Fundamentals of Radiation Heat Transfer: A Comprehensive Guide for Mechanical Engineers

Question 1

What is the unit of thermal radiation intensity in the International System of Units (SI)?

Accepted Answer

Watts per square meter per steradian

Answer

Watts per square meter

Answer

Watts per meter

Answer

Watts per steradian

Question 2

What is the purpose of the Stefan-Boltzmann constant?

Accepted Answer

To calculate net radiation heat transfer

Answer

To determine the emissivity of a surface

Answer

To find the absorptivity of a surface

Answer

To calculate the thermal conductivity of a material

Question 3

What is the definition of radiosity for a surface?

Accepted Answer

Total radiation emitted per unit area

Answer

Total radiation absorbed per unit area

Answer

Net radiation exchanged per unit area

Answer

Incident radiation per unit area

Question 4

What does irradiation of a surface represent?

Accepted Answer

Total radiation incident per unit area

Answer

Total radiation emitted per unit area

Answer

Net radiation exchanged per unit area

Answer

Incident radiation per unit time

Question 5

State Wien's displacement law and explain its significance in understanding the emission spectrum of a blackbody.

Accepted Answer

Wien's displacement law states that the wavelength of maximum emission (λmax) of a blackbody is inversely proportional to its absolute temperature (T): λmax = b/T, where 'b' is Wien's displacement constant.

Answer

Wien's displacement law states that the wavelength of maximum emission is directly proportional to the absolute temperature of the blackbody.

Answer

Wien's displacement law is only applicable to non-blackbody emitters.

Answer

Wien's displacement law is not applicable to thermal radiation.

Question 6

Which of the following accurately describes thermal radiation?

Accepted Answer

A form of energy transfer via electromagnetic waves.

Answer

Requiring a physical medium for propagation.

Answer

Emitted only by objects at temperatures exceeding 0 Kelvin.

Answer

Traveling at the velocity of sound.

Question 7

Identify the theoretical object that absorbs and emits all incident radiation.

Accepted Answer

Blackbody

Answer

Graybody

Answer

Whitebody

Answer

Transparent body

Question 8

Which factor does NOT influence the emissivity of a surface?

Accepted Answer

Thickness of the surface

Answer

Surface temperature

Answer

Surface roughness

Answer

Wavelength of radiation

Question 9

What is an advantage of radiation heat transfer over other modes of heat transfer, such as conduction and convection?

Accepted Answer

It can occur in a vacuum.

Answer

It is more efficient.

Answer

It is less likely to cause burns.

Answer

It is easier to control.

Question 10

Identify a common application of radiative cooling.

Accepted Answer

Passive cooling of buildings

Answer

Infrared cameras

Answer

Microwave ovens

Answer

Laser cutting

Question 11

The emissivity of a surface represents the ratio between:

Accepted Answer

Thermal radiation emitted by the surface and that emitted by a blackbody at the same temperature.

Answer

Thermal radiation absorbed by the surface and that emitted by a blackbody at the same temperature.

Answer

Thermal radiation reflected by the surface and that emitted by a blackbody at the same temperature.

Answer

Thermal radiation transmitted by the surface and that emitted by a blackbody at the same temperature.

Question 12

Which statement accurately describes a blackbody?

Accepted Answer

It absorbs and emits all thermal radiation at all wavelengths.

Answer

It reflects and transmits all thermal radiation at all wavelengths.

Answer

It absorbs and reflects all thermal radiation at all wavelengths.

Answer

It emits and transmits all thermal radiation at all wavelengths.

Question 13

The Stefan-Boltzmann constant establishes the relationship between:

Accepted Answer

The thermal radiation emitted by a surface and its temperature.

Answer

The emissivity of a surface and its temperature.

Answer

The absorptivity of a surface and its temperature.

Answer

The thermal radiation reflected by a surface and its temperature.

Question 14

Which of the following does NOT influence the absorptivity of a surface?

Accepted Answer

Temperature of the surface

Answer

Wavelength of the incident radiation

Answer

Angle of incidence of the radiation

Answer

Emissivity of the surface

Question 15

The net radiative heat transfer between two surfaces is determined by:

Accepted Answer

The difference between the radiation emitted and absorbed by each surface.

Answer

The sum of the radiation emitted and absorbed by each surface.

Answer

The product of the radiation emitted and absorbed by each surface.

Answer

The quotient of the radiation emitted and absorbed by each surface.

Question 16

Which material typically exhibits the highest emissivity?

Accepted Answer

Flat black paint

Answer

Polished aluminum

Answer

Clear glass

Answer

White ceramic

Question 17

The net radiation exchange between two surfaces at different temperatures is influenced by:

Accepted Answer

The emissivities and areas of the surfaces, and the temperature difference

Answer

The distance between the surfaces

Answer

The pressure of the surrounding gas

Answer

The velocity of the surrounding gas

Question 18

The solar constant represents the:

Accepted Answer

Irradiance of solar radiation just outside the Earth's atmosphere

Answer

Temperature of the Sun

Answer

Intensity of solar radiation at the Earth's surface

Answer

Amount of solar radiation absorbed by the Earth