NCEES Heat Transfer

Question 1

According to Fourier's Law of heat conduction, the heat flux q" is proportional to which of the following?

Accepted Answer

Negative temperature gradient

Answer

Positive temperature gradient

Answer

Thermal diffusivity only

Answer

Convection coefficient

Question 2

A flat wall has thermal conductivity k = 2 W/(m·K), area A = 5 m², thickness L = 0.2 m, and surface temperatures of 100°C and 20°C. What is the conductive heat transfer rate?

Accepted Answer

4 kW

Answer

2 kW

Answer

8 kW

Answer

16 kW

Question 3

The thermal resistance for convection from a surface with area A and convection coefficient h is expressed as:

Accepted Answer

1/(hA)

Answer

L/(kA)

Answer

hA

Answer

k/(LA)

Question 4

Which dimensionless number represents the ratio of convective heat transfer to conductive heat transfer at a surface?

Accepted Answer

Nusselt number

Answer

Reynolds number

Answer

Prandtl number

Answer

Biot number

Question 5

For a composite plane wall with three layers in series, the total thermal resistance is:

Accepted Answer

Sum of individual resistances

Answer

Product of individual resistances

Answer

Harmonic mean of individual resistances

Answer

Geometric mean of individual resistances

Question 6

The Stefan-Boltzmann Law for a blackbody states that emissive power is proportional to which power of absolute temperature?

Accepted Answer

Fourth power (T⁴)

Answer

Second power (T²)

Answer

Third power (T³)

Answer

First power (T)

Question 7

The Biot number (Bi = hLc/k) less than 0.1 indicates that which simplifying assumption is valid?

Accepted Answer

Lumped capacitance method

Answer

Quasi-steady conduction

Answer

Blackbody radiation dominance

Answer

Turbulent natural convection