Two long concentric horizontal aluminum tubes of 0.2 m and 0.25 m diameter are maintained at 300 K and 400 K respectively. The space between the tubes is filled with nitrogen. If the surfaces of the tubes are polished to prevent radiation, estimate the rate of heat transfer for gas pressure of (a) 10 atm and
(b) 0.1 atm in the annulus.
GIVEN
Two concentric horizontal aluminum tubes with nitrogen between them
Diameters: Di = 0.2 m Do = 0.25 m
Temperatures: Ti = 300 K To = 400 K
Surface of tubes is polished
ASSUMPTIONS
Steady state conditions
Radiative heat transfer is negligible
Only the density of the nitrogen is affected by the pressure