Case fans - more intake or more exhaust?

Hello guys,

So i got myself a Fractal Design define R3. The case comes with 2 fans, one in the front and one at the rear.

I have 4 more fans i would like to add.

Should i:

1) 2 front intake, 1 bottom intake, 1 top exhaust, 1 rear exaust [More intake fans]
2) 2 front intake, 2 top exhaus, 1 rear exhaust [More exhaust fans]

Which way do you think it would produce better airflow?

Thanks

 

2, but why not add a bottom fan as well to make 5?

 

Intake airflow should always exceed exhaust. With positive air pressure you avoid taking in dust from openings that are not filtered. Mine is set up like this:

Intakes: two front 120mm, one bottom 140mm
Exhausts: one rear 120mm, one top-rear 120mm
Unused: open second top-front slot, blocked side slot

I used to have all slots filled but it wasn't worth it. The second top exhaust and the side fan are only needed for dual GPU setups.

 

In situations where dust is a concern. In situations where it is not, negative pressure is better.

If you don't have filters on your fans, the whole thing is moot anyway. Dust is getting in.

 

positive air pressure doesn't circulate hot air in the case, it forces it out of the openings that aren't occupied by fans, e.g. in my case, the unoccupied top fan slot. Temperatures in my case are the same with and without that exhaust fan

 

I'm a supporter of positive pressure flow, but ultimately, I feel that it depends on your case design. An optimal design is based on a thermal map and the amount of air passing over the components with varying thermal properties.

For example, if your graphics card is going to emit the most heat into your case, make sure the fans are applying flow to that region. Keep in mind your card is also exhausting air (keeping the pressure lower than what your configurable fans would create).

Also, keep an idea in mind of how you would like the air to move through your case. You want to keep turbulance to a minimum as well as thermal pockets. Attempt to keep a design that causes flow to all go in one direction while maintaining movement throughout the case.

Given your chasis/hardware setup, I would recommend purchasing one more fan and setting the front 2, and bottom 1 to intake. While the top 2 and rear 1 to exhaust. I would shoot for intake fans with a slightly higher CFM rating than the exhaust, though not by a huge margin. Also, make sure that you have a filter on the bottom intake if you're going to use it. This could heavily pollute your case without one. If you need to purchase a filter, they can be very cheap.

If you follow the 6 fan design, you would end up with approximately balanced, to slightly positive pressure due to graphics card fan outflow. Under that configuration, the rest of the air would still escape through cracks or vents and will not be lost air flow.

Finally, just so that I don't ignore your two options, if you must stick to a 5 fan design, I would take the first option, and confirm that you utilize a filter for the bottom intake.

Good luck!

 

Ok thanks guys.

 

This...

More exhaust than intake = hot air exits faster.

 

more intake than exhaust increases pressure in the case which forces air out the case faster as air always flows from regions of high pressure to regions of low pressure.

either way, doesnt really matter too much. i prefer more intake than exhaust, but thats because my silverstone raven 2 works better that way. for a cm haf x, more more intake is better.

for a fractal r3, it has enough dust filters. plus, the foam covers some of the exposed slots, which helps to reduce dust intake as well. but there are no dust filters on the top fan holes or the rear fan, so a positive pressure system would reduce the amount of dust entering there.

 

It dont matter how many exhaust or intake that you have as long as you have cool air coming in blowing over hardware in general.

Although i would lean more to intake,i would rather have more cool air coming in and circulating in the case than lots of hot air waiting to be exhausted

 

my case I have the thermaltake v9

http://www.newegg.com/Product/Product.aspx?Item=N82E16811133182


but I mod the case and changed all the fans. so there is two intake 120mm 60-70cfm on the front and 133cfm exhaust fan on the back and the 230mm exhaust fan on top

my cpu cooler is the XIGMATEK Dark Knight

my system stays nice and cool, even in gaming and video encoding.

running prime95 for 2 hours and cpu never went past 70c

my system would stay cooler if the vid card didnt blow heat into the case.

 

My preference is neutral to positive pressure. My current config is 1-140mm intake and 1-140mm exhaust. Cold intake air in the front lower portion of my case with hot exhaust air out the top rear. A direct non-turbulent path of air over and past your components is the most important aspect.

 

A turbulent flow cools components more quickly than laminar.

I think what you mean is a largely unobstructed flow over components. No cables, wires, etc, blocking redirecting flow. But turbulence on its on is good.

 

It all depends on where yu place them, visualize yo air flow and remember hot air rises up and the coolest air is at the lowest point. Positive air pressure makes sure your case always have a supply of fresh/cool air but becareful the ratio of intake/exhaust is not to big.
Ta

 

My Ventilation Setup is "Positive Air Pressure"

These are my Fans arrangement, as follows:

Function: Exhaust
1.) 2pcs-(Static Pressure) SP120 (1500rpm) attached to the Radiator, located at Top;
2.) 1pc.-AF140 (1500rpm) at Top Rear.

Function: Intake
1.) 2pcs-Static Pressure (SP) 120 (2500rpm) and 1pc-AF120 (1500rpm) at Bottom-Center Front; and,
2.) 2pcs-AF120 (1500rpm) at Bottom;
3.) 2pcs-AF120 (1500rpm) at Left-Side

Other fan, i.e. for the PSU which is at fixed 40% but automatically increases its rpm as the PSU's temperature rise up.

Chassis: Full Tower Colossus

Environment: Air-conditioned Bedroom

Rig Location: On top of my Computer Table. In fact, I never put my rig below that is almost near the floor as it'll be more prone to dust and other dirt.. so I usually prefer it to be at least 1.00 meter above the Floor.

 

no this is totally wrong.

more intakes means more cool, clean (filtered) air coming in and keep the temperature down. Also having more intakes means you have less chance of getting dust being filtered in through vents that are no covered. This is how positive air pressure works.

More intakes to keep air inside case cool and less outtakes.

Think of it this way, with more intakes then outtakes just for the sake of keeping the hot air in the case out means your PC will heat up faster as there is less cool air coming in from outside. Your suffocating the PC by not giving it more clean cool filtered air. Having more intakes than outtakes lets that cool air circulate inside the PC before being removed.

 

Agreed.

 

I think that the real question has to be, how does the air flow?

Have you ever examined a Xbox360 or a PS3 on the insides? of course they don't generate as much heat as a OC PC, but they do generate high temps, that's why they have a designed airflow channels with plastic cases, and that should be everyone's goal (with plastic cases or not...)

Right now, the airflow system on my PC is something like that:

2 120mm for intake at the front (positive pressure, that way a constant flow of cool air comes into the case and also is better at dissipate hot air)

2 120mm for exhaust 1 at the back and 1 on top (high performance, we all know hot air tends to go up, so it's better to use high perf, high rpm fans to take out the heat, leaving more room to the positive pressure fans to do it's magic).

and for my CPU I have two fans attached to the cooler, one takes air in and the other takes it away. Thing is that usually the cooler is aligned with the back fan in most of the rigs, and so it is in my rig. The thing is that the cooler fan that is looking towards the front of the case it's set as intake, as it receives cooled air from the 2 intake fans. And the fan from the cooler that is looking to the back of the case, it's set as exhaust, so the hot air emitted by the own copper cooler it's blown out of the case by the back fan, thus creating an airflow.

PS: if I'm not clear enough maybe later I can take a picture for all of you to see, if you're interested to see what I'm talking about.

 

Every case is different so there is no perfect answer.

Depending upon where you set up fans and what components you have inside, you can dramatically change the airflow. You want to avoid the creation of dead pockets of air that don't change frequently enough.

I used to try to create a positive pressure (to avoid non-filtered intake) but I've found that dust is a never ending battle so I've yanked my filters and just go with max flow.