Micro cooling fan manufacturers tell you: What are the technical indicators of cooling fans ? The following Juwang Electronics will explain:
Air volume refers to the total amount of air that is expelled or absorbed by a cooling fan per minute. Air volume units are CFM if calculated in cubic feet or CMM if calculated in cubic meters. The commonly used air volume unit for cooling fans is CFM (about 0.028 cubic meters per minute). Air volume is an important indicator to measure the cooling capacity of the cooling fan. Obviously, the larger the air volume, the higher the cooling capacity of the cooling fan. 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, in the case of the same air volume, the heat dissipation effect is related to the flow of the wind.
Wind pressure and wind pressure are two relative concepts. Generally speaking, in the case of manufacturers considering cost savings, it is necessary to sacrifice some wind pressure when designing a fan with a large air volume. If the fan can drive a lot of airflow, 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 If the air volume is small, there is not enough cold air to exchange heat with the radiator, which will also cause poor heat dissipation.
speed of the fan
Fan speed is the number of times the fan blades rotate per minute, in 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 angle of inclination, the height, the diameter and the bearing system. There is no necessary connection between speed and fan quality. The rotational speed of the fan can be measured by an internal rotational speed signal, or it can be measured externally.
As application conditions and ambient temperature change, fans with different speeds are sometimes required to meet the needs. Some manufacturers have specially designed cooling fans with adjustable fan speed, which are divided into manual and automatic. The main purpose of manual is to let users use low speed for low noise in winter and high speed for good cooling in summer. The thermostatic 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 is increased, and when the temperature is low, the speed is reduced to achieve dynamic balance and reduce wind noise. Keep a better combination with the heat dissipation effect.
Fan noise In addition to the cooling effect, the working noise of the fan is also a common concern. Fan noise is the amount of noise generated by the fan when it is working. It is affected by many factors and is measured in decibels (dB). When measuring the fan noise, it needs to be carried out in an anechoic room with noise less than 17dB, one meter away from the fan, and aligned with the fan inlet along the fan axis, and the A-weighted method is used for measurement. The spectral characteristics of fan noise are also important, so a spectrum analyzer is also required to record the fan noise frequency distribution. Generally, the noise of the fan should be as small as possible, and there should be no abnormal noise.
Fan noise is related to friction and airflow. The higher the fan speed, the greater the air volume and the louder the noise. In addition, the vibration of the fan itself is also a factor that cannot be ignored. Sure, a high-quality fan will have very little vibration, but the first two are hard to overcome. To solve this problem, we can try to use a larger size fan. Under the same air volume, the working noise of the large fan at low speed is smaller than that of the small fan at high speed. Another factor we tend to ignore is the fan's bearings. When the fan rotates at high speed, there is friction and collision between the shaft and the bearing, so it is also the main source of fan noise.