If you’ve ever wondered whether pushing air into your device is more effective than pulling hot air out, or if a bigger fan really means better cooling, then you’re in the right place.
I recently ran a series of cooling experiments using a Raspberry Pi 3. While my setup was Pi-specific, the findings could easily apply to other compact devices like mini PCs, routers, or other devices.
Why test cooling at all?
Tiny computers like the Raspberry Pi tend to heat up fast under heavy workloads—think compiling code, emulation, web browsing, or running as a server. Even if they don’t hit dangerous temperatures right away, sustained heat can lead to thermal throttling and even reduce the lifespan of components.
So I started wondering what is the most effective way to cool this type of device and does the direction of fan rotation really matter?
Test #1: Fan Orientation
I began with a 5V medium-sized fan I had lying around—larger than the typical ones bundled with basic cooling kits. I wrote a small script to simulate a heavy CPU load, monitor the temperature every few seconds, and log it to a CSV file for graphing.
🔹 Blowing air in:
Starting at 45°C, the CPU temperature dropped steadily to around 36°C after 5 minutes. A solid result.
🔹 Pulling air out:
Same test conditions, same fan—but this time configured to extract hot air. The final temperature hovered just under 39°C, clearly less effective.
Takeaway: If you’ve only got one fan, using it to push cool air into the case works better than trying to suck warm air out.
Test #2: Comparing Fan Sizes and Types
Next, I tried a variety of fans I had on hand, all under the same conditions: starting at 45°C, 5 minutes of stress, measuring the results.
🔹 Small 5V fan:
Quiet but underwhelming. It only brought temps down to just under 41°C.
🔹 Laptop cooling fan:
Compact and thin, yet surprisingly powerful. When aimed directly at the heatsink, it cooled the Pi to nearly 36°C—but it was fairly noisy.
🔹 Large 12V PC fan (powered by 5V):
Barely audible, but the lower voltage meant it spun too slowly. The result? A modest drop to below 40°C—not terrible, but not impressive either.
Final Thoughts
The best results came from the medium 5V fan and the laptop fan—both used to blow air inward.
If you’re after a silent setup, the small 5V and underpowered 12V fans are your best bet, but you’ll be trading off a few degrees of cooling.
Overall, drawing air in was consistently better than pulling it out—at least when using a single fan.
As always, it’s a balance between noise and cooling efficiency. If your Raspberry Pi is running right next to you all day, go for a quieter option. If it’s tucked away in a server cabinet somewhere, prioritize performance.
🎥 Want to see all the data in action?
In the video linked below, I walk through each test step-by-step, show real-time temperature graphs, and demonstrate how each fan performed.
Watch: "Blow In or Pull Out? I Tested 4 Fans on a Raspberry Pi"