A 2.54-cm-OD, 1.9-cm-ID steel pipe carries dry air at a velocity of 7.6 m/s and a temperature of –7°C. Ambient air is at 21°C and has a dew point of 10°C. How much insulation with a conductivity of 0.18 W/(m K) is needed to prevent condensation on the exterior of the insulation if h = 2.4 W/(m2 K) on the outside?
GIVEN
Dry air flowing through an insulated steel pipe
Pipe diameters
Inside (Di) = 1.9 cm = 0.019 m
Outside (Do) = 2.54 cm = 0.0254 m
Air velocity (V) = 7.6 m/s
Air temperature (Ta) = –7°C
Ambient temperature (T