efficiency
The thermal efficiency of
air cycle is known as air standard efficiency
Air
standard efficiency = work done/heat supplied.
3. What is Compression Ratio?
It is the ratio of total
volume to the clearance volume of cylinder.
It is
denoted by Letter r.
r =
total volume/clearance volume.
4. Define reversible process
A thermodynamics process is said to be reversible. If it
follows the same parts in the reversed direction when the process is reversed,
the amount of energy transfer is same in either direction.
Example:
ü
Constant volume process,
ü
isothermal process ,
ü Adiabatic
process.
5. Define irreversible process.
Give example.
A thermodynamics process
which con not be operated in reverse direction is known as irreversible
process.
Example: Throttling process, free expansion process.
6. What are the types of
thermodynamic cycle?
·
Carnot cycle
·
Otto cycle
·
Joule cycle (or) constant pressure cycle (or)
brayton cycle
·
Diesel cycle
·
Duel combustion Cycle.
7.
No engine can work on Carnot cycle? Why
During the First half of the
stroke, piston has to move very quickly (adiabatic process) and during the next
half of the stroke, piston has to move very slowly (Isothermal process) To
design such an engine is impossible. That is why, no engine can work on Carnot
cycle.
8. Define cut-off ratio
It is defined as ratio between
cut-off volume and clearance volume of engine cylinder
Cut-off ratio = cut off volume / clearance
volume.
|
9. Draw the P V and T S
diagram of Carnot cycle
10 Draw the P V and T S diagram of Otto cycle
11. Draw the PV and TS
diagram of Diesel cycle
12. Draw the PV and TS
diagram of Brayton cycle
13. Compare Otto cycle and
diesel cycle
SL.NO
|
Otto cycle
|
Diesel cycle
|
1.
|
It is used in petrol engine
|
It is used in diesel engine
|
2.
|
|
Heat is added at constant
volume
|
|
|
|
Heat is added at constant
pressure
|
|
|
|
|
3.
|
|
Compression ratio =
expansion ratio
|
|
Compression ratio ≠ expansion ratio
|
4.
|
|
Compression ratio is 6 to 8
|
|
Compression ratio is 12 to 18
|
UNIT-III
AIR COMPRESSOR
1.
What is
air compressor?
Air
compressor is a machine which converts mechanical energy into pressure energy
2.
What are the uses of compressed air
1. To operate the Pneumatic drills, coal cutter.
2. To operate Pneumatic breaks for automobiles.
3. In spray planting work.
4. In sand blasting.
5. For pumping water from deep well.
6. For super charging the I.C engine.
7. For
blast furnaces and air-compressor.
3.
Classification of air compressor?
1. According
to the design and principle of operation.
a)
Reciprocating compressor.
b) Rotary
compressor.
2. According
to the number of stages.
a) Single
stage.
b) Multi
stage.
3. According
to the pressure stage.
a) Low
pressure compressor.
b) Medium
pressure compressor.
c) High
pressure compressor.
4. According
to the capacity.
a) Low
capacity.
b) Medium
capacity.
c) High capacity.
5. According
to the method of cooling.
a) Air cooled
compressor.
b) Water cooled compressor.
4.
What are the effects of clearance volume in air compressor?
Ø Suction volume is reduced.
Ø Mass of air is reduced.
Ø Increased clearance volume result in heavy
compression.
Ø Heavy compression increase mechanical loss.
Ø It reduces volumetric efficiency.
5. Define volumetric
efficiency
It is
defined as effective suction volume to the stroke volume of the cylinder.
Volumetric efficiency =
effective suction volume / stroke volume
|
6. Define clearance ratio
It is
defined as the ratio of clearance volume to stroke volume.
C = Clearance volume /
swept volume.
|
7. Define pressure ratio
It is
the ratio of delivery pressure to the suction pressure. It is denoted by the
letter Rp.
Rp =
delivery pressure / suction pressure.
|
8. What are the various
types of the efficiency of compressor?
Ø Isothermal efficiency.
Ø Adiabatic efficiency.
Ø Mechanical efficiency.
Ø Overall efficiency.
9. Define isothermal
efficiency
ŋiso
= isothermal work input / actual
work input.
|
10. Define adiabatic
efficiency
ŋadi =
adiabatic work input / actual work input.
|
11. Define mechanical
efficiency
ŋmech =
actual indicted / power input to the compressor.
|
12. Define overall
efficiency
ŋo = air power supplied / power
supplied by the prime mover
|
13. What are the merits and
demerits of multi stage air compressor?
SL.NO
|
MERITS
|
DEMERITS
|
1.
|
Volumetric efficiency is more.
|
Initial cost is high.
|
2.
|
Power required to drive the compressor is less
|
More cooling water is required.
|
3.
|
It has better lubricating resulting in minimum
leakage.
|
Construction is complicated
|
14. Classification of rotary
compressor?
a) Positive displacement compressor
1. Root
blower.
2. Vane
blower.
b)
Non-positive displacement compressor.
1.
Centrifugal compressor.
2. Axial flow compressor.
15. What is gas turbine?
A gas
turbine is a rotary machine. Which convert heat energy into mechanical energy.
16. State the classification
of gas turbine.
1. According to the pats of the working substance
a) Open
cycle.
b) Closed
cycle.
c) Semi
closed cycle.
2. According to the process of heat absorption.
a) Constant
pressure cycle.
b) Constant
volume cycle.
3. According to the field of application.
a) Industrial
gas turbine.
b) Aircraft gas turbine.
17. What are the main
elements of a gas turbine?
1. Compressor.
2. Combustion
chamber.
3. Lubrication.
18. Name the type of air
cycle usually adopted in gas turbine?
Brayton
cycle (or) joule cycle
19. What is open cycle gas
turbine?
If the
exhaust gases from turbine are left to automobile, the gas turbine is known as
open cycle gas turbine.
20. What is closed cycle gas
turbine?
If the
exhaust gases from turbine are reused into the system again and again, the gas
turbine is known as closed cycle gas turbine.
21. What are the
applications of gas turbine?
1. Aircraft.
2. Propeller ship.
3. Electric power plant.
4.
Portable Electric generator.
22. What are the advantages
and disadvantages of gas turbine?
Advantages:-
Ø More power output and high mechanical efficiency.
Ø Less weight.
Ø Compact sign.
Ø Low grade fuel can be early burnt.
Ø Less pollution.
Ø Less maintenance.
Disadvantages:-
Ø Low thermal efficiency.
Ø It requires more space.
Ø Initial cost is high.
Ø The starting of gas turbine is difficult.
23. What are methods used to
improve the power output of a gas turbine?
1. Using regenerator with gas turbine.
2. Using intercooler with gas turbine.
3.
Using reheater with gas turbine.
24. What are the effects of
intercooler in gas turbine?
1. Work output is increase.
2. Power is saved.
3. Water required in intercooler.
4.
Size of compressor is reduced.
25. What are the effects of
regeneration in gas turbine?
1. It requires fuel consumption.
2. It increases thermal efficiency.
3.
There is no change in compressor.
26. What are the effects of
reheater in gas turbine?
1. It increases power output of gas turbine.
2. It increase total plant size.
3. As more heat is supplied.
4.
Thermal efficiency reduced.
27. What are advantages of
open cycle gas?
1. Compact size.
2. Simple construction.
3. Suitable for aircraft.
4. Better combustion efficiency.
5.
Coolant water in not required.
28. What are the advantages
of closed cycle gas turbine?
1. High thermal efficiency.
2. High capacity.
3. External combustion.
4.
Long life.
29. What are the
applications of the jet propulsion?
1. Turbo jet.
2. Turbo propeller.
3. Ram jet.
4.
Pulse jet.
30. What are the advantages
and disadvantages of turbo jet engine?
Advantages:-
1. It is
simple in construction.
2. Low grade
fuel can be used.
3. It can be
operated high speed.
4. It has less moving parts.
5. Wear and tear is considerably low.
6. No less of power.
Disadvantages:-
1. Less power
is developed.
2. It has
higher fuel consumption.
3. The
materials used are consumption.
4. Life of
the unit is shorter.
5. It produces more noise.
31. What are the advantages
and disadvantages of turbo propeller?
Advantages:-
1. It is
simple in construction.
2. During
takeoff, more power is developed due to propeller.
3. It has
less weight.
4. It has
high efficiency.
5. It has
less vibration and less noise.
6. It has less maintenance.
Disadvantages:-
1. It has low
propulsive efficiency at high speed.
2. The
propeller cannot run at high speed.
3. It occupied more space.
32. What are the advantages
and disadvantages of ramjet?
Advantages:-
1. It has no
moving path.
2. Less
maintenance.
3. Less
weight.
4. Low cost.
5. Very high speed.
Disadvantages:-
1. It
requires an external starting drive.
2. Designs
are very difficult.
3. Fuel
consumption is more at low speed.
4. For steady
combustion, flame holders are necessary.
33. What are the
applications of rocket?
1. Research.
2. For space ship.
3. For satellite.
4.
Latest weapons.
UNIT-IV
FUEL AND COMBUSTION
1. What is fuel?
Fuel
is substance which releases. Next energy during combustion with air.
2.
Classification of fuels?
1. Solid fuels
2. Liquid fuels.
3.
Gaseous fuels
3. Give some example for
solid fuels?
Coal,
wood, peat, lignite coal, etc.
4. Give some example for
liquid fuels?
Gasoline,
diesel, petrol, kerosene, methanol, etc.
5. Give some examples for
gaseous fuels?
LPG,
CNG, Natural gas, etc.
6.
What are requirements of good fuels?
1. High calorific value.
2. Low ignition temperature.
3. Not produce any harmful gases.
4. Less smoke.
5. Low cost.
6. No ash.
7.
Easily stored and transported.
7. What are the merits and
demerits of solid fuels?
Merits:
1. Low cost.
2. Early
available.
3. It has no risk of fire as compared to other fuels.
Demerits:
1. Low
calorific value.
2. More
storage space.
3. It produces more smoke.
8. What are the merits and
demerits of liquid fuels?
Merits:
1. High
calorific value.
2. Less
space.
3. Combustion
can be easily controlled.
4. No damage.
Demerits:
1. High cost.
2. Fire risk.
3. More cost.
9. What are the merits and
demerits of gaseous fuels?
Merits:
1. Free from
ash.
2. Less
smoke.
3. Burn
completely.
4. Combustion can be easily controlled.
Demerits:
1. It is
easily inflammable.
2. It requires mono storage space.
10. What is excess air?
In
order to ensure the complete combustion of fuels, some extra quantity air is
supplied along with theoretical quantity of air. This extra air supplied is
known as excess air. Generally 25% to 50% excess air is used.
11. What are the types of
calorific values?
There
are two types of calorific values.
1. Higher
calorific values.
2. Lower calorific values.
12. What is higher calorific
value?
It is
defined as the amount of heat obtained by complete combustion of unit mass of a
fuel, when the products of combustion are cooled down to the temperature of the
air supply.
13. What is lower calorific
value?
It is
defined as the amount of heat obtained by complete combustion of unit mass of a
fuel, when heat energy taken away by steam is not recovered.
14. Name the apparatus used
to find calorific value of solid and liquid fuels.
Bomb calorimeter.
15. Name the apparatus to
fined calorific value of gaseous fuels?
Junker’s gas calorimeter,
boy’s gas calorimeter.
|
16. Write the Delong’s
formula of two find HCV?
HCV = 33,800°C + 144000 [H2 = O2/8] +
92705KJ/KG.
|
17. What is the purpose of
orsat apparatus?
Orsat
apparatus is used to analyze fuel gas or exhaust gas.
19. What is heat engine?
Heat
engine is a machine which converts heat energy into mechanical energy.
20. What are types of heat
engine?
1. Internal combustion engine.
2.
External combustion engine.
21. Classification of
internal combustion engine?
1. Numbers
of stroke / cycle.
a. Two stroke
cycle engine
b. Four
stroke cycle engine.
2. Operating
thermodynamics cycle.
a. Otto cycle
engine.
b. Diesel
cycle engine.
c. Duel
combustion engine.
3. Types of
fuel used.
a. Petrol.
b. Diesel.
c. Gas.
4. Types of
ignition methods.
a. Spark
ignition (SI) engine.
b.
Compression ignition (CI) engine.
5. Number of
cylinder.
a. Single
cylinder.
b. Multi
cylinder.
6. Working
speed
a. Low speed.
b. High speed.
22. What is scavenging?
Scavenging is the process of forcing
out the burnt gases out of the cylinder by admitting fresh charge into the
cylinder. This type of action takes place in two stroke cycle engine.
23. Compare of two stroke engine and
four stroke cycle engine
1
|
One power stroke in every
revolution of the crank shaft
|
One power stroke in two
revolution of the crank shaft
|
2
|
Uniform torque developed
|
Fluctuating torque developed
|
3
|
Lighter flywheel required
|
Heavier flywheel required
|
4
|
No valve mechanism used
|
valve mechanism used
|
5
|
Starting is easy
|
Starting is not so easy
|
6
|
High mechanical efficiency
|
Low mechanical efficiency
|
7
|
It is simple in design
|
Design is complex
|
24.
Compare petrol engine and diesel engine
S.NO
|
Petrol engine
|
Diesel engine
|
1
|
Otto cycle is employed in petrol engine
|
Diesel cycle is employed in diesel engine
|
2
|
Operating speed is more
|
Operating speed is low
|
3
|
Starting is easy
|
Starting is not so easy
|
4
|
It produces less noise
|
It produces more noise
|
5
|
Maintenance cost is low
|
Starting is not so easy
|
6
|
High mechanical efficiency
|
Low mechanical efficiency
|
7
|
It is simple in design
|
Design is complex
|
UNIT-V
HEAT EXCHANGER
1. State
the methods of heat transfer
1. Conduction.
2. Convection.
3. Radiation.
2. Define: conduction,
convection, radiation
Conduction:-
Conduction is the transfer of
heat between two bodies in direct contact.
Convection:-
Convection is the transfer of
heat between a wall and fluid system in motion.
Radiation:-
Radiation is the transfer
of heat between two bodies separated by empty space or gases.
3. State the Fourier’s law
Fourier law of heat condition state that “the
rate of heat flow is direct proportional to the are section at right angle to
the direction of heat flow and to change of temperature with respect to the
length of the path of the heat flow.
4. Define thermal
conductivity
The amount of energy conducted
through a body of unit area and unit thickness in unit time, when unit
temperature difference between the faces causing heat flow.
5.
State the assumptions mode in heat conductivity
1. Steady state flow of heat
takes place.
2. Thermal conductivity remains
constant and does not vary with temperature.
6. What are the types of
convection?
i. Natural convection.
ii. Forced convection.
7. What is heat exchanger?
Heat exchanger is equipment used
to transfer the energy from a hot fluid to a cold fluid with maximum rate and
minimum investment and running costs.
8.
What are the types of heat exchanger?
1. Parallel flow.
2. Counter flow.
3. Cross flow.
9. Define Parallel Flow
Both fluid enter at the same end and leave at
the other end.
10. Define Counter Flow
The
two fluids flow in the opposite direction.
11. Define LMTD
Logarithmic mean temperature
difference is defined as the constant temperature difference would give the
same rate of heat transfer under variable condition of fluid.
12. What is black body?
A body which absorbs all the
incidence radiation is called “black body”.
13. What is transparent or
diathermanous body?
A body which transmits all the
incident radiation is called diathermanous body.
14. What is white body?
A body which reflects all the
incidence radiation is called white body.
15. What is opaque body?
A body which does not transmit any incident radiation
is called opaque body.
Prepared by,
SUBIN.P .NADARAJAN,
LECTURER, DME
KUMARAN POLYTECHNIC COLLEGE.
