Heat Transfer Operations Mcqs

Q:

If the condensation occurs at the outside surface of the tubes, then the equation for the heat transfer coefficient does not change.

A) True B) False
 
Answer & Explanation Answer: B) False

Explanation: Not available for this question

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Q:

An increase in number of tubes will lead to larger condensate thickness in the lower tubes leading to ____________ heat transfer coefficient

A) Larger B) Smaller
C) Zero D) Infinite
 
Answer & Explanation Answer: B) Smaller

Explanation: If the number of tubes increases then the condensate thickness too increases in the lower tubes leading to smaller heat transfer coefficient.

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15
Q:

A large value of temperature difference will lead to more condensation and hence a __________ heat transfer coefficient

A) Larger B) Smaller
C) Zero D) Infinite
 
Answer & Explanation Answer: B) Smaller

Explanation: A large temperature difference will lead to more condensation on the wall and bigger condensate thickness which will lead to a small heat transfer coefficient.

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14
Q:

An increase in diameter means a _________ heat transfer coefficient.

A) Larger B) Smaller
C) Zero D) Infinite
 
Answer & Explanation Answer: B) Smaller

Explanation: If the diameter increases then the thickness of the film at the bottom increases and hence a smaller heat transfer coefficient.

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12
Q:

A high value of latent heat hfg means that the heat transfer coefficient would __________

A) Increase B) Decrease
C) Remains same D) Becomes zero
 
Answer & Explanation Answer: A) Increase

Explanation: A high value of latent heat means that for each kilo-Watt of heat transfer occurred, there will be thinner condensate thickness and hence the heat transfer coefficient augments.

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21
Q:

If there is a decrease in viscosity, the heat transfer coefficient ____________

A) Increase B) Decrease
C) Remains same D) Becomes zero
 
Answer & Explanation Answer: A) Increase

Explanation: If the viscosity decreases or density increases, it will offer less frictional resistance and cause quick draining of the condensate, thereby causing an increase in heat transfer coefficient.

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10
Q:

As thermal conductivity kF increases, the heat transfer coefficient ________

A) Increases B) Decreases
C) Remains same D) Jumps to a high value
 
Answer & Explanation Answer: A) Increases

Explanation: As thermal conductivity kf increases, the heat transfer coefficient increases since thermal resistance of the condensate film decreases.

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19
Q:

What is the equation for Coefficient of performance of a condenser?

A) COP = Qe/Qc B) COP = We/Qc
C) COP = Wc/Qe D) COP = Qe/Wc
 
Answer & Explanation Answer: D) COP = Qe/Wc

Explanation: The coefficient of performance is technically equal to the ratio of Heat absorbed Qe to the work done Wc.

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