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THERMAL ENGINEERING II MCQ (MODEL EXAM - 5)

Total questions: 100

Worksheet time: 50mins

Name
Class
Date
1.

Find the exit velocity of steam , when steam enters into the nozzle with 50 m/s, 3000kJ/kg and leaves at 1500 kJ/kg.

a)

1514 m/s

b)

1415 m/s

c)

1123 m/s

d)

1523 m/s

2.

Find the exit velocity of steam, when steam enters into the nozzle with 3000kJ/kg and leaves at 1500 kJ/kg.

a)

1732 m/s

b)

1372 m/s

c)

1237 m/s

d)

1111 m/s

3.

1 J/kg is equal to

a)

1 m2s\frac{m^2}{s}

b)

1 m2s2\frac{m^2}{s^2}

c)

1 ms2\frac{m}{s^2}

d)

1 ms\frac{m}{s}

4.

In steam nozzle

a)

Pressure energy only decreases

b)

kinetic energy only increases

c)

pressure energy increases and kinetic energy decreases

d)

pressure energy decreases and kinetic energy increases

5.

Steam nozzle is

a)

a work producing device

b)

a work consuming device

c)

used to increase the kinetic energy of the fluid

d)

used to increase the pressure energy of the fluid

6.
The equivalent evaporation (kg/hr) of a boiler producing 2000 kg/hr ofsteam withenthalpy content of 2426 kJ/kg from feed water at temperature40°C (liquid enthalpy= 168 kJ/kg, enthalpy of vaporisation of water at100°C = 2258 kJ/kg) is
a)
2000
b)
2149
c)
1682
d)
1649
7.
Heat is mainly transferred by conduction, convection and radiation in
a)
Insulated pipes carrying hot water
b)
Refrigerator freezer coil
c)
Boiler furnaces
d)
condensation of steam in a condenser
8.
The shell diameter and length of locomotive boiler are
a)
1.5 m, 4 m
b)
1.5 m, 6 m
c)
1 m, 4 m
d)
2 m, 4 m
9.
Which one of the following statements is not true for a supercritical steam generator?
a)
It has a very small drum compared to a conventional boiler
b)
A supercritical pressure plant has higher efficiency than a subcriticalpressure plant
c)
The feed pressure required is very high, almost 1.2 to 1.4 times the boilerpressure
d)
As it requires absolutely pure feed water, preparation of feed water is moreimportant than in a subcritical pressure boiler
10.
The distinguishing feature of Velox boiler is that it
a)
Is drumless
b)
uses supersonic
c)
Operates under supercritical pressure
d)
uses indirect heating
11.
For a single stage impulse turbine with a rotor diameter of 2 m and aspeed of 3000 rpmwhen the nozzle angle is 20 , the optimum velocity ofsteam in m/s is
a)
314
b)
356
c)
668
d)
711
12.
In steam turbine terminology, diaphragm refers to
a)
Separating wall between rotors carrying nozzles
b)
The ring of guide blades between rotors
c)
A partition between low and high pressure sides
d)
The flange connecting the turbine exit to the condenser
13.
A single-stage impulse turbine with a diameter of 120 cm runs at 3000 rpm.If the bladespeed ratio is 0.42 then, the inlet velocity of steam will be
a)
79 m/s
b)
188m/s
c)
450 m/s
d)
900 m/s
14.
Which one of the following is used to bring down the speed of an impulse steam turbine to practical limits?
a)
Differential Gear
b)
Compounding of the turbine
c)
A large flywheel
d)
A gear box
15.
Why is compounding of steam turbines done?
a)
To improve efficiency
b)
To reduce the speed of rotor
c)
To reduce exit losses
d)
To increase the turbine output
16.
On Mollier chart, flow th rough t urbine is represented by'
a)
horizontal straight line
b)
vertical straight line
c)
straight inclined line
d)
curved line
17.
While steam expands in t urbines, theoretically t he entropy
a)
remains constant
b)
increases
c)
decreases
d)
behaves unpredictably
18.
Equiva lent evaporation of water is the evaporation "for a feed water supply at 100°C
a)
and its corresponding conversion i nto dry sat urated steam at toooc and 1.033 kg/cm2
b)
and its corresponding conversion i nto dry steam at desired boiler pressure
c)
conversion i nto steam at atmospheric condition
d)
none of the above.
19.
The evaporation of 15.653 kg of water per hour from and at 100 degree celcius is called
a)
evaporative capacity
b)
factor of evaporation
c)
equivalent evaporation
d)
one boiler h.p .
20.
Cochran boiler is a
a)
horizontal fire-tube boiler
b)
horizontal water-tube boiler
c)
veritcal water-tube boiler
d)
vertical fire tube boiler
21.
The lenght of Cornish boiler is of th e ord er of
a)
2-4m
b)
3·5 m
c)
5-7.5 m
d)
7-9 m
22.
Locomotive type boiler is
a)
hortzontal multitubular water tube boiler
b)
water wall enclosed furnace type
c)
vertical tubular fire tube type
d)
hortzontal multi-tubular fire tube type
23.
Which of the following substance will have same percentage in both proximate and ultimate analysis
a)
ash
b)
volatile matter
c)
moisture
d)
hydrogen
24.
The biggest size of thermal power unit operating in India is
a)
30 MW
b)
60 MW
c)
100 MW
d)
500 MW
25.
The crown of t he fire box is mad e hemispherical in order to
a)
give maximum space
b)
give max imum strength
c)
resist intense heat in fire box
d)
withstand pressure inside boiler
26.
A boiler in India should conform to safety regulations of
a)
DIN
b)
IBR
c)
ASTM
d)
BS
27.
The fusible plug in small boilers is located
a)
in the drum
b)
in the fire tubes
c)
above steam dome
d)
over the combustion chamber
28.
Steam in water t ube boiler as compared to fire tube boiler
a)
can be raised rapidly
b)
is raised at slower rate
c)
is raised at same rate
d)
could be r aised at fast/slow rate depending on d esi
29.
Thermal efficiency of well mainta ined boiler will be of the order
a)
0.2
b)
0.4
c)
0.5
d)
0.9
30.
Fire tube boilers a re lim ited to a maximum design working pressure of
a)
1 kg/cm2
b)
6 kg/cm2
c)
17 kg/cm 2
d)
100 kg/cm2
31.
For Parson’s reaction steam turbine, degree of reaction is
a)
0.75
b)
1
c)
0.5
d)
0.6
32.
Parson’s turbine is
a)
pressure compounded steam turbine
b)
simple single wheel, impulse steam turbine
c)
simple single wheel reaction steam turbine
d)
multi wheel reaction steam turbine
33.
Rateau steam turbine is
a)
reaction steam turbine
b)
velocity compounded impulse steam turbine
c)
pressure compounded impulse steam turbine
d)
pressure velocity compounded steam turbine
34.
The modern steam turbines are
a)
impulse turbines
b)
reaction turbines
c)
impulse-reaction turbines
d)
none of the above
35.
A Curtis stage, Rateau stage and a 50% reaction stage in a steam turbine<br />are examples of
a)
Different types of impulse stages
b)
Different types of reaction stages
c)
A simple impulse stage, a velocity compounded impulse stage and reaction stage
d)
A velocity compounded impulse stage, a simple impulse stage and a reaction<br />stage
36.
In an ideal impulse turbine, the
a)
Absolute velocity at the inlet of moving blade is equal to that at the outlet
b)
Relative velocity at the inlet of the moving blade is equal to that at the outlet
c)
Axial, velocity at the inlet is equal to that at the outlet
d)
Whirl velocity at the inlet is equal to that at the outlet
37.
Steam enters a De Laval steam turbine with an inlet velocity of 30 m/s and leaves with an outlet velocity of 10 m/s. The work done by 1kg of steam is
a)
400 Nm
b)
600 Nm
c)
800 Nm
d)
1200Nm
38.
An impulse turbine produces 50 kW of power when the blade mean speed is 400 m/s. What is the rate of change of momentum tangential to the rotor?
a)
200 N
b)
175 N
c)
150 N
d)
125 N
39.
A single-stage impulse turbine with a diameter of 120 cm runs at 3000 rpm.If the blade speed ratio is 0.42 then, the inlet velocity of steam will be
a)
79 m/s
b)
188m/s
c)
450 m/s
d)
900 m/s
40.
If the enthalpy drop in the moving blades and fixed blades of a steam turbine is 10 kJ/kg and 15 kJ/kg respectively then what is the degree of reaction?
a)
0.67
b)
0.6
c)
0.4
d)
0.33
41.
Assertion (A): Throttle governing is used only in small steam turbines. Reason(R): At part loads, the efficiency of steam turbine reduces considerably with throttle governing
a)
Both A and R are individually true and R is the correct explanation of A
b)
Both A and R are individually true but R is not the correct explanation of A
c)
A is true but R is false
d)
A is false but R is true
42.

A human body feels comfortable when the heat produced by the metabolism of human body is equal to the

a)

(A) Heat dissipated to the surroundings

b)

(B) Heat stored in the human body

c)

(C) Sum of (A) and (B)

d)

(D) Difference of (A) and (B)

43.

In larger industrial and commercial reciprocating compression systems, refrigerant widely used is

a)

(A) Ammonia

b)

(B) Carbon dioxide

c)

(C) Sulphur dioxide

d)

(D) R-12

44.

One ton of the refrigeration is

a)

(A) The standard unit used in refrigeration problems

b)

(B) The cooling effect produced by melting 1 ton of ice

c)

(C) The refrigeration effect to freeze 1 ton of water at 0°C into ice at 0°C in 24 hours

d)

(D) The refrigeration effect to produce 1 ton of ice at NTP conditions

45.

Freon group of refrigerants are

a)

(A) Inflammable

b)

(B) Toxic

c)

(C) Non-inflammable and toxic

d)

(D) Nontoxic and non-inflammable

46.

The boiling point of ammonia is

a)

(A) -10.5°C

b)

(B) -30°C

c)

(C) -33.3°C

d)

(D) -77.7°C

47.

A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be

a)

(A) 1.33

b)

(B) 2.33

c)

(C) 3.33

d)

(D) 4.33

48.

In a refrigeration system, the expansion device is connected

a)

(A) Compressor and condenser

b)

(B) Condenser and receiver

c)

(C) Receiver and evaporator

d)

(D) Evaporator and compressor

49.

The vapour compression refrigerator employs the following cycle

a)

(A) Rankine

b)

(B) Carnot

c)

(C) Reversed Rankine

d)

(D) Reversed Carnot

50.

The condition of refrigerant after passing through the condenser in a vapour compression system is

a)

(A) Saturated liquid

b)

(B) Wet vapour

c)

(C) Dry saturated vapour

d)

(D) Superheated vapour

51.

Environmental protection agencies advice against the use of chlorofluorocarbon refrigerants since

a)

(A) These react with water vapour and cause acid rain

b)

(B) These react with plants and cause greenhouse effect

c)

(C) These react with oxygen and cause its depletion

d)

(D) These react with ozone layer

52.

When the lower temperature of a refrigerating machine is fixed, then the coefficient of performance can be improved by

a)

(A) Operating the machine at higher speeds

b)

(B) Operating the machine at lower speeds

c)

(C) Raising the higher temperature

d)

(D) Lowering the higher temperature

53.

The C.O.P. of a heat pump working on a reversed Carnot cycle is ( T₂- high temperature, T₁ - Low Temperature)

a)

(A) T₁/(T₂ - T₁)

b)

(B) (T₂ - T₁)/T₁

c)

(C) (T₁ - T₂)/T₁

d)

(D) T₂/(T₂ - T₁)

54.

A refrigerating system operating on reversed Brayton refrigeration cycle is used for maintaining 250 K. If the temperature at the end of constant pressure cooling is 300 K and rise in the temperature of air in the refrigerator is 50 K, then the net work of compression will be (assume air as working substance with Cp = 1 kJ/kg)

a)

(A) 25 kJ/kg

b)

(B) 50 kJ/kg

c)

(C) 100 kJ/kg

d)

(D) 125 kJ/kg

55.

Which of the following is not a desirable property of a refrigerant?

a)

(A) High misibility with oil

b)

(B) Low boiling point

c)

(C) Good electrical conductor

d)

(D) Large latent heat

56.

The refrigerant after condensation process is cooled below the saturation temperature before throttling. Such a process is called

a)

(A) Sub-cooling or under-cooling

b)

(B) Super-cooling

c)

(C) Normal cooling

d)

(D) None of these

57.

If a heat pump cycle operates between the condenser temperature of +27°C and evaporator temperature of -23°C, then the Carnot COP will be

a)

(A) 0.2

b)

(B) 1.2

c)

(C) 5

d)

(D) 6

58.

Critical temperature is the temperature above which

a)

(A) A gas will never liquefy

b)

(B) A gas will immediately liquefy

c)

(C) Water will evaporate

d)

(D) Water will never evaporate

59.

A heat pump working on a reversed Carnot cycle has a C.O.P. of 5. It works as a refrigerator taking 1 kW of work input. The refrigerating effect will be

a)

(A) 1 kW

b)

(B) 4 kW

c)

(C) 3 kW

d)

(D) 2 kW

60.

Air refrigerator works on......

a)

A. Carnot cycle

b)

B.Rankine cycle

c)

C.Reversed carnot cycle

d)

D.Bell-Coleman cycle

e)

E.Both C and D

61.

Which of the following refrigerant is highly toxic and flammable.......

a)

A.Ammonia

b)

B.Carbon dioxide

c)

C.Sulphur dioxide

d)

D.Freon-12

62.

The sub-cooling in a refrigeration cycle ....

a)

A.Does not alter C.O.P.

b)

B.Increases C.O.P.

c)

C.Decreases C.O.P.

d)

C.None of the above

63.

The highest temperature during the cycle,in a vapour compression system,occures after .......

a)

A.Compression

b)

B.Condensation

c)

C.Expansion

d)

C.Evaporation

64.

A reversible engine has ideal thermal efficiency of 30%. When it is used as a refrigerating machine with all other conditions unchanged, the coefficient of performance will be

a)

(A) 1.33

b)

(B) 2.33

c)

(C) 3.33

d)

(D) 4.33

65.

Efficiency of a Carnot engine is given as 80%. If the cycle direction be reversed, what will be the value of C.O.P. of reversed Carnot Cycle?

a)

(A) 1.25

b)

(B) 0.8

c)

(C) 0.5

d)

(D) 0.25

66.

Effect of superheating on COP is

a)

remains the same

b)

increases

c)

decreases

67.

Air refrigeration operates on

a)

A.Carnot cycle

b)

B.Brayton cycle.

c)

C.Rankine cycle

d)

D.Erricson cycle

68.

Air refrigeration cycle is used in

a)

A.Domestic refrigerators

b)

B.Commercial refrigerators

c)

C.Air conditioning

d)

D.Gas liquefaction

69.

The value of COP in vapour compression cycle is usually

a)

A.Always less than unity

b)

B.Always more than unity

c)

C.Equal to unity

d)

D.Any one of the above

70.

Moisture in a refrigerant system is removed by

a)

A.Driers

b)

B.Filter-driers

c)

C.Dessicants

d)

D.All of the above

71.

The refrigerator which does not require compressor is known as

a)

A.Vapour absorption refrigerator

b)

B.Vapour compression refrigerator

c)

C.Electrolux refrigerator

d)

D.Carnot refrigerator

72.

The refrigerator which does not require compressor is known as

a)

A.Vapour absorption refrigerator

b)

B.Vapour compression refrigerator

c)

C.Electrolux refrigerator

d)

D.Carnot refrigerator

73.

Chemical formula of Freon-12 is

a)

A.C C12 F2

b)

B.C C12 f3.L.

c)

C.C C13 F2

d)

D.C C13 F3

74.

Air conditioning is concerned with maintaining

a)

A.Temperature

b)

B.Littriudity

c)

C.Cleanliness

d)

D.All the three above

75.

Relative humidity is

a)

A.Something concerned with air conditioning

b)

B.The ratio of moisture present in air to the capability of air to hold maximum moisture

c)

C.The ratio of actual humidity to absolute humidity

d)

D.Representative of amount of moisture held in air

76.

D.Representative of amount of moisture held in air

a)

A.Dry bulb temperature

b)

B.Wet bulb temperature

c)

C.Saturation temperature

d)

D.Dew point temperature

77.

Wet bulb temperature is

a)

A.Indication of amount of moisture in air

b)

B.Measured by wetting the bulb of the thermometer

c)

C.Less than dry-bulb temperature

d)

D.Dependent on the dryness and temperature of air

78.
Which of the following is not a benefit of cogeneration
a)
Increased efficiency of energy conversion and use
b)
Reduced greenhouse gas emissions
c)
Reduced power factor
d)
Reduced transmission losses
79.
Cogeneration is the simultaneous generation of
a)
Heat and power
b)
Mechanical energy and power
c)
Steam and condensate
d)
All of the above
80.
The Ranking Cycle is related to
a)
Boiler
b)
Steam turbine
c)
Condenser
d)
All of the above
81.
What is an important advantage of closed-cycle gas turbine cogeneration systems?
a)
Working fluid remains clean and it does not cause corrosion or erosion
b)
Low capital costs
c)
High pressure of produced steam
d)
High temperature of produced steam
82.
The cogeneration system which has a high overall efficiency is the
a)
Gas turbine
b)
Back pressure steam turbine
c)
Reciprocating engine
d)
Combined cycle
83.
Which of the following statements is not correct
a)
A topping cycle plant generates electricity or mechanical power first
b)
A bottoming cycle plant generates heat first
c)
A bottoming cycle plant generates electricity or mechanical power first
d)
Both a and b
84.
How is the efficiency of cogeneration measured?
a)
Electrical conversion
b)
Thermal recovery
c)
Both a and b
d)
None of the above
85.
The cogeneration is not applicable to which type of industry?
a)
Sugar
b)
Paper and pulp
c)
Refinery
d)
Refractory / brick-making
86.
What is a typical efficiency of a cogeneration system?
a)
0.58
b)
0.68
c)
0.85
d)
0.95
87.
Find the thermodynamic cycle not related to cogeneration
a)
Brayton cycle
b)
Rankine cycle
c)
Otto cycle
d)
Bell-Coleman cycle
88.
In a combined cycle power plant consisting of gas turbine and waste heat boiler, the exhaust gas temperature is ____.
a)
around 150 °C
b)
around 500 °C
c)
around 300 °C
d)
around 400 °C
89.
Heat to power ratio in a paper industry is in the range of ------------
a)
1.1 – 4.5
b)
1.5 – 2.5
c)
0.8 – 3.0
d)
1.5 – 2.5
90.
Heat to power ratio of combined cycle cogeneration is in the range of-------------
a)
4.0 – 5.0
b)
1.0 – 1.7
c)
2.0 – 10
d)
1.0 – 5.0
91.
Major advantage of waste heat recovery in industry is:
a)
reduction in pollution
b)
increase in efficiency
c)
both a & b
d)
none of the above
92.
Heat recovery equipment will be most effective when the temperature of flue gas is:
a)
250 C
b)
200 C
c)
400 C
d)
280 C
93.
Ceramic recuperators can withstand temperatures up to
a)
600 C
b)
1300 C
c)
1700 C
d)
950 C
94.
In a low to medium temperature waste heat recovery system which of the device is most suitable
a)
economiser
b)
heat wheels
c)
air preheater
d)
recuperator
95.
Recovery of heat from dryer exhaust air is a typical application of:
a)
waste heat recovery boiler
b)
heat pump
c)
heat wheels
d)
economizer
96.
Regenerator is widely used in:
a)
reheating Furnaces
b)
heat treatment furnaces
c)
baking Ovens
d)
glass melting furnaces
97.
An economizer is provided to reuse flue gas heat for
a)
Preheating the boiler feed water
b)
Preheating the combustion air
c)
Preheating the stock
d)
Preheating fuel
98.
 Which of these is not considered economical for cogeneration?
a)
a high fraction of electric to total energy
b)
a low fraction of electric to total energy
c)
a low fraction of total energy to electric energy
d)
none of the mentioned
99.
Back pressure turbine is placed between ____________
a)
Turbine & Pump
b)
Boiler & Pump
c)
Turbine & Heat Exchanger
d)
Boiler & Turbine
100.
 In a by-product power cycle
a)
the power is produced initially
b)
power production is in the middle stages of the cycle
c)
power production is after the cycle has ended
d)
none of the mentioned

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