Mass transfer treybal

3.3 Water flows down the inside wall of a wetted-wall tower of the design of Fig. 3.11, while air flows upward through the core. In a particular case, the ID is 25 mm (or I in), and dry air enters at the rate 7.0 kg/m2.s of inside cross section (or 5000 lb/ft?. h). Assume the air is everywhere at its average temperature, 36C, the water at 21C, and the mass-transfer coefficient constant. Pressure = 1 std atm. Compute the average partial pressure of water in the air leaving if the tower is 1 m (3 ft) long. Ans.: 1620 N/mm