# Heat Transfer MCQ’s – Fourier Equation

1 - Question

The famous Fourier series is named after
a) Diller and Ryan
b) J.B. Joseph Fourier
c) Stefan- Boltzmann
d) Wein’s
Explanation: He gave this theory in 1824.

2 - Question

Fourier law of heat conduction is best represented by
a) Q = -k A d t /d x
b) Q = k A d x/d t
c) Q = -k A
d) Q = k d t/d x
Explanation: According to Fourier law of heat conduction, Q = -k A d t /d x.

3 - Question

Here are some assumptions that are made for Fourier law. Identify the wrong one
a) No internal heat generation
c) Non- linear temperature profile
d) Isotropic and homogenous material
Explanation: It has constant temperature gradient and a linear temperature profile.

4 - Question

Consider the following statements:
The Fourier heat conduction equation
Q = -k A d t /d x
Presumes
ii) Constant value of thermal conductivity
iii) Uniform temperature at the wall surface
iv) One dimensional heat flow
Which of these statements are correct?

a) i, ii and iii
b) i, ii and iv
c) i, iii and iv
d) i, iii and iv
Explanation: Thermal conductivity is different for different materials.

5 - Question

The diagram shows heat conduction through a plane wall. The surface temperature is 475 K and it radiates heat to the surroundings at 335 K. If thermal conductivity of the material is 12.5 W/m degree, find the temperature gradient. Let convective coefficient be 80 W/m2 degree and radiation factor is 0.9 a) – 1052.4 degree celsius
b) – 2052.4 degree celsius
c) – 3052.4 degree celsius
d) – 4052.4 degree celsius
Explanation: Heat conducted through the plate = convection heat losses + radiation heat losses. So, d t /d x = – 13155/12.5 = – 1052.4 degree Celsius.

6 - Question

a) Heat always flow is in the direction of positive temperature gradient
b) Heat always flow in the direction of negative temperature gradient
c) No heat flow is there
d) Data is insufficient
Explanation: The ratio d t/d x represents the change in temperature per unit thickness i.e. the temperature gradient. So it represents heat flow in the direction of negative temperature gradient.

7 - Question

Transmission of heat i.e. molecular is smallest in case of
a) Gases
b) Liquids
c) Alloys
d) Solids
Explanation: In gases, atoms are arranged loosely, there is less molecular transmission of heat as compared to solids, liquids and alloys.

8 - Question

Which one is not the unit of thermal conductivity?
a) kcal/m hr K
b) KJ/m hr K
c) W/m s K
d) Cal/cm s K
Explanation: The unit kcal/m hr K could also be specified as J/m s K or W/m s K and this is actually done while quoting the numerical values of thermal conductivity.

9 - Question

“Thermal conductivity represents the amount of heat conducted across the unit area when a temperature difference of one kelvin”.
a) True
b) False
Explanation: It is across unit area and through unit distance.

10 - Question

Which of the following is the unit of thermal resistance?
a) degree/kcal
b) hour degree
c) s degree/kcal
d) degree/W