Main Page | See live article | Alphabetical index The Biot number (Bi) is a dimensionless number used in unsteady-state and heat transfer calculations. It relates the heat transfer resistance inside and at the surface of a body. It is defined as follows: Where: h - overall heat transfer coefficient L - charcteristic 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) This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.