Radiation Exchange Between Surfaces Quiz: Test Your Knowledge

Question 1

Two parallel, infinite plates are maintained at temperatures T1 and T2, with T1 > T2.  What is the net radiative heat flux between the plates if their emissivity is ε?

Accepted Answer

σ * ε * (T1^4 - T2^4)

Answer

σ * (T1 - T2)

Answer

σ * ε * (T1 - T2)

Answer

σ * (T1^4 - T2^4)

Question 2

A small, spherical object is placed inside a large, isothermal enclosure.  What is the view factor from the sphere to the enclosure?

Accepted Answer

1

Answer

0

Answer

0.5

Answer

It depends on the size of the sphere.

Question 3

Two surfaces, A1 and A2, have view factors F12 and F21 respectively.  Which of the following is always true?

Accepted Answer

A1 * F12 = A2 * F21

Answer

F12 < F21

Answer

F12 = F21

Answer

F12 > F21

Question 4

A radiation shield is placed between two surfaces to reduce heat transfer.  Which of the following statements about the shield is TRUE?

Accepted Answer

The shield should have a high emissivity on both sides.

Answer

The shield should have a high emissivity on one side and a low emissivity on the other.

Answer

The shield should have a low emissivity on both sides.

Question 5

Two surfaces are exchanging heat by radiation.  If the temperature of both surfaces is doubled, the net radiative heat transfer will:

Accepted Answer

Increase by a factor of 16

Answer

Double

Answer

Remain the same

Answer

Increase by a factor of 4

Question 6

A large, flat plate is exposed to solar radiation.  The plate's temperature is 300 K and its emissivity is 0.8.  The solar irradiance is 1000 W/m^2.  What is the net radiative heat flux absorbed by the plate?

Accepted Answer

600 W/m^2

Answer

400 W/m^2

Answer

1000 W/m^2

Question 7

Which of the following factors does NOT affect the view factor between two surfaces?

Accepted Answer

Surface emissivity

Answer

Surface area

Answer

Relative position and orientation

Answer

Shape of the surfaces

Question 8

A blackbody is defined as a surface that:

Accepted Answer

Absorbs all incident radiation

Answer

Emits no radiation

Answer

Reflects all incident radiation

Answer

Transmits all incident radiation

Question 9

A gray body is a surface that:

Accepted Answer

Has a constant emissivity and absorptivity over all wavelengths

Answer

Absorbs all incident radiation

Answer

Reflects all incident radiation

Question 10

In a radiation network analysis, a resistance between two surfaces is inversely proportional to:

Accepted Answer

The product of their areas and the view factor between them

Answer

The difference in their temperatures

Answer

The emissivity of the surfaces