Centrifugal vs Axial Fans

  • Ja Redden
  • June 28, 2024
  • Blogs
JA Redden Pte. Ltd.
Industrial fan manufacturers play a crucial role in various industries. Yet, their exact function often needs to be clarified in the market. The term "industrial fan" lacks a precise definition, leading to confusion about its true purpose and application. This article aims to uncover the concept of centrifugal and axial fans, clearly explains what they are, and addresses several other related questions. This discussion seeks to offer comprehensive insights into the world of industrial fans, ensuring that the reader gains a thorough understanding of their importance and usage. To delve deeper, we will explore these fans' diverse roles in different industrial settings. Understanding the functionality and significance of industrial fans is essential for comprehending their impact across various sectors.  

The Two Basic Types of Industrial Fans

Industrial fans come in two fundamental types: Axial and Centrifugal Fans. But these two categories encompass a wide array of fans and blowers, each falling under different classifications such as Industrial Blowers, Industrial Ventilation Fans, Exhaust Blowers, and Industrial Exhaust Fans. Terms like HVAC fans and blowers are also commonly used. Despite the variety of names and classifications, all these devices can be broadly categorised as axial or centrifugal fans.  

1. Axial Flow Fan

Axial flow fan is commonly utilised for moving air. Imagine a ceiling fan or a small desk fan; these are everyday examples of axial flow fans. The key characteristic of regular and axial flow fans is that the air flows in a direction parallel to the fan's rotor shaft. It is the axis around which the fan's blades rotate. In simpler terms, this fan type draws air from behind it and then pushes it out in front, in the same direction as the spinning blades. This is distinct from other fans. High-speed axial fans are widely used for their simplicity and effectiveness in moving large volumes of air. They are often found when the primary requirement is significant airflow, such as ventilation systems, cooling computers, or large industrial applications. Their design can vary in size, from tiny fans used in electronics to massive fans used in wind tunnels. Key technical aspects that interest those looking to research further include blade design, airflow rate, pressure generation, and efficiency.
Axial flow fan Diagram
 

2. Centrifugal Fan

Sometimes known as blower, this fan is commonly used in various settings and distinguished by its unique method of moving air. Unlike axial flow fans, where the air moves along the axis of the fan, the blower draws air into the centre of the fan and then expels it at a 90-degree angle. The design of this fan is like a hamster wheel. It consists of a rotating set of blades and an impeller enclosed in a casing. The air enters the fan wheel through the central hole, is caught by the impeller blades, and is flung outward due to centrifugal force to the fan's outlet. This design allows centrifugal fans to generate higher pressures, making them suitable for applications that require air to move through resistance, like air conditioning systems, industrial ventilation, and various air pollution control systems. Fans under centrifugal design are appreciated for their versatility in different performance conditions and ability to handle air with particulates. Key technical aspects for further research may include impeller design, efficiency, pressure head, and noise levels.
Centrifugal Fan Diagram
 

Comparing Centrifugal and Axial Flow Fans

When comparing a centrifugal to an axial fan, with equal flow and pressure, the former exhibits several distinct characteristics:
  • It features a smaller impeller diameter.
  • It generates higher dynamic pressure.
  • It operates at a considerably higher speed, both in terms of operating and specific speed (considering equal Q and P).
  • The peripheral speed is greater.
  • It has lower efficiency, leading to increased power consumption.
  • It tends to be noisier.
  • It is considerably more compact, lighter, and more cost-effective.
When comparing centrifugal and axial flow fans, the main factors are weight, operational speed, and noise levels. Fans manufactured axially can achieve similar airflow and pressure characteristics at higher operating and peripheral speeds than centrifugal fans. However, there are limits to the stress that rotating parts can endure, which affects their speed. Consequently, centrifugal flow fans are generally more adept at generating higher pressures. A notable disadvantage of axial flow fans is their noise; they frequently require silencers to mitigate sound, whereas blowers typically do not need them. Axial flow fans are commonly used in low-pressure environments (up to 100 mmWg). Regarding efficiency, they are comparable to centrifugal (or radial) fans, especially for large-sized fans. Another advantage of high-speed axial fans is their design, facilitating easy system integration. They can seamlessly fit into existing pipelines as part of the ductwork. At the same time, centrifugal flow fans often necessitate more complex and costly installation. Centrifugal flow fans can have a single width suction inlet (SWSI) or double width suction inlet (DWDI). A DWDI fan, with identical size, speed, and pressure specifications, can handle double the capacity and consumes twice the power of a SWSI fan. It's important to note, however, that the casing size of a DWDI fan is not always double that of a SWSI fan.  

Types of Axial Flow Fans

1. Tube axial Fans

Tube axial fans consist of a wheel positioned inside a cylindrical housing, designed with minimal clearance between the blade and housing to enhance airflow efficiency. These fans rotate faster than propeller fans and can operate under higher pressures, typically ranging from 250 to 400 mmWg. Their efficiency can reach up to 65%. Tube axial fans are well-suited for scenarios where high-efficiency airflow is needed.
Tube Axial Fan Diagram
 

2. Vane axial Fans

Vane axial fans are like tube axial fans but include additional guide vanes. These vanes help direct and straighten the airflow, increasing efficiency. Ideal for commercial and industrial applications, these fans are designed to handle large volumes of air at moderate to high pressures. Vane axial fans are among the most energy-efficient options. They are broadly used for heat, smoke, fume removal, process drying, cooling, and general ventilation.
Vane Axial Fan Diagram
 

3. Propeller Fans

Operating typically at low speeds, these fans can move large volumes of air at low pressure, making them suitable for indoor exhaust and outdoor applications like air-cooled condensers and cooling towers. However, their efficiency is relatively low. They are sensitive to changes in static pressure, leading to significant airflow variation.
Propeller Fan Diagram
 

Specialised Axial Fans: Bifurcated Fans

Bifurcated fans are a unique type of axial flow fan designed to isolate the electric motor and support from the airflow. This separation is crucial in environments where the air contains corrosive elements or has high temperatures, as it protects the motor and supports it from damage. This fan is typically used for extracting hot fumes in environments with high humidity and grease, such as kitchens, painting booths, furnaces, and foundries. Cross-ventilation for the electric motor or supports is often incorporated for high-temperature applications.
Bifurcated Fan Diagram
 

Understanding Industrial Fan Selection

Choosing the right industrial fan, whether centrifugal or high-speed axial fan, involves carefully looking at the needs of the place where the fan will be used and understanding the specific features of the fan you're interested in. The fan supplier must share detailed information to ensure the fan matches the buyer's needs. The fan supplier's job is more than just selling a product and understanding customer needs. This means figuring out how much air the fan needs to move (its flow rate) and how strong it needs to push this air (its pressure). Customers need to know their system’s requirements, whether an axial flow fan or a centrifugal fan. The fan's job is to move air or another fluid at a specific rate, measured by how much there is of it over time and at a certain pressure, often measured in Pa (Pascals) or mmWg (millimetres of water). This pressure is needed to push the air through any obstacles or resistance. The fan gets power from an electric motor, but not all is transferred directly to the air. This is because not all machines are 100% efficient; there's always some loss of power. So, the motor's power to the axial or centrifugal fan is always more than what gets used to move the air. The efficiency of a fan is about how much of this power is successfully used to move the air.  

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Looking for the perfect industrial fan solution? Contact us now at +(65) 6451 6168 or email sales@jaredden.com.sg. JA Redden’s expert team is ready to understand your specific needs and guide you to the best choice. Don't wait any longer to enhance your system's efficiency with our top-quality axial and centrifugal fans. Reach out today—we're here to help you every step of the way!

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