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Information About

Biot Number





DEFINITION

The Biot number is defined as:
:\mathit{Bi} = rac{h L_C}{\lambda_b}

where:
  • h = overall Heat Transfer coefficient

  • LC = characteristic length, which is commonly defined as the volume of the body divided by the surface area of the body, such that

  • \mathit{L_C} = rac{V_{body}}{A_{surface}}.




APPLICATIONS

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.


HEAT TRANSFER ANALOG

An analogous version of the Biot number (usually called the "mass transfer Biot number", or \mathit{Bi}_m) is also used in mass diffusion processes:

:\mathit{Bi}_m= rac{h_m L}{D_{AB}}

where:
  • h - overall Mass Transfer coefficient

  • LC - characteristic length

  • DAB - mass diffusivity.