Cooling fans, English name: Cooling fans.The technology and performance of the cooling fan has reached a mature stage, and new technologies are constantly emerging.The size of the fan ranges from 8mm to 280mm. The voltage range is 5V, 12V, 24V, 48V, 110V, 220V, 380V. The shape range is square, round, olive, etc.
The working principle of the cooling fan is based on energy conversion, that is, electric energy →Electromagnetic energy→ Mechanical energy → Kinetic energy.Its circuit principle is generally divided into various formsCircuitDifferent fans will have different performance.
Parameters are shown in the following table:
classification
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Axial fan
Axial fanThe blades of push air in the same direction as the shaft.The impeller of the axial fan is similar to the propeller. When it works, most of the airflow flows parallel to the axis, in other words, along the axis.When the inlet air flow of the axial flow fan is free air with zero static pressure, its power consumption is the lowest. When it runs, its power consumption will increase with the increase of the air flow back pressure.The axial fan is usually installed on the cabinet of electrical equipment and sometimes integrated on the motor. Because of its compact structure, it can save a lot of moneyspaceAt the same time, it is easy to install, so it is widely used.
Its characteristics: high flow rate, medium wind pressure
Centrifugal fan
Centrifugal fanDuring operation, the blade pushes the air to flow in a direction perpendicular to the axis (i.e. radial). The inlet air is along the axis direction, while the outlet air is perpendicular to the axis direction.In most cases, use theAxial fanThe cooling effect can be achieved. However, sometimes if the air flow needs to rotate 90 degrees to discharge or a large air pressure is required, centrifugal fans must be used.Strictly speaking, the fan is also a centrifugal fan.
Features: limited flow rate, high wind pressure
Mixed flow fan
Mixed flow fan is also called diagonal flow fan. At first glance, mixed flow fan andAxial fanIt's no different. In fact, the inlet of the mixed flow fan is along the axis, while the outlet is along the diagonal direction of the axis and the vertical axis.This fan has high wind pressure due to its conical blades and cover. Compared with axial flow fan,Centrifugal fanThe noise is lower.
Its characteristics: high flow rate and relatively high wind pressure
Cross flow fan
Figure 1 Tubular Fan
The cross flow air flow can produce a large area of air flow, which is usually used to cool the large surface of equipment.The inlet and outlet of this fan are perpendicular to the axis (as shown in Figure 1).Cross flow fanIt is to use a relatively long cylindrical fan impeller to work. The diameter of this cylindrical fan blade is relatively large, because the diameter is large, the overallAir circulationOn the basis of quantity, use relatively lowspeedThereby reducing the noise caused by high-speed operation.
Its characteristics: low flow rate, low wind pressure
Ball bearingBall Bearing has changed the friction mode of the bearing, adopting rolling friction. There are somesteel ballOr steel column, supplemented by some grease lubrication.This method can effectively reduce the friction between bearing surfaces and effectively improve theFan bearingTherefore, the heating capacity of the radiator will be reduced and the service life will be extended.The disadvantage is that the process is more complex, resulting in higher costs and higher working noise.
Oil bearing
Oil bearing(Sleeve Bearing) is a sleeve bearing with sliding friction, which uses lubricating oil as lubricant andDrag reducing agent。It can be said that it is the most common bearing technology in the market. Due to its low cost and simple manufacturing, many products, including well-known brands, are still in use.Its advantages are quiet in initial use, low noise and low price.
magnetic bearing
magnetic bearing (Magnetic Bearing) motor adopts magnetic system (MS) designmagnetic forceThe function is to suspend the rotor in the air, so that there is no mechanical contact between the rotor and the stator.The principle isMagnetic induction lineIt is perpendicular to the magnetic levitation line, and the axis core is parallel to the magnetic levitation line, so the weight of the rotor is fixed on the running track. The almost no-load axis core is used to support the rotor in the direction of the anti magnetic levitation line, forming the whole rotor suspended on the fixed running track.And traditionalBall bearing、Oil bearingcomparison,Magnetic bearingThere is no mechanical contact, the rotor can run to a very high speed, withMechanical wearSmall, low energy consumption, low noise, long life, no lubrication, no oil pollution and other advantages, especially suitable for high-speed, vacuum, ultra clean and other special environments.In fact, magnetic levitation is only an auxiliary function, not an independent functionBearing typeFor specific application, other bearing forms must be matched, such as magnetic suspension+ball bearing, magnetic suspension+oil bearing, magnetic suspension+VAPO Bearing wait.
Technical indicators
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Air volume
Air volume refers to the total volume of air discharged or incorporated by the cooling fan per minute. If it is calculated in cubic feet, the air volume unit isCFM；If calculated in cubic meters, it isCMM。The unit of air volume frequently used by the cooling fan is CFM (about 0.028 m3/min).
Air volume is the most important index to measure the cooling capacity of the cooling fan.Obviously, the greater the air volume, the higher the cooling capacity of the cooling fan.This is because the heat capacity ratio of the air is fixed, and the larger the air volume, that is, more air can take away more heat per unit time.Of course, the heat dissipation effect under the same air volume is related to the air flow mode.
wind pressure
Air pressure and air volume are two relative concepts.Generally speaking, considering the cost saving of manufacturers, to design a fan with large air volume, it is necessary to sacrifice some air pressure.If the fan can drive a large amount of air to flow, but the wind pressure is low, the wind cannot blow to the bottom of the radiator (this is why some fans rotate at a high speed, and the air volume is large, but the heat dissipation effect is poor). On the contrary, a large wind pressure often means that the air volume is small, and there is not enough cold air andHeat sinkHeat exchange will also cause poor heat dissipation effect.
Fan speed
Fan speed refers to the number of revolutions of fan blades per minute, in rpm.The fan speed is determined by the number of turns of coils in the motor, the working voltage, the number, inclination, height, diameter of fan blades and the bearing system.There is no necessary relationship between the speed and the fan quality.The fan speed can be measured by internal speed signal or external speed signal.
With the change of application and ambient temperature, different speed fans are sometimes required to meet the demand.Some manufacturers have specially designed cooling fans with adjustable fan speed, which can be divided into two types: dynamic and automatic.The manual mode mainly allows users to use low rotation speed to obtain low noise in winter, and use high rotation speed to obtain good heat dissipation effect in summer.The automatic temperature regulating radiator is generally equipped with a temperature control sensor, which can automatically control the speed of the fan according to the current working temperature. If the temperature is high, the speed will be increased, and if the temperature is low, the speed will be reduced to achieve a dynamic balance, so that the wind noise and heat dissipation effect can maintain an optimal combination point.
Fan noise
In addition to the heat dissipation effect, the working noise of fans is also a common concern.Fan noise is the noise generated by the fan when it is working. It is affected by many factors, and the unit is dB.When measuring the noise of the fan, it is necessary to measure the noise of the fan when the noise is less than 17dBAnechoic chamberIn the middle, one meter away from the fan, and along the fanRotating shaftThe direction of is aligned with the air inlet of the fan, and the A-weighted method is used for measurement.The spectral characteristics of fan noise are also very important, so it is also necessary to use a spectrometer to record the noise frequency distribution of the fan. Generally, the noise of the fan should be as small as possible, and there should be no abnormal sound.
Fan noise is related to friction and air flow.The higher the fan speed and the larger the air volume, the greater the noise will be. In addition, the vibration of the fan itself is also a factor that cannot be ignored.Of course, the self vibration of high-quality fans will be very small, but the first two are difficult to overcome.To solve this problem, we can try to use a larger fan.Under the same air volume,Large fanThe working noise at low speed is less than that of small fan at high speed.Another factor that we tend to overlook is the fan bearing.Because the fan rotates at high speedRotating shaftFriction and collision with bearings are also a major source of fan noise.
application
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Widely used incomputer, communication products, photoelectric products, consumer electronic products, automotive electronic equipment, exchangers, medical equipment,heater, air conditioner, frequency converter, teller machine, automobile refrigeratorWelding machine、Electromagnetic furnace, audio equipment, environmental protection equipment, refrigeration equipment and other traditional or modern instruments and equipment.
