Technical indicators Air volume

Air volume refers to the total volume of air discharged or taken in by the cooling fan per minute. If calculated in cubic feet, the unit of air volume is CFM; if calculated in cubic meters, it is CMM. The air volume unit often used by cooling fans is CFM (about 0.028 cubic meters per minute).
The air volume is the most important index to measure the cooling capacity of the cooling fan. Obviously, a cooling fan with a larger air volume has a higher cooling capacity. This is because the heat

capacity ratio of the air is constant, and a larger air volume, that is, more air per unit time can take away more heat. Of course, under the same air volume, the heat dissipation effect is related to the flow mode of the wind.

Technical indicators Wind pressure

Wind pressure and air volume are two relative concepts. Generally speaking, in order to save costs, manufacturers need to sacrifice some wind pressure if they want to design a fan with a large air volume. If the fan can drive a large amount of air flow, but the wind pressure is small, the wind will not blow to the bottom of the radiator (this is why some fans have a high speed and a large air volume, but the cooling effect is not good), on the contrary, Large wind pressure often means that the air volume is small, and there is not enough cold air to exchange heat with the heat sink, which will also cause poor heat dissipation.

Technical indicators Wind speed

The fan speed refers to the number of times the fan blades rotate per minute, and the unit is rpm. The fan speed is determined by the number of turns of the inner coil of the motor, the operating voltage, the number of fan blades, the inclination angle, the height, the diameter and the bearing system. There is no necessary relationship between speed and fan quality. The rotational speed of the fan can be measured through the internal rotational speed signal, and can also be measured externally.
As the application conditions and ambient temperature change, fans with different speeds are sometimes required to meet the requirements. Some manufacturers have specially designed cooling fans with adjustable fan speed, which are

divided into manual and automatic. Manual is mainly to allow users to use low speed to obtain low noise in winter, and use high speed to obtain good heat dissipation in summer. Automatic temperature-adjusting radiators generally have a temperature control sensor, which can automatically control the speed of the fan according to the current working temperature. Keep an optimal combination point with the heat dissipation effect.

Technical indicators Wind noise

In addition to the heat dissipation effect, the working noise of the fan is also a common concern of people. Fan noise is the amount of noise generated by the fan when it is working. It is affected by many factors and the unit is decibel (dB). The noise of the fan needs to be measured in

an anechoic room with a noise less than 17dB, one meter away from the fan, and aligned with the air inlet of the fan along the direction of the fan shaft, and measured by A-weighted method. The spectrum characteristics of fan noise are also very important, so it is also necessary to use a spectrum analyzer to record the frequency distribution of fan noise. Generally, it is required that the noise of the fan should be as small as possible, and there should be no abnormal sound.
Fan noise is related to friction, air flow. The higher the fan speed and the greater the air volume, the greater the noise will be. In addition, the vibration of the fan itself is also a factor that cannot be ignored. Of course, the vibration of a high-quality fan will be very small, but the first two are difficult to overcome. To solve this problem, we can try to use a larger size fan. Under the condition of the same air volume, the working noise of a large fan at a lower speed is smaller than that of a small fan at a high speed. Another factor that we tend to overlook is the bearing of the fan. Due to the friction and collision between the shaft and the bearing when the fan rotates at high speed, it is also a major source of fan noise.