Biot Number

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Biot Number

Biot Number ( \(Bi\) ) (dimensionless number) is the ratio of internal thermal resistance of solid to fluid thermal resistance.  This is used for heat transfer between fluids and solids.

Biot Number FORMULA

\(Bi=\frac{hl_c}{k}\)          \( biot \; number   \;=\;   \frac {  heat \; transfer \; coefficient  \;\;x\;\;  characteristic \; length  }  { thermal \; conductivity } \)

\(Bi=\frac{h_D l_c}{D}\)      


\(Bi\) = biot number

\(c_d\) = diffusion coefficient

\(c_m\) = mass transfer coefficient

\(h\) = heat transfer coefficient

\(k\) = thermal conductivity of the body

\(l_c\) = characteristic length


Tags: Equations for Heat Transfer