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Common technical specifications of cooling fans

Back to list Release date: Sep 21, 2018

Air volume

Air volume refers to the total volume of air discharged or contained by the cooling fan per minute.If measured in cubic feet, the unit of air volume is CFM. If measured in cubic meters, it is CMM. The air volume unit often used by cooling fans is CFM ( about 0.028 cubic meters/minute ).

Air volume is the most important index 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 air is fixed, and more air volume, that is, more air can take away more heat per unit time. Of course, the heat dissipation effect and wind flow pattern are related under the same air volume.

wind pressure

Wind pressure and air volume are two opposite concepts. Generally speaking, in consideration of cost saving by manufacturers, to design a fan with large air volume, some wind pressure will have to be sacrificed. If the fan can drive a large amount of air to flow, but the wind pressure is small, the wind will not blow to the bottom of the radiator ( this is why some fans have high rotation speed and large air volume, but this is why the heat dissipation effect is not good ).On the contrary, large wind pressure often means that the air volume is small, and there is not enough cold air to exchange heat with the heat sink, which will also cause poor heat dissipation effect.

Fan speed

Fan speed refers to the number of rotations of fan blades per minute in rpm. The rotation speed of the fan is determined by the number of turns of the coil in the motor, the working voltage, the number of fan blades, the inclination angle, the height, the diameter and the bearing system. The speed of rotation is not necessarily related to the quality of the fan. The rotational speed of the fan can be measured by the internal rotational speed signal or by the external.

With the change of application and ambient temperature, fans with different rotational speeds are sometimes required to meet the demand. Some manufacturers have specially designed cooling fans that can adjust the speed of the fans, which can be divided into automatic and automatic ones. The main purpose of manual operation is to allow users to use low rotation speed to obtain low noise in winter and high rotation speed to obtain good heat dissipation effect in summer. Automatic temperature control radiators usually have a temperature control inductor, which can automatically control the rotation speed of the fan according to the current working temperature.If the temperature is high, the rotation speed will be increased, and if the temperature is low, the rotation speed will be decreased to achieve a dynamic balance, so that the wind noise and heat dissipation effect will maintain an optimal combination point.

Fan noise

In addition to the heat dissipation effect, the working noise of the fan is also a common concern. Fan noise is the amount of noise generated when the fan works and is affected by many factors, in decibels ( dB ). The noise of the fan needs to be measured in a silencing room with noise less than 17dB, one meter away from the fan, and aligned with the air inlet of the fan along the direction of the fan rotating shaft, and the measurement should be carried out in an A-weighted manner. The frequency spectrum characteristics of fan noise are also very important, so it is also necessary to record the noise frequency distribution of the fan with a spectrograph.Generally, it is required that 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 speed of the fan and the larger the air volume, the more noise will be caused.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 small, but the first two are hard to overcome. To solve this problem, we can try to use larger fans. When the air volume is the same, the working noise of a large fan at a lower speed is smaller than that of a small fan at a higher speed. Another factor that we tend to overlook is the bearing of the fan. Because of the friction and collision between the rotating shaft and the bearing when the fan rotates at high speed, it is also a major source of fan noise.

Size of fan

In 2005, most of the cooling fans were under 8 cm in size when the computer was just entering the fourth running period. The 12 cm fan gradually expands its territory in the PC, first with the chassis fan and power fan, then with the high-end CPU radiator. Intel TA C 1.1 Chassis Standard ( commonly known as " 38-degree Chassis" in which the size of the rear exhaust fan has changed from two 8 cm fans that have not changed for ten thousand years to one 12 cm fan has been officially installed in the chassis since then.

such as 60180252038, etc. Taking the four-digit " 6010" as an example, I generally refer to the fan size as a number. " 60" stands for 60 mm " 10" stands for 10 mm " 12025" in thickness, that is, 120 mm in length and 25 mm in thickness of the outer frame, and all the fans in this cross-evaluation are 12025 fans.

To weigh a fan is to stop evaluating its function, task tone and life span. As for Diyer, generally speaking. Appearance and added value are also the criteria for weighing whether a fan is good or not.

use

Generally, the unit is CFM or cubic feet per minute-CubicFEETPERMINUT or CMM or cubic meters per minute-CubicMETPERMINUT air volume=uniform wind speed x over-wind area. It can be seen that the two main goals of weighing the function of a fan are the wind pressure and breeze of the fan. Air volume:the volume of air passing through the fan outlet ( or air inlet ) section per unit time. The size of the fan air volume basically depends on the size of the upper and lower wind speeds and the area of passing wind. On the contrary, the higher the wind speed, the greater the air volume. On the contrary, the larger the area of passing wind, the larger the air volume. The air-cooled radiator is a clear way to take away the heat accumulated on the heat sink by using heat exchange.Using a different heat sink structure and atmosphere activity mode, the more atmosphere you pass in a unit time, the more heat you take away. Therefore, under the condition that other conditions remain unchanged, it can be said that the actual air volume plays a decisive role in the effectiveness of air cooling and heat dissipation.

In general, the unit is mmcmwatercolumn, i.e., millimeter ( centimeter ) water column ( similar to millimeter mercury weighing atmospheric pressure, wind pressure:wind pressure is the pressure difference between the air outlet and the air inlet that can be caused by the fan. However, due to the small pressure difference, the wind pressure in water column is the main target to weigh the " weak" degree of the fan, and the wind pressure indirectly affects the air supply interval of the fan. As for those heavy radiators or chassis air duct fans, a fan with high wind pressure is essential.


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