An alternate system uses a fog or great mist injected into the intake air stream. Although a number of commercial systems can be found, growers can assemble and set up their own system utilizing a high pressure piston pump and fog nozzles. The basic components are demonstrated in Fig. 1. A two-stage system controlled by a two- stage thermostat allows more water to be applied on excessively warm, shiny days. Temperature settings ought to be 5-10°F apart.
Algae growth in the pads may become a problem which will reduce the effectiveness of the machine and lead to accelerated deterioration of the pads. The addition of an algaecide to the drinking water supply can help in control.
It really is desirable, especially in hard water areas, to add a wetting agent to the drinking water to obtain more uniform wetting of the pads. A commercial materials or liquid home detergent at the rate of 2 tablespoons per 100 gallons can be used.
Drinking water for the pads ought to be clean and lower in mineral content to prevent clogging and coating of the pads. A pump, pipes and gutters are used to recirculate the drinking water. A flow rate 113 gallon per minute per linear foot of pad system ought to be provided to assure adequate wetting.
In the most typical coolant system (fan and pad), the fans draw air through wet pads that prolong the length of one endwall or sidewall. Aspen and covered cellulose are normal pad materials that always have life of one to 3 years. Approximately one square foot of pad are is needed for 20 square foot of floor area.
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