If the air volume of DC fans is big, the air pressure will be small; while if the air pressure is big, the air volume will be small. High air volume can drive a lot of air to flow; but if the air pressure is small, wind can not blow to the bottom of radiator, so the heat radiation effect is not good; if the air pressure is big, the air volume will be small, and there is no enough cold air for heat exchange with heat sink, so the heat radiation effect is not good.

1. Noise: the noise of fans and the working noise of radiator fans are also quite important indexes. Generally, it is required that the noise of fans shall be as small as possible and there should be no abnormal sound.
2. Air volume: volume is the air volume discharged by the radiator fan per minute and is one of the most important indexes to measure the heat radiation capacity of radiator fans. The radiator fans with higher air volume have better heat radiation capacity.
3. Rotation speed: the rotation speed of radiator fans refers to the number of rotations of fan blades per minute, and its unit is rpm. It is easier to understand.
4. Air pressure: the air pressure and the air volume of radiator fans are completely different and they are relative. The air pressure means the resistance that the radiator fan needs to overcome in the fan ventilation period for normal ventilation.

The radiator fans are generally recommended to select ball bearing, because the service life of radiator fans usually depends on the reliability of their bearing, and the ball bearing system has been proved to have high efficiency and low heat generation. The ball bearing belongs to rolling friction, which is rolled by metal beads with small contact surface and small friction coefficient; while the sleeve bearing belongs to sliding friction with large contact surface. After long-term use, the oil will be volatilized and the bearing wears easily, the friction coefficient is large, late noise is large and the service life is short. The fan with good quality has large ventilation and high air pressure, in addition, has good reliability. So, the form of bearing used by fans is very important.
The ball bearing is uniformly used by high speed fans, while the sleeve bearing of low cost are used by low speed fans. The fan with sleeve bearing only uses a bearing; while the fan with ball bearing needs two bearings. Single ball bearing is “1 Ball + 1 Sleeve”, with the ingredient of sleeve bearing. Two balls bearing is more advanced than single ball bearing. The service life of sleeve bearing is generally 10,000 hours, while that of single ball bearing is 30,000 hours, and that of two balls bearing is more than 50,000 hours (when the ambient temperature is set below 25 degrees Celsius).

The sleeve bearing used by radiator fans is sintered from copper based powder. When using sleeve bearing, it needs to add lubricate so as to reduce sliding friction factor, and the lubricant is made of lithium base grease and special engine oil. With long-time operation, the engine oil in the bearing will be volatilized and dried, the friction coefficient will be large, the fan operation will be effected and abnormal noise may occur, the rotation becomes slower even stops. While the ball bearing adopts rolling friction instead of sliding friction and the friction coefficient is small which overcomes the shortcoming that friction coefficient is easy to change, thus the operation stability is high and the service life is much longer.

Matters need to be notified when using a radiator fan: 

(1) Please do not touch the blade and the power line around the fan or use your hand to pull the power line, which will damage the axle center and power line;

(2) Please avoid dust, water drops and insects from entering so as not to affect the service life and produce defective products;

(3) Please do not use it in the environment with combustible gas or any harmful environment;

(4) Please use it within six months because the long-time storage will affect the performance of the fan due to the storage environment; 

(5) When the fan is in operation, do not attempt to lock it for a long time, which will make the fan burned due to heat generation caused by continuous stop;

(6) When installing the fan, please pay special attention to the noise arising from resonance or vibration; 

(7) When carrying or operating, if the fan falls from the height of 1500px, it will have some influence on the blade balance, especially avoid the ball bearing from falling; 

(8) The torsion of screw used to lock enclosure shall not exceed 4Kgf; please do not use a screwdriver, pontil or other objects to block the fan, which will damage the fan;

(9) Please note that the fan will hurt your fingers when running at high speed.

After careful leaning, you may find the fan has a new look. Then we shall put it back. When installing the fan, you could add some lubricant to the middle axle of the fan, and then reassemble the fan according to the method of disassembly before, finally the fan is cleaned up.