Air volume
Air volume refers to the total volume of air released or incorporated by the cooling fan per minute. If measured in cubic feet, the air volume unit is CFM; And if you do it in cubic meters, that's the CMM. The ventilation fan is often used in CFM (about 0.028 cubic meters per minute).
Air volume is the most important measure of heat dissipation capacity. Obviously, the larger the air volume, the higher the heat dissipation capacity of the fan. That's because the heat capacity ratio of the air is a certain, larger air volume, which is that more air per unit of time can take away more heat. Of course, the cooling effect is related to the flow of wind in the same amount of air.
Wind pressure
Wind pressure and air volume are two relative concepts. Generally speaking, in the consideration of the cost of the manufacturer, to design the fan's air volume, some wind pressure will be sacrificed. If the fan can bring a lot of air flow, but the wind pressure is small, the wind is less than the bottom of the radiator (this is why some of the fan speed is high, volume is very big, but it is the reason why cooling effect is not good), on the contrary, the wind is often means that the air volume is small, there is not enough air and heat sink for heat exchange, also causes the cooling effect is not good.
Fan speed
Fan speed is the number of times the fan blade rotates per minute, in RPM. Fan speed is determined by the number of turns, working voltage, fan blade number, inclination, height, diameter and bearing system of the motor coil. There is no necessary connection between speed and fan quality. The fan's speed can be measured by internal rotating speed signals or by external measurements.
As the application and environment temperature change, different speed fans are needed to meet the demand. Some manufacturers have designed a cooling fan that can adjust fan speed, break up and automatic two kinds. The main manual is to let the user can use low speed to obtain low noise in winter, use high speed to obtain good heat dissipation effect in summer. Automatic temperature radiator with a temperature sensor, according to the current working temperature automatic control fan speed, high temperature, improve the speed, low temperature, reduce the speed, in order to achieve a dynamic balance, so that the wind noise and cooling effect to keep a best combining site.
Fan noise
In addition to the cooling effect, the work noise of fans is also a common concern. Fan noise is the size of the noise produced by the fan, which is affected by several factors, including dB (dB). When measuring the noise of the fan needs in the sound attenuation of noise is less than 17 db and fan, one meter distance along the direction of the fan rotor on the fan air inlet, measured using A weighted way. The fan noise spectrum characteristics is also very important, so you also need to use spectrometer to record the noise of the fan frequency distribution, generally requires little as far as possible, the noise of the fan and cannot exist different sounds.
Fan noise is associated with friction and air flow. The higher the fan speed, the larger the air volume, the more noise will be caused, and the vibration of the fan itself cannot be ignored. Of course, the high quality fan's own vibration will be small, but the first two are insurmountable. To solve this problem, we can try to use a larger fan. In the case of the same air volume, the working noise of the large fan at lower speed is smaller than that of the small fan at high speed. Another factor that we tend to overlook is the fan's bearings. It is also a main source of fan noise because of the friction between the shaft and the bearing during the high-speed rotation of the fan.