Axial Flow Fan: Components, Design & General Characteristics
An axial flow fan is a type of industrial fan used to cool machines and equipment which heat up after use. Axial flow fans are the type of compressor, which produces airflow parallel to the axis, thus the name. These fans are equipped with impellers, which suck the air in and discharge in the same direction of the axis.
There are AC as well as DC axial flow fans. It may be designed in different ways such as with a duct or a mounting ring, and so on, depending upon the requirement. So, there are different standard designs which can be customized based on your device and installation type. The materials and accessories used for the fan are decided on these and other physical factors such as the environment it would be exposed to, temperature, moisture, pressure, and so on. This post discusses various designs of axial flow fans, and general features.
Components of Axial Flow Fan
The most basic part of an axial flow fan is the motor. Other than that it has ball bearings, blades, and impellers. The fan has a housing or an enclosure which protects it from external damage, spillage, shock, vibration, and so on. The enclosure is metallic and made of steel, aluminum, or alloys. The impellers are usually made of cast aluminum with black paint, thermoplastic, or steel, and designed to be corrosion resistant. The thermoplastic impellers are generally not considered ideal for commercial applications, so they are usually reserved for residential applications. The propellers feature blades. There can be 2 to 20 blades on the propellers. The fan is connected to a motor drive, which is usually placed in a housing parallel to the direction of airflow. The blades are usually made of aluminum. These fans are designed to be resistant to extreme temperatures, flames, shock, corrosive materials, and so on. A few common accessories of this fan include suitable connecting points, silencer, protection grill, counter flange, vibration controller, feet for the required positioning, and a variable inlet vane.
Design of Axial Flow Fans
As mentioned, the fan has various standard designs. Here are a few pointers:
- The fans may be duct mountable or wall mountable.
- Ducted fans have a duct through for a seamless airflow.
- The ring mountable fans allow the airflow from one big enough area to another; so, it is suitable for large spaces.
- The circulator fan has rotating impellers, which are typically used in ceiling fans.
- Axial flow fans offer large airflow rates at low pressures because of their working principle. The blades of these fans draw air parallel to its axis and move it in the forward in the same direction within the axis of the fan.
How Does an Axial Flow Fan Works?
Axial fans work similar to an aircraft wing, which possesses an airfoil shape and produce lift. Due to the airfoil shape of the wing, the air above and below it are divided and have different air velocities. This is because the air in above section travels farther than air in the bottom section. The air above has a high air velocity, which produces a high dynamic force and low static pressure. Against this, the air in the below section has low air velocity and produces a high static pressure. These pressure differences create the lift. Now coming to the axial fan, the blades of the propellers act like wings and they push air forward, thereby causing a lift. As a result of this lift, the air is propelled, as well as pushed back. The speed of air continues to increase up to a point even after the air leaves the fan. The airflow is great at the exit than at the entry point.
Some General Characteristics of Axial Flow Fans
These fans are typically used for sucking hot air from heat generating machines, trenches, and so on. They are also used for ventilation in enclosed spaces. These fans find a great application in quiet zones. Here are some general features of axial flow fans.
- These fans have a wide size range from 25mm to 250mm.
- These fans usually have ball or sleeve bearings which can last up to as high as 50,000 hours and at reasonably high temperatures.
- Their operating range is usually from -10 to +70, depending upon the bearing type.
- They operate quietly without noise, and have a good dielectric strength.
- They require minimal power input to operate.
- Apart from cooling industrial equipment, they find applications in diverse segments such as snow making machines, vending machines, refrigeration systems, HVAC systems, and so on.
Applications of Axial Flow Fans
Axial fans are generally used for cooling applications like the ones mentioned below:
- Process cooling in systems or machinery
- Spot cooling of transformers and generators and industrial equipment
- Ventilation in warehouses, factories, foundries, laundries, garages, equipment rooms, and engines
- Cooling work areas where heat is produced
In addition to this, industrial axial fans are also used for removing toxic gases and fumes from:
- Paint spray booths
- Welding booths
- Kilns, steel mills, and forges
- Paper mills or industrial parts washers
Benefits of Using Industrial Axial Flow Fans
Industrial axial flow fans assure efficient airflow, which is why they are cooling towers and exhausts. The cooling towers cannot dissipate heat if the airflow is not proper. The water system and fill material inside these fans operate properly due to a consistent airflow from the cooler fan, which is an axial fan. The axial fans can produce a large volume of air at a regular pace and they also ensure even air circulation due to the airfoil blades.
The speed of axial flow fans can be easily altered to suit the needs of the cooling tower or exhaust fans. The fans will continue to produce high airflow even if the speed is decreased. Against this, decreasing the speed can have a direct impact on the airflow of centrifugal fans.
Most industrial axial fans are made from aluminum, which makes them durable, reliable, lightweight, and user-friendly at the same time. Sometimes they are also made of stainless steel, which improves their performance in harsh environments. Many manufacturers provide industrial axial fans equipped with spark-resistant and cast aluminum made propellers, which assures their safety in high-temperature applications. Their durable construction is one of the prime reasons for employing these fans in ships, aircraft, helicopters, and hydrofoils.
Axial fans possess simpler designs than other industrial fan types. These fans have simple and open designs. Thus, any operational issues that arise can be easily identified and rectified. This is one of the reasons why these fans are widely used in industrial cooling and exhaust applications.
Improved Lifespan of Mechanical Components:
These fans possess compact footprint and lightweight designs than their earlier counterparts, which helps improves the lifespan of different mechanical components in it. Generally, the axial fans have improved lifespan than other industrial fans due to their high mechanical strength and optimal designs.
Quieter Than Most Other Industrial Fans:
Industrial axial flow fans produce low mechanical noise than conventional fans. This makes it an ideal choice for applications where noise can be a big concern.
If you are an OEM and have newly installed equipment which require axial flow fans, ensure you source them from a reliable manufacturer and supplier. Also, ensure they have features which meet your specifications. Sofasco designs, develops, and manufactures AC and DC axial fans in a huge size range, along with other integrated cooling solutions which can be customized to suit your requirements.