BME Heat Transfer 1

Question 1

Fourier's law of heat conduction states that heat flux is proportional to:

Accepted Answer

Temperature gradient

Answer

Fourier's law states q = -k(dT/dx), meaning heat flux is directly proportional to the negative temperature gradient.

Question 2

Which mode of heat transfer does not require a medium?

Accepted Answer

Radiation

Answer

Radiation transfers heat via electromagnetic waves and can occur through a vacuum, unlike conduction and convection which require matter.

Question 3

The Biot number (Bi) in transient heat conduction represents the ratio of:

Accepted Answer

Convective to conductive resistance

Answer

The Biot number Bi = hL/k is the ratio of convective heat transfer resistance at the surface to conductive resistance within the body.

Question 4

In a fin, the efficiency is defined as the ratio of actual heat transfer to:

Accepted Answer

Maximum possible heat transfer if the entire fin were at base temperature

Answer

Fin efficiency compares actual heat transfer to the ideal case where the whole fin surface is at the base (maximum) temperature.

Question 5

What is the thermal resistance for conduction through a flat wall?

Accepted Answer

L/(kA)

Answer

For a flat wall, thermal resistance R = L/(kA), analogous to electrical resistance, where L is thickness, k is conductivity, and A is area.

BME - Bachelor of Mechanical Engineering Practice Test