What is biot number?

The Biot number (Bi) is a dimensionless number used in heat transfer calculations. It characterizes the ratio of heat transfer resistance inside a solid material to the heat transfer resistance at the surface of the material. It is defined as the product of the convective heat transfer coefficient and a characteristic length divided by the thermal conductivity of the material.

The Biot number is commonly used in problems involving transient heat transfer, such as when a solid object is suddenly exposed to a different temperature environment. It helps in determining the rate of heat transfer and the temperature distribution within the solid material.

A Biot number significantly less than 1 indicates that heat conduction within the solid material is much faster than heat convection at the surface, so the temperature distribution can be assumed as uniform. On the other hand, a Biot number greater than 1 indicates that heat convection at the surface is a dominant factor and needs to be considered in the heat transfer analysis.

Overall, the Biot number is a useful parameter in analyzing heat transfer processes involving solid materials and the surrounding fluid, helping engineers and researchers in designing efficient heat transfer systems.