An alternate system uses a fog or good mist injected in to the intake air stream. Although a number of commercial systems can be found, growers can assemble and install their own system using 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 employed on excessively warm, bright days. Temperature settings ought to be 5-10°F apart.
Algae growth in the pads can become a problem which will decrease 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 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 material or liquid household detergent at the rate of 2 tablespoons per 100 gallons can be used.
Water for the pads should be clean and lower in mineral content to avoid clogging and coating of the pads. A pump, pipes and gutters are used to recirculate the water. A flow rate 113 gallon each and every minute per linear foot of pad system should be provided to guarantee adequate wetting.
In the most typical coolant system (fan and pad), the fans draw air through wet pads that expand the length of one endwall or sidewall. Aspen and coated cellulose are normal pad materials that always have life of 1 to three years. Approximately one square foot of pad are is needed for 20 square feet of floor area.
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