Chemical Engineering Basics MCQ Questions & Answers | Chemical Engineering Page-6 section-6

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51.
Which of the following is an undesirable property of slag produced during the pyrometallurgical method of metal extraction from its ore?

A. High fusibility & fluidity

B. High thermal conductivity

C. Low density

D. High chemical activity

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52.
Which of the following is a neutral flux used in the pyrometallurgy of metal extraction?

A. Quartz

B. Flourspar

C. Dolomite

D. Manganese ore

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53.
Air/fuel ratio on molar (volume) basis for combustion of methane with theoretical quantity of air with be

A. 9.5:1

B. 12.5:1

C. 15.5 :1

D. 18.5 : 1

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54.
Fog is an example of colloidal system of

A. Solid dispersed in gas

B. Solid dispersed in liquid

C. Liquid dispersed in gas

D. Gas dispersed in liquid

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55.
Even though heat transfer co-efficients in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling.

A. Film

B. Nucleate

C. Transition

D. All of the above

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56.
In spite of large heat transfer co-efficients in boiling liquids, fins are used advantageously, where the entire surface is exposed to __________ boiling.

A. Film

B. Nucleate

C. Transition

D. All of the above

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Answer & Solution

Answer: Option A

Solution:

Option A: Film Boiling
In film boiling, a stable layer of vapor forms between the heating surface and the boiling liquid.
This vapor layer acts as an insulator, creating significant thermal resistance and reducing heat transfer efficiency.
Fins are helpful in film boiling because they increase the surface area available for heat transfer, partially overcoming the insulating effect of the vapor layer.
Therefore, fins can improve the overall heat transfer rate in this mode of boiling.

Option B: Nucleate Boiling
In nucleate boiling, bubbles form and release directly at the heating surface.
This direct liquid-to-surface contact results in very high heat transfer rates.
Since nucleate boiling already has an efficient heat transfer mechanism, adding fins typically offers minimal additional benefit.
Fins are generally not necessary in nucleate boiling, as the high localized heat transfer reduces the need for increased surface area.

Option C: Transition Boiling
Transition boiling is an unstable phase between nucleate and film boiling, where the heat transfer rate fluctuates due to intermittent formation and collapse of the vapor layer.
Due to these fluctuations, the use of fins does not consistently improve heat transfer, as the conditions vary between efficient and inefficient phases.
Fins are less effective in this mode, as the intermittent nature of heat transfer in transition boiling limits their impact.

Option D: All of the Above
This option suggests that fins are beneficial across all boiling regimes.
However, fins are primarily effective in film boiling, where the insulating vapor layer creates a thermal resistance that fins can help mitigate.
In nucleate and transition boiling, the benefits of fins are limited or negligible due to already efficient heat transfer mechanisms or unstable conditions.

Conclusion:
The correct answer is Option A: Film boiling.
Fins are used advantageously in film boiling to increase the surface area and improve heat transfer efficiency, overcoming the thermal resistance created by the vapor layer.

57.
Maximum change in the hardness of mar tensite occurs in the carbon content range of __________ percent in steel.

A. 0.01 to 0.10

B. 0.2 to 0.4

C. 0.5 to 0.7

D. 0.8 to 1.0

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58.
The underground well of a biogas plant is called the

A. Septic tank

B. Oxidation well

C. Digestor

D. Lagoon

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59.
Heat required to raise the temperature of a body by 1°C is called its

A. Heat capacity

B. Specific heat capacity

C. Thermal conductivity

D. Water equivalent

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60.
Energy to be supplied to the radioactive nucleus for the emission of a neutron is __________ MeV.

A. 0.8

B. 7.8

C. 200

D. 10000

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Chemical Engineering Basics MCQ Questions & Answers | Chemical Engineering

51. Which of the following is an undesirable property of slag produced during the pyrometallurgical method of metal extraction from its ore?

Answer & Solution

52. Which of the following is a neutral flux used in the pyrometallurgy of metal extraction?

Answer & Solution

53. Air/fuel ratio on molar (volume) basis for combustion of methane with theoretical quantity of air with be

Answer & Solution

54. Fog is an example of colloidal system of

Answer & Solution

55. Even though heat transfer co-efficients in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling.

Answer & Solution

56. In spite of large heat transfer co-efficients in boiling liquids, fins are used advantageously, where the entire surface is exposed to __________ boiling.

Answer & Solution

57. Maximum change in the hardness of mar tensite occurs in the carbon content range of __________ percent in steel.

Answer & Solution

58. The underground well of a biogas plant is called the

Answer & Solution

59. Heat required to raise the temperature of a body by 1°C is called its

Answer & Solution

60. Energy to be supplied to the radioactive nucleus for the emission of a neutron is __________ MeV.

Answer & Solution

Read More Section(Chemical Engineering Basics)

51.
Which of the following is an undesirable property of slag produced during the pyrometallurgical method of metal extraction from its ore?

52.
Which of the following is a neutral flux used in the pyrometallurgy of metal extraction?

53.
Air/fuel ratio on molar (volume) basis for combustion of methane with theoretical quantity of air with be

54.
Fog is an example of colloidal system of

55.
Even though heat transfer co-efficients in boiling liquids is large, use of fins is advantageous, when the entire surface is exposed to __________ boiling.

56.
In spite of large heat transfer co-efficients in boiling liquids, fins are used advantageously, where the entire surface is exposed to __________ boiling.

57.
Maximum change in the hardness of mar tensite occurs in the carbon content range of __________ percent in steel.

58.
The underground well of a biogas plant is called the

59.
Heat required to raise the temperature of a body by 1°C is called its

60.
Energy to be supplied to the radioactive nucleus for the emission of a neutron is __________ MeV.