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Analysis on Cooling Effect of the Fan: Use convection to take away the heat source

“Fan” is a kind of aerodynamic machinery that uses air to apply energy to increase the air pressure and speed. In the heat dissipation system, the fan is used to increase the speed of the air to achieve the effect of forced convection and take away more heat emitted by the heat source. According to the direction of the rotation axis and the direction of the wind, the fan products can be roughly divided into two kinds of products: An axial fan and a centrifugal fan product.

 

To understand whether a fan is suitable for use or not, we must check the most important information - the fan performance curve. The below figure1 mainly shows the air volume on the horizontal axis, and the pressure, power, speed and efficiency on the vertical axis, and it uses a curve to show the relationship between them. In the figure, the horizontal axis is the air volume Q, and the vertical axis is the pressure ΔP. The solid line is the performance curve of fan flow and pressure, and the dashed line is the impedance curve of the system. The intersection of the two lines is called the operating point.

 

 

 

The flow rate is the amount of fluid medium that passes through the machine in a unit time. The expression method can be divided into volume flow rate and mass flow rate. The unit of volume flow rate is m3/s, m3/h or L/s, and the unit of mass flow rate is kg/s, kg/min or kg/h. According to the law of conservation of mass, if we ignored the leakage inside the machine, the mass flow rate through each section of the machine is the same when the machine is working stably, and if it is the case of incompressible flow, the volume flow rate is also the same.

 

The volume flow rate in the fan is also called the air volume, and the air volume is expressed in CFM (ft3/min). The following table is the conversion table of the air volume unit.

 

 

Fan efficiency is the efficiency of the input fan shaft power converted into fluid kinetic energy, which can be divided into: total pressure efficiency, static pressure efficiency and hydraulic efficiency, respectively:

 

 

In terms of fan usage, natural convection is sufficient when the smaller heat source is about 10W or less. As the wattage of the heat source increases, a fan needs to be used to form forced convection to take away more heat, and the fan mainly depends on the available space. The size, coupled with the effective airflow design, can reduce the temperature more effectively.

 


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T-Global R&D team

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A team of professional heat flow engineers, with independent and innovative research and development, provides customers with preliminary thermal simulation planning and institutional heat dissipation design consulting. In the face of evolving market trends, they can quickly respond and continue to provide innovative anti-heat solutions.

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