is known as
Grashof number
Biot number
Stanton number
Prandtlnumber
Biot number
The Biot number is the ratio of the internal resistance of a body to heat conduction to its external resistance to heat convection.
Biot number 
Where, h= Heat transfer coefficient
k=
L=
Biot number is a dimensionless quantityused
in heat transfer.
Hence, the correct option is (B).
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