Example

Determine the rate of heat loss from a heated pipe as a result of natural (free) convection.

Ts=100?C

T?=0°C

D=0.1 m

Film temperature( Tf): averaged boundary layer temperature Tf=1/2(Ts+T ?)=50 ?C.

kf=0.03 W/m.K, Pr=0.7, n=2?10-5 m2/s, b=1/Tf=1/(273+50)=0.0031(1/K)