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How can you design a cooling fan to be noise-reducing?

Category:

Industry Trends

Release time:

2019-11-25

How to design Cooling fan How to prevent noise
1. Principle of noise generation in cooling fans:
What causes noise from cooling fans? The central shaft of a fan consists of a shaft and bearings. The center of gravity of the entire fan is slightly offset from the central axis at a certain angle. Initially, the fan is lubricated by oil, but after prolonged use, as the fan spins at high speeds, it starts to vibrate up and down, generating noise.
Moreover, as usage time increases, friction between the shaft and bearings will inevitably lead to vibrations, which in turn will generate noise. The higher the frequency, the more powerful the accessories we use; the faster the rotational speed, the greater the fan noise we’ll have to contend with.
The cooling fan is a key component of air-cooling systems and plays a crucial role in determining their cooling performance. However, the quality of a fan largely depends on the type of bearing used. Of course, other factors such as fan speed and blade characteristics (diameter, weight, blade angle, shape, etc.) also influence its performance. Currently, fans can be classified—based on their shaft orientation and airflow direction—into axial-flow fans and centrifugal (or radial-flow) fans. Centrifugal fans are also known as centrifugal blowers. They utilize centrifugal force to drive air radially along the blades, thereby achieving heat dissipation. This type of fan is primarily used in hard-drive and CPU coolers and is relatively rare on the market. Axial-flow fans, on the other hand, are the most common and mainstream products available on the market. Typically, their fan blades are directly connected to the motor, and the lift generated by the blades causes air to flow axially for effective heat dissipation.
2 Ways to Reduce Fan Noise
(1) Pay attention to fan selection:
For fan products that are used frequently, the faster the rotational speed, the better the cooling performance—but of course, the louder the noise. When we’re shopping, we can hold the fan close to our ears and listen carefully. If we can clearly hear the fan’s noise, we’d advise against purchasing such a product. Additionally, under normal conditions, fans with relatively larger diagonal lengths are worth considering. This is because, to achieve the same cooling effect, a larger fan needs to rotate at a lower speed than a smaller fan, resulting in comparatively less noise.
(2) Enhance the “lubrication” of the fan.
Due to the low oil prices, most computers use motorized cooling fans with oil-lubricated bearings. After a period of use, these fans need to be re-oiled. Otherwise, the coefficient of friction will increase significantly, resulting in noticeably “noisy” operation and resonance in the chassis.
The method for lubricating the fan motor is very simple: Remove the cooling fan from the heatsink, then peel off the sealing tape on the back of the fan. At this point, you’ll see the oiling hole at the center of the fan. After dropping a few drops of lubricant (you can use sewing machine lubricant) into the oiling hole, reattach the sealing tape to the fan.
(3) “Slow down” to reduce noise:
By reducing the fan speed, it is possible to effectively lower—or even completely eliminate—the noise intensity. Currently, the market offers... Cooling fan Manual and automatic speed controllers. The automatic controller can automatically adjust the fan speed (equipped with a thermal probe) based on the temperature of the central processing unit’s heatsink. Once installed, there’s no need to open the case again. However, manual speed controllers typically offer only three settings—normal, medium, and low—and each time you use the manual speed controller, you’ll need to open the chassis.
(4) Use a “replacement” radiator:
The so-called replacement radiator refers to substituting traditional “air-cooled” radiators with ultra-large-area radiators, heat pipes, liquid-cooled radiators, and the like.
Ultra-large-area heatsink: By replacing the air-cooled heatsink with an ultra-large-area heatsink, we eliminate the noisy cooling fan, but we must use a heatsink that is several times larger than the previous one to achieve adequate cooling.
2) Heat pipe radiator:
A heat pipe leverages the physical principle that water and gases continuously absorb and release heat during phase transitions to transfer thermal energy. Its exceptional thermal conductivity enables it to transfer heat from the bottom to the top of the heat pipe at an extremely rapid pace. This outstanding thermal conductivity prevents heat from accumulating in the heated component and ensures that heat is evenly distributed throughout every fin of the heatsink. Thanks to its excellent thermal conductivity, the entire heatsink requires only minimal air convection to function effectively.
3) Water-cooling circulation system:
The liquid-cooling system uses water circulation for heat dissipation. We often see many DIY experts using liquid-cooling devices in overclocking tests. However, since the system still includes fans, there’s still some noise generated. Moreover, liquid cooling isn’t widely adopted because adequate protective measures must be taken to prevent leaks. At the same time, liquid-cooling radiators are not inexpensive and their installation is relatively complex. Although they deliver top-notch cooling performance, they’re not ideal for novice users.

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