K.S.RANGASAMY COLLEGE OF TECHNOLOGY, TIRUCHENGODE – 637215 DEPARTMENT OF MECHATRONICS ENGINEERING 2010 – 2011 IV SEM / II YEAR 08150403C, APPLIED THERMODYNAMICS AND HEAT TRANSFER 2 MARKS QUESTION BANK UNIT – I SYSTEM AND LAWS OF THERMODYNAMICS 1. What is meant by thermodynamic system (or) Define thermodynamic system? It can be defined as a definite quantity of matter bounded in a closed surface (or) Encloser. SURROUNDING BOUNDARY SYSTEM SURROUNDING 2. What is meant by surroundings? Anything outside the boundary is called surroundings.(or) the system and surroundings is separated by boundary. 3. Write the types of system? Open system Closed System Isolated System Study state flow system unsteady state flow system 4. What is meant by closed system? (or) Define closed system? It is defined as energy transfer, work transfer, not mass transfer in this system is called closed system 5. What is meant by open system? (or) define open system? It is defined as energy transfer, work transfer and mass transfer 6. What is meant by steady state flow system? In open system, the mass transfer and energy transfer with respect to time is constant is known as study state flow system. 7. What is meant by unsteady state flow system? In open system, the mass transfer and energy transfer with respect to time is not constant is known as unsteady state flow system. 1
Transcript
K.S.RANGASAMY COLLEGE OF TECHNOLOGY, TIRUCHENGODE – 637215
DEPARTMENT OF MECHATRONICS ENGINEERING
2010 – 2011 IV SEM / II YEAR
08150403C, APPLIED THERMODYNAMICS AND HEAT TRANSFER
2 MARKS QUESTION BANK
UNIT – I
SYSTEM AND LAWS OF THERMODYNAMICS
1. What is meant by thermodynamic system (or) Define thermodynamic system?It can be defined as a definite quantity of matter bounded in a closed surface (or) Encloser.
SURROUNDING BOUNDARY
SYSTEM
SURROUNDING
2. What is meant by surroundings?Anything outside the boundary is called surroundings.(or) the system and surroundings is
separated by boundary.
3. Write the types of system?
Open system Closed System Isolated System
Study state flow system unsteady state flow system
4. What is meant by closed system? (or) Define closed system?It is defined as energy transfer, work transfer, not mass transfer in this system is called
closed system
5. What is meant by open system? (or) define open system?It is defined as energy transfer, work transfer and mass transfer
6. What is meant by steady state flow system?In open system, the mass transfer and energy transfer with respect to time is constant is
known as study state flow system.
7. What is meant by unsteady state flow system?In open system, the mass transfer and energy transfer with respect to time is not constant
is known as unsteady state flow system.
8. What is meant by isolated system?Neither energy nor mass transfer occurs between the system and surroundings.
Practically no system is isolated
9. What is meant by properties of a system?Any abservable characteristics of the system is an properties.
Eg: Volume temperature pressure and density
10. Write the types of properties?1. Intensive property2. Extensive property
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11. Define Intensive properties?It is define as does not depends on mass It is called intensive property
Ex.Pressure temperature, sp weight and specific volume
12. Define extensive properties?It is defined as depends on mass is called as intensive properties. Eg.
Volume, energy (heat and work)
13. What is mean by state of a system?The state of a system (when the system is in thermodynamic equilibrium) is the condition of
the system at any particular moment, which can be identified by the statement of its properties such as pressure, volume, and temperature, etc.,
14. Define path?The path can be defined as any line (or) curve connecting (ioining) the all the state point is
available.(Or)
It is a graphical representation to denote the state point.
15. What is mean by process?It means reason for change of state
16. How to divide the process?1. Cyclic process2. Quasistatic process
17. What is mean by cyclic process?It is the process in which number of process are made finally it will come back to the original
position is known as cyclic process.
18. What is mean by quasi – static process (or) quasi equilibrium process?When the process is carried out in such a way that at every instant the system deviation from
the thermodynamic equilibrium is infinitesimal then the process is known as quasi static (or) quasi – equilibrium process.
19. Distinguish between open and closed system?Open system Closed system
Energy transfer Energy transfer
Work transfer Work transfer
Mass transfer No mass transfer
20. What is mean by thermodynamic equilibrium?A system is said to be in thermodynamics equilibrium it is satisfies the following three
requirement of equilibrium.(i) Mechanical equilibrium:
It means, the uniform pressure at all points in the system(ii) Thermal equilibrium
It means, the uniform temperature at all point in the system(iii) Chemical equilibrium
It means there is no chemical reaction.
21. Define energy?It is defines as the capacity to do work, in other words, a system is said to posses energy
when it is capable of doing work.
22. What are the different forms of energy?1. Potential energy 2. Kinetic energy 3. Pressure energy 4. Work 5. Heat
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23. What is mean by internal energy?It is the energy possessed by a body (or) a system due to molecular arrangement and motion
of the molecules.
24. State the law of conservation of energy?It states the energy can neither be created nor destroyed through it can be transfer from one
form to any other form, in which the energy can exit.
25. What is meant by enthalpy(H)?The total heat content is called enthalpy.
26. What is meant by specific enthalpy?The sum of specific internal energy and flow work (pv) is called specific enthalpyH = u + pv in J/kg
27. Define specific heat?The specific heat of a subtonic is defined as the amount of heat required to raise the
temperature of a unit mass of any substance thought one degree.
28. Define thermal (or) heat capacity?It is defined as the heat required to raise the temperature of whole mass of substance
through one degree (or) the specific heat multiplied by its mass is called heat capacity.
29. Calculate the quantity of heat required to raise the temperature of a steel forging of mass 180kg from 300k to 1265k the specific heat of steel 0.49 kJ/kg.k
To find: Amount (quantity) of heat required?Solution:Q = m.c.dt = 180 X .49 X (1265 – 180)Q = 85113kJ
30. Define work?In mechanics the work is define as the product of the force (F) and the distance moved (x) in
the direction of the forceMathematically, work done.
W = F x X
31. Write the comparison similarities between heat and work?1. The heat and work are both transient phenomena the system do not possess heat (or) work
when a. The system undergoes a change heat transfer (or) work done may occur.2. The heat and work are boundary phenomena they are observed at the boundary of the
system.3. The heat and work present the energy crossing the boundary of the system.4. The heat and work are path functions are hence they are inexact differentials they are written
as sq and sw
32. Define power?It is defined as the rate of doing work (or) work done per unit time,mathematically
Power = work done / time taken.
33. What are all the laws of thermos dynamics?1. Zeroth law of thermo dynamics,2. First law of thermo dynamics3. Second law of thermo dynamics
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34. State the zeroth law of thermos dynamics?This law states when tow systems are each in thermal equilibrium with a third system then
the two systems are also in thermal equilibrium with one another.
35. What is the laws of conservation of energy?(i) Energy (corollary 1 of first law)
There exists a property of a system is called energy E such that change in its value is the algebraic sum of the heat and work change in state.
(ii) Corollary – IIEnergy can neither created nor be destroyed this law is second corollary of the first law of thermodynamics it states.In an isolated system the energy of the system remains constant.Perpetual motion of machine first kind pmm 1Perpetual motion machine of first kind is impossible because this machine (engine) will continuous work with out receives any energy from the other system (or) surrounding
It will create energy and thus violated the first law of thermodynamics.Q = w
36. Application of first law to non flow (or) closed system?1. Constant volume process (isochoric process) (v = c) (n = 0)2. Constant pressure process (isobhoric process) (p = c) (n = 0)3. Constant temperature process (or) (isotherimal process)
(t = c or pv = c,) n = 14. Isentropic process or reversible adiabatic process (pvr = c) n =
37. Write the Limitation of first law of thermodynamics?The first law of thermodynamics merely state that the work transfer cauts to heat transfer and
does not place any restriction the direction of heat and work transfer. According to the law, it is assumed that any change of Thermodynamics State can take place in either direction.
The heat flow from the high temperature block to the low temperature block till the temperatures of the both block are equal from the experience the reverse process of the heat flow is impossible the heat flow the low tempereature block high temperature block is impossible.
The funning automobile can be stopped using the brake where the kinetic energy of automobile is converted in heat which increases the energy of the brake drum.
But this energy is not possible to accelerate the automobile by the cooling of the hot broke drum.
38. What is mean by heat engine?Any machine is designed to carry out the thermodynamic cycle to convert the heat energy
supplied to it in mechanical energy is called a heat engine.
39. Define energy reservoirs? (or) sources?A thermal energy reservoir (TER) is defined as a large body of infinite heat capacity. Which is
capable of absorbing (or) rejecting an unlimited quantity of heat with out suffereing appreciable change in its thermodynamics co-ordinates.
40. Define sink?It is low temperature reservoir it absorbs Q2 heat is rejected from the system. (engine)
41. Write the statement of second law of thermodynamics?1. Kelvin – Plank – Statement2. Calusisus – Statement
42. State the Kelvin Planck Statement?It is impossible to construct a heat engine which will convert all het energy into equal amount
of work in a cyclic process ie. All heat cannot be converted in to work. Some heat will be rejected to the surroundings.
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43. State the clauses Statement?It is impossible to construct a device, which will transfer the heat from cold body to hot body
with out external work.i.e., heat cannot flow from cold body to hot body with out any external work.
44. Perpetual motion of machine kind – II – pmm2?A heat engine which will produce work in a complete cycle by exchanging het with only one
reservoir, is called pmm2. This engine is not possible since it violated second law Kelvin Planck statement.
45. What is meant by reversibility?A reversible process is a process in which both the system and surroundings may be process
is reversed.A reversible process is an ideal process. It is a Quasi – static process because this process is
carried out very slowly so that every state passed through by the system is an equilibrium state so this process is not possible All real process are irreversible processes.
46. State the cannot theorem?All heat engines operating between a given constant temperature source, and a given
constant temperature sink, none has a higher efficiency than reversible engine.
47. What is carnot engine? (1)Carnot engine is a reversible engine having higher thermal efficiency than any other engine.
48. What is carnot theorem?(2)All reversible engines working between same temperature limits will have same efficiengy.
49. State the carnot theorem(3)Efficiency of ideal engine (Carnot engine) working between two fixed temperature is
independent of working substances, but depending only on temperature.
50. What is mean by Entropy?Entropy is a measure of molecular disorder the entropy of a system is changed because of
irreversibility i.e friction heat transfer and work transferThe unit of specific entropy is kJ/kg,0kFor reversible process ds = d/TFor any process d/T<s
51. When a system is said to be thermal equilibrium?A system is said to exist in a state of thermodynamic equilibrium when no change in any
macroscopic property is registered if the system is isolated from its surrounding.
52. Sketch isothermal expansion on p-v diagram and state the properties that remain constant
(i) There is no change in temperature T = c(ii) There is no change in internal energy du = c(iii) There is no change in enthalpy dh = c
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UNIT – IIPOWER CYCLES AND INTERNAL COMBUSTION
1. What is meant by an air cycle?When air is assumed to be the working substances inside the engine cylinder the cycle is
called as an air cycle.
2. What are the assumptions are made in thermodynamics cycles?1. The gas in the engine cylinder is a perfect gas i.e. if obeys the gas laws and constant specific
heats.2. The physical constants of the gas in the engine cylinder are same as these of air at moderate
temperature3. All the compression and expression process are adiabatic and they take place without any
internal friction.4. Heat is supplied by bringing a hot body in contact with the cylinder at appropriate points
during the process similarly heat is rejected by bringing a cold in contact with their cylinder at these points.
5. The cycle is considered to be a closed one and the same air is used again and again to the repeat the cycle.
6. No chemical reaction whatever takes place in the engine cylinder.
3. How to classify the thermodynamics cycle?1. Reversible (or) ideal cycle.2. Irreversible (or) natural (or) real cycle
4. What is mean by reversible (or) ideal cycle? (or) process?In a reversible process there should not be any loss of heat due to friction radiation (or)
conduction etc., a cycle will be reversible if all the processes constituting the cycle are reversible. Thus in a reversible cycle the initial conditions are restored at the end of the cycle.
5. What is mean by irreversible cycle? (or) process?The heat and work are not completely restored back by reversing the process then the
process is known as irreversible process also called natural (or) real process.
6. What is the causes for irreversible cycle (or) process takes place?1. Mechanical and fluid friction2. Unrestricted expansion3. Heat transfer with a finite temperature difference. Moreover friction converts the mechanical
work into heat this heat cannot supply back the same amount of mechanical work which was consumed for its production.
7. Relation between cycle and engine?The basic theory of a heat engine it is assumed that the working fluid is used again and in the
cylinder we say that the fluid has undergone a cycle when it passes through different processes and return back to its original state.
In a actual practices, the working fluid in an actual engine does not go through a complete cycle. But for the purpose of simplicity in analysis.
8. Write the important terms used in thermodynamics cycle?1. Cylinder bore 2. Stroke length 3. Clearance volume4. Swept volume 5. Total cylinder volume 6. Compression ratio7. Mean effective pressure.
9. What is mean by cylinder bore?This is the diameter of cylinder in which the piston moves
10. What is mean by stroke length?The piston moves in the cylinder due to rotation of the crank the extreme position of the
piston are known as top dead center (TDC) and bottom most position (BD) is bottom dead center the distance between there TDC and BDC is known as stroke length.
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The volume swept by the piston (TDC and BDC) is known as stroke volume (or) swept volume is represented by Vs
Vs = piston area X stroke lengthVs = /4 X d2 X L
11. What is mean by clearance volume?This is volume occupied by the working fluid when the piston reaches top dead center (TDC)
and is represented by Vc
12. Define the cylinder volume?This is the volume occupied by the working fluid when the piston reaches the bottom dead
center.(BDC)Cylinder volume: Vs + Vc
13. Define compression ratio?The ratio of the cylinder volume to the clearance volume is know as the compression ratio. It
is represented by “r” r=vs+vc%vc.Compression ration is also called as expansion ratio.
14. Define mean effective pressure?It is defined as the average pressure acting on the piston during the working stroke. Pm = mep = work done per cycle (KN-m)/Stroke volume (or) swept volume m3 KN/m2
15. Define efficiency of a thermodynamic cycle?It may be defined as the ratio of work done to the heat supplied during a cycle.= work done/Heat supplied = Heat supplied – heat rejected / heat supplied
16. Define air – standard efficiency?In order to compare the efficiency of the thermo dynamics cycles, ‘air is assumed to be the
working substance inside the engine cylinder moreover, air is assumed to behave as a perfect gas, the efficiency thus obtained is known as air standard efficiency, it is also called ideal efficiency.
17. What are the different types of air standard cycles.Air Standard cycle:
1. Burning of fuel (combustion) the takes place inside the cylinder. Example: Petrol Engine,(Otto Cycle) Diesel Engine (diesel cycle) Brayton cycle.
Burning of fuel (combustion) takes place outside Cylinder. Example: gas turbine cycle or joules cycle or Diesel.
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18. What are the types of thermodynamics cycles?1. Carnot cycle 2. Starling cycle 3. Ericson cycle 4. Joule cycle5. Otto cycle 6. Diesel cycle 7. Dual combustion.
19. What is mean by Carnot cycle?Said Carnot, was a French scientist to analyze the [problem of the efficiency of heat engine,
disregarding its mechanical details. He focused his attention on the basic features of a heat engine. In a Carnot cycle, the working substance to a cyclic operation consisting of two isothermal and two reversible adiabatic (or) isentropic operations.
It consists of a two isentropic processes (compression 4-1 and expansion 2-3 and two ISO thermal process (compression 3-4 and expansion 1-2)
30. The diesel cycle efficiency increases with decrease in cut off ratio and approaches maximum (equal to Otto cycle efficiency)
31. What is the effect of cut-off ratio on the efficiency of diesel cycle when the compression ratio is kept constant?
The efficiency of the ideal diesel cycle is lower than that of Otto cycle, for the same compression ratio. This is due to the fact that the cut-off ratio (p) is always greater than unity.
Diesel cycle efficiency increases with decreases in cut-off ratio and approaches maximum equal to Otto cycle efficiency.
32. What is mean by dual combustion cycle (or) semi diesel cycle?This cycle is combination of Otto and diesel cycles. It is some times called semi-diesel engine
work on this cycle, in this cycle heat is absorbed partly at a constant volume and partly at a constant pressure.
34. What the effect of efficiency in dual combustion ascle?The efficiency of dual combustion cycle is greater than diesel cycle and less than Otto cycle,
for the same compression ratio.
35. What is mean by brayton cycle (or) joule cycle (or) gas turbine cycle? External combustion engine cycle?
Brayton cycle is the air standard cycle for gas turbine plant. It consists of two constant pressure and two reversible adiabatic process this cycle is also called external combustion engine cycle since the burning takes place outside the cylinder.
36. Draw the P-v and T-s diagram for brayton cycle? 1-2 constant pressure heat supply 2-3 isentropic expansion 3-4 constant pressure heat rejection4-1 isotropic compression
37. What is the efficiency of the brayton cycle?Brayton = 1-1/(r) -1
38. What is the effect of efficiency in brayton cycle?The efficiency joules cycle is lower than carnot efficiency because of all the heat is not taken
in at the higher temperature and rejection at lowest temperature.The brayton cycle is applied to refrigeration where air is used as refrigeration.
39. What are the mernogs are used to the increases the efficiency of brayton cycle?1. Regeneration 2. Rehearing 3. Inter cooling
40. What is mean by internal combustion engine?(IC Engines)The combustion of fuel takes place in side the engine cylinder is known external combustion
engine. Example: Petrol, diesel and gas engine.
41. What is mean by external, combustion engine?Combustion of fuel takes place out side the engine cylinder is known external combustion
engine. Example: gas turbine engine, steam engine.
42. Comparison between the steam engine (external combustion) and internal combustion engine.
Steam Engine I.C Engine
The combustion of fuel takes place outside the engine cylinder.(ie in boiler)
The combination of fuel takes place inside the engine cylinder,.
Running the engine is smooth and silentRunning the engine noice and very high vibration.
Working pressure and temperature, Inside the engine cylinder is low.
The working pressure and temperature inside the engine cylinder is very high.
Ordinary alloy steels are used to manufacturing of engine cylinder.
Special alloys are used to manufacturing of engine cylinder.
Efficiency of steam engine is about 15-20% Efficiency of I.C engine is about 35-40%It can not be started instantaneously It can be started instantaneously.
43. How to classify the I.C engine?According to be type of fuel used
1. Petrol engine, diesel engine, (or) oil engine, 2. Gas engine
According to the method of ignition of the fuel.1. Spank ignition engine (SI engine)2. Compression ignition engine (C.I engine)3. Hot spot ignition engine.
According to number of stroke / cycle.1. Otto cycle, (constant volume cycle)2. Diesel cycle (constant pressure cycle)3. Dual combustion cycle (semi – diesel cycle)
According to the speed of the engine1. Low speed engine 2. Medium speed engine3. High speed engine
According to the cooling system.1. Air-cooled engines 2. Water – cooled engines3. Evaporative cooling engines
According to the method of fuel injection.1. Carburetor engine2. Air injection engines3. Air less (or) solid injection engine.
According to the arrangement of cylner1. Vertical engine2. Horizondal engines3. redial engines4. In – line multicylinder – engine5. V – type multicylinder engine 6. Opposite – cylinder engines 7. Opposite – piston engine
According to valce mechanism 1. Over head value engine 2. Side value engine
According to method of governing 1. Hit and miss governed engine 2. Quantitatively governed engines.
rings, cylinder inter and exhaust valves, rocker arm, inlet and exhaust port, water jacket, spark plug or fuel injector.
45. What is mean by compression ratio(R)It is ratio of initial volume to final volume. Ie the ratio of total cylinder volume critical volume
(initial volume) to the clearance volume (final volume)R = (Vs+Vc)/Vc
46. How much the compression ratio for petrol and diesel engine?For petrol engine = 5.2 to 9.1
For diesel engine = 12.1 to 22.1
47. What is mean by piston speed?Piston speed = 21NM/min
Where N = r.p.m of the engine or speed of engine in r.p.m (revaluation per minute)
48. What are all the sequence of operation IC engines?1. Suction stroke2. Compression stroke 3. Expansion or power stroke4. Exhaust stroke
49. What is the different between the two stroke and four stroke cycle engine.Two stroke Four stroke
1. One power stroke in one revolution of the crank shaft
One power stroke in two revolution of the crank shaft
2. Power developed for the same engine speed is theoretically twice that if a four-stroke cycle engine.
Power developed for the same engine speed is theoretically half that of a two stroke cycle engine
3. For the same power, this is simple in design and lighter in construction.
For the same power, this is heavier in construction
4. Fuel consumti9on is more Fuel consumption is less 5. Limited parts is enough Large no of parts are required 6. Maintenance charge is less Maintenance charge is more7. Not possible for large power production
Possible large power production
50. What is the difference between the petrol and diesel engine? Petrol Engine Diesel Engine
1. Petrol and air draws during suction Stroke
Air is only draws during the suction stroke
2. Carburetor is used Fuel injector or atomizer is used 3. Pressure at end of compression is about 10 bar
Pressure at and of compression is about 35 bar
4. Spank plug is used to ignite the fuel.Fuel injector is used to ignite the fuel in fine spray for and hot air (about 600C at 35 bar) is ignited
5. Compression ratio of petrol approximately 6 to 10
Compression ratio for diesel engine is approximately 15 to 25.
6. Lighter in construction are cost is also less
Heavier in construction and cost is also high
7. Thermal efficiency about 26% Thermal efficiency is about 40% 8. Those are high-speed engine. These are relatively low speed engine 9. Starting the engine is very easy due to low compression.
Starting the engine is little difficult due to high compression ratio.
51. What is the effect of cut-off ratio on the efficiency of diesel cycle when the compression ratio is kept constant?
Diesel = 1 - 1 1 Rc
2-1 V
52. Sketch Otto and diesel cycle for the same compression ratio and heat input and compare the efficiency.
53. Sketch the schematic arrangement of open cycle gas turbine plant and name the component
54. Explain why nozzle are made convergent and divergent.
Reducing the presser increasing velocity COMPRESSORS – II
1. What is a reciprocating air compressor?A machine which takes in atmospheric air during suction stroke and compresses in to
high pressure in a piston cylinder arrangement is a reciprocating compressor.
2. Mention any four application of compressed air?1. Operating pneumatic drills2. Reverts, road drills, spray painting3. Starting and super changing of internal combustion4. Gasturbine plant5. Jet engines6. Air motors
3. What are the basic types of compressor working?1. reciprocating air compressor2. rotary air compressor
4. Classify the air compressor?1. According to the working
(i) reciprocating air compressor(ii) rotary air compressor
2. According to the action(i) single acting compressor(ii) double acting compressor
3. According to number of stages(i) single stages compressor(ii) multistage compressor.
5. What are the principle parts of a reciprocating compressor?1. cylinder2. cylinder head3. suction and delivery valve4. connecting rod5. piston6. water jacket for cooling
6. What is the compressor ratio (or pressure ratio)?It is ratio of discharge pressure to the inlet pressure since the discharge pressure is always
more than the inlet pressure therefore the value of compression ratio is more than unity.
7. What is mean by compressor capacity?It is the volume of air delivered by the compressor, and is expressed in m3 / min (m3 /
sec)
8. What is mean by Free air delivery?It is the actual volume delivered by a compressor when reduced to the normal temperature
and pressure condition. The capacity of compressor is generally given interns of free air delivery. 9. What is swept volume? (or) displacement volume?
It is the volume of air succeed by the compressor during its suction stroke mathematically the swept volume (or) displacement of a single acting air compressor is given by
Vc = / 4 D2 XLD = diameter of cylinder bore L = Length of piston stroke
10. What is mean by mean effective pressure?The air pressure on the compressor piston keeps on changing with the movement of the
piston in the cylinder. He mean effective pressure of the compressor is found out automatically by dividing the work done per cycle to the stroke volume
11. Draw P – V and diagram for a single stage reciprocating air compressor with out clearance?
12. What is mean by multistage compression?In order to increases the pressure of out let air form the compressor above to 12 bar single
stage is impossible to over come the difficulties, two(or) more cylinder are provided in series with intercooling arrangement between them such an arrangement is known as multistage compression.
13. What are the advantages of multistage compression?1. Work done per kg of air is reduced2. It improves the volumetric efficiency for the given pressure ratio3. The sizes of the two cylinders line high pressure and low pressure may be adjusted to suit the
volume and pressure of the air4. It reauces leakage loss considerably5. It gives more uniform torque, and hence a smaller side flywheel is required6. It provides effective lubrication because of lower temperature range7. It reduces the cast of compressor
14. What is mean by inter cooler?In multistage compressor the air is first compressed in the low pressure compressor and
passed to inter cooler, to reduce the temperature of air before entering in to high pressure cylinder (or it is located in between the in to high pressure cylinder. (or it is located in between the L.P and H.P Cylinder to cooler the L.P air
15. What is the effect of inter cooling in a multistage reciprocating compressor?He amount of work saved with incomplete intercooling is less than that in case of complete
inter cooling. 16. What basics rotary air compressor working?
In rotary air compressor, the air is entrapped between two sets of engaging surface and the pressure of air is increased by squeezing action (or) back flow of air.
17. Write the comparison between the reciprocating and rotary air compressor?S.No. Reciprocation air compressor Rotary air compressor
1. Maximum delivery pressure of air is 1000 bar
Maximum delivery pressure of air is 10 bar only
2. Maximum free air discharge is about 300 m/min
The Maximum free air discharge is a high as 3000 m/min
3. They are suitable for low discharge of air at very high pressure
They are suitable for large discharge of air at low pressure
4. Speed of the air compressor is slow The speed of the air compressor is high5. The air supply is intermittent The air supply is continuous6. Balancing is a major problem There is no balancing problem
18. Name any two rotary type of air compressors?1. Roots blower 2. Vane blower 3. Centrifugal blower 4. Axial flow
compressor
19. What is a reciprocating air compressor?A machine which takes in atmospheric air during suction stroke and compresses in to high
pressure in a piston cylinder arrangement is a reciprocating compressor.
20. Mention any four application of compressed air?1. Operating pneumatic drills2. Reverts, road drills, spray painting3. Starting and super changing of internal combustion4. Gasturbine plant5. Jet engines6. Air motors
21. What are the basic types of compressor working?1. Reciprocating air compressor2. Rotary air compressor
22. Classify the air compressor?
1. According to the working(i) Reciprocating air compressor(ii) Rotary air compresssor
2. According to the action(i) Single acting compressor(ii) Double acting compressor
3. According to number of stages(i) Single stages compressor(ii) Multistage compressor
23. What are the principle parts of a reciprocating compressor?1. Cylinder2. Cylinder head3. Suction and delivery valve4. Connecting rod5. Piston6. Water jacket for cooling
24. What is the compressor ratio (or pressure ratio)?It is the ratio of discharge pressure to the inlet pressure since the discharge pressure is
always more than the inlet pressure therefore the value of compression ratio is more than unity.
25. What is mean by compressor capacity?It is the volume of air delivered by the compressor, and is expressed in m3/min (m3/sec)
26. What is mean by Free air delivery?It is the actual volume delivered by a compressor when reduced to the normal temperature
and pressure condition. The capacity of compressor is generally given interns of free air delivery.
27. What is swept volume? (or) displacement volume?It is the volume of air succeed by the compressor during its suction stroke mathematically the
swept volume (or) displacement of a single acting air compressor is given byVs = / 4 D2 XLD = diameter of cylinder bore L = Length of piston stroke
28. What is mean by mean effective pressure?The air pressure on the compressor piston keeps on changing with the movement of the
piston in the cylinder. He mean effective pressure of the compressor is found out automatically by dividing the work done per cycle to the stroke volume.
29. Draw P – V and diagram for a single stage reciprocating air compressor with out clearance? 30. What is mean by multistage compression?
In order to increases the pressure of out let air form the compressor above to 12 bar single stage is impossible to over come the difficulties, two (or) more cylinder are provided in series with intercooling arrangement between them such an arrangement is known as multistage compression.
31. What are the advantages of multistage compression?1. Work done per kg of air is reduced2. It improves the volumetric efficiency for the given pressure ratio3. The sizes of the two cylinders line high pressure and low pressure may be adjusted to
suit the volume and pressure of the air4. It reauces leakage loss considerably5. It gives more uniform torque, and hence a smaller side flywheel is required6. It provides effective lubrication because of lower temperature range7. It reduces the cast of compressor
32. What is mean by inter cooler?In multistage compressor the air is first compressed in the low pressure compressor and
passed to inter cooler, to reduce the temperature of air before entering in to high pressure cylinder (or it is located in between the in to high pressure cylinder. (or it is located in between the L.P and H.P Cylinder to cooler the L.P air
33. What is the effect of inter cooling in a multistage reciprocating compressor?He amount of work saved with incomplete intercooling is less than that in case of complete
inter cooling
34. What basics rotary air compressor working?In rotary air compressor, the air is entrapped between two sets of engaging surface and the
pressure of air is increased by squeezing action (or) back flow of air35. Write the comparison between the reciprocating and rotary air compressor?
S.No. Reciprocating air compressor Rotary air compressor1. Maximum delivery pressure of air is 1000
barMaximum delivery pressure of air is 10 bar only
2. Maximum free air discharge is about 300 m/min
The maximum free air discharge is a high as 3000 m/min
3. They are suitable for low discharge of air at very high pressure
They are suitable for large discharge of air at low pressure
4. Speed of the air compressor is slow The speed of the air compressor is high5. The air supply is intermittent The air supply is continuous6. Balancing is a major problem There is no balancing problem
36. Name any two rotary type of air compressors?1. Roots blower 2. Vane blower 3. Centrifugal blower 4. Axial flow
compressor
UNIT - IIISTEAM BOILERS AND TURBINES
1. What is mean by steam? And where it is used?Steam is a vapor from of water, it is used for operating steam engines, steam turbine, etc.,
2. What are the three forms of steam?1. wet steam 2. dry steam 3. super heated steam
3. What is wet steam?When the steam contains moisture (or) particles of water in suspension it is said to be wet steam.
4. What is dry steam?When the wet steam is further heated, and if does not contain any suspended particles of water, it
isknown as dru saturated steam. ie perfect gas. 5. What is super heated steam?
When the dry steam further heated at constant pressure. Thus raising its temperature is know as super heated steam
(Since the pressure is constant their fore tre volume of super heated steam is increase it may be noted that the volume of one kg of super heated steam is considerably greater than the volume of one kg dry saturated steam at the same pressure. In actual practice the super headed steam is produced in a separate apparatus know as super heater so that it is out of contact with water from which it was formed.)
6. Define dryness fraction or quality of wet steam?It is defined as the ratio of the mass of actual dry steam to the mass of same quantity of wet
steam and is generally denoted by x mathematically.X = mg/mg+mf mg = mass of actual dry steam
Mf = mass of water in suppression M = mass of wet steam mg+mf
The value of x=1 that condition is known as dry steam i.e mass of water in suspension is zero.
7. What is mean by sensible heat of water?It is the amount of heat absorbed by 1 kg of water, when heated at a constant pressure from the
freezing point (0c) to the temperature of formation of steam ie saturation temperature (t) if is also know as liquid heat.
The specific heat of water at constant pressure is usually taken as 4.2 kj/kg.k therefore heat absorbed by 1 kg of water form 0c to tc (or) sensible heat.
= mass X sp. Heat X rise in temperature 1 X 4.2 [(ct+273)] (0+273)
Sensible heat = 4.2kj/kg
8. What is mean by laten heat of vaporization?It is the amount of heat absorb to evaporate 1 kg of water at its boiling point (or) saturation
temperature with out change of temperature it is denoted by hfg and its value depends upon the latent heat of steam is 2257 kj/kg at atmospheric pressure.
9. What is enthalpy of steam? Or total heat of steam?
It is amount of heat absorbed by water from freezing point to saturation temperature + the heat absorbed during evaporation
Enthalpy (or) total heat of steam = sensible heat + latent heat a) enthalpy of wet stem
h = hf + x hfgx = dryness fraction
b) enthalpy of dry steam h = hf + hfgx = 1
c) enthalpy of super heated steamh sup = Total heat fro dry steam + heat for super heated steam = hf + hfg + cp (tsup – t) = hg + cp (tsup – t)
Cp = specific heat of at constant pressure of super heated steam. tsup = temperature of super heated steam
10. What is the function of steam boilers or steam generation?It is closed vessel made of steel it is used to produce the steam from water.
11. How to classify the boilers?1. Fire tube and water tube boilers
2. Horizontal, vertical and incline boilers3. Externally fired and internally fired boilers 4. Locomotive marine, stationary and portable boilers 5. Natural circulation and forced circulation boilers.
12. What is mean by fire tube and water tube and water tube boilers?In the fire tube boilers, the hot gases from the furnace pass through the tunes surrounded by
13. What is mean by natural circulation and forced circulation boiler?When the circulation of water in the boiler due to natural conversion neat transfer.
14. Name the two important boiler assessors and state there functionEccomoiser
It used to heat feed water by utilizing the heat in the exhausts flue gases before leave through the chimneyAir per hether
It is used to recover heat form the exhaust flue gases it installed between the economiser and chimney
STEAM POWER CYCLE(OR)
THERMODYNAMIC VAPOUR CYCLES
1. What is mean by thermodynamic vapour cycle (or) steam power cycle?The basic theory of air cycles and vapour cycles are remains same. In air cycle air is a working
substance. In vapour power cycle, the steam is working substance in the form of wet, drystaurated (or) super heated
2. What are the cycles available in steam power cycle?i). Carnot cycleii). Rankine cycle
3. Why carnot cycle gices maximum possible efficiecy?Since the heat is absorbed at higher temperature (T1 = T2) and rejected at the lowest
temperature (T3 = T4). So the carnot cycle will give the maximum possible efficiency.
4. Define efficiency ratio?It is defined as the ratio of thermal efficiency (or actual cycle efficiency) to rankine efficiency (or
ideal cycle efficiency) Thermal efficiency
Efficiency ratio = Ranking efficiency
5. Define work ratio?
It is defined as the ratio of net work out put to the gross (engine or turbine) output Net work output
Work ratio = Gross output Turbine work – compressor work
= Turbine work
6. Define specific steam consumption? (or) Steam rate (or) Specific rate of flow of steam?It is defined as the mass of steam that must be supplied to a steam engine (or) turbine in order to
develop a unit amount of work (or) power output.
7. Draw the flow diagram of Rankine cycle indicating the main components?
8. Drw the P – V and T – S diagram for Rankine cycle?
9. Write the comparison between the Ranking and carnot cycle?
S.No. Rankine cycle Carnot Cycle
1. It is a practical standard and cycle for compression of actual power plant
It is a theoretical cycle
2. Complete condensation of steam after expansion
Practical condensation of steam after expansion
3. It is possible for using super heated steam Not possible for super heated steam
REFREIGERATION AND AIR CONDITIONING SYSTEM
1. What is mean by refrigeration?It is processes of removing the heat from the substance and maintaining the body at a
temperature below the atmospheric temperature
2. What is mean by units (tones) of refrigeration?The amount of refrigeration effect produced by the uniform melting of one tone (1000 kg) of ice
from and at 00C in 24 hours. Since the latout heat of ice is 335 kj/min1 TR = 1000 X 335 kj in 24 hours
= 1000 335 / 24 X 60 = 232.6kj/minIn actual practice 1 TR = 216 kj/min = 3.5kw
3. Define C.O.P of refrigeration?It is defined as the ratio of heat entreated in the refrigeration to the work done on the
refrigeratient. It is also known as theoretical C.O.PMathematicallyTheoretical C.O.P = Q / W
Q – Mount of heat interacted in the refrigeratorW – Amount of work done
4. What is mean by vapour compression refrigeration system?The low pressure vapour refrigerant from evaporator is compressed in to high pressure vapour
refrigerant in the compressor is known as vapour compression refrigeration system
5. Write the advantages and disadvantages of vapour compression system over a air refrigeration system?
Advantages1. It is smaller size for the given capacity of refrigeration2. It has less running cost3. It can be employed over a large range of temperature4. The co-efficient of performance is quite high
Disadvantages1. Initial cost is high2. The prevention of leakage of the refrigerant is the major problem in vapour
compression system
6. What is the effect of sub cooling on refrigeration effect and C.O.P?Some times the refrigerant after condensation process 2-3 is cooled below the saturation
temperature (T3) before expansion by throttling such a process is called under cooling (or) sub cooling
7. What is use of pressure – Enthalopy (P–h) chart?It is the useful chart for finding out the behaviour of refrigerant at different temperature and
pressure
8. What are the properties of good refrigerant?1. Low boiling point 2. High critical temperature3. High latent heat of vaporization 4. Low specific heat of liquid5. Low specific volume of vapour 6. Non – Corrosive of metal7. Non – Flammable and non – explosive 8. Non – toxic9. Easy to liquefy at moderate pressure and temperature10. Easy of locating leaks by odour (or) suitable indicator11. Low cast 12. Mixes well with oil
9. Write the name of commonly used refrigeration’s?1. Ammonia 2. Carbon dioxide 3. Sulpher dioxide 4. Freon
10. What are the factors affecting comfort air conditioning?1. Temperature of air 2. Humidity of air 3. Purity of air 4. Motion of air
11. What are the equipment’s used in A/C system?1. Circulation fan 2. A/C unit 3. Supply duct 4. Supply outlets5. Refresh outlet 6. Filiters
12. How to classify the A/C?1. According to the purpose (i) Comfort A/C (ii) Industrial A/C2. According to season of the year (i) Winter A/C (ii) Summer A/C3. According to the arrangement of equipment
(i) Unitary A/C (ii) Central A/C
13. Draw the lay out of vapour compression refrigeration cycle and explain it principle of operation.
The low pressure vapour refrigerant from evaporator is changed in to high pressure vapour refrigerant in the compressor there for it is named as vapour compression refreigeration system.
UNIT – IV & V
HEAT TRANSFER
1. What is heat transfer?Heat transfer can be derfined as the transmission of energy from one reign to another as a result
of temperature difference or gradient.
2. What are the application of heat transfer?The heat transfer is applied in various application like design of IC engines refrigeration, air
conditioning plants, steam generators and many others.
3. What are the modes of heat transfer?The three types of heat transfer are
1. Condition2. Convection3. Radiation
4. What is meant by conduction?Conduction the mode of heat transfer in which energy exchange takes place from the regin of
high temperature to the low temperature by the kinetic motion or direct impact of molecules, as in case of fluid in rest and by drift of electrons in metals.
5. What is convection?When fluid flows over a solid body or inside a tunnel while the temperature of fluid and the solid
surface are different heat transfer between fluid and solid surface. This mechanism is called convection.
6. What is radiation?The heat transfer from one body to another without any transmitting medium is known as
radiation heat transfer.
7. What is steady state heat conduction?In the conduction, if the heat flow various with position or length of the material and not various
with time it is called steady state conduction.DT/dx = 0 dt/dt = 0
8. What is unsteady state heat conduction?If the heat flow varies with position of the material and also with time then it is called unsteady
state heat conduction.DT/dx = 0 dt/dt = 0
9. What is fourier law of conduction?The fourier law of conduction is represented by the equation that,
Q = KA dt/dxThat is the heat transfer a body per unit time is directly proportional to that surface area of heat
flow and the temperature gradient.Q = Heat flow through a body per unit time in (KJ/Sec) (or) KwA = Surface area of heat flow in m2
dt = Temperature difference of me take of block of thickness ‘dx’ through which het flows (k) dx = Thickness of body along the direction of flow(m)Q = KA dT/dn
10. What is thermal conductivity of the material?It is defined as the amount of energy conducted through body of unit area and thickness is unit
time when the difference in temperature between the faces causing the heat flow is i.c
11. What are the parameters influencing the thermal conductivity of a material?The thermal conductivity of the material mainly depends of the structure the specific gravity,
moisture content, temperature etc.,
12. Metals are ………. (goods) conductors andInsulators are ……… (poor) conductors.
13. What is the conduction heat transfer through a slab?We know the Fourier eqn that
Q = Ka dt/dnIntegrating the above eqn, between the limits of X = 0 to LAnd T = ti to T2 as the temperature changes from T = ti to T2 through a thickness of slab.
14. What is the conduction of heat through a hollow cylinder. It inner outer radius of cylinder given?Q = 2LK [T1 – T2] Loge (R2/R1)
15. What is the conduction through hollow sphere it inner and outer radius are given?Q = T1 – T2 R1 & R2 = Inner & Outter Radias of sphere R2 – R1 R2 – R1 = Thermal Resistance of Hollow sphere 4KR1R2 4KR1R2
16. What is Newton Rikhan law of convection?The heat transfer from proving fluid to the solid wall surface is directly proportional to surface area
through which heat is flowing and the temperature difference from hot fluid to solid surface.
17. Give the units for heat transfer, thermal conductivity, corrective heat transfer co-efficient and overall heat transfer co-efficient.
Heat transfer per unit time Q =Thermal conductivity K =Corrective heat transfer Co-efficient =Over all heat transfer Co-efficient =
18. What is natural convictions?Whenever the flow of fluid over a hot or cold surface takes place due to the temperature
difference only. The heat transfer between solid surface and fluid is said it take place by natural convention or free convention.
19. What is forced convention?When the fluid flows on a hot or cold surface external pressure, the flow is known as forced flow
and the heat transfer under such condition is known as forced circulation.
20. The force which acts on the fluid to cause its motion is known as ------(buoyancy force)
21. The heat flow is (directly/indirectly)________ proportional to the temperature difference and heat transfer co-efficient as also _______ (directly/indirectly) proportional to the temperature difference.
22. For most of the solid bodies transitivity is equal to (Zero)
23. For absolute transparent or diathe enaneous body the absorptivity and refiectivity are_______ (Zero)
24. For the block body the transmittivity and refletivity are _______ (Zero)
25. What is black body?A body which absorbs all the incident radiation and emits maximum energy compared with other
bodies is called black body.
26. What is monochromatic emissive power?The energy radiated ata particular wavelength for a given temperature of black body per unit are
of the body and per unit time is known as monochromatic emissive power of the body.
27. What is plank’s law of radiation?The relation between monochromatic emissive power of a black body and warelength of a
radiation at a particular temperature is given by plankWhere c1 & c2 are constants and M is the wavelength and T is the temperature in day kelvin
28. What is Stefan bolz man law?The total energy emitted by a black body at a particular temperature is directly proporational to
the fourth power of that particular temperature.
29. What is weins displacement law of radiation?The product of maximum wavelength of a black body and its temperature will not exceed 2.2 mnk
30. The emissive power of a grey body is _____ (lesser/higher) than that of the body.
31. The emissive power of a grey body is ____ (lessor/higher) than that of the black body.
32. What is emissivity of grey body?The ratio of emissive power of a grey body to that of black body at a given temperature is
constant at all wavelengths and is known as emissivity of the grey body.
Prepared by Approved by(Dr.A.Murugesam Ph.D., & Mr. M.Bharathiraja) (Dr.A.Murugesan)
