How Do Centrifugal Fans Work?
Published on 14 Mar 2025
What is a Centrifugal Fan?
Centrifugal fans are a powerhouse in industrial ventilation that ensures smooth operations for cooling systems, air filtration, and material handling by moving air and gases efficiently. Unlike axial fans that push air straight through, centrifugal fans use a spinning impeller to create a powerful airflow that exits at an angle. In this blog, we’ll explore how centrifugal fans work, their key components, and the types available to suit different applications.
A centrifugal fan is designed to move air or gases at a right angle to the intake flow, making it ideal for high-pressure applications. Often referred to as blowers, these industrial fans are built to overcome air resistance while maintaining efficient airflow. Centrifugal fans are commonly used in ducted systems where airflow needs to be pushed through ducts or across heat exchangers.
Centrifugal Force
A radial wheel equipped with curved blades rotates consistently in a drum-like enclosure. These blades, called impellers, draw air or gas into the fan along the wheel's axis. The centrifugal force generated by the impellers accelerates and directs the air or gas through ducts or tubes, exiting at an angle different from its entry point.
Mechanical Elements
Centrifugal fans support industrial processes and ventilation systems because they can efficiently generate high airflow and pressure. Each component ensures that the fan operates reliably and effectively according to its intended application.
- Impeller
- The impeller is the central component of a centrifugal fan that generates airflow with blades that rotate and accelerate air outward from the centre to the fan housing.
- Fan Housing
- The fan housing, also known as the fan casing or volute, encloses the impeller and directs the airflow in a specific direction to smoothly guide the air from the inlet to the outlet.
- Inlet and Outlet
- Air enters the centrifugal fan through the inlet, which captures and directs the incoming air towards the impeller blades. Air exits through the outlet after being accelerated by the impeller and guided through the fan housing.
- Motor
- The motor is typically housed outside the airflow path to avoid being exposed to contaminated air and drives the impeller of the centrifugal fan.
- Bearings
- Bearings support the impeller shaft within the fan housing by reducing friction between rotating parts, which allows the impeller to spin smoothly and efficiently. Bearings in centrifugal fans are designed to handle radial and axial loads produced by the impeller.
- Shaft
- The shaft transmits rotational motion and connects the impeller to the motor. It must be precisely balanced so the impeller can run smoothly and help minimise vibrations that could affect fan performance.
- Mounting Frame
- This frame provides structural support for the entire centrifugal fan assembly by securing the fan housing and internal components and ensuring proper alignment.
Types of Centrifugal Fans
Centrifugal fans are used to support a broad scope of industrial environments, so as varied as industries are, centrifugal fans also come in numerous styles to sustain optimal conditions in unique settings.
Direct Drive
In a direct drive centrifugal fan system, the fan motor is directly connected to a shaft or fan axle to keep the fan blades rotating at the same speed as the motor. This configuration is extra efficient and minimises energy loss by reducing friction. Unlike belt-driven fans, direct-drive models eliminate the need for belts, reducing maintenance costs and preventing belt wear or residue buildup. They are also easier to clean. However, direct-drive fans offer less flexibility in speed adjustments and are often more expensive when compared to belt-driven alternatives of similar size. Furthermore, compared to their belt-driven counterparts, they typically make more noise.
Centrifugal fan
Lagged
Acoustically lagged centrifugal fans minimise radiated noise by featuring a double-skinned casing lined with sound-absorbent material. This built-in insulation effectively reduces noise levels produced by the fan housing. Take RHF Fan's lagged fans as an example. These fans have integrated lagging as a core feature rather than an add-on. This design has a superior finish and performance compared to fans insulated on-site by contractors. These pre-lagged fans offer the highest quality finish available. Additionally, they provide a significant maintenance advantage—if the fan impeller needs to be removed, disassembly is straightforward, requiring only unbolting and reassembly. In contrast, fans lagged on-site and required additional labour and costs to cut insulation away and repair or pat the panels.
Belt Driven
Belt-driven centrifugal fan systems have a motor that operates independently of the fan blades, with one or more belts transferring power to the fan's moving components. The benefit of this setup is added flexibility in adjusting RPM speed and using the pulley ratio provides a more reliable and cost-effective motor. Additionally, belt-driven fans are often more affordable than direct-drive models of similar size and tend to operate more quietly. However, the increased friction between moving parts can result in higher maintenance requirements and greater energy consumption over time.
This special configuration offers a safety net in case of motor failure by including an additional motor and belt system. This feature is incredibly well-liked in fast-food and restaurant businesses, where downtime can significantly impact business operations.
Coupling Drive
Centrifugal fans with a coupling drive are used when the motor bearings are not designed to support direct mounting of the impeller onto the motor shaft. This configuration is often used instead of a direct-driven fan when the fan and motor's physical size make future maintenance a key consideration because the fan and impeller can be removed independently.
UK Specialists in Centrifugal Fans
When selecting a centrifugal fan, you must consider the most suitable and reliable type for your application. As a leading UK-based supplier, RHF Fans offers an extensive range of centrifugal industrial fans designed for superior performance and efficiency with tailored solutions that enhance airflow, improve energy efficiency, and ensure long-term durability. Whether you need a high-pressure fan for demanding industrial applications or a noise-reducing lagged fan, RHF Fans has the expertise and product range to support your operational needs. Contact our fan specialists today to learn more about our range of centrifugal fans.