How to judge which air supply method to use for the heat sink?

How to determine which air supply method the heat sink adopts?
The axial flow fan is a fan that pushes the air flow in the same direction as the shaft when the blades are working.
The cooling fins are classified according to the direction of the wind axis and the exhaust direction. The cooling fins can be divided into: axial fan, centrifugal fan (the air inlet is along the axis direction, and the air outlet is perpendicular to the axis direction), cross flow fan (this The inlet and outlet of these fans are perpendicular to the axis) can be divided into: axial fan, centrifugal fan (inlet is perpendicular to the axis), cross-flow (cross-flow) fan (intake of this kind of fan).
Axial fan | The air supply form of the fan. The commonly used form is an axial flow fan, which blows downwards. The reason why it is so popular is that it has good comprehensive efficiency and low cost. In addition, the direction of the axial flow fan has also been correspondingly changed to the form of upward suction, which seems to be more and more common.
The difference between the two forms of air supply lies in the different forms of airflow. The turbulence produced by blast is turbulent, and the wind pressure is high but it is susceptible to resistance loss; the air extraction produces laminar flow, the wind pressure is small, but the airflow is stable. The theory believes that the heat transfer efficiency of turbulent flow is much greater than that of laminar flow, so it has become the mainstream design form. But for some heat sink designs (such as too tight heat sink), the heat sink has a great obstacle to the air flow, and the use of air extraction at this time can have a better effect.
If the air supply method is adopted, the heat is more dispersed in the equipment, and the distribution is more uniform. When the wind resistance of the cooling surface is small, the suction cooling is generally used; when the heat distribution in the equipment is uneven, the wind resistance is large, and the components are large, generally Air-cooled. Fans can be used in series (increase wind pressure), parallel (increase high air volume) or mixed according to needs.
Cross flow fan is also called cross flow fan, so it refers to the same thing, but the name is different!
Cross-flow fan, also called cross-flow fan, was proposed in 1892 by French engineer Mottier. The blades are multi-lobed, long cylindrical, and front multi-wing blades. As the impeller rotates, the airflow enters the cascade from the opening of the impeller, passes through the interior of the impeller, and the other side of the cascade is introduced into the volute to form a working airflow. The flow in the leaf is very complicated and the velocity field is unstable. There is a vortex in the impeller, the center is near the volute tongue. The existence of the vortex makes the output end of the impeller produce circulating flow. The inner streamline of the impeller is arc-shaped outside the vortex. As a result, the speed of each point around the impeller is not consistent. The closer to the middle of the vortex, the greater the speed, the faster the speed, and the slower the speed.
Due to the uneven flow rate and pressure at the air outlet of the fan, the flow rate and pressure coefficient of the fan are average values. The position of the vortex greatly affects the performance of the cross-flow fan. The middle of the propeller is close to the inner circumference of the impeller and near the tongue of the volute, the fan performance is good; the center of the vortex tongue is far away from the vortex tongue, the circulation flow area increases, the efficiency of the fan decreases, and the flow instability increases.

Post time: Aug-19-2021