Chapter 18, Problem 1P

To determine

Define the physical importance of the Biot number. State whether the Biot number is more likely to be higher for poorly conducting solids or heavily conducting solids.

Explanation of Solution

Biot number:

Biot number is referred to as the ratio between conduction resistance inside the object and convection resistance at the surface of the object. It is also defined as the ratio of the internal resistance of the object to conduction of heat to its external resistance to convection of heat.

Write the expression to calculate the Biot number as follows:

  $\text{Bi}=\frac{h{L}_c}{k}$

Here, $\text{Bi}$ is the Biot number, $h$ is the convection heat transfer coefficient, $L_c$ is the characteristics length, and $k$ is the thermal conductivity.

The Biot number is more likely to be higher for poorly conducting solids because the poorly conducting objects have greater resistance against the conduction of heat.