Heat Transfer MCQ Questions & Answers

51

Heat transfer by radiation between two bodies at T₁ & T₂ and in an ambient temperature of T_a°C depends on

A) T₁ - T₂ B) T₁ - T_a C) T₂ - T_a D) None of these

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Answer & Solution

Answer: Option D

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52

Which of the following is correct?

A) Rate = Driving force × Resistance B) Driving force = Rate × Resistance C) Resistance = Driving force × Rate D) $${\text{Rate}} = \frac{{{\text{Resistance}}}}{{{\text{Driving force}}}}$$

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Answer & Solution

Answer: Option B

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53

Double pipe heat exchangers are used

A) When heat transfer area required is very high B) When heat transfer area required is very low, i.e (100 - 200 ft²) C) Because it occupies less floor area D) Because it is less costly

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Answer & Solution

Answer: Option B

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54

Loss of heat from untagged steam pipe to the ambient air is by

A) Conduction B) Convection C) Radiation D) All of the above

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Answer & Solution

Answer: Option D

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55

A hot liquid is kept in a big room. The logorithm of the numerical value of the temperature difference between the liquid and the room is plotted against time. The plot will be very nearly a/an

A) Ellipse B) Straight line C) Parabola D) Circular arc

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Answer & Solution

Answer: Option B

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56

Pick out the wrong statement.

A) Superheated steam is preferably not used for process heating because of its low heat transfer film co-efficient B) In a shell and tube heat exchanger, the shell pressure drop is maximum for orifice baffles C) S.I. unit of fouling factor is Watt/m².°K D) Longitudinal fins are used in extended surface heat exchangers, when the direction of fluid flow is parallel to the axis of the tube

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Answer & Solution

Answer: Option C

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57

The equivalent diameter for the annulus of a double pipe heat exchanger, whose inner pipe has fins on the outside is __________ compared to the same size pipes without fins.

A) More B) Less C) Same D) Unpredictable

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Answer & Solution

Answer: Option B

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58

Steam is to be condensed in a shell and tube heat exchanger, 5 m long with a shell diameter of 1 m. Cooling water is to be used for removing the heat. Heat transfer co-efficient for the cooling water, whether on shell side or tube side is the same. The best arrangement is

A) Vertical heat exchanger with steam on tube side B) Vertical heat exchanger with steam on shell side C) Horizontal heat exchanger with steam on tube side D) Horizontal heat exchanger with steam on shell side

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Answer & Solution

Answer: Option B

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59

Baffles in the shell side of a shell and tube heat exchanger

A) Increase the cross-section of the shell side liquid B) Force the liquid to flow parallel to the bank C) Increase the shell side heat transfer co-efficient D) Decrease the shell side heat transfer co-efficient

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Answer & Solution

Answer: Option C

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60

Overall heat transfer co-efficient of a particular tube is U₁. If the same tube with some dirt deposited on either side has coefficient U₂, then

A) U₁ = U₂ B) U₂ > U₁ C) U₁ > U₂ D) U₁ = dirt factor - U₂

Discuss

Answer & Solution

Answer: Option C

Solution:

The overall heat transfer coefficient of a tube, denoted as U, decreases when dirt is deposited on either side of the tube. This is because the dirt layer adds thermal resistance, making heat transfer less efficient.

Initially, the tube has an overall heat transfer coefficient U₁. After dirt deposition, the new coefficient is U₂.

Since the dirt layer increases thermal resistance, it reduces the overall heat transfer coefficient:

U₁ > U₂

Therefore, the correct answer is Option C: U₁ > U₂.

Heat Transfer MCQ Questions & Answers | Chemical Engineering