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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 ...
In the case of an ideal lossless fan system (i.e. =) the SFP is exactly equal to the fan pressure rise (i.e. total pressure loss in the ventilation system). In reality the fan system efficiency is often in the range 0 to 60% (i.e. η t o t < 0.6 {\displaystyle \eta _{tot}<0.6} ); it is lowest for small fans or inefficient operating points (e.g ...
The affinity laws (also known as the "Fan Laws" or "Pump Laws") for pumps/fans are used in hydraulics, hydronics and/or HVAC to express the relationship between variables involved in pump or fan performance (such as head, volumetric flow rate, shaft speed) and power. They apply to pumps, fans, and hydraulic turbines. In these rotary implements ...
is the static pressure at the point at which pressure coefficient is being evaluated is the static pressure in the freestream (i.e. remote from any disturbance) is the freestream fluid density (Air at sea level and 15 °C is 1.225 /)
At least one author takes a different approach in order to avoid a need for the expression freestream static pressure. Gracey has written "The static pressure is the atmospheric pressure at the flight level of the aircraft". [15] [16] Gracey then refers to the air pressure at any point close to the aircraft as the local static pressure.
The fan maintains a constant static pressure in the discharge duct regardless of the position of the VAV box. Therefore, as the box closes, the fan slows down or restricts the amount of air going into the supply duct. As the box opens, the fan speeds up and allows more air flow into the duct, maintaining a constant static pressure. [11]
The figure shows one such ideal expansion fan. A supersonic expansion fan, technically known as Prandtl–Meyer expansion fan, a two-dimensional simple wave, is a centered expansion process that occurs when a supersonic flow turns around a convex corner. The fan consists of an infinite number of Mach waves, diverging from a sharp corner. When a ...
Air flow through the fan creates an internal, uniform, static pressure within the building. The aim of this type of measurement is to relate the pressure differential across the envelope to the air flow rate required to produce it. Generally, the higher the flow rate required to produce a given pressure difference, the less airtight the ...