How Industrial Fans and Blowers Work
Industrial fans and blowers facilitate airflow to various processes of many industries. As it may have many applications, it holds particular value in processes that require process cooling, exhaust, or material handling, to name a few.
Industrial Fans and blowers move air through to address limitations in the process that is inhibited by:
a. Environment – for instance, supplying cooler air to an otherwise humid/hot structure.
b. Design – for example, more modern equipment requires a continuous flow of air to prevent from overheating.
c. Air Exchange – it is a simple exchange of airflow to maintain quality where airborne contaminants or odors may be present.
While our perceptions of industrial fans and blowers are limited to blades that rotate at moderate speeds, the concept of industrial fans are not too far off – only this time, imagine the generated airflow or pressure is increased exponentially.
To understand further how they operate, we must look at how they are designed. Categorizing them into two main types, you have centrifugal fans and axial fans, varying in functionality, air flow direction, and system design.
Centrifugal Fans and Blowers
In centrifugal fan types, you have the following components:
- Inlet/Outlet – Inlet pertains to the entryway in an industrial fan system. The inlet ducts control the flow of air entering the system, while the outlet duct provides resistance to the air coming out.
- Fan Housing/Casing – The metal body that houses the entire fan system. The housing also offers protection from moving parts such as the impeller. This is where the centrifugal power is generated, and for that reason, fan housings are built with rigid materials.
- Impellers/Fan Blades – These are the blade tips that carry the airflow through the system. The design of impellers or the blade ribs will also impact the type of airflow induced by the system – as it cuts through air to create drag.
- Motor – That is the primary input source where the electrical energy is generated to transform that into rotational motion (e.g., pressure).
- Rotor Shaft – This is the component that connects the motor and respective to the configurations, will determine the speed the fan blades can rotate.
These types of fans and blowers can be distinguished by the fan housing. Its scroll-shaped body allows air to enter through the center of the system. In centrifugal-type fans, as air enters through the inlet and is carried through the casing, airflow is increased by the centrifugal force generated in the movement of the fan blades. As the fan blades rotate, the airstream is thrown off away from the impellers hitting the fan casing.
From the kinetic energy gained from the moving blade tips, it is in that rapid movement that pressure is generated – as it moves against the resistance of the ducts, or the dampers installed. As air is displaced radially, the air is discharged and exits through the outlet – positioned 90 degrees from where it entered. With the air thrown off and a deficiency in pressure missing from the center, the negative pressure rushes air from the inlet to supplement, simultaneously drawing new air in and creating the cycle.
The design of this fan system allows for a buildup of high air pressure as a result of the centrifugal force. This makes them suitable for processes requiring high pressure applications, such as those operating in chemical industries, as in the extraction of fumes, hazardous pollutants in the air, wherein a constant replenishment of clean air is needed to ensure safety in the workplace.
With the use of centrifugal fans in these applications, these types of fans have to be designed to withstand various operating conditions such as corrosion, abrasive materials, chemical fumes, high temperatures, and other particulates that pass through. Given the design, the pressure creates a ton of resistance and the need of a very rigid machinery is required.
Axial Fans
For axial-type fans, as in the name, they use impellers attached to a central hub, allowing it to rotate on its axis to draw air into the system and discharge it in the same direction outward.
In terms of its components, axial fan systems can be divided into 3 main sections:
- Inflow – This contains the inlet cone, the bell which helps direct ambient air into the propeller mechanism.
- Fan Mechanism – This contains the impeller, the rotor, and the wheel. On top of the actual rotary device that drives the airflow, we also require additional components such as guide vanes, or straightening vanes that help direct airflow for it to pass more smoothly.
- Outflow – This is the outlet cone that leads the airflow outward.
Putting that all together, once air passes into the chamber, the pressure is built up from the aerodynamic lift caused by the fan blades, and this pitching helps facilitate this. This blade pitch refers to the angle on which the blades are turned to create that differential pressure. Simply put, it’s from that pressure difference builds up that draws air in from behind the mechanism and the act of the rotary movement brings it to move air forward.
This is used for systems that require a high flow rate, but with low pressure. For this reason, axial fans are suited for various applications, excelling at moving a larger volumetric flow. This is seen most commonly in ventilation systems, exhaust fans, or in a smaller scale, in computers, the axial fan design helps draw cooler air into the housing of the PC, to prevent the components from overheating. In this example, the distinctly cramped space inside of a PC casing is unable to cool its components passively anymore, especially with many modern components requiring more active cooling. In more industrial applications, axial fans can vary in size where fan blades can reach up to 15 meters in diameter. This enables a larger coverage to bring larger volumes of air across a certain area.
Where else do we see the different uses of both centrifugal and axial-type fans? Here are few applications and how fans operate to supplement a certain need or how they offer solutions to process limitations:
Industrial Use and Applications
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- HVAC/Cooling – HVAC (Heating, ventilating, and air conditioning) systems are designed to provide thermal control and create an acceptable indoor air quality. These are essential to environments that require certain health regulations to be followed – to maintain a consistent level of humidity and temperature. Fans, in this regard, are used to mitigate the instances where the temperature may rise and drop. For this purpose, centrifugal fans and axial fans may be used depending on the intention and the amount of pressure needed to provide ventilation or air-conditioning.
- Dedusting – Industrial fans and blowers are used in dedusting applications. That is, in the proper collection, so that work environments are able to reduce pollution and contaminants in the air including to create a safer working condition. Dedusting requires a filtration process to exhaust clean air and avoid particles from entering the airstream. In this application, the process requires high pressure to do so, so most commonly, centrifugal fan systems may be selected for this.
- Exhaust – Especially in production plants that require dealing with hazardous materials and toxic gases, these fume and chemical emissions have to be properly disposed of. Proper handling supposes the safety of all plant workers, all the while, meeting safety regulations and emissions imposed by local and national regulatory bodies. Since the main purpose of this is to draw air out, here you see axial fans may be used to blow.
- Personnel/Workspace – As in large warehouses, being able to supply constant conditioning is key to maintaining an appropriate working condition where small-scale air conditioning becomes costly. Depending on what is required, axial fans can cover a large surface area to deliver higher CFMs, while centrifugal fans are used in tandem with an entire ventilation duct system.
- Process Cooling – This is to facilitate an immediate change in temperature and direct air to flow directed towards the cooling of machineries that have tendencies of overheating. These are the additional tweaks/components that will ensure a process runs efficiently and smoothly end to end.
- Pressure Blowers – These are used mainly in pneumatic-conveying, or the use of air to transport materials through a duct system. For example, in timber processing, sawdust collection is a requirement to ensure this does not collect in the work areas.
The key in knowing how to select the right fan for the application comes with understanding the dynamics of how a fan operates. Given the two types of fans, and how these two differ in system design, this will help enable consumers to decide where a certain fan type may have an advantage over the other.
Furthermore, fans and blowers are regarded in the total system in which it operates. This means that beyond the consideration on how the fan is intended to operate, it is important to understand how it will operate in the duct system as it collects and moves air through and across the different steps of the production process.
In the end, these fan systems have to address a requirement: whether it’s fume control, process efficiency, cooling, or ventilation.
Do you need industrial fans? If yes, check out our fans here. You can also contact us for customized fans for many industries.