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How to select an axial flow fan?

From: Quisure2020-08-09

How to select an axial flow fan?

What is an axial flow fan?

When an axial flow fan works, the blade pushes the air to flow in the same direction as the shaft, so it is called axial-flow fan, tube axial fan or axial fan blower. an axial flow fan is very different from a centrifugal fan in the design and function. Therefore, the differences make them each suited for different applications. An axial fans are mainly used for ventilation and heat dissipation of mechanical equipment, such as: electrical cabinet etc.

What are the advantages and disadvantages of an axial flow fan?

No matter how high is the rotating speed of axial-flow fan, there will be no air flow under the center of shaft. However under shaft center of the fan is the main heating source. This situation caused the air flow could not reach the central area smoothly, resulting in a “blind area“. The existence of blind area affects the overall cooling effect. But the advantages are obvious. Structure of axial-flow is simple, price is more acceptable by user, flow rate of air is large, has a wide used as industrial exhaust fan.

How to design air flow system?

It is important measure to force ventilation by axial fan to take away the heat generated of the working equipment system. We should refer to the application environment, operating conditions, temperature, humidity, corrosion, fan control characteristics, noise, air flow pressure, etc. during the cooling system designed stage.

Axial flow fan calculation:

Q=2.99W/Tc  W: Heat dissipated in WATTS  Tc: Allowable temperature in ℃

How to select fan’s pressure?

Equipment designed according to AMCA210 standard, can accurately measure the air flow volume, static pressure and drag system.


Q=60C/4 D2=M2G/R PN (M3/min)

C: Air nozzle coefficient

D: Diameter of nozzle

R: Air density=1.293

T: Temperature

P: Air pressure (mm H2o)

PN: Differential pressure of air volume (mm H2O)

PS: Air static pressure (mm H2O)

G: Gravity acceleration (9.8m/s2)

Test max air flow (0 pressure) and Max static pressure (0 flow)

Adjust the fan speed, test air pressure and air flow, and draw the P-Q curve.

How to determine the working point of fan?

When the air flow system is designed to meet the requirement of the fan, next step, the fan characteristic curve and the air flow system characteristic curve will be selected. How to select? Designers need to test out the drag characteristic curve, the resistance curve and fan characteristic curve of the cross graph, the air flow volume and the air pressure of the intersection meet the requirements of air flow volume and air pressure of the fan cooling system. The axial fan performance curve is as follow;

Axial Fan Curve

The crossed point of fan performance curve and air flow system resistance curve is the best working point of air flow system. This is the determining factor when your select fan.

How to test the level of noise?

When axial flow fan working, a noise meter is set to 1m away from air flow entrance at 90 degree angle.  The tested fan runs in an echo-free room with free air flow and background noise under 15db.

How to select bearing system of fan?

Axial flow fan bearing is an important part to evaluate the performance of the axial fan. it is generally used for sleeve bearing and ball bearing.

According to the requirements, user will select the right fan with different type bearing. The characteristics sheets of the two types of bearings are as follows.

No.ItemsSleeve (S)Ball (B)
1MaterialsCopper based powder metallurgyStainless steel
2FrictionSurface contactPoint contact
3Sealing propertyNo sealing propertyWith dust cover, sealing performance better
4Installation methodSuitable for vertical stallationAny installation method
5Lubricating oilMoreLess
6Speed rangeLow speedHigh speed
7Temperature range10℃ – 70℃-30℃ – 75℃
8Life time20000-30000 hrs30000-50000hrs
9NoiseHigh and instableLower and stable

According to the requirements of the user, the user should select the right fan with different type bearing.

In addition to the above technical factors, users also need to care the axial fan motor, which is a very important core component, it will be introduced in another blog “Industrial exhaust fan installation“. In purchase axial fans, the following business factors need to be considered.

Price: axial flow fan price directly affects the purchase budget of the project.

Manufacturer: it is very important to choose the original manufacturer of axial fans. axial flow fan manufacturers in india, in China and Vietnam. Because the make and supply chain of axial flow fans are relatively mature in Shenzhen, China, a large number of axial flow fan manufacturers are gathered. However, they are generally small in scale, weak in design and innovation, and lack of in quality control, but the price is cheaper. The industrial axial fans manufacturers are mainly located in Chengdu and Shanghai.

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