QUESTION 3 A horizontal electrical heater of outside diameter
D=0.025m
and length
L=2m
dissipates heat by free convection into atmospheric air at
T_(\infty )=27C
. If the surface temperature of the heater is 227 C , calculate the rate of heat transfer from heater to the air.
\Nu _(D)=(0.60+(0.387Ra_(D)^((1)/(6)))/((1+((0.559)/(P)r)^((9)/(16)))^((8)/(27))))^(2)Ra_(D)<=10^(12),\Nu _(D)=(hD)/(k),Ra_(D)=(g\beta (T_(s)-T_(\infty ))D^(3))/(v\alpha )
\beta =-(1)/(\rho )((del\rho )/(delT))_(P),\rho =(P)/(RT) (ideal gaz)