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To intake, or to exhaust: that is the question!

post #1 of 20
Thread Starter 
So I just had an epiphany and could use your great opinions. thumb.gif

I originally was going to do the following:

Intake (with individual dust filters per fan):

3 x 2250 RPM front
1 x 2250 RPM back

Exhaust

4 x 1950 RPM top

Yeah, I thought that was cool and all. Hot air rises so why not bring in the cool air from the bottom and middle and vent out the top. Then I just realized something: My case is very long. We're talking about a Case Labs SMH10 here. What does this mean? Those front fans are a good 6 inches from the hardware. By the time the air makes it over there, it would have already been sucked up and out, right?

So I came up with this new plan and I was wondering if I could get some opinions.

Intake (with one large dust filter on the top since the top is removal - this will make for VERY easy monthly or weekly cleaning):

4 x 2250 RPM top

Exhaust

3 x 1950 RPM front
1 x 1950 RPM back

Basically make it backwards and adjust the RPMs accordingly. There are two fans that would essentially blow directly on the GPU and CPU. The other two would help the case temperature. My issue with this was two-fold:

#1) The case is so tall there's about an inch between the top of the case and my desk. Will this restrict airflow or will the air find it's way in nonetheless?

#2) Is putting intake fans up top a bad idea? Heat rises so I know it has to vent somewhere. The highest exhaust fan would be on the back of the case close to the top. The other 3 fans are in the middle front and bottom front and I'm not sure if the hot air would vent as easily if it's trying to force it out the bottom of the case. My guess is that the back exhaust fan would get most of the heat since the hardware is closest to it.

The whole objective for me is ease of use. It would be very nice to be able to take off the top and side panel, wash my dust filter, put it back and be done. As a matter of fact, the bottom front dust filter would not be cleaned for a while as they can't come out unless I take the radiator out, and that would only happen for cleaning or possibly changing the water.

Can anyone help with these questions or my ideas?
post #2 of 20
Forget the "heat rises".
Most cases have a volume of 2 cubic feet or less.
So, even a single 50 CFM fan will be changing all the air in the case
25 times per minute!

You're on the right track though. Add fans INSIDE the case to direct the
cool air entering the case to the components that need it.
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post #3 of 20
What have you got watercooled? How much rad? and are the rads intake or exhaust?
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post #4 of 20
Thread Starter 
Quote:
Originally Posted by billbartuska View Post

Forget the "heat rises".
Most cases have a volume of 2 cubic feet or less.
So, even a single 50 CFM fan will be changing all the air in the case
25 times per minute!
You're on the right track though. Add fans INSIDE the case to direct the
cool air entering the case to the components that need it.

Yeah true, thanks. I just want to make sure the case temperatures are also reasonable so that heat doesn't stagnate in the bottom of the chamber.
Quote:
Originally Posted by Darren9 View Post

What have you got watercooled? How much rad? and are the rads intake or exhaust?

I have my dual GPUs and my CPU watercooled using EK blocks. I have a separate chamber in the bottom of my case with a Black Ice GTX 480 radiator intake and a GTX 360 as exhaust so as to keep positive pressure. My goal here was to use the 360 to vent out the hot water coming down after the GPUs and CPU and then use the 480 to cool the water going back up.

Nonetheless, I'm not sure what the better route would be for the interior of the case?
post #5 of 20
If your WC'ing CPU and GPU's and exhausting all of it (none back into the mobo chamber) then in my experience there isn't much else to heat it up. With all rads exhausting (CPU and 2 GPU watercooled) the inside of my case barely gets 2C hotter than ambient. If your planning 4 intake and 4 exhausting 2000 rpm's in the mobo chamber as well as the rads in a separate compartment you shouldn't need to worry about the flow too much, if you need to then point a fan at the mobo but I don't think you'll have to. That amount of fans would be good enough if you weren't running WC. I'd just do whatever is easiest for the cleaning/filters ect..
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post #6 of 20
Thread Starter 
Quote:
Originally Posted by Darren9 View Post

If your WC'ing CPU and GPU's and exhausting all of it (none back into the mobo chamber) then in my experience there isn't much else to heat it up. With all rads exhausting (CPU and 2 GPU watercooled) the inside of my case barely gets 2C hotter than ambient. If your planning 4 intake and 4 exhausting 2000 rpm's in the mobo chamber as well as the rads in a separate compartment you shouldn't need to worry about the flow too much, if you need to then point a fan at the mobo but I don't think you'll have to. That amount of fans would be good enough if you weren't running WC. I'd just do whatever is easiest for the cleaning/filters ect..

Thanks for that. Will do. So I have oriented the 4 fans on the top in an intake position now.

My final question is this (as you can tell, I always try to squeeze as much juice as possible out of my rig):

Hypothetically (but really) speaking, lets say I needed to go with the single most optimum airflow build I could. So with the top 4 fans now oriented as intake, that leaves me with 4 more fans to choose what to do with.

Should I:

#1) Orient the only fan on the back of the case as intake to even further cool the motherboard, CPU, and GPUs? This would mean I have 5 intake fans, 2 of which are blowing down from above (directly on the GPUs) and one on the back of the case blowing in from the side (more on the CPU and essentially missing the GPUs) or would this mess with the intake from above and essentially blow it all away from the GPUs?

#2) Orient the other 4 fans as originally planned: exhaust?

Thanks again! Only thing I'm sad about now is that the motherboard chamber was looking SO freaking clean. Like the only wires you could see were GPU and CPU and motherboard. Now (if you look close enough, and maybe only I would) you can slightly see the fan wires. frown.gif But hey, if it makes cleaning easier I'm game.
post #7 of 20
I have the back one as an intake, just because it's the closest to the mobo so in theory the mobo gets some flow/cold air- it's a totally different case though, I'd just be guessing for you.
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post #8 of 20
Thread Starter 
Quote:
Originally Posted by Darren9 View Post

I have the back one as an intake, just because it's the closest to the mobo so in theory the mobo gets some flow/cold air- it's a totally different case though, I'd just be guessing for you.

Any help on this would be good.

For me I guess it's a tough call. If it was the only fan intaking directly on the components then yes, absolutely I would have it doing so. But I have two fans above it intaking down onto the GPU. I'm sure they're hitting the CPU as well. So there's two things I see:

#1) If it's intake, the air from this fan and the two above it will clash. The air coming down will hit the air coming in from the back and some will get pushed into the case itself and some will hit the GPUs. I'm not sure if it's more effective to just have the top two come straight down onto the GPUs and part of the CPU.

#2) If it's exhaust, the air from this fan will vent some of the air from the above fans out the back completely eliminating the cooling effect altogether. However, it's also the only close fan to the hardware components that's actually venting the air on this side of the case. Not sure which makes more sense.

Personally, I'm feeling exhaust on this fan, but I'd like someone to confirm or prove me wrong. The challenge is out! thumb.gif
post #9 of 20
Since you are trying to cool the "secondary" heat producers, I would imagine that a steady, stronger flow of air in a defined direction would be ideal. With 8 fans, and with ones as powerful as yours, you are essentially exchanging the entirety of the cases air once per second. The most important thing is that you prevent dead spots or stagnation, and provide the coolest possible air so as to transfer the most possible heat as air is a horrible heat conductor. I don't know if you will be able to determine the best way to set your fans simply by thinking it through, I am of the opinion that you will need to experiment with every possible orientation in order to actually get the results you want. I have found that sometimes what sounds like it would be best is actually counterproductive, such as the use of only one fan and placing it intake vs exhaust (exhaust is better). Your first goal should be to remove the hot air as quickly as possible, as cooler air will take its place regardless
   
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post #10 of 20
Thread Starter 
Awesome description. Thanks a lot. +rep

I will start by orienting that back fan as an exhaust fan. The only reason I feel it difficult to turn them around (as intake) is that I'm really trying to limit the dust getting into my case. My M8 build was so terrible I will never let that happen again. There were 3 intake fans on the left and 3 exhaust up top. On the right side of my case, however, I had 4 more fans intake and 3 exhaust. The only issue was that I didn't have dust filters. It was disgusting. After about 3 months I opened the case up and could literally pull cotton ball sized bunches of dust out of the fans themselves. Some of them would even get stuck when I was pulling them out due to my hair, my girlfriends hair, or the cats hair. I refuse to let that happen again and after about 4 months with DEMCifilter filters in my M8 in the exhaust vents (custom sized to fit), there was just a slight layer of dust atop everything that you wouldn't even notice without running your finger over it.

A little off topic I guess, but explains my reasoning and difficulty for just switching a fan as intake without a filter. smile.gif
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