Air at atmospheric pressure flows in a duct that has a diameter of 15 cm. The volumetric flow rate of air is 0.418 m3 /s. The duct inner surface is hydraulically smooth. At an axial location where the...

Air at atmospheric pressure flows in a duct that has a diameter of 15 cm. The volumetric flow rate of air is 0.418 m3 /s. The duct inner surface is hydraulically smooth. At an axial location where the flow field can be assumed to be thermally developed, because of external heating, the inner surface of the duct is at a uniform temperature of 360 K, while the air mean temperature is 330 K

a. Calculate the turbulent eddy diffusivity at a distance of 1.5 mm from the wall.

b. Air contains viruses that can be idealized as spheres 50 nm in diameter and have a density of 700 kg/m³
. Calculate the mean (time-average) velocity that viruses are exposed to at a distance of 1.5 mm from the wall.

 c. This particular virus becomes inactive when its temperature is raised above 350 K. Does a virus that is at 1 mm from the wall become inactive?

d. How does the size of these viruses compare with the Kolmogorov’s microscale in the duct?