Evaluate the rate of heat loss per meter from pressurized water flowing at 200°C through a 10-cm-ID pipe at a velocity of 3 m/s. The pipe is covered with a 5-cm-thick layer of 85% magnesia wool which has an emissivity of 0.5. Heat is transferred to the surroundings at 20°C by natural convection and radiation. Draw the thermal circuit and state all assumptions.
GIVEN
Pressurized water flowing through an insulated pipe
Water temperature (Tw) = 200°C = 493 K
Pipe inside diameter (Di) = 10 cm = 0.1 m
Water velocity (V) = 3 m/s
Magnesia wool insulation thickness (t) = 5 cm = 0.05 m
Emissivity of the wool insulation (