Detailed analysis of DC fans
Fan frame, fan blade, bearing, PCB control circuit, drive motor
Rotation speed refers to the rotation speed of the electric fan, usually measured by the number of revolutions in 1 minute, namely: rpm. The speed is related to the number of turns of the electromechanical winding, the diameter of the wire, the outer diameter and the bottom diameter of the fan blade impeller, the shape of the blade and the bearing used. The increase in the speed increases the air volume correspondingly.
The size of the speed value represents the size of the air volume to a certain extent. When the conditions are punctual, the higher the speed, the greater the noise and vibration. Therefore, when the air volume meets the heat dissipation requirements, it should be done as much as possible Use low-speed electric fans.
General speed (take DC axial fan as an example): 2510 electric fan 7000～12000rpm; 3010 electric fan 5000～9000rpm; 4010 electric fan 5000～7000rpm; 5010 electric fan 3500～5000rpm; 6025 electric fan 2600～4500rpm; 7025 electric fan 2400～ 3600rpm; 8025 electric fan 2000～3500rpm; 9225 electric fan 1600～3100rpm; 12025 electric fan 1500～2500rpm; 12038 electric fan 2000～3200rpm.
The speed of the DC cooling fan can be tested by the BIOS when the computer is started, or by the monitoring software that comes with other motherboards; it can also be tested by the speed tester. Note: The first two methods must be tested by an electric fan that supports the speed measurement function.
1. Air volume and pressure of DC fan:
There are two ways to test air volume and wind pressure, one is to test with a wind tunnel instrument, and the other is to test with a double-box method. But for the average user, there is no such device. It can only be based on the data provided by the manufacturer as a reference, and ultimately depends on the cooling effect.
2. Air volume of DC fan:
Air volume refers to the product of the velocity of the fan's ventilating area. The ventilation area is the exit area minus the projected area at the vortex tongue. The plane velocity is the velocity of the gas moving through the entire plane, and the unit is m3/s. When the plane speed is punctual, the larger the outer diameter of the fan blade impeller, the larger the ventilation area, and the larger the air volume. The plane speed is determined by the rotor speed and wind pressure. When the ventilation area is punctual, the greater the plane speed, the greater the air volume. The greater the air volume, the greater the heat absorbed by the air, and the more heat can be taken away by the surrounding energy when the air moves, and the fan's heat effect is more significant.
3. Wind pressure of DC fan:
In order to carry out normal ventilation, it is necessary to overcome the resistance in the ventilation stroke. The electric fan must generate a pressure that overcomes the resistance of the air supply. The measured pressure change is called static pressure, which is the difference between the maximum static pressure and the atmospheric pressure. It is the pressure of gas acting parallel to the surface of an object, and the static pressure is measured through a hole perpendicular to its surface. Converting the kinetic energy required in gas activities into pressure is called dynamic pressure.
In order to complete the purpose of air supply, static pressure and dynamic pressure are required. The total pressure is the algebraic sum of the static pressure and the dynamic pressure. The total pressure refers to the increase in the total pressure given by the electric fan, that is, the total pressure difference between the outlet and the inlet. In practical use, the nominal maximum air volume value is not the air volume obtained by practicing the fan heater. Large air volume does not mean that the ventilation capacity is strong. When the air is moving, the airflow will encounter the obstruction of the fan heat check sheet or the component in its moving path, and its impedance will restrict the free flow of the air. That is, when the air volume increases, the wind pressure will decrease. Therefore, there must be a best operating point, that is, the intersection of the fan performance curve and the wind resistance curve. At the operating point, the slope of the fan characteristic curve is the smallest, and the change rate of the system characteristic curve is the smallest. Note that the static efficiency of the fan at this moment (air volume and pressure power consumption) is the best. Of course, sometimes in order to reduce the impedance of the system, even a small-scale electric fan is used to obtain the same air volume.
Main performance parameters:
The main parameters of the cooling fan include flow, pressure, speed, power, etc...