Positive or negative pressure? Fan direction?

G

Gorilla

Supreme [H]ardness
Joined
Sep 14, 2007
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So I have a Thermaltake X71 case arriving tomorrow and I'm going to my system into it and out of my Xigmatek Elysium. I liked my Elysium but it is showing some wear and the cost of sprucing it up was not that much less than the cost of a new case.


Anyway, loop will be tube res -> mcp35x -> xspc rs240 -> 2500k with Raystorm block -> ex120 -> gtx 970 with raystorm universal gpu block -> ex360 -> ex480 -> tube res. As long as things fit the way I expect then that will be the loop order. Fans are yate loon high speeds on a controller.


Here is a rough MS paint diagram.




So those are the three options I am considering. The bottom triple rad doesn't really matter as it is in a pedestal of sorts.

Positive pressure: will make use of dust filters but I don't really like the idea of the top radiator pulling air in from the top as hot air rises which makes me think it is just going to end up recycling hot air.

Negative pressure, won't use use dust filters really, hard to tell exactly where air will enter case from, air will pass over hot components before going through radiators.

Mix and match: basically positive pressure but with hot air exhausted out of top through a 240 rad. I don't really like hot air through a rad, but it seems like it would be best to exhaust it up and out.
 
can you shift the top rad forward and add another exhaust fan at the top back? if you can I would have that and the back top exhausting and the rads as intake. otherwise i'd go with option 3 but maybe play with the back top fan to see if its better as intake or exhaust.
oh and F filters! i'd rather clean more often and have better airflow.
 
pretty damn good paint diagram haha. In my 900D I have the bottom 480 and the front 120s as intake, and the top 480 and back 140 as exhaust.

Gives me juuuust a hint of positive pressure to keep the dist filters working
 
I've ran with the exhaust out the top for a long time, but the rear of the case does exhaust also.

The CPU cooler shoots into a 220.

ajJnwVI.jpg


Pulls a lot of heat off the GPU also.

The RAID cards and the sound card seem pretty happy on the bottom end, the CP-850 has a 120 fan on the front and seems to handle the bottom end of the case pretty well for excess heat.

Have three old AC fans on the drive bays in the front that have run over 8 years now.

They have always been much better than the stock fans the case came with, the stock ones were stupidly loud for what they were doing.

Just a pic of really old AC fans that are running still.

54triI0.jpg


They aren't pretty these days, but have been running 24/7 about 8 years.

Those are some old workhorse fans.

Are almost as sturdy as Deltas, but those things are loud as hell of course, even if they move a ton of air.
 
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Positive pressure will help prevent dust buildup in your case. Too much positive pressure would restrict airflow.

Fan airflow will overcome any kind of convective forces. Convective forces are extremely weak and not worth considering.

Here are my suggestions:

You have a massive overkill of radiators for what you're cooling. I would ditch the rear 120mm radiator. That area gets crowded easily with the CPU waterblock, RAM, etc, and any cooling benefit you get would be minimal at best, and basically nonexistent.

Front and bottom should be intakes, top and rear should be exhaust.

Have you ever heard of countercurrent exchange? The basic principal in this case is that no matter what temperature the water is, it would always be interacting with colder air. For your setup and my suggestions, the hottest water should go to the exhaust radiator first, and then to the other radiators.
 
Tsumi said:
Positive pressure will help prevent dust buildup in your case. Too much positive pressure would restrict airflow.

Fan airflow will overcome any kind of convective forces. Convective forces are extremely weak and not worth considering.

Here are my suggestions:

You have a massive overkill of radiators for what you're cooling. I would ditch the rear 120mm radiator. That area gets crowded easily with the CPU waterblock, RAM, etc, and any cooling benefit you get would be minimal at best, and basically nonexistent.

Front and bottom should be intakes, top and rear should be exhaust.

Have you ever heard of countercurrent exchange? The basic principal in this case is that no matter what temperature the water is, it would always be interacting with colder air. For your setup and my suggestions, the hottest water should go to the exhaust radiator first, and then to the other radiators.
Click to expand...

OyzSZxi.jpg



Yeah, I know, that 120mm is probably negligible, but I actually added it more for aesthetics than anything else. I just like how it looks back there.

Regardless, first, just to clarify, the bottom 360 is in a pedestal, so any air that passes through it really isn't going to interact with air from other radiators or components. There will also be a power supply down there, but the PSU will be pulling air in from the back side of the case and blowing it out the back of the case.

Second, are you suggesting that I reverse the flow order? So it would go res/pump -> 480mm intake -> 360mm intake -> gtx 970 -> 120mm back exhaust -> 2500k -> 240mm top exhaust -> reservoir?
 
Indeed I am suggesting reversing the flow order. Well, not necessarily reversing flow order, just having the top 240 right after all of the components. However, if the bottom radiator is separate from the rest, then I suppose it wouldn't matter all that much.

Just having a 480 for a 2500k and 970 is already overkill. 480 + 360 + 240 + 120 is ultra mega [H] overkill.
 
Front and bottom (whatever is filtered) as intakes, rear and top as exhaust, as said. Then check around some vents or gaps with some sort of source of smoke (e.g. incense) and adjust fan speeds accordingly to keep a slight positive pressure (smoke being blown away, not sucked into the case).
 
Gorilla said:
So I have a Thermaltake X71 case arriving tomorrow and I'm going to my system into it and out of my Xigmatek Elysium. I liked my Elysium but it is showing some wear and the cost of sprucing it up was not that much less than the cost of a new case.


Anyway, loop will be tube res -> mcp35x -> xspc rs240 -> 2500k with Raystorm block -> ex120 -> gtx 970 with raystorm universal gpu block -> ex360 -> ex480 -> tube res. As long as things fit the way I expect then that will be the loop order. Fans are yate loon high speeds on a controller.
Click to expand...

That's way too many useless rads. After the 480 and 360, the 240 and 120 is adding complexity for no reason. Those spots should be used as your intakes or exhausts instead, ie no rads there just air.
 
thesmokingman said:
That's way too many useless rads. After the 480 and 360, the 240 and 120 is adding complexity for no reason. Those spots should be used as your intakes or exhausts instead, ie no rads there just air.
Click to expand...

Your forum title should be revoked and changed to 2[soft]4U.

Come on guys, I am at the point where I barely even need fans anymore (obviously I still need them because even just barely turning they make a huge difference over passive cooling). I will do some testing at some point, but last time I did some tests with both cpu and gpu under constant load there was no meaningful difference between fans on high and fans just barely moving. That was before I moved to this new case with an extra 240mm rad. Right now my pump is the loudest part of my system (I haven't set up pwm in speedfan yet). It's not even like it is loud, it's just that it's the only thing making any noticeable noise.
 
Gorilla said:
Your forum title should be revoked and changed to 2[soft]4U.

Come on guys, I am at the point where I barely even need fans anymore (obviously I still need them because even just barely turning they make a huge difference over passive cooling). I will do some testing at some point, but last time I did some tests with both cpu and gpu under constant load there was no meaningful difference between fans on high and fans just barely moving. That was before I moved to this new case with an extra 240mm rad. Right now my pump is the loudest part of my system (I haven't set up pwm in speedfan yet). It's not even like it is loud, it's just that it's the only thing making any noticeable noise.
Click to expand...

I'm all for overkill, but every fitting you add is one more potential leak. If you can run all the fans at a couple hundred RPM and keep the temps to a minimum, why add more? There's a line between being "[H]ard" and just wasting money and time.
 
A single 480 will keep those compinents cool at minimal fan speed... Let alone a 480 + 360 + 240 + 120.
 
thesmokingman said:
Seriously? There's overkill and there's stupid. You're not even using any parts that put out serious heat to even need overkill.
Click to expand...

If you could "need" overkill it wouldn't technically be overkill.............


Anyway, still working on it. I had to order some more fans (good news is that means I will have enough for push/pull on some radiators because I obviously need that) so I haven't bothered with cable management in the back yet. I currently have a 5.25" fan controller in the pedestal, but that is kind of inconvenient. I initially placed it there because I thought the 480mm radiator in the front would block use of the 5.25" drive bays. It turns out that this case is so huge that I still have an unblocked 5.25" drive bay. I don't like the way the fan controller looks though because it does not match the front of this case at all. Hmm, decisions decisions.

I haven't decided if I am going to keep the lighting in the bottom pedestal yet. I also need to fix my 3mm LEDs for the raystorm cpu block.





 
Enough/sufficient: works within specified limits
More than enough/plenty: Works even when exceeding specified limits
Over kill: Your system will crash before you see a change in the efficiency of your cooling system.
 
You want your case to be positively pressured. That means more CFM intake than exhausting. This method has two benefits. 1) It helps to keep your system clean if you have a case that will have a filter over the intakes because air can only enter the case by the fans. A negatively pressured case means air leaks in wherever it can make way bringing dust with it. 2) Higher pressure equals more air density which means better transfer of heat due to physically more air in the case available to move heat away from the motherboard.

And while I'm not a major OCer, I prefer my radiator front mounted because I want the coolest air possible coming over the radiator. I don't want warm case air used to cool my water.
 
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