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Is air flow short-circuitry always a bad idea?

post #1 of 29
Thread Starter 
Afternoon gents

As has been said a bunch of times, short circuiting airflow in you case can be a very bad idea. It can ruin air pressure and generate large pockets of "stale" hot air in a case.

But is it never viable to do it? I don't have a case I can test with, but I have seen examples of cases with a single intake fan, a single outtake, and two or more expansion slots in the top of the case. Assuming the case succesfully moves air from front to back, would it not be possible to have one of these top slots take air in and the other blow it out, effectively short circuiting air over the top of the motherboard?

I'm gonna go play with paint to show what I mean.
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post #2 of 29
Thread Starter 
Alright say we have a case that works like this:

But it can do this:
(Yeah the top fans there probably wouldn't be so close together, but work with me.)


The first thing everyone would recommend would be to add another front intake fan. So we do that, but the outtake fans still outnumber the intake fans.

Would this not be doable?


Obviously I'm fishing for experiences here.
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post #3 of 29
i do that now in my case, i also have a side intake, but yeah i do that right now and it works, the only thing is i have a 212+ in between the top intake and top exhaust
   
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post #4 of 29
imo, an ideal setup would be to create negative ventilation. more air coming out than coming in. by just adding another fan on top pass the intake of the cpu cooler. but not all cases allows such a setup. another solution would be to put a stronger fan for exhaust.

in my mobo the sys fan connector makes the fan run in max speed, while the chasis fan connector regulates the same fan. i put the exhaust fan in the former coz i don't mnd the higher rpm noise. my system with two case fans my temp is about 4-5 C cooler with the exhaust fan running faster than the front fan..
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post #5 of 29
why negative? you get more dust going in places without filters, i think its better to have positive air flow, ideally, the best would be to have all intake and then no rear exhaust fan and no rear grill and just let the heat sink fan be the exhaust fan and let it exhaust the air, as well as open PCI slots, that imo is the best air flow
   
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post #6 of 29
Quote:
Originally Posted by chinesethunda View Post
why negative? you get more dust going in places without filters, i think its better to have positive air flow, ideally, the best would be to have all intake and then no rear exhaust fan and no rear grill and just let the heat sink fan be the exhaust fan and let it exhaust the air, as well as open PCI slots, that imo is the best air flow
Yes, that would present a problem if you priority is keeping the inside clean. Here is a very old study but i think still applicable to today's computer cases.

http://tech.icrontic.com/articles/pc...cooling_guide/

anyway, i worked down the engine rooms of ships and it gets pretty hot down there and we always have our ventilation in negative for a number of reasons and one of them is to keep ambient temp down.

thanks for your input.
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post #7 of 29
Here is a picture of my air flow. Adding a blow hole lowered my temps by around 5C.


I am not sure if this is pertinent to your question though.
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post #8 of 29
but what if all were intake? wouldn't that keep it even cooler? if by ambient you mean the inside of the case an all intake case would push more cool air into the case and whatever hot air would be expelled the back of the case no?
   
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post #9 of 29
If they were all intakes this would make the case high pressure and the fans would not be able to push more air in because of the pressures created (reducing the amount of fresh air in). I think that I called back pressure. You need to have negative pressure to allow cool air to enter easily.

Positive pressure would mean that warm air would go around the case causing an increase in case temperature because it is unable to escape.
post #10 of 29
well as i had said before, everything would be intake except for the back, which would be no fan and no grill, so all the air would go out there
   
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