Heat-Transfer : 100 Most Important Questions with Solutions

By Akhil Gupta|Updated : March 26th, 2021

HI Gradians,

You have completed the syllabus of the RVUNL exam for Heat transfer. Now BYJU'S Exam Prep brings you the 100 most important questions of the Heat transfer subject.

Here you will find the 100 most important questions for the Heat transfer subject of the Mechanical Engineering syllabus. The top 10 questions are attached here rest questions you can find in the below pdf.

                                                                                                                                                                                                                        

HI Gradians,

You have completed the syllabus of the RVUNL exam for Heat transfer. Now BYJU'S Exam Prep brings you the 100 most important questions of the Heat transfer subject.

Here you will find the 100 most important questions for the Heat transfer subject of the Mechanical Engineering syllabus. The top 10 questions are attached here rest questions you can find in the below pdf.

 

PDF OF 100 MOST IMPORTANT QUESTIONS OF HEAT TRANSFER

1.The relationship λmaxT = constant, between the temperature of a black body and the wavelength at which maximum value of monochromatic emissive power occurs is known as ________.

A. Planck’s law

B. Kirchhoff’s law

C. Lambert’s law

D. Wein’s law

Ans.  D

Sol.

This is Wien’s law. From the spectral distribution of black body emissive power, it is apparent that the wavelength associated with a maximum rate of emission depends upon the absolute temperature of the radiating surface.

 

2.Consider the following statements and choose the correct statements __________?

1) Fins should be attached on the side where the heat transfer coefficient is small.

2) Effective new of fins depend on thermal conductivity only.

3) fins must have small thick new for better heat dissipation.

A.Only 1 and 2

B. Only 2 and 3

C. Only 1 and 3

D. 1, 2 and 3

Ans. C

Sol.

  • Fins should be attached to the side where the heat transfer coefficient is small, and fins must have small thickens to accommodate a greater number of fins and have adequate between the fins for better heat dissipation.

 

3. The time constant of a thermocouple is __________.

A.the time taken to attain the final temperature to be measured

B. the time taken to attain 50% of the value of the initial temperature difference

C. the time taken to attain 63.2% of the value of initial temperature difference

D. determined by the time taken to reach 100C from 0C

Ans.  C

Sol.

  • The time constant of a thermocouple is the time taken to attain 63.2% of the value of the initial temperature difference.

 

 

4. In a two-fluid heat exchanger, the inlet and outlet temperature of the hot fluid is 65°C and 40°C respectively. For the cold fluid, these are 15°C and 42°C. The heat exchanger is a___.

A.Parallel flow heat exchanger

B. Counterflow heat exchanger

C. Heat exchange device where both parallel flow and counter flow operations are possible

D. None of the above

Ans. B

Sol.

  • Here, the Outlet temperature of cold fluid is higher than the outlet temperature of hot fluid which can only possible in counter-flow heat exchanger, so it is a counter flow heat exchanger.

 

5. In the vapour compression refrigeration cycle ________.

A. dry compression is always preferred

B. wet compression is always preferred

C. may be dry or wet depending upon the refrigerant

D. mixer of dry and wet compression is preferred

Ans. A

Sol.

  • There is a problem with wet compression because chances of liquid refrigerant being trapped in the head of the cylinder which may damage the cylinder head and liquid refrigerant may wash away the lubricating oil from the walls, so wear rate increases.

6. In which of the following refrigeration cycle, does the waste heat gets effectively used?

A. Vapor compression cycle

B. Vapor absorption cycle

C. Air refrigeration cycle

D. Vapor expansion cycle

Ans. B

Sol.

Consider the following statement regarding VARS:

  • VARS is a heat operating device that works on low-grade energy.
  • It is used extensively where waste heat is available.

7. Freon leakage is detected by____.

A.Sulphur stick

B. Halide torch

C. Ammonia swab test

D. None of the above

Ans. B

Sol.

  •  Freon leakages are detected by “halide torch test”.
  • Ammonia leakages are detected by “sulphur stick test”.
  • Sulphides leakages are detected by “Ammonia swab test”.

 

8. Subcooling is beneficial as it___.

1) Increases specific refrigeration effect

2) Decreases work of compression

3) Ensures liquid entry into the expansion device

4) All of the above

A. 1 & 2

B. 2 & 3

C. 1 & 3

D. 4

Ans. C

Sol.

  • Subcooling is beneficial as it increases the refrigeration effect by reducing the throttling loss at no additional specific work input.
  • Also, subcooling ensures that only liquid enters into the throttling device leading to its efficient operation.

PDF OF 100 MOST IMPORTANT QUESTIONS OF HEAT TRANSFER

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