ok i have 2 scenarios attached to this thread. now logically it tells me that you would get more airflow with version1, but since we arent dealing with a high powered fan, then the difference between airflow wont be that different anyways. is this true?

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yeh i saw this on THG on their Cebit colum i think. I belive what the answer is, is the 2nd one, but the airflow is in reverse - if that helps, otherwise it is B. the reason i think the airflow is wrong is because the flap things would act like the flaps you would see on a jet airplane - i thnk its a case of more airflow and pressure variables.

I belive the top diagram will be more efficient. at any velocity

Quote: Originally Posted by ZENNZZO I belive the top diagram will be more efficient. at any velocity

Ya im sayin what he's sayiin

for intake, as you have it drawn, the first one is more efficient.
If you were blowing out of the ducts into the case, number two would increase the velocity of the air by forcing it through a smaller hole.

One other thing to consider.


The Fan motor hub

Most of the actual air is moved from the outer area and none from the center because of the motor hub. So you need to collect that air, not exclude it.


Oops strike that. It's not that you should forget about the hub, just that I relooked the diagram and wasn't seeing the question properly.

I believe that the airodynamics still have a role to play even though this isn't a high speed fan. You see, it looks to me that in the lower diagram you have a given amount of air that can enter the shroud, and the expanding area of the shroud will effect this given volume of air.

In the top example there is no real limitation on the volume other then what the fran can pull, but the shroud helps "select" or direct where that air is coming from, ie.. the vicinity of a CPU heatsink.

When I spoke of ducting earlier, I intended a full duct that begins at the outer skin of the case at some location and goes all the way to the heatsink itself. If only one fan is going to be used, put it at the outer end of the duck so the airflow to the heatsink isn't blocked by the motor hub.

In other words, I would use something like an SLK HS designed for 80mm fans, but an 80mm to 92/120mm adapter on the heatsink, and run the duct from the adapter to the outer case and a 120mm fan of your choice at that location.

This should move a decent volume of air and direct it solidly against the full area of the HS.