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 20 of 21

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Q191.
Two parallel square plates, each 4 m² area, are large compared to a gap of 5 mm separating them. One plate has a temperature of 800 K and surface emissivity of 0.6, while the other has a temperature of 300 K and surface emissivity of 0.9. Find the net energy exchange by radiations between the plates

a.

61.176 k W

b.

51.176 k W

c.

41.176 k W

d.

31.176 k W

Discuss
Answer: (b).51.176 k W
Q192.
The furnace of a boiler is laid from fire clay brick with outside lagging from the plate steel, the distance between the two is quite small compared with the size of the furnace. The brick setting is at an average temperature of 365 K whilst the steel lagging is at 290 K. Calculate the radiant heat flux. Assume the following emissivity values

For brick = 0.85
For steel = 0.65

a.

352.9 W/m²

b.

452.9 W/m²

c.

552.9 W/m²

d.

652.9 W/m²

Discuss
Answer: (a).352.9 W/m²
Q193.
Two black discs each of diameter 50 cm are placed parallel to each other concentrically at a distance of one meter. The discs are maintained at 1000 K and 500 K. Calculate the heat flow between the discs when no other surface is present

a.

317.27 W

b.

417.27 W

c.

517.27 W

d.

617.27 W

Discuss
Answer: (b).417.27 W
Q194.
Two black discs each of diameter 50 cm are placed parallel to each other concentrically at a distance of one meter. The discs are maintained at 1000 K and 500 K. Calculate the heat flow between the discs when the disks are connected by a cylindrical black no-flux surface

a.

2417.68 W

b.

3417.68 W

c.

4417.68 W

d.

5417.68 W

Discuss
Answer: (d).5417.68 W
Q195.
A cavity in the shape of a frustum of a cone has diameter 30 cm and 60 cm and the height is 80 cm. If the cavity is maintained at temperature of 800 K, determine the heat loss from the cavity when the smaller diameter is at the bottom

a.

6577 W

b.

2367 W

c.

8794 W

d.

3675 W

Discuss
Answer: (a).6577 W
Q196.
A conical cavity of base diameter 15 cm and height 20 cm has inside surface temperature 650 K. If emissivity of each surface is 0.85, determine the net radiative heat transfer from the cavity

a.

168.3 W

b.

158.3 W

c.

148.3 W

d.

138.3 W

Discuss
Answer: (a).168.3 W
Q197.
Consider radiant heat exchange between two non-black parallel surfaces. The surface 1 emits radiant energy E 1 which strikes the surface 2. Identify the correct option

a.

The value of B is ฮฑ E1

b.

The value of C is (1 โ€“ ฮฑ1) E 1

c.

The value of D is (1 โ€“ ฮฑ1) (1 โ€“ ฮฑ2)² E 1

d.

The value of E is (1 โ€“ ฮฑ1)² (1 โ€“ ฮฑ2) E 1

Discuss
Answer: (c).The value of D is (1 โ€“ ฮฑ1) (1 โ€“ ฮฑ2)² E 1
Q198.
Two large parallel planes with emissivity 0.4 are maintained at different temperatures and exchange heat only by radiation. What percentage change in net radiative heat transfer would occur if two equally large radiation shields with surface emissivity 0.04 are introduced in parallel to the plates?

a.

65.1%

b.

75.1%

c.

85.1%

d.

95.1%

Discuss
Answer: (d).95.1%
Q199.
A blind cylindrical hole of 2 cm diameter and 3 cm length is drilled into a metal slab having emissivity 0.7. If the metal slab is maintained at 650 K, make calculations for the radiation heat escape from the hole

a.

7 W

b.

3 W

c.

1 W

d.

9 W

Discuss
Answer: (b).3 W
Q200.
Consider an enclosure formed by three surfaces having the following values of shape factors, emissivities and temperatures.

Surface 1 i.e. curved cylindrical has an emissivity 0.75 and temperature 800 K
Surface 2 i.e. closing disc has an emissivity 0.8 and temperature 700 K
Surface 3 i.e. closing disc has an emissivity 0.8 and temperature 700 K
The closing flat discs are 25 mm in diameter and they have interspacing distance equal to 100 mm. If the shape factor between these two identical discs is 0.05, calculate the net rate of radiant heat flow from the curve surface to each of the closing end surface.

a.

1.561 W

b.

2.561 W

c.

3.561 W

d.

4.561 W

Discuss
Answer: (c).3.561 W
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