Question

Which one of the following is not a material property?
A. thermal conductivity
B. heat transfer coefficient
C. emissivity

Answer 1

A . thermal conductivity

Answer 2

Answer:

The correct option is Option B

Explanation:

• Heat transfer coefficient is not a thermophysical property of material, while it depends on the surface geometry and the conditions of boundary layer . But the conductivity is thought to be a thermophysical property of the material.
• Actually the boundaries of this classification are limited to the scales of the phenomena and to the governing rules we use. Usually, materials characteristics are defined in constitutive equations as an empirical rule (e.g. Furrier's law of conduction), and these rules are not of fundamentals law.
• Therefore their classifications are not fundamental and are very limited to the specified scales of time, space and physics of the equations. Thus you can roughly say "the Conductivity is a thermophysical property and the Heat Transfer Coefficient is not" but you know that the conductivity is a an anisotropic tensor of forth order (with 81 component, like Elastic modulus) which, in the atomic scales, could be a function of everything happening through the material, even the heat flow!