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How many Fans for CPU Duct?

post #1 of 15
Thread Starter 
Hi,
I am planning on purchasing an extendable duct to run from the side of my case to my CPU HSF. My case came with an 80mm side airhole and this is perfect. My question is, should I put 1 fan on the Heatsink, one fan on the side of the case, and then run this duct between the 2, or should I just run the duct from the side hole(no fan) to the fan on the processor. Basically. I can have 1 fan on each end of the duct(1 fan being CPU fan), Or the cpu fan pulling air from outside the case, through the duct to the heatsink.

Me and my roommate have talked about this and we cant figured out whether 2 fans would increase airflow or just make more noise. Thanks for your input.
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post #2 of 15
Hey planes86,

Assuming you have another air intake at least (if not more), I think you would have good luck mounting an 80mm fan in the side airhole exhausting the air. A fan on the heatsink not only is necessary for the safety of the chip, but will initiate the removal of heat from that area. If possible, you should consider installing another fan at the other end of the case to draw cooler air into it to aid in the overall heat removal process. If there is no hole or some sort of opening there, give some serious consideration to modding that end of the case if necessary. I would try the original option first and see how that works; it could be all that is needed, unless you have an unusual amount of heat (like from a high end video card or gpu).
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post #3 of 15
2 fans for assurance... one dies the other is on the job!
    
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post #4 of 15
Thread Starter 
Quote:
Originally Posted by hvacgaspiping
Hey planes86,

Assuming you have another air intake at least (if not more), I think you would have good luck mounting an 80mm fan in the side airhole exhausting the air. A fan on the heatsink not only is necessary for the safety of the chip, but will initiate the removal of heat from that area. If possible, you should consider installing another fan at the other end of the case to draw cooler air into it to aid in the overall heat removal process. If there is no hole or some sort of opening there, give some serious consideration to modding that end of the case if necessary. I would try the original option first and see how that works; it could be all that is needed, unless you have an unusual amount of heat (like from a high end video card or gpu).
I think u missunderstood.... I Have 2 80mm intakes in front of case and 1 92mm Exhaust in back.. My question is about adding a duct to the side to run fresh air to the cpu... I dont know if using 1 fan on each end of the duct is going to move more air than just letting 1 pull it all through. If i have 1 40 cfm fan on the processor pulling air through the duct, will I get closer to 80 cfm if I have a 40cfm blowing into the duct as well as the 40cfm pulling it out and over the heatsink, or will it still be 40 cfm with just more noise?
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post #5 of 15
I would be inclined to just use the ducting as a transfer tube for the intake air to the CPU fan.

Can you upgrade the fan on the CPU heatsink to a 92/120mm fan ?
What cfm rating is the current CPU fan ?

cheers
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post #6 of 15
Thread Starter 
Quote:
Originally Posted by xie67
I would be inclined to just use the ducting as a transfer tube for the intake air to the CPU fan.

Can you upgrade the fan on the CPU heatsink to a 92/120mm fan ?
What cfm rating is the current CPU fan ?

cheers

When i do this mod I will be using stock heatsink with either a 40 CFM or 72 CFM 80mm (Havent decided due to noise considerations). It can only be upgraded if I use an adapter, but the ducting and side hole are both 80mm, so I would have to use an adapter on each side of the fan to make it work...
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post #7 of 15
Quote:
Originally Posted by planes86
I think u missunderstood.... I Have 2 80mm intakes in front of case and 1 92mm Exhaust in back.. My question is about adding a duct to the side to run fresh air to the cpu... I dont know if using 1 fan on each end of the duct is going to move more air than just letting 1 pull it all through. If i have 1 40 cfm fan on the processor pulling air through the duct, will I get closer to 80 cfm if I have a 40cfm blowing into the duct as well as the 40cfm pulling it out and over the heatsink, or will it still be 40 cfm with just more noise?
Since the duct is very short, 10 inches or so I don't think it's really necesary to put another fan to bring the air towards the cpu fan. If you plan on using one 40cfm fan on the cpu cooler, and one 40cfm fan for the duct intake you'll have a double-noise 40cfm cooling system,not a 80cfm.
The fan at the duct intake could make sense if it had a bigger cfm, let's say 50 - 60cfm so that it would force cool air onto the cpu fan and thus improve cooling, but only if the duct and the fan-edges are perfectly sealed.
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post #8 of 15
Thread Starter 
So basically the fans do not add up, all that 1 on each end would do would be help to assure that I get as close to the rated CFM as possible?
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post #9 of 15
Yep, that's the thing, they don't add up, but putting at the intake a 50cfm fan that would work probably @47-48cfm woul make the cpu fan work at least @40cfm, maybe evan a little above, wich is not bad as far as I can see.
Me with only one fan + the duct I had a 3 degrees cooler CPU, dunno how much a second fan could help, but surely it would make some extra noise.

EDIT* POST 300
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post #10 of 15
Thread Starter 
Thanks Alot for your help
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