Question

Lumped heat transfer analysis of a solid object suddenly exposed to a fluid medium at a different temp is valid when

• A.
  $\text{Biot number}<0.1$
• B.
  $\text{Biot number}>0.1$
• C.
  $\text{Fourier number}<0.1$
• D.
  $\text{Fourier number}>0.1$

Answer 1

The correct option is A

$\text{Biot number}<0.1$
Biot number is defined as

$Bi=\frac{R_{\text{cond}}}{R_{\text{conv}}}$

The value of the Biot number is very small (less than $0.01$). When the conductive resistance of solid is negligible.