View Full Version : Regarding Chassis Fan

01-21-2012, 08:06 AM
I'm currently using Cooler Master Turbine Master 1.8MACH chassis fan. I'd like to know whether the fan should be sucking air into the chassis or sucking air of the chassis for better cooling?

01-21-2012, 11:14 AM
Your air flow should include a fan either blowing fresh cool air into your system and an exhaust or venting fan sucking the hot air out of your system. Now because hot air rises it is normally to have the colder air entering from either the front bottom of the chassis, hard drive area or from the side near the graphic card, the hot air would be vented near the major heat source your CPU. So your case fan at the top of the case will be blowing the hot air out and away from your case.

01-21-2012, 03:11 PM
This is the basics of airflow and fan placement that I've come found yet. I've made a cut and paste from the techpowerup forum on the subject.

Guide to Proper Case Airflow Design by keakar@techpowerup forums

Airflow and case circulation:


Rule #1 - Airflow is best if it can flow in one direction only and better off (stays stronger) flowing in a straight line. Also always cut out a hole where you mount a fan, never use it with those predrilled holes or you canít get good airflow. Redrill all those small holes in the back of the case with a 3/16" drill bit to increase ventilation and cooling. The holes are too close together to use a 1/4" drill bit without having it blow out into the next hole and make a mess of things.


Rule #2 - Heat naturally rises so to remove heat it is best to draw air in from the cases lowest points and exhaust it from the cases highest points.

The Direction of Airflow:

The airflow can be directed in a few different ways as long as you remember rules 1 & 2 above. The most common setup for cases is intake from the bottom front and exhausted out the top and back. The reason they do it this way is it takes best advantage of rules 1 & 2 above. The air is drawn in from the coolest point (bottom front) and moves in an "S" to flow across the motherboard and out the exhaust fans (top rear and psu fans).


Side fans - side fans can and do interfere with this "S" flow of air so keep this in mind if youíre thinking of a high cfm side fan. It may improve cooling in one spot and allow a "dead spot" for airflow somewhere else. Side fans are great cooling aids but donít go overboard with the cfms. To reduce the interference cases use air ducts to direct the cool air right into the CPU fan so it will not interfere with airflow through the case.

Video Cooling:

VGA - the video card area tends to be a dead spot for airflow. This is why they have fans now that exhaust hot air directly out the back of the case. Adding a side fan blowing cool air into this bottom corner helps "stir" the air so heat doesnít get trapped there and it can rise up and be exhausted by the rear fan. This works well as long as you donít over do it to the point that it will interfere with the vga cooling fan and the airflow going through the heat sink. Just remember the fan is there to stir the air and thatís all. It should not blow high cfms directly across the heat sink or its fan or you could actually reduce its cooling ability by canceling out the airflow moving across and though the heat sink.

Balanced Airflow:

Push / pull or Fan In / Fan Out System - It's not as easy as just having your fan cfms and sizes matching because they donít always give you evenly balanced airflow through your case. This is because it is a lot harder to push air into a case than out of the case so you need a little more cfms from your exhaust fans to equal out the airflow or the result will be, you will end up with a slightly negative pressure airflow system unless you have slightly bigger intake fans than exhaust fans even though they are of the same size so donít just assume two 80mm 45cfm fans in the front and two 80mm 45cfm fans in the rear will give you a balanced airflow. (Although it should be close enough not to matter)

Positive Pressure Airflow System:

More Air in Than Air Out - the benefit to this type of system is supposed to be that it pulls in less dust than a negative airflow system but this is a false idea. Weather the fan draws the air in or directly blows it in it is still the same air from your room. If your room is dusty your case will be dusty.

A simple air supply test is to just check the amount of air your system is exhausting through the small holes in the back of your case, if you can feel a gentle draft coming out then you are restricted and should adjust the airflow by reducing the cfms of your intake fans or making bigger exhaust openings to balance things out.

Negative Pressure Airflow System:

More Air Out Than Air In - the benefit to this type of system is they are quieter because they have slower fans that move less cfms so they run quieter. one main disadvantage is because of the slower airflow it can build up heat quickly if the airflow is restricted in any way so you need to be sure you temperatures are in the safe ranges during heavy gaming activity when heat can build up quickly.

Often people will use fan controllers to speed up fans for better cooling while gaming and yet still have a nice quiet computer when they are just doing normal computing activities.

Why does a positive airflow system get less dusty than a negative airflow system?

Both systems have the exact same amount of dust moving through them but it tends to settle on things in a negative airflow system more, only because the air is moving slower. Think of a fan blowing feathers around in a small room, as long as the fan keeps blowing fast they all stay airborne but put the fan on slow speed and everything will be covered in feathers. The same applies to dust in your computer; it is the airflow "inside" the computer that determines how fast your computer gets dusty. You can reduce dust building up by putting a fan inside the case just to keep the air stirred up so dust wonít settle and it can then be exhausted out the back of the case by the fans.

Air Supply Test:

A simple air supply test is to just check the amount of air your system is exhausting (rear exhaust fan) and also checking the air your psu is exhausting, and then remove the side cover on your computer. It will always move more air with the door open so if you notice only a minor difference then you are fine but if you notice a big difference then you need to investigate where your restriction is and provide a larger air intake opening.

A person with high cfm exhaust fans who doesn't have proper sized intake openings for his case can actually cause a slight vacuum inside the case and prevent the psu from getting enough air because it is being held back by that vacuum causing the psu to overheat. Some PSU that have high cfm fans can have the reverse effect and cancel out the rear exhaust fans ability to remove air from the case. Most problems people have with negative airflow systems are with the cfms of the fans and not the negative airflow design itself.

If you arenít over clocking, a properly designed negative pressure airflow system will work great with exhaust fans only and no intake fans at all unless spot cooling is needed for a hot spot. It just needs to have an unobstructed opening (no air filter) that is equal to or bigger than the total size and shape of the exhaust fan openings. If for example, if you have two 80mm exhaust fans (plus the 80mm psu fan) then you need an unobstructed opening that is equal to four 80mm holes with open grills. This wonít work with filters because with the extra restriction of the filters you don't get proper airflow.

Another overlooked obstruction is the front panel cover; it can restrict airflow no matter how big the opening is behind it so test with and without the front panel in place to see if air must be brought in from a different place (maybe the bottom panel).

I hope this helps. Also for those that need pictures look here: http://www.xoxide.com/computer-cooling.html.

01-24-2012, 05:27 PM
Depends on where your chassis fan is located on the case, and what you plan on running.

Usually Air flow of cases have cool air being sucked into the case from front and on the side of the case. Then the hot air of the case is blown out from the back exhaust fan and the top exhaust fans of the case. The main reason why most setups are like this is because HOT AIR Raises, take a look at the below diagram as this is the most general/basic and recommended setups are like.


However there are a few unique setups which causes some changes that could alter the general/basic air flow setup of most builds. Such as the following setup. Most are changed because of watercooling. This is one Idea that I took for my build and that is how I have mine setup. I have my top fans reversed to draw in cool air, as I have a radiator for my watercooling from my H100 mounted at the top of the case. The cool air passes through the 2x200mm fans at the top through the rad, and I have another 2x120mm fans forcing the air down into the case from the rad. I have a pretty strong exhaust fan blowing out all the hot air that accumulates in the upper half of the case which is the CPU/RAM area. I have a 230mm and a 200mm fans at the front and on the sides to draw cool air in. Notice how in this setup there's essentially two zones? Because of the Crossfire setup in this picture little hot air raises from the video card zone to the top since the massive video cards create a chamber, so essentially you have separate hot zones, which is your CPU/RAM area and your video cards.

02-04-2012, 09:30 PM
When your using spinner drives, you want to make sure your sucking enough air through the front side of the computer. A quick and easy test to assure you have sufficient air being drawn through the front side, by using a sheet of paper place it on the front panel of the computer, right where the spinner drives are located, and from the air suction alone should be able to hold that sheet of paper in place. The power supply, rear fan and VGA card(s) draws air out from the case.
Depending on the sheet of paper test will determine of the upper fans should be sucking or drawing out of the case.
If the sheet of paper test allows, with a water cooling radiator on top of the case, it is best to have those fans pushing air in to the case, to help cool the VRM's heat sink and memory effectively. If your using fan cooling on your CPU, your top fans should exhaust air from the case.

Humm.. pretty much exactly what InnervateD had posted already, but most importantly to be sure you have proper cooling over those hard drives using the sheet of paper test, because if you run the top fans pushing air in to your system, frontal airflow over the drives may become non existing, then hard drive failure becomes eminent.

04-06-2012, 05:24 AM
usually as others mantioned fans must blow the air out from the top and rear of the case and suck in from the front and the bottom! and be carefull with the cgange of preasure you got inside the case!!