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Additional Cooling Fans - Airflow Direction?

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Matt-T

New Member
Joined
Aug 18, 2021
Hi All,


My younger brother has a basic gaming PC with a failed case fan (intake), i figure whilst I am replacing one it make sense to upgrade to some quieter units all round.
The case itself has two fans 'intake' fans at the front and a single exhaust fan at the rear, and room for 140mm on the top of the case.

If I was install the two case fans to the top of the case, should they pull air into the case or blow it out?
I work in the basis heat rises to they should expel it, i just don't want to get it wrong.

The case is a Coolmaster MB320L


Thanks in advance.
 

tRidiot

Premium Member
Joined
May 17, 2003
Lots of debate about this topic, all depends on so many factors it's insane. For instance, you can search articles and watch YouTube videos on the fan/airflow direction on a specific case all over - like say the Lian Li 011 Dynamic or 011 Dynamic-XL.

Bottom line, there's no simple answer, it is affected by too many variables. You have to try your particular setup and find out, most of the time.
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
High level....for 'normal' cases like that, front/sides = intake, top/rear = exhaust. Provides airFLOW. :thup:

I'd replace the bad intake up front and add 140mm to the top. Viola! :bday:


Edit: A more complicated question is more CFM coming in or out of the case... to which testing is going to give you that answer.
 

Brutal-Force

Member
Joined
Feb 22, 2009
Lots of debate about this topic, all depends on so many factors it's insane. For instance, you can search articles and watch YouTube videos on the fan/airflow direction on a specific case all over - like say the Lian Li 011 Dynamic or 011 Dynamic-XL.

Bottom line, there's no simple answer, it is affected by too many variables. You have to try your particular setup and find out, most of the time.

Like tRidiot pointed out. Your best bet is to install the number of fans you plan, run some benches, then turn the fans around in the combinations that you think will work. Go with the best set up. I found on my system that pulling air in over the cooler was better than blowing the case recycled air over the cooler by a margin of about 5 degrees. YMMV.
 

Blaylock

"That Backfired" Senior Member
Joined
Jun 5, 2013
Location
Go Blue!
I wouldn't worry much about heat rising. Your fans will easily overcome the normal and very slow rise of heat. What is more important is airflow. If the top fan location is more towards the front of the case then make it an intake to feed the CPU cooler. If it is more to the rear of the case then make it exhaust to assist the rear exhaust fan. High CFM, low noise fans are best for case fans. These are generally more money but definitely worth the extra investment.
 

roidroo

New Member
Joined
Sep 7, 2021
In - sides, bottom, front
Out - top, rear
Dont worry about negative/positive pressure. Won't apply to you.
 

GotNoRice

Member
Joined
Dec 6, 2002
I think that with sufficient airflow, the location of the inputs and exhausts is less of an issue. If you run a whisper-quiet setup with very low CFM, then convection currents carrying heat to the top inside the case might play a bigger role.

I'm still using my ~12+ year old Corsair 800D. The case does not have any front fans. There are places for fans on the bottom, on the top, and in the rear. I have my 360mm radiator up top and I wanted cool air flowing into the radiator so I made that an intake, despite being on the top. But with 6 high static pressure, high CFM fans in push pull, it's more than enough to brute-force past any effect convection currents would create.

I think the question of intake vs exhaust CFM is incredibly important, especially if you employ dust filters on your intakes. By maintaining positive pressure in my case, I can control the locations at which air enters my case and place dust filters in front of those fans. The hot air not only exhausts via my rear exhaust fan, but also exhausts via misc holes in the rear of my case. If I had negative pressure in my case, then the case would be sucking in air (and dust) through every single little hole in my case including those in the rear of the case.