Figure 1: Computer fan.
The chassis fan is one of the very important accessories in the
computer. It can effectively cool down the temperature, help the computer to dissipate heat and improve the
stability of the entire system. However, when installing a chassis fan, many users do not know how to correctly
judge the wind direction of the fan. Here is how to correctly judge the wind direction of the chassis fan.
By searching the information, we found some methods to judge the wind direction of the computer fan, among which
there are 4 most effective and error-free methods.
1. Observe the Appearance of the Chassis Fan Frame
Some brands of cooling fans will have two arrows indicating the direction on the side. A horizontal arrow indicates
the direction of blade rotation and a vertical arrow indicates the wind direction. The direction indicated by the
vertical arrow is the direction of fan blowing.
If there is no arrow mark on the fan, you can use the following methods to determine the fan wind direction.
2. Feel the Wind Direction with Your Hands
Use your hands to sense the wind direction. If you feel the wind outside the case, it is the air outlet. If you feel suction, it is the air inlet.
3. Paper Test
Tear a piece of toilet paper, and put it in front of the fan. You can see if the paper is blown or sucked, and you will know the direction of the wind.
4. Observe the Bending Direction of the Fan Blades
Another way to determine the direction of air flow from a case fan is to look at the direction in which the blades
bend. Convex (blades curving back you) air in, concave (blades curving toward you) air out.
First, let's look at the shape of the spoon. One side of the spoon is concave and the other side is convex. Everyone
knows that when you use a spoon to scoop up soup, the soup should be on the concave side so that you can deliver the
soup to your mouth. Otherwise you won't be able to scoop the soup if you turn the spoon over!
Figure 2: Spoon.
You use the spoon to scoop the soup from the bowl to your mouth. What if the spoon scooped up the wind instead of
the soup?
The shape of the whole fan blades bending back or toward you is actually similar to the shape of a spoon. One side
is concave and the other is convex. The fan blades send the wind from the convex side to the concave side.
For example, in the fan below, it is obvious that the side of the fan blade facing us is convex, like the back of a
spoon, and the other side is concave, like the front of a spoon.
The wind blows from the convex surface to the concave surface. So the side of the fan below that faces us is the air
intake side.
Figure 3: The convex surface of the fan is the air intake side.
In the same way:
The fan in the picture below faces us with the air intake side. The convex side we see is the back of the spoon, so
this side is the air intake. The wind blows from top to bottom.
Figure 4: The convex surface of the fan is the air intake side.
The surface of the fan we see in the picture below is concave, and it can be seen as the front of the spoon, so this side is where the wind comes out. The wind blows from bottom to top.
Figure 5: The concave surface of the fan is the air exhaust side.
Have you learned it? Convex air in, concave air out, it's that simple.
5. Other Methods
1. Check the wiring (except for reverse fans). The figure below distinguishes the front and back of the cooling fan. The one without the power cord is the front, and the one with the power cord is the back. Generally, the air enters from the front and exits from the back.
 and exits from the back (right)-min.png)
Figure 6: The front (left) and back (right) of the computer fan.
2. Observe the direction of the motor base. If the arrow logo is not visible on the side of the case fan, you can
also observe which side the motor base is on. The side where the motor is located is the back of the fan, that is,
the air exhaust side (except for reverse fans).
3. Look at the bracket. Where the bracket is, the wind will blow in that direction (except for reverse fans).
Correctly judging the wind direction of the chassis fan is very important for the cooling and stability of the
entire system. The above lists are all ways to judge the chassis fan. It should be noted that when using the methods
of observing wiring, the direction of the motor base, and the bracket, it is not applicable to the reverse blade
fan. So what is a reverse fan?
Figure 7: General fan VS. reverse fan.
Compared with the general fan (the convex side of the fan faces), the concave side (air exhaust side) of the reverse fan faces you. As the following picture shows, you can't see the wiring, the motor base, nor the bracket on these two fans. Judging by the above three methods, the sides of the two fans facing you are both air intake sides, but actually they are not.
