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It determines the temperature transient behaviour and its gradient inside a solid body while it heats or cools over time.

Relation to Nusselt number  

Both numbers naturally arise in modelling the heat exchange between solid body and fluid.

Both numbers have similar definition except that Biot Number is based on thermal conductivity of the solid body while Nusselt number is based on thermal conductivity of the fluid.

Normally Biot Number indicates whether significant thermal gradient will develop inside a solid body based on the ratio of heat transfer away from the surface of a solid body to heat transfer within the solid body.

While Nusselt number indicates whether conductive or convective heat transfer dominates across the interface between solid body and fluid.

See also

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Physics / Thermodynamics / Heat Transfer

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