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Test: Absorptivity


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10 Questions MCQ Test Heat Transfer | Test: Absorptivity

Test: Absorptivity for Chemical Engineering 2022 is part of Heat Transfer preparation. The Test: Absorptivity questions and answers have been prepared according to the Chemical Engineering exam syllabus.The Test: Absorptivity MCQs are made for Chemical Engineering 2022 Exam. Find important definitions, questions, notes, meanings, examples, exercises, MCQs and online tests for Test: Absorptivity below.
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Test: Absorptivity - Question 1

Energy strikes a vertical hemispherical plate with an intensity of 640 W/m2. The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of transmission

Detailed Solution for Test: Absorptivity - Question 1

Rate os transmission = (0.5455) (640)/3 = 116.37 W/m2.

Test: Absorptivity - Question 2

The absorptivity of a surface depends upon
(i) Direction of reflected radiation
(ii) Temperature of the surface
(iii) Composition
Identify the correct statements

Detailed Solution for Test: Absorptivity - Question 2

It depend upon the direction of incident radiation. Absorptivity is the fraction of total energy absorbed by the body.

Test: Absorptivity - Question 3

What is the absorptivity of gray body?

Detailed Solution for Test: Absorptivity - Question 3

Gray body absorbs a certain fixed percentage of impinging radiations.

Test: Absorptivity - Question 4

A body that reflects all the incident thermal radiations is called a

Detailed Solution for Test: Absorptivity - Question 4

In this case reflection is regular. For such bodies reflectivity is unity and transmissivity is equal to zero.

Test: Absorptivity - Question 5

Energy strikes a vertical hemispherical plate with an intensity of 640 W/m2. The absorptivity is thrice the transmissivity and twice the reflectivity. Determine the rate of absorption

Detailed Solution for Test: Absorptivity - Question 5

Rate of absorption = (0.5455) (640) = 349.12 W/m2.

Test: Absorptivity - Question 6

Let 220 W/m2 of radiant energy is absorbed by a convex surface, 90 W/m2 is reflected and 40 W/m2 is transmitted through it. What is the value of absorptivity?

Detailed Solution for Test: Absorptivity - Question 6

It is the ratio of incident energy flow to that of absorbed radiations. Absorptivity = 220/(220 + 90 + 40) = 0.62.

Test: Absorptivity - Question 7

For a grey surface

Detailed Solution for Test: Absorptivity - Question 7

Emissivity is constant only for grey surfaces because grey surface radiates much more than any of the other surface.

Test: Absorptivity - Question 8

Which quantity can be neglected for gases?

Detailed Solution for Test: Absorptivity - Question 8

Gases are known to reflect very little of the radiation incident on their surface.

Test: Absorptivity - Question 9

Absorptivity of a body is equal to its emissivity

Detailed Solution for Test: Absorptivity - Question 9

In most case absorptivity of a body is equal to its emissivity under thermal equilibrium conditions.

Test: Absorptivity - Question 10

Electromagnetic waves strikes a hot body maintained at 900 degree Celsius which has a reflectivity of 0.66 and a transmissivity of 0.022. Let the absorbed flux be 60 W/m2. Determine the rate of incident flux

Detailed Solution for Test: Absorptivity - Question 10

Absorptivity + Reflectivity + Transmissivity = 1. So, incident flux = 60/0.318 = 188.67 W/m2.

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