Centrifugal Fans: The Three Main Types
There are three main types of centrifugal fan, based on the design of their impeller:
• Forward curved – facetiously dubbed the ‘hamster wheel’ type. These fans have the greatest specific output relative to their size, but often at the cost of efficiency.
• Backward curved – these are generally much more efficient than their forward-curved counterparts but are larger and less compact.
• Radial – these centrifugal fans are simple, robust and capable of working against high resistance.
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Which Type Of Fan Is Best For My Application?
You’ll find more information on the pros and cons of each type of centrifugal fan in this blog post. Meanwhile, let’s explore their benefits and disadvantages based on the factors you’ll need to consider when specifying a fan for your application…
Space: Will Your Centrifugal Fan Fit?
You probably saw the news story about Spain spending €258 million on trains that were too big for its railway tunnels. Granted, it’s not a fan-related example, but it does hit the nail squarely on the head – your new kit has to fit!
And as the main elements of the production line expand within a finite area of available factory space, so there becomes less room for add-ons such as blowers and their associated ducting. This can be frustrating if you need to upgrade your fan because a faster production line has created the need for greater air delivery.
But don’t despair – some very compact centrifugal blowers are now available. These are mostly forward-curved centrifugal fans because they tend to be more compact than their backward-curved counterparts.
Radial fans tend to have large-diameter impellers capable of delivering high volumes of air even when working against significant resistance. This can be an advantage if duct diameter is restricted.
Temperature: How Hot Is The Air You Need To Move?
Heat is the enemy of fan motors: it reduces their longevity. Hot air can damage the bearings of electric motors by causing lubrication breakdown – leading to accelerated wear and premature failure.
Excessive heat will also cause deterioration of the winding insulation. It is commonly said that the insulation lifespan is halved for every 10 degrees C of excess heat above the maximum rated temperature.
Where there is a requirement to process hot air within a fan, a heat spinner can be used to prevent damage to the motor. A heat spinner will help dissipate the heat propagating up the motor shaft.
Heat spinners are simple and effective. The hotter they get, the more efficiently they work. When used in combination with insulative materials, they can be employed to great effect to protect a fan’s motor.
Noise: Which Centrifugal Fans Are Quieter?
Backward-curved centrifugal fans tend to be quieter than forward-curved units because of the efficient design of the impeller blade.
In a forward-curved centrifugal fan, the blades curve in the direction of rotation. This creates a greater movement of air but also generates more noise due to the turbulence caused by the airflow around the blade edges.
But in a backward-curved centrifugal fan, the blades curve away from the direction of rotation . This results in less turbulence – which in turn reduces the amount of noise generated by the fan.
Additionally, backward-curved centrifugal fans are often designed with larger impeller diameters and lower rotational speeds, contributing to their quieter operation. These design features allow the fan to move a significant amount of air at fewer decibels, making them ideal for applications where noise reduction is a priority.
Radial fans can be noisier than the other two types because they push larger volumes of air at significant velocity through a narrower discharge point.
Worried that your preferred fan may be too noisy for your application? We can create an enclosure to help reduce noise.
Air Quality: Which Type Of Centrifugal Fan Copes Better With Particles?
Not all air is clean – some airflows contain blown particles that can cause damage or wear over time.
Backward-curved or radial centrifugal fans tend to cope better with this because the lower number of blades reduces the likelihood of objects colliding with the impeller. The other contributory factor is that the design of backward or radial fan blades means they do not hold dust or abrasive particles.
Forward-curved centrifugal fans have impeller blades that can catch and hold debris, making these suitable for filtered or cleaner air applications only.
Fans can be equipped with air filters to further improve air quality. These filters are designed to remove small particles and contaminants from the air stream, providing additional protection against airborne pollutants.
The key factor to consider when selecting a filter is the airflow rate of the fan. Different types of filters have varying levels of resistance to airflow; this can affect the fan’s performance and efficiency.
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