The cooling fan brand tells you that the bigger the cooling fan, the better.mini fan heater Production

　　The cooling fan can be said to be the standard configuration of the computer case. Almost every computer is equipped with a cooling fan to ensure that the components inside the computer can operate normally and are not affected by heat. Many people have always had a feeling that the bigger the chassis cooling fan, the better and more powerful. So is the truth really what everyone thinks it is? The cooling fan brand tells us that this is not the case.

　　Fans are very familiar to us. When we are young, we will send gusts of cool breeze every summer, accompanying us through every sweltering heat in our lives.

　　For computers, fans are even more indispensable. Whether it is the case of relieving the old and the new, or the forced cooling of the CPU/GPU, or the visual impact of Ambilight, the fan has a heavy responsibility.

　　The fans used in the computer are all DC fans (the following fans refer to this), and its operating principle is also very simple. When a conductor passes current, a magnetic field will be generated around it. If the conductor is placed in another magnetic field, suction or repulsion will be generated. So let the object move, that is, Ampere's right-hand rule. I have learned physics in middle school, so I won't go into details. This time, I mainly look at some common indicators of DC fans, which are used in the selection and use of fans.

　　From the performance data, the fan has 4 key parameters, namely air volume, air pressure, speed and noise. Of course, the fan blade shape, motor bearing and fan frame are also affected by the fan performance.

　　A good fan can be sold for hundreds of dollars, the ordinary range is 30-80 yuan, and the cheapest 5 yuan has free shipping. It can be seen that the middle is quite particular.

　　1 Air volume

　　Air volume = Average wind speed? Wind passing area

　　Air volume is one of the most basic indicators. It is not limited by the size and structure. It refers to the volume of air passing through the air passage area per unit time. The air passage area is basically equal to the area of the outer frame of the fan minus the area of the inner frame of the motor part.

　　The air volume is generally expressed by CFM (cubic feet per minute, cubic feet per minute), and a few people will use m3/min, and the air volume of a 12cm fan is mostly between 30-80CFM.

　　Obviously, when the average wind speed is constant, the larger the diameter of the fan, the larger the air passing area, the larger the air volume, and the more air participating in the heat exchange. In most cases, the heat dissipation effect is more obvious.

　　However, it is also not advisable to blindly pursue air volume, because there is also a "wind pressure" closely related to it that we have to worry about.

　　1 Wind pressure

　　If the air volume refers to the total amount of air that participates in heat exchange per unit time, then the wind pressure determines the position that the air can reach. To be precise, the wind pressure is the pressure difference between the air outlet and the air inlet. In layman's terms, the wind pressure defines how far the wind can blow. Since the pressure difference described by the wind pressure is relatively small, it is generally in the unit of water column. That is, mmH2O (millimeter water column), and the wind pressure of a 12cm fan is mostly between 0.3-1.0mmH2O.

　　The wind pressure mainly depends on the shape, area, height and speed of the fan blade. The influence of the first three is more complicated, and the relationship with the speed is very simple. Under the same conditions, the faster the speed, the greater the wind pressure.

　　The air volume and air pressure are mutually restrictive. Under the condition of constant speed, the larger the air volume, the smaller the air pressure. The greater the air pressure, the smaller the air volume. The degree of restriction between them depends on the shape of the fan blades and the overall structure. , the following is a typical air volume - air pressure characteristic diagram.

　　In our daily application, the choice of a fan with a large air volume or a high air pressure depends on the actual situation. For example, the front fan of the chassis should be selected with a large air pressure, so that the cold air can be blown as far as possible into the interior of the chassis, while the rear fan You can choose a fan with a large air volume to allow more hot air to be discharged out of the chassis, such as a radiator with dense fins or a thicker radiator. The matching fan also has certain requirements for wind pressure.

　　1 speed

　　The rotational speed refers to the number of turns of the fan blades per minute, and the unit is rpm (revolutions per minute). But the noise will also be louder.

　　The fan speed is determined by the motor, operating voltage, the number of fan blades, inclination angle, height, diameter and bearing system.

　　Most of the fan speed can be adjusted, this is because their speed will change synchronously with the change of the working voltage. The governor we usually use is actually just a small rheostat, and the air volume/air pressure Different, the speed can be checked by simple instrument measurement or software, and the speed of 12cm fan is generally 800-2000rpm.

　　1 Noise

　　Fan noise is the noise generated by the fan when it is working, and at the same time, the noise is also a factor that directly affects the user. The noise is affected by many factors, such as speed, size and number of fan blades, etc. The nominal fan noise value is measured in an anechoic chamber with noise less than 17dB, 1 meter away from the fan, and aligned with the fan along the direction of the fan shaft. The air intakes are A-weighted.

　　Generally, it is required that the noise of the fan should be as small as possible, and there should be no abnormal noise. Inferior fans, the center of gravity of the fan blades is often not on the axis. After a period of use, the fan bearings gradually wear out, which will aggravate the vibration and increase the noise.

　　1 fan blade

　　The design of the fan blade plays a decisive role in the performance of the fan, and the technical skills of manufacturers are mostly expressed through a variety of fan blades. There are several main parameters of the fan blade that affect the air volume, wind pressure and wind speed of the fan.

　　The greater the curvature of the blade, the greater the air volume and wind pressure, the greater the resistance to the blade, and the greater the torque required for the motor.

　　The larger the blade inclination angle (the angle to the airflow direction), the greater the wind pressure, but it may cause backflow and reduce the performance of the fan

　　If the blade spacing is too small, the airflow will disturb, increase the surface friction, and reduce the efficiency. If the spacing is too large, the pressure loss will increase and the wind pressure will be insufficient.

　　The radian of the blade can concentrate the blown air in the columnar space directly in front of the air outlet, which can increase the wind pressure

　　In addition, the number of blades also has a great influence. The number of blades of the fan is basically an odd number such as 5, 7, and 9. This is to balance and avoid resonance. Under the same conditions, increasing the number of blades can increase the air volume, but the wind pressure will drop. , or, to ensure the same air volume, by increasing the fan blade can effectively reduce the speed, thereby reducing noise.

　　In addition to the above-mentioned indicators, fan bearings are also very important, which are usually divided into oil-impregnated bearings, hydraulic bearings, ball bearings and magnetic bearings.

　　Each of these bearings has different advantages and disadvantages, such as low cost, low noise, low technical content, and short life (5000-8000 hours) of oil-impregnated bearings; compared with oil-impregnated bearings, hydraulic bearings have a much longer life (40,000 hours); The double ball bearing favored by DIY players has a long life span of 50,000-10 hours, high price, and loud noise; the magnetic bearing is an all-in-one with high technical content, long life (50,000 hours), and extremely low noise. , the price is also very high.

　　1 How to choose the right fan?

　　Fans can be simply classified into three categories, one is air volume fans, the other is air pressure fans, and the last one is all-balanced fans. All of them are a little bit but not big (all are big or expensive or noisy), and then choose according to the actual needs of the scene.

　　It should be said that the air volume fan is suitable for most application environments, allowing more air to participate in the heat exchange process. For example, the rear, top, and side fans of the chassis can be used for air volume fans. If the air duct is unobstructed, the front fan of the chassis can also be used. A fan with high air volume can be used.

　　If the hard disk cage or the like is near the fan, the air pressure fan will be better. For the fan with the radiator, if the fins are not very dense, the radiator is not very thick.

　　It is still mainly based on air volume fans. The basic principle is that fans with large air volume should be used for exhaust fans, and fans with high air pressure should be used for blowing fans in areas with dense and high resistance. At least in the dead of night you can't hear it huh huh huh huh!

　　To sum up, the cooling fan brand tells us that the larger the cooling fan of the chassis, the better the performance. The choice of cooling fan depends not only on the size, but also on its own power and the amount of air it can generate. At the same time, you must also consider your actual needs, so that you can scientifically choose a cooling fan suitable for your computer, so that the computer will not overheat in summer.

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