Centrifugal and Axial Fans Selection Tips:
- Overall, given the importance of access to clean air, centrifugal and axial fans are used for depleting, circulating, and supplying air in workshops, catering kitchens, poultry farms, greenhouses, and kitchens and restrooms in residential buildings.
- It must be noted that the axial or window-mounted fan is capable of moving a larger amount of air than centrifugal fans but they are not suitable for use with ducts (without static pressure).
- Various types of centrifugal or cylindrical fans are used to provide the pressure required to push air through air supply ducts but they cannot move as much air as their axial counterparts.
- It is emphasized that only centrifugal fans can be used when the air supply is delivered via a duct system.
- The static or dynamic balance of the fans and the pitch-accurate placement of the fins in axial and centrifugal fans (forward or backward-curved) are factors determining the correct function of the fans at their nominal dimensions and capacities.
- Thanks to their noise-free operation and excellent performance at high pressure, centrifugal fans are commonly integrated into air conditioning equipment for providing thermal comfort.
- Centrifugal fans with forward-curved fins offer maximum efficiency at low speed, low capacity, and high static pressure.
- This type of fan is often integrated into low-pressure heating, ventilation, and air conditioning systems (from household units to forced air furnaces) with efficiencies ranging from 55 to 65%.
- Backward-curved centrifugal fans are used in ventilation, air conditioning, and industrial heating systems in environments prone to mechanical or chemical corrosion or for other technical reasons and have an efficiency of up to 80%.
Centrifugal fans operate by two driving factors
- Centrifugal force—hence the name centrifugal fan
- The curvature of the leaving stream of air by fins from axial, as the angles at which molecules enter and leave the fan make 90°. Centrifugal fans are used in cases with low aeration capacity (in comparison with axial fans of similar power) and high static pressure
Operating Principles of Axial Fans (Impellers)The axial fan works based on the forced flow of air as a result of the angle of the impeller fins. In this type of fan, the flow of air is parallel to the fan axis. This type of fan is often used in cases with large aeration capacity and low static pressure.
Selecting and Placing an Order for Fans
- Type of fan (centrifugal or axial)
- Air displacement capacity (in CFM or m3/hr)
- The static pressure of the fan (for forwarding or backward-curved centrifugal fans)
- Single-phase or three-phase electric motor
- Fin dimensions and material (in particular, about axial or window-mounted fans)
Often, to select a centrifugal fan, first, the length is multiplied by the height by the number of times the air is required to be changed (from Table 3-14 depending on the use of the space, according to air conditioning standards) to find the volume of air that can be changed. Then, the dimensions of the output duct are calculated from technical and ductulator tables based on the speed (1500–2000 FPM) of the exhaust air from the duct. Next, the pressure drop or the static pressure is calculated based on the volume of air, obtained duct dimensions, duct length, possible bends, and other parameters, which is then used to calculate the required electric motor power.
Note the following when implementing air displacement systems
- Humidity at the installation location
- Whether the passing air is acidic or alkali
- Whether the electric motor is explosion and spark-proof
- The temperature at which the air passes the AC system is also important to some extent
Given the significance of balancing of centrifugal and axial fans and its direct impact on the durability of the fan and electric motor, make sure to have the fans installed perfectly horizontally and balanced to maintain the dynamic balance of the fan.
For consultation and further information, you can contact our specialists at DamaTajhiz.
Placing an Order and Warranties for Centrifugal and Axial Fans