An air washer essentially consists of a row of spray nozzles inside a chamber or casing. Atank at the bottom of the chamber provides for collection of water as it falls through the air and comes into intimate contact with the wet surface of the chamber baffles. The water is generally circulated by means of a pump, the warm water being passed over refrigerating coils or blocks of ice to cool it before being passed to the spray chamber. The water lost in evaporation is usually replaced automatically by the use of a float arrangement, which admits water from the main tank as required. In many locations, the water is sufficiently cool to use as it is drawn from the source. In other places, the water is not cool enough and must be cooled by means of ice or with a refrigerating machine.
The principal functions of the air washer are to cool the air passed through the spray chamber and to control humidity. In many cases, the cooling coils are located in the bottom of the spray chamber so that as the warm spray descends, it is cooled and ready to be again sprayed by the pump. In some cases, the water is passed through a double-pipe arrangement and is cooled on the counter-current principle.
Figure 3-14 shows a sketch of an air washer. In this case, the spray pipes are mounted vertically. In some instances, the spray pipes are horizontal so that the sprays are directed downward. As some of the finer water particles tend to be carried along with the air current, a series of curved plates or baffles is generally used, which forces the cooled and humidified air to change the direction of flow, throwing out or eliminating the water particles in the process.