Fans for Greenhouses
Fans are used in processing applications involved with drying, ventilating, heating, cooling, aspirating, elevating and conveying. Processing and other agricultural activities requiring fans are greatly increasing. Costs are becoming more and more important; therefore, it is necessary that a person be able to select and apply the best fan for any installation, taking economic factors into consideration.
A fan is an air pump--a machine that creates a pressure difference and causes air to flow. The impeller does work on the air in giving it both static and kinetic energy that varies ln proportion, depending on the fan type.
Fans have generally been classified as either centrifugal or axial flow, based on the direction of air flow through the impeller. Axial flow fans are generally classified as propeller fans, duct fans, vane axial fans, and disc fans. The propeller fan, essentially an air screw, is used for moving large quantities of air against low static pressures and is most commonly used for general ventilation applications. Centrifugal fans are generally used for moving air against high static pressure, such as experienced in grain drying applications. The propeller fan is the most common fan used for ventilation in greenhouses; however, other types of axial flow fans are also used.