Centrifugal fans or blowers are one of the most efficient and versatile air moving devices. Below are some basic definitions and guidelines for choosing the right centrifugal fan for your system needs.
How Does a Centrifugal Fan Work?
A centrifugal fan is a mechanical device that moves air or other gases in a radial direction using an impeller. The impeller is a rotating component that consists of a hub and several blades. The hub is attached to a motor, and the blades are positioned in such a way as to create a circular flow of air.
When the impeller rotates, it generates centrifugal force, which pushes air outward from the center of the fan. This results in a high-speed flow of air that is expelled through the outlet of the fan.
The design of a centrifugal fan can be optimized for various applications, such as ventilation, cooling, or air conditioning. By controlling the speed of the impeller, the volume and pressure of the air flow can be adjusted to meet specific requirements.
Centrifugal fan parameters
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Flow (CFM)
If you are transporting material, make sure you have enough CFM for the pipe, pipe or hose size so that the material maintains the required velocity to travel completely through the system without settling in the pipe, pipe or hose.
SCFM stands for Standard Cubic Feet per Minute. It is the CFM at standard density, defined as .075 lb/cubic foot.
ACFM stands for Actual Cubic Feet per Minute. It is the CFM at an identified density other than .075 lb/ft3. Since fans and blowers handle the same volume of air regardless of density, the ACFM value (and corresponding density) is the preferred value to use when selecting a fan or blower. Note that ACFM and SCFM are not interchangeable except at 0.075 lb/ft3 density.
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Static pressure (SP)
Static pressure is the resistance to airflow (friction) that occurs when air flows through a duct, duct, hose, filter, hood slot, air control damper, or louver. Static pressure is in inches of water gauge (SPWG).
Standard air has a density of .075 lb/ft3 and is based on a temperature of 70°F and 29.92" Hg barometric pressure (sea level). Fan performance tables are based on using standard air. Corrections for density changes resulting from temperature and/or barometric pressure variations, such as higher altitudes, must be made to the static pressure before selecting a fan or blower based on standard performance data. The metric equivalent is in kilograms per cubic meter (kg/m3). lb/ft3 = 16.018 x kg/m3.
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Air/Gas Density
Altitude can have a large effect on air density. And, the fan airflow is the same regardless of the air density.
When the air density differs from the standard air density, the system pressure and fan motor to air density ratio change proportionally.
Types of centrifugal fans
Centrifugal fans and blowers are one of the most efficient air flow devices, and you need to choose the right type of centrifugal fan for your system.
There are four basic types of centrifugal fans, each with its own specific purpose.
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Radial centrifugal fan
These are high pressure fans with moderate airflow. Radial blade fans are best suited for dusty industrial applications, or environments with gas or moisture in the air.
These centrifugal fans are best suited for medium pressure and medium volume applications with stable flow requirements as they can also be overloaded. Due to the robust construction of the wheel, it is suitable for applications where the airflow is corrosive or contains materials. Applications include conveying powdered or granular materials and filamentous confetti or fibers.
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Forward Curved Centrifugal Fan
Forward Curve Centrifugal Fans These are medium pressure, high airflow fans for clean air, ventilation and exhaust applications.
They are best suited for applications requiring constant airflow under low static pressure conditions. Because forward-leaning wheels can overload, they are not recommended for variable flow applications. One of the best properties of a forward-leaning wheel is that it produces the same volume of air at a lower speed at a lower speed than a backward-leaning or radial wheel, so it is quieter. For these reasons, forward tilt wheels are widely used in residential and commercial air conditioners. Other applications include oven and dryer venting, and process drying and cooling.
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Backward Curved Centrifugal Fan
Backward Curve Centrifugal Fans These are high pressure, high flow, high efficiency fans. As the flow in the most efficient area of the system increases, the power decreases.
They are more energy efficient than the other two types of wheels, and with curved or airfoil blades, they can approach the efficiency of an axial fan. The back-tilted wheels do not overload or stall, making them ideal for variable flow applications. Common applications include dust collectors, fume extractors and emission control systems.
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Airfoil centrifugal fan
These are the most efficient fans and are best suited for clean air applications.
Application environment of centrifugal fan
The application environment and working state of your centrifugal fan will seriously affect the life, efficiency and subsequent maintenance costs of your centrifugal fan and system.
Therefore, you need to carefully consider the application environment of your centrifugal fan.
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Air quality
Air quality can affect the life and efficiency of centrifugal fans, and even threaten the safety of the system. So we list a few common examples and applications:
Clean Air Consider forward-bend, rear-bend, or airfoil fans for greater efficiency.
For slightly dusty air consider radial or high pressure blowers. For very light, non-abrasive dusts, a backward-curved fan can be used.
Heavier, more abrasive dust, filings and shavings For this environment, you may need an industrial material handling blower.
Corrosive In wet, humid, corrosive environments, you should choose stainless steel fans, preferably stainless steel cleaning motors.
Combustible If there is combustible dust or particles in the air, choose a non-sparking fansuch as a radial or high pressure fan with an explosion-proof motor.
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Density
Density changes due to changes in temperature and/or air pressure should be corrected for standard conditions.
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Air temperature
The temperature of the air passing through the fan or blower can affect the performance of the fan or blower.
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Altitude
The altitude at which the fan or blower operates can also affect the performance of the fan or blower.
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Material handling
If the material will be conveyed by a fan or blower, the material characteristics should be considered.
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Ambient temperature
The air temperature or ambient temperature outside the fan or blower can affect the operation of the fan or blower.
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Safety conditions
Special accommodation may be required if any material passing through the fan is flammable or combustible.
Conclusion
Centrifugal fans are a critical part of the air system, and choosing the right centrifugal fan is critical.
You need to carefully consider the important parameters and ask your centrifugal fan manufacturer in detail, they will provide you with detailed centrifugal fan information and reference.
If you are looking for a suitable centrifugal fan manufacturer, please contact us.
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