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Multiple choice question for engineering

Set 1

1. Turbochargers are centrifugal compressors driven by the exhaust gas turbines.
a) True
b) False

View Answer

Answer: a

2. A typical petrol engine may harness up to ____________ of the energy contained in the fuel supplied.
a) 20%
b) 30%
c) 40%
d) none of the mentioned

View Answer

Answer: b [Reason:] Up to 30% of the energy contained in the fuel supplied is harnessed in a typical petrol engine.

3. ____________ of fuel energy is wasted as heat energy to friction, pumping and dynamic movement.
a) 7%
b) 9%
c) 16%
d) 38%

View Answer

Answer: a [Reason:] Approximately 7% of fuel energy is wasted as heat energy to friction, pumping and dynamic movement and 9% of fuel energy is wasted as heat energy to surrounding air.

4. ____________ of fuel energy is wasted as heat energy to surrounding air.
a) 7%
b) 9%
c) 16%
d) 38%

View Answer

Answer: b [Reason:] 9% of fuel energy is wasted as heat energy to surrounding air while 16% of fuel energy is wasted as heat energy to engine’s coolant system.

5. ____________ of fuel energy is wasted as heat energy to engine’s coolant system.
a) 7%
b) 9%
c) 16%
d) 38%

View Answer

Answer: c [Reason:] 16% of fuel energy is wasted as heat energy to engine’s coolant system while approximately 7% of fuel energy is wasted as heat energy to friction, pumping and dynamic movement and 9% of fuel energy is wasted as heat energy to surrounding air.

6. ____________ of fuel energy is wasted as heat energy to outgoing exhaust gases.
a) 7%
b) 9%
c) 16%
d) 38%

View Answer

Answer: d [Reason:] 38% of fuel energy is wasted as heat energy to outgoing exhaust gases and 16% of fuel energy is wasted as heat energy to engine’s coolant system while approximately 7% of fuel energy is wasted as heat energy to friction, pumping and dynamic movement and 9% of fuel energy is wasted as heat energy to surrounding air.

7. The turbocharger relies solely on extracting up to a third of the wasted energy passing out from the engine’s cylinders to impart power to the turbine wheel and compressor wheel assembly.
a) True
b) False

View Answer

Answer: a [Reason:] The turbocharger relies solely on extracting up to a third of the wasted energy passing out from the engine’s cylinders to impart power to the turbine wheel and compressor wheel assembly.

8. Turbocharged engines produce lower cylinder volumetric efficiencies compared with the normally aspirated induction systems.
a) True
b) False

View Answer

Answer: b [Reason:] In fact turbocharged engines produce higher cylinder volumetric efficiencies compared with the normally aspirated induction systems.

9. The compression of the charge entering the cells of the impeller depends upon the centrifugal force effect which decreases with the square of the rotational speed of the impeller wheel.
a) True
b) False

View Answer

Answer: b [Reason:] In fact the compression of the charge entering the cells of the impeller depends upon the centrifugal force effect which increases with the square of the rotational speed of the impeller wheel.

10. When the engine is suddenly accelerated there will be a small time delay before the extra energy discharged into the turbine housing volute can speed up the turbine wheel.
a) True
b) False

View Answer

Answer: a [Reason:] Yes, when the engine is suddenly accelerated there will be a small time delay before the extra energy discharged into the turbine housing volute can speed up the turbine wheel.

Set 2

1. High speed two stroke engines are ____________ efficient owing to the reduced volumetric efficiency.
a) high
b) less
c) equal
d) none of the mentioned

View Answer

Answer: b

2. With engines working on Otto cycle, a part of the mixture is lost as it escapes through the exhaust port during scavenging.
a) True
b) False

View Answer

Answer: a

3. In Otto cycle, with increase in fuel consumption, thermal efficiency is
a) increased
b) reduced
c) remains same
d) none of the mentioned

View Answer

Answer: b

4. Part of the piston stroke is lost with the provision of the ports thus the effective compression is less in case of two stroke engines.
a) True
b) False

View Answer

Answer: a

5. Two stroke engines are liable to cause a ____________ consumption of lubricating oil.
a) lighter
b) heavier
c) unpredictable
d) none of the mentioned

View Answer

Answer: b [Reason:] Two stroke engines are liable to cause a heavier consumption of lubricating oil while in four stroke the consumption is less.

6. With heavy loads, two stroke engines get heated due to excessive heat produced.
a) True
b) False

View Answer

Answer: a

7. At light loads, the running of engine is not very smooth because of the __________ dilution of charge.
a) decreased
b) increased
c) equal
d) none of the mentioned

View Answer

Answer: b

8. Which of the following engines will have heavier flywheel than the remaining ones?
a) 30 kW four stroke petrol engine running at 1500 r.p.m
b) 30 kW two stroke petrol engine running at 1500 r.p.m
c) 30 kW two stroke diesel engine running at 750 r.p.m
d) 30 kW four stroke diesel engine running at 750 r.p.m

View Answer

Answer: a [Reason:] The flywheel in a four stroke petrol engine is heavier than in a two stroke petrol engine and there is no flywheel in a diesel engine.

Set 3

1. Large number of flash distillation equals a differential distillation.
a) True
b) False

View Answer

Answer: b [Reason:] In flash vaporization only small portion of liquid gets flashed.

2. The column used for differential distillation is_______________
a) Still
b) Differential column
c) Batch column
d) None of the mentioned

View Answer

Answer: a [Reason:] Still is the distillation column used for differential distillation.

3. Simple distillation is a___________ process.
a) Batch
b) Continuous
c) Adiabatic
d) None of the mentioned

View Answer

Answer: a [Reason:] Here, the liquid mixture is filled in the still for certain time to attain the vapour liquid equilibrium.

4. The initial portion of the distillate will be a low volatile component.
a) True
b) False

View Answer

Answer: b [Reason:] Since the low volatile component has high boiling point it will be the final portion.

5. After the separation by differential distillation, the high volatile and low volatile components are stored in _____________
a) Batch
b) Cuts
c) Distill
d) None of the mentioned

View Answer

Answer: b [Reason:] Cuts are the place where the different volatile components are stored.

6. For a ternary mixture, the number of cuts required is_________
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: b [Reason:] The first two high volatile components are stored in two cuts and the low volatile remains in the still itself.

7. The differential distillation in order to maintain the equilibrium the process should be slow.
a) True
b) False

View Answer

Answer: a [Reason:] For the differential distillation to get the effective distillation the process must be slow to attain the vapour- liquid equilibrium.

8. Pre-cooling is required before passing the vapour to the condenser in a still.
a) True
b) False

View Answer

Answer: b [Reason:] If pre-cooling occurs, the vapour gets condense in the still itself so there will be alter in equilibrium.

9. The equation applicable for batch distillation is _________
a) Frenske’s equation
b) Rayleigh equation
c) Wilke-chan equation
d) None of the mentioned

View Answer

Answer: b [Reason:] Rayleigh proposed the numerical analysis of the batch distillation.

10. Estimate the feed rate, if the composition of the more volatile component in the feed is 50% and the residue is 10% and the equilibrium relation is given by y*= 1.975x. Also the rate of residue is 60 mol/hr.
a) 213 mol/hr
b) 313 mol/hr
c) 413 mol/hr
d) 513 mol/hr

View Answer

Answer: b [Reason:] Using Rayleigh equation, we can estimate ln (F/W)= 1.657 F= 313 mol/hr.

11. Find the feed rate by analysing the graph,
mass-transfer-multiple-choice-questions-answers-q11
a) 153 mol/hr
b) 163 mol/hr
c) 173 mol/hr
d) 183 mol/hr

View Answer

Answer: b [Reason:] Using Rayleigh equation, Ln (F/W) = Area under the curve = 1 F= 163.

12. Find the composited distillate composition,

Mol/hr
Feed1000.45
Distillate600.95
Residue400.2

a) 0.52
b) 0.62
c) 0.72
d) 0.82

View Answer

Answer: b [Reason:]; F*xf= D*yd+ W*xw Yd= 0.62.

13. Find the value of relative volatility for a constant pressure process if

Rate(mol/s)Composition
Feed10045%
Residue3020%

a) 1
b) 2
c) 2.43
d) Data inadequate

View Answer

Answer: For a constant pressure process, the will be a constant relative volatility. So from modified Rayleigh method we can determine relative volatility, Log(F*xf/W*xw)= A log ( F(1-xf)/W(1-xw)), where A- constant relative volatility A= 2.43.

14. Find the distillate rate, if a differential condenser is used and the equilibrium relation is given as x*= 0.2y. Also the rate of feed is 100 mol/hr.
mass-transfer-multiple-choice-questions-answers-q14
a) 12 mol/hr
b) 22 mol/hr
c) 33 mol/hr
d) 44 mol/hr

View Answer

Answer: b [Reason:] From the Rayleigh equation for differential condenser, we get distillate rate = 22.

15. Find the rate of distillate, if the composition of the more volatile component in the feed is 50% and the residue is 10% and the equilibrium relation is given by y*= 1.975x. Also the rate of residue is 60 mol/hr.
a) 153 mol/hr
b) 253 mol/hr
c) 353 mol/hr
d) 453 mol/hr

View Answer

Answer: b [Reason:] Using Rayleigh equation, we can estimate ln (F/W)= 1.657 F= 313 mol/hr then D= 253 mol/hr.

Set 4

1. The mass transfer by convection can take place under how many conditions?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: b [Reason:] Free or forced conditions.

2. Lewis number is given by
a) 4 α/D
b) 3 α/D
c) 2 α/D
d) α/D

View Answer

Answer: d [Reason:] It forms the connecting link between the temperature and concentration profiles.

3. Prandtl number is given by
a) V/α
b) 2 V/α
c) 3 V/α
d) 4 V/α

View Answer

Answer: a [Reason:] It is related with velocity and temperature profiles.

4. Schmidt number is given by
a) 2 V/D
b) D/V
c) V/D
d) 2 D/V

View Answer

Answer: c [Reason:] It is related with velocity and concentration profiles.

5. Sherwood number is given by
a) 3/2 h m L/D
b) ½ h m L/D
c) 3 h m L/D
d) h m L/D

View Answer

Answer: d [Reason:] It is a non-dimensional mass transfer number.

6. The solution for velocity, concentration and temperature boundary layers will be same if
a) Prandtl number = Schmidt number= Lewis number
b) Prandtl number = 2 Schmidt number= Lewis number
c) Prandtl number = Schmidt number= 2 Lewis number
d) 2 Prandtl number = Schmidt number= Lewis number

View Answer

Answer: a [Reason:] All the three boundary layers must coincide.

7. Convective mass transfer involves the transportation of material between a boundary surface and a moving fluid or between two immiscible fluids. It is prescribed by the relation
a) 2 h m (d C B)
b) ½ h m (d C B)
c) h m (d C B)
d) 3/2 h m (d C B)

View Answer

Answer: c [Reason:] It is equal to m/A = h m (d C B).

8. Which number forms the connecting link between the velocity and temperature profiles?
a) Fourier number
b) Prandtl number
c) Stanton number
d) Biot number

View Answer

Answer: b [Reason:] These profiles becomes identical when Prandtl number is equal to one.

9. Which number forms the connecting link between the velocity and concentration profiles?
a) Schmidt number
b) Reynolds number
c) Stanton number
d) Fourier number

View Answer

Answer: a [Reason:] These profiles becomes identical when Schmidt number is equal to one.

10. Which number forms the connecting link between the temperature and concentration profiles?
a) Prandtl number
b) Schmidt number
c) Fourier number
d) Lewis number

View Answer

Answer: d [Reason:] When Lewis number is equal to unity, these two profiles are identical.

Set 5

1. Flash vaporization is a
a) Equilibrium distillation
b) Differential distillation
c) Simple distillation
d) None of the mentioned

View Answer

Answer: a [Reason:] Since the liquids are partially vaporized and allowed to be in equilibrium with vapour.

2. The feed is directly passed to the flash vaporization column
a) True
b) False

View Answer

Answer: b [Reason:] The feed must be pre-heated.

3. Find the X and Y from the flash column given below
mass-transfer-questions-answers-distillation-flash-vaporization-q3
a) X-more volatile, Y-less volatile
b) X-less volatile, Y- more volatile
c) X-non volatile, Y-less volatile
d) X-non volatile, Y-more volatile

View Answer

Answer: a [Reason:] Since the more volatile component has the low vapour pressure it will becomes vapour and comes out in the top.

4. Binary mixture of 100 kmol/hr enters into a flash drum has equimolar composition. The distillate obtained is 60 kmol/hr and the enthalpy of distillate, residue and feed are 500 KJ/kmol, 200 KJ/kmol and 400 KJ/kmol. Find the bottom flow rate in kmol/hr.
a) 10
b) 20
c) 30
d) 40

View Answer

Answer: c [Reason:] -W/D = HD-HF/HW-HF Where, HD, HW,HF are enthalpy of distillate, residue and feed. -W/60 = -0.5 W= 30

5. Find the ratio of distillate to residual flow rates, if a binary mixture containing 65% of more volatile component while the distillate and the residue compositions are 90% and 30%.
a) 0.4
b) 1.4
c) 2.4
d) 3.4

View Answer

Answer: c [Reason:] -W/D=(xd – xf)/(xw-xf) Finally we ger –W/D= -0.416 D/W= 2.4

6. What happens to the liquid after preheating when enter to the cyclonic flash drum?
a) Starts to evaporate
b) Split with centrifugal force
c) Comes out in residue
d) None of the mentioned

View Answer

Answer: b [Reason:] Since the column is like cyclone it will split the liquid with centrifugal force for the further separation.

7. Express the flash vaporization
a) Single stage operation
b) Multi component operation
c) Still operation
d) None of the mentioned

View Answer

Answer: a [Reason:] Only single drum is used.

8. Find the heat given( in KJ) to the feed for the flash vaporization process if the ratio of residue to the distillate is 0.65 and the enthalpy of feed, distillate and the residue are 500, 800 and 200 KJ/kmol respectively. The feed rate is 100 kmol/hr.
a) 4343
b) 5353
c) 6363
d) 7373

View Answer

Answer: c [Reason:] -W/D = (HD-(Hf+Q/f))/ (Hw- (Hf+Q/F)) On apply the values, we get 6363 KJ

9. Find the distillate and the residue rates in mole/hr, if the feed rate is 100 mol/hr; The compositions of feed, distillate and residue in terms of mole fraction are 0.65, 0.9 and 0.2.
a) 36,64
b) 64,36
c) 20,80
d) 80,20

View Answer

Answer: b [Reason:] F*xf= D*xd+ W*xw On applying the values, we get distillate rate= 64 mol/hr and residue rate is 36 mol/hr.

10. Find the feed composition of more volatile component by analysing the table below.

Enthalapy(kj/kmol)Composition
Distillate8000.95
Residue2000.2
Feed500?

Hint: can neglect pre-heater.
a) 0.45
b) 0.575
c) 0.6
d) 0.65

View Answer

Answer: b [Reason:] (xd- xf)/(xw- xf) =Hd- Hf/(Hw-Hf) On applying values, we get xf= 0.575