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Ratings found in centrifugal fan performance tables and curves are based on standard cubic feet per minute (SCFM). Fan manufacturers define standard air as clean, dry air with a density of 0.075 pounds mass per cubic foot, with the atmospheric pressure at sea level of 29.92 inches of mercury and a temperature of 70°F.
An axial fan is a type of fan that causes gas to flow through it in an axial direction, parallel to the shaft about which the blades rotate. The flow is axial at entry and exit. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan. Factors which determine the performance of the fan include the ...
Figure 1: Components of a centrifugal fan An external motor belt driven inline centrifugal fan discharging inline to the exterior of a building through a duct. Unlike non-inline/non-concentric impeller casing design with a cutoff blade above, the concentrically symetric cylinder casing and impeller geometry of inline type redirects the outflow around so that it is parallel to the inflow of gases.
Backward inclined – These fans have simple flat blades, backwardly inclined to match the velocity pattern of the air passing through the fan wheel for high-efficiency operation. These fans are typically used in high-volume, relatively low-pressure, clean air applications. Radial blade – The flat blades of this type are arranged in a radial ...
The cross-flow or tangential fan, sometimes known as a tubular fan, was patented in 1893 by Paul Mortier, [17] [18] and is used extensively in heating, ventilation, and air conditioning (HVAC), especially in ductless split air conditioners. The fan is usually long relative to its diameter, so the flow remains approximately two-dimensional away ...
Provided the ceiling fan is properly sized for the room in which it is operating, its efficiency of moving air far exceeds that of an air conditioning unit, therefore, for peak efficiency, the air conditioner should be set to a low fan setting and the ceiling fan should be used to circulate the air.
Air-side economizers also use outside air to condition spaces, but do so using fans, ducts, dampers, and control systems to introduce and distribute cool outdoor air when appropriate. An important component of natural ventilation is air change rate or air changes per hour : the hourly rate of ventilation divided by the volume of the space.
is the gross amount of air circulated through the fan (or ventilation system) [m 3 /s] There are various sub-definitions of SFP for different specific applications, including SFP e (building energy performance calculations), SFP v (for performance verification tests), SFP i (individual fan), SFP AHU (air handling unit), SFP FCU (fan coil unit ...