How to arrange airflow in your system.

How to arrange airflow in your system?

    This article will detail how to properly plan and organize the chassis interior for optimal airflow.  Optimizing chassis airflow can help to increase the efficiency of case fans, which in term will help provide better cooling performance and lower noise level
To begin, below are situations to avoid :
1. Intake and exhaust in close proximity on the same side of the chassis
This will cause the exhausted warm air to flow back into the chassis, lowering overall cooling performance
2. Airflow blocking surfaces
There are lots of panels and components that may get in the way of airflow such as graphics card, motherboard, hard drives, etc…
When moving air encounters a perpendicularly surface, it is forced to turn in another direction, which results in loss of energy and reduced airflow.
3. Air path size reduction
Air path size reduction is often seen in inadequately designed front panel or exhaust area on a chassis where intake venting area is less than 40% and exhaust venting area is less than 50%.  This situation will result in lower airflow volume.
4. Narrow angled air duct
    This maybe the worst scenario, as air duct becomes narrower and redirected in another direction, airflow is reduced extensively.
Adding narrow fan duct on the exhaust side will cause:
A: Air to twirl in the area and creating dead spot
B: Air to turn sharply, creating a spot that has weak or no airflow
C: Air to flow mostly on one side, reducing the effective exit for airflow
5. Having air exhaust to the front panel
    This does not affect cooling performance in general, however, blowing warm exhausted air to the front panel often causes user discomfort.
6. Two fans located perpendicular to each other fighting for air
This will cause air pressure imbalance and reduced flow efficiency so having one fan as intake and the other as exhaust is highly recommended.
7. Numerous small fans in different directions
Small heat generating components in most systems such as chipset, mosfet, and memory should operate normally when chassis airflow is adequate.  Adding too many small size fans can add more sources of high-pitched noise without necessarily helping the chassis in exhausting heated air.
We recommend the following methods for cooling different parts of the system

(1) CPU area
Use of a tower style cooler is preferred in most situations.  Horizontal style cooler usually ends up fighting air with the rear chassis fan and reducing overall airflow efficiency.  So the use of horizontal style CPU cooler is not recommended unless the chassis is large or is specifically designed to cope with this type of cooler.  In a normal ATX chassis, an aligned tower style CPU cooler can help drive heated air out of the chassis.
(2) Graphics card area
Most mainstream to high-end graphics card now uses sealed off air duct over their coolers, this method helps to expel heated air toward the back of the chassis.  If possible, getting a case with vents next to the graphics card slots or even in between the slots (e.g. Aero Slots) is helpful.  Having a side panel vent that blows over the graphics card may not be as helpful as heated air from the graphics card is easily blown over to the CPU area.  A front to back airflow direction for graphics card is still the preferred choice.
(3) Motherboard area
The motherboard area is the combination of both CPU area and the graphics card area, so if the graphics card used is long enough, it is likely to divide the motherboard into two separate sections.  This effect is akin to what some enthusiasts or system builders have done in the past where they make custom duct to isolate the CPU area from the graphics card area to prevent heated air from one area affecting the other.  However, if the chassis airflow is maintained uniformly throughout from the front to the back, it is not necessary to make a custom duct or separate the two cooling sections.
(4) Hard drive area
Most hard drives has operating temperatures with a maximum rating of 55°C ~ 60°C.  If this temperature range is exceeded, the lifetime of the drive may decrease.  In practice, maintaining an operating temperature of 50°C or lower is sufficient for hard drives and since they cannot be overclocked, purposefully decreasing the hard drive temperature does not result in better drive performance or longevity.  So the main goal to good hard drive cooling is to at least maintain airflow over the drives.  When choosing a chassis, look for sufficient gaps between each drive space and airflow direction of the fan to be parallel to the hard drives.  Avoid designs that place the hard drives too close to the fan, this may create a large area of air blocking surface for the fan.
(5) Power supply area
Most power supplies on the market now have fan speed control that varies fan output/speed depending on temperature or loading condition.  If possible, selecting a case with power supply farther away from the CPU area can prevent the power supply from having to absorb heated air and speed its fan up.

Conclusion:  When properly planned, a uniform chassis airflow layout can dramatically increase airflow and cooling efficiency, thus reducing the need for more fans installed or running at higher speeds.