Two moist air streams flow into a modified cooling tower to cool liquid water from 120 F to 75 F. The first moist air stream has a relative humidity of 60 percent and enters the cooling tower at 80 F. The second moist air stream enters the cooling tower at 40 F with a relative humidity of 40 percent and a dry air mass flow rate that is 1/4 that of the 80 F air stream. The air exiting the cooling tower exits with a relative humidity of 90 percent at 110 F. Assuming that no makeup water is supplied to the return water stream and that atmospheric pressure is 14.7 lb/in2, determine
(Using English units)
a. the amount of water evaporated from the incoming stream, in lb/mass dry air.
b. the mass flow rate of the hot water stream, in lb/mass dry air.
c. If all of the same conditions hold (including the mass evaporation rate that you found) from a-b, determine the rate of air flow for the 80 F stream (in lb/hr) if a 7 hp fan is added to homogenize the air mixture within the cooling tower.