Axial fans are in fact classified as mechanical fans. M […]
Axial fans are in fact classified as mechanical fans. Mechanical fans are defined as being machines designed to create a flow within a fluid. Air is the most common gas that axial fans are created to move.
Axial fans are not good for long duct runs. Anything over 5m will seriously impair their ability to extract air because of the larger air pressures present in the duct. When installing an axial type one should also avoid bending the duct if possible as this will also add to the pressure in the duct. In these situations one should use a centrifugal fan.
Centrifugal fans extract air at right angles to the intake of the fan, and spin the air outwards to the outlet by deflection and centrifugal force. The impeller rotates, causing air to enter the fan near the shaft and move perpendicularly from the shaft to the opening in the fan casing.
A centrifugal fan produces more pressure for a given air volume, and is used in installations where duct run is over 5 metres. Indeed, such is their efficiency that some centrifugal fans.
Centrifugal fans come in two main types: As an Inline duct fan or as a wall mounted fan. The wall mounted centrifugal fan looks just like a standard axial fan. Since the impellar is hidden by the front grille and casing it can be hard to differentiate the two but the price will usually give it away: Centrifugal wall fans are usually more expensive than axial fans.
Wall mounted centrifugal fans are often see in rooms which do not have exterior walls. Such rooms do not have windows or any natural ventilation and these circumstances usually require a long duct run to reach the outside of the building. The most common problem when air is not being extracted properly is when an axial fan is installed in this type of room... They are simply not designed for this operation.
You will find these units in industrial applications as well as in residential ones. The world relies heavily on these items to do the normal day to day activities of living. Without them we would have difficulties getting to work, controlling the temperature in our homes, and even doing things like playing our video games.