Biot number is a dimensionless parameter that represents the ratio of convection to conduction from solid interior $Bi=\frac{hL}{k}$ where, $h$ - heat transfer coefficient, $L$ - characteristic length, $k$ - thermal conductivity ## 1 Interpretation of Biot Number - If Biot number is small eg. $Bi <1$ conduction is faster than convection and the temperature distribution is uniform. - When Biot number is large $Bi > 1$ conduction is slower than convection and temperature gradient of the solid interior needs to be taken into account