To judge the quality of a fan, we have to talk about the common technical indicators of the cooling fan, including air volume, air pressure, fan speed, and fan noise.

Air volume:

Air volume refers to the total volume of air discharged or taken in by the cooling fan per minute. If it is calculated in cubic feet, the air volume unit is CFM; if it is 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). Air volume is the most important indicator to measure the heat dissipation capacity of a cooling fan. Obviously, the larger the air volume, the higher the heat dissipation capacity of the cooling fan. This is because the heat capacity ratio of the air is constant, and the greater the air volume, that is, the more air per unit time can take away more heat. Of course, the heat dissipation effect is related to the way the wind flows under the same air volume.

Wind pressure:

Wind pressure and air volume are two relative concepts. Generally speaking, in consideration of cost-saving by the manufacturer, to design a fan with a large air volume, some air pressure must be sacrificed. If the fan can drive a large amount of air flow, but the wind pressure is small, the wind cannot blow to the bottom of the radiator (this is why some fans have high speed and large air volume, but the heat dissipation effect is not good). On the contrary, High 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.

Fan noise:

In addition to the heat dissipation effect, the working noise of the fan is also a common concern. Fan noise is the size of the noise generated by the fan when it is working, which is affected by many factors, and the unit is decibels (dB). When measuring the noise of the fan, it needs to be carried out in an anechoic room with a noise of less than 17dB, one meter away from the fan, and aligned with the fan's air inlet along the direction of the fan's shaft, and the A-weighted method is used for measurement. The spectral characteristics of fan noise are also very important. Therefore, it is also necessary to record the frequency distribution of fan noise with a spectrum analyzer. Generally, the fan noise is required to be as small as possible, and there should be no abnormal noise. Fan noise is related to friction and air flow. The higher the fan speed and the greater the air volume, the greater the noise caused, and 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 fan. When the air volume is the same, the working noise of a large fan at a lower speed should be smaller than that of a small fan at a high speed. Another factor that we easily overlook is the bearing of the fan. As the fan rotates at a high speed, there is friction and collision between the shaft and the bearing, so it is also a major source of fan noise.

speed of the fan:

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 coil in the motor, the operating voltage, the number of fan blades, the inclination angle, the height, the diameter and the bearing system. Speed and fan quality are not necessarily related. The speed of the fan can be measured by the internal speed signal or externally. As the application situation and the ambient temperature change, fans with different speeds are sometimes required to meet the demand. Some manufacturers have deliberately designed cooling fans with adjustable fan speed, which are divided into two types: manual and automatic. The main purpose of manual is to allow users to use low speed in winter to get low noise, and use high speed in summer to get good heat dissipation effect. The automatic temperature control radiator generally has a temperature control sensor, which can automatically control the fan speed according to the current working temperature. When the temperature is high, the speed will be increased, and when the temperature is low, the speed will be reduced to achieve a dynamic balance, thereby allowing wind noise. Maintain an optimal combination with the heat dissipation effect.