Dry air, flowing at a velocity of 1.5 m/s, enters a 6-mlong, 0.15-m-diameter tube at 310 K and 1:013 × 105 Pa. The inner surface of the tube is lined with a felt material (diameter-to rough ness ratio, D/e, of 10,000) that is continuously saturated with water at 290 K.
Assuming constant temperature of the air and the pipe wall, determine the rate at which water must be added to keep the felt continuously saturated.
It is important to realize that the bulk composition of the gas stream will be continuously increasing with the length.