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Test: Absorptivity


10 Questions MCQ Test Heat Transfer | Test: Absorptivity


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This mock test of Test: Absorptivity for Chemical Engineering helps you for every Chemical Engineering entrance exam. This contains 10 Multiple Choice Questions for Chemical Engineering Test: Absorptivity (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Absorptivity quiz give you a good mix of easy questions and tough questions. Chemical Engineering students definitely take this Test: Absorptivity exercise for a better result in the exam. You can find other Test: Absorptivity extra questions, long questions & short questions for Chemical Engineering on EduRev as well by searching above.
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

Solution:

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

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

Solution:

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

QUESTION: 3

What is the absorptivity of gray body?

Solution:

Gray body absorbs a certain fixed percentage of impinging radiations.

QUESTION: 4

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

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

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
Solution:

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

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?
Solution:

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

QUESTION: 7

For a grey surface
Solution:

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

QUESTION: 8

Which quantity can be neglected for gases?
Solution:

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

QUESTION: 9

Absorptivity of a body is equal to its emissivity
Solution:

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

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
Solution:

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

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