CPU Heatsink Fan Airflow and Orientation Help !

Hi guys,
I just received my power supply, thermal paste, hard drive AND heatsink (Xigmatek Dark Knight), initially i thought installing all this would be easily done in 30 min but as I went along I realised I had a lot of questions and had a few technical difficulties removing all the parts and motherboard, so i wasted lots of time searching online... Anyhow 3 hours later im almost done and am now ready to put on the thermal paste, however im not quite sure of the way I should orient the cpu heatsink/fan... The Xigmatek Dark Knight heatsink doesnt allow the fan to be mounted on any side, it can only be mounted on 1 side thus i really want to be sure im doing it right the first time to avoid starting over... I have 2 main issue :

1. This might be very obvious to some, but i want to be sure... By looking at the fan that will be attached to the heatsink, how do i know which side pulls or push air ? I assume that the side that appears "nicer" will be the side that will be visible and thus that is the side that will be blowing air. This leaves the "ugly" side as the side that pulls air... By nice/ugly i mean the side which has a sticker logo (nice) or side which has the electric wires and frames in front of the fan fins(ugly).

2. Once I know which side of the fan push and which side pulls, then how should I place the fan ?

A ) the fan should SUCK air from the heatsink's fins, thus BLOWING it towards the case's back exhaust fan which is only 2 inches away.

Ugly Diagram A:

<<<--[Back Exhaust Fan]--<<<--[Fan]-[Heatsink's fins]---

B) The fan should BLOW air through the heatsink's fin, thus SUCKING air from the front of the case and sending it through the fins and into the back exhaust fan ( which would be 5 inches away from the heatsink fan instead of just 2 ).

Ugly Diagram B :

<<<--[Back Exhaust Fan]----<<<--[Heatsink's fins]-[Fan]---

By looking at the illustration in the instruction manual, I think it looks like option A) is what Xigmatex is recommending, however to me B) makes a lot more sense...

Of course there are other possible way to orient the fan, it could be blowing towards the front of the case or top/bottom, but I dont think these are good options...

Thanks for reading through and please do leave me your opinion, it would be much appreciated !
3 answers Last reply
More about heatsink airflow orientation
  1. Of the two choices, I vote for B. However, I have Antec 900 cases with large top mounted fans. I mount the fans on the lower side of the heatsink blowing upward.

    I figure warm air wants to rise. Why fight physics.
  2. B is the classic configuration.

    The problems with A are synching the two fans, the turbulence, and the amount of space between the heatsink fan and the exhaust fan on the rear panel. The two fans would never be in synch. That is an impossible objective. The air turbulence created between the two fans would actually restrict airflow and cooling. For it to work there would have to be a space of at least 1 inch to 1.5 inches between the two fans.
  3. B is best. there are usually little arrows on one of the sides of pc fans that tell which way the fan spins and which direction the air goes. if not, usually the side of the fan with the frame/wires is the direction air gets blown to. however, i do have a fan thats the other way around. but it came out of an imac g4 so of course apple had to make it different!
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