Heat Radiation MCQs

Welcome to our comprehensive collection of Multiple Choice Questions (MCQs) on Heat Radiation, a fundamental topic in the field of Heat Transfer. Whether you're preparing for competitive exams, honing your problem-solving skills, or simply looking to enhance your abilities in this field, our Heat Radiation MCQs are designed to help you grasp the core concepts and excel in solving problems.

In this section, you'll find a wide range of Heat Radiation mcq questions that explore various aspects of Heat Radiation problems. Each MCQ is crafted to challenge your understanding of Heat Radiation principles, enabling you to refine your problem-solving techniques. Whether you're a student aiming to ace Heat Transfer tests, a job seeker preparing for interviews, or someone simply interested in sharpening their skills, our Heat Radiation MCQs are your pathway to success in mastering this essential Heat Transfer topic.

Note: Each of the following question comes with multiple answer choices. Select the most appropriate option and test your understanding of Heat Radiation. You can click on an option to test your knowledge before viewing the solution for a MCQ. Happy learning!

So, are you ready to put your Heat Radiation knowledge to the test? Let's get started with our carefully curated MCQs!

Heat Radiation MCQs | Page 13 of 21

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Q121.
A thin shield of emissivity E3 on both sides is placed between two infinite parallel plates of emissivities E1 and E2 and temperatures T1 and T2. If E1 = E2 = E3, then the fraction radiant energy transfer without shield takes the value

a.

0.25

b.

0.50

c.

0.75

d.

1.25

Discuss
Answer: (b).0.50
Q122.
The grey body shape factor for radiant heat exchange between a small body (emissivity = 0.4) in a large enclosure (emissivity = 0.5) is

a.

0.1

b.

0.2

c.

0.4

d.

0.5

Discuss
Answer: (c).0.4
Q123.
Two long parallel surfaces, each of emissivity 0.7 are at different temperatures and accordingly have radiation exchange between them. It is desired to reduce 75% of this radiant heat transfer by inserting thin parallel shields of equal emissivity 0.7 on both sides. What should be the number of shields?

a.

2

b.

4

c.

1

d.

3

Discuss
Answer: (d).3
Q124.
An enclosure consists of four surfaces 1, 2, 3 and 4. The view factors for radiation heat transfers are

F 11 = 0.1

F 12 = 0.4

F 13 = 0.25

The surface areas A 1 and A 2 are 4 m² and 2 m². The view factor F 41 is

a.

0.50

b.

0.75

c.

0.1

d.

0.25

Discuss
Answer: (a).0.50
Q125.
The value of shape factor depends on how many factors?

a.

4

b.

1

c.

2

d.

3

Discuss
Answer: (c).2
Q126.
A large plane, perfectly insulated on one face and maintained at a fixed temperature T 1 on the bare face, has an emissivity of 0.84 and loses 250 W/m² when exposed to surroundings at nearly 0 K. The radiant heat loss from another plane of the same size is 125 W/m² when bare face having emissivity 0.42 and is maintained at temperature T 2 is exposed to the same surroundings. Subsequently these two planes are brought together so that the parallel bare faces lie only 1 cm apart and the heat supply to each is so regulated that their respective temperatures T 1 and T 2 remains unchanged. Determine he net heat flux between the planes

a.

0

b.

1

c.

2

d.

3

Discuss
Answer: (a).0
Q127.
Interchange factor for body 1 completely enclosed by body 2 (body 1 is large) is given by

a.

2/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].

b.

1/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].

c.

4/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].

d.

3/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].

Discuss
Answer: (b).1/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].
Q128.
A thermos flask has a double walled bottle and the space between the walls is evacuated so as to reduce the heat flow. The bottle surfaces are silver plated and the emissivity of each surface is 0.025. If the contents of the bottle are at 375 K, find the rate of heat loss from the thermos bottle to the ambient air at 300 K

a.

5.38 W

b.

6.38 W

c.

7.38 W

d.

8.38 W

Discuss
Answer: (d).8.38 W
Q129.
A 250 mm by 250 mm ingot casting, 1.5 m high and at 1225 K temperature, is stripped from its mold. The casting is made to stand on end on the floor of a large foundry whose wall, floor and roof can be assumed to be at 300 K temperature. Make calculation for the rate of radiant heat interchange between the casting and the room. The casting material has an emissivity of 0.85

a.

161120 W

b.

171120 W

c.

181120 W

d.

191120 W

Discuss
Answer: (b).171120 W
Q130.
Interchange factor for infinitely long concentric cylinders is given by

a.

1/ [A₁/A₂ (1/E₂ – 1)].

b.

[1/E₁ + A₁/A₂ (1/E₂ – 1)].

c.

2/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].

d.

1/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].

Discuss
Answer: (d).1/ [1/E₁ + A₁/A₂ (1/E₂ – 1)].
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