Biot number
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The Biot number (Bi) is a dimensionless number used in unsteady-state heat transfer calculations. It relates the heat transfer resistance inside and at the surface of a body.
It is defined as follows:
<math> \mathit{Bi} = \frac{h L}{\lambda_b}. <math>
Where:
- h - overall heat transfer coefficient
- L - characteristic length
- λb - Thermal conductivity of the body
Values of the Biot number larger than 1 imply that the heat conduction inside the body is slower than at its surface, and temperature gradients are non-negligible inside it.
It is named after the French physicist Jean-Baptiste Biot (1774-1862)nl:Getal van Biot