An alternate system uses a fog or fine mist injected into the intake air stream. Although several commercial systems are available, growers can assemble and set up their own system utilizing a high pressure piston pump and fog nozzles. The essential components are shown in Fig. 1. A two-stage system controlled by a two- stage thermostat enables more water to be applied on excessively warm, bright days. Temperature settings should be 5-10°F apart.
Algae growth in the pads can become a problem that may decrease the effectiveness of the system and result in 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 drinking water areas, to add a wetting agent to the water to obtain more uniform wetting of the pads. A commercial material or liquid home detergent at the price of 2 tablespoons per 100 gallons may be used.
Drinking water for the pads should be clean and low in mineral content to prevent clogging and coating of the pads. A pump, pipes and gutters are accustomed to recirculate the water. A flow rate 113 gallon per minute per linear foot of pad system should be provided to assure adequate wetting.
In the most common coolant system (fan and pad), the fans draw air through wet pads that prolong the length of one endwall or sidewall. Aspen and coated cellulose are common pad materials that always have life of one to 3 years. Approximately one sq . foot of pad are is necessary for 20 square feet of floor area.
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