HVAC Fan Applications
The numerous applications of fans in the field of air-conditioning and ventilation are well known, particularly to engineers and air-conditioning repair and maintenance personnel. The various fan applications are as follows:
■ Exhaust fans
■ Circulating fans
■ Cooling-tower fans
■ Kitchen fans
■ Attic fans
Exhaust fans are found in all types of applications, according to the American Society of Heating and Ventilating Engineers. Wall fans are predominantly of the propeller type, since they operate against little or no resistance. They are listed in capacities from 1000 to 75,000 ft3/min. They are sometimes incorporated in factory-built penthouses and roof caps or provided with matching automatic louvers. Hood exhaust fans involving ductwork are predominantly centrifugal, especially in handling hot or corrosive fumes.
Spray-booth exhaust fans are frequently centrifugal, especially if built into self-contained booths. Tubeaxial fans lend themselves particularly well to this application where the case of cleaning and of suspension in a section of ductwork is advantageous. For such applications, built-in cleanout doors are desirable.
Circulating fans are invariably propeller or disk-type units and are made in a vast variety of blade shapes and arrangements. They are designed for appearance as well as utility. Cooling-tower fans are predominantly the propeller type. However, axial types are also used for packed towers, and occasionally a centrifugal fan is used to supply draft. Kitchen fans for domestic use are small propeller fans arranged for window or wall mounting and with various useful fixtures. They are listed in capacity ranges of from 300 to 800 ft3/min.
Attic fans are used during the summer to draw large volumes of outside air through the house or building whenever the outside temperature is lower than that of the inside. It is in this manner that the relatively cool evening or night air is utilized to cool the interior in one or several rooms, depending on the location of the air-cooling unit. It should be clearly understood, however, that the attic fan is not strictly a piece of air-conditioning equipment since it only moves air and does not cool, clean, or dehumidify. Attic fans are used primarily because of their low cost and economy of operation, combined with their ability to produce comfort cooling by circulating air rather than conditioning it.