Question

A stainlesss steel cylinder diameter 60 mm is cooled in a air with h = 10 W/m^2-K. If the thermal conductivity is 20 W/m-K, the Biot number for this sphere is a)-0.005 b)-0.03 c)-8 d)-30

Answer 1

The Biot number for this sphere is 0.03

Step-by-step explanation:

Given data in equation

diameter (d) = 60 mm = 60/1000 = 0.06 m

heat transfer coefficient (h) = 10 w/m²-K

thermal conductivity (K) = 20 W/m-K

To find out

Biot number for sphere

Solution

we will find boit number by this given formula

Biot Number = ( h × S ) / K ..................1

here h and K value is given in question

and S = diameter/2

S= 60/2 = 30 mm = 0.03 m

Now put these value S, h and K in equation 1

Biot Number = ( 10 × 0.03 ) / 10

Biot Number = 0.03