First post and Liquid Cooling question

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TheRohBoat

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Mar 7, 2014
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Hi guys! This is my first post! Mostly a lurker, I've decided to finally ask my own question because I can't seem the answer for a question others may have asked.

So I've been doing this computer thing for a while now, did some builds (nothing too crazy) and as my savings is getting closer to how much my supreme-uber-pc master plan costs, I thought I'd ask a question about my cooling that I have planned. I hate being that guy who says "money is of no object", but I have been saving up for a while. It's not like I have unlimited money either.

I plan to run multiple graphics cards. I was thinking three, perhaps even four, for multiple monitors. I also plan to water cool these cards, as well as the cpu. I think I'm confident in saying that [up to] four cards and 1 cpu can be cooled sufficiently by 2x480mm rads, and 2x240mm rads. But I'm lost as to how to mount the orientation of the fans (intake or exhaust) on a corsair 900d. For anyone who knows the case, I plan to put 1x480 and 1x240 in the basement, 1x240 in the front intake, and 1x480 on the roof of the case.

The whole idea of rads is to pass cool air over them, so they should all be intake. But that means that 1440mm of rads doing intake, but only 120 exhaust in the back which is horrible. So how can I balance between cool air intake, and good air pressure in the case? Any suggestions and protips would be appreciated!

Thank you!
 
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navysealbrian

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Jan 18, 2006
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First of all, 3-4 cards is usually wasteful. The 4th card is almost always a waste of money, and the 3rd usually is unnecessary. I can run 4800x1200 on off of my single Radeon HD 7970. I don't know what you're expecting to cool with 2x480mm and 2x240mm radiators, you are over estimating the heat output you need to dissipate. If I remember correctly, a 1x120 or 1x140mm radiator from Koolance is rated at about 300W of dissipation. At most you would need a single 1x480mm or a combination of radiators that will accommodate four 120mm fans or larger. That would easily dissipate over 1k watts of power, which will easily cover a CPU + 2 cards, even 3 cards (again 3 cards is usually unneeded). Radiators are best placed with exhaust fans. You don't want to be arranging radiators with fans as intakes as all you will be doing is pumping heat back into the case.
 
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Brantyn Gerik

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radiators on the bottom provide the best thermal performance, as it is drawing cold air from outside directly over the radiator, heat in the case is almost irrelivant for water cooling, but if you do decide to go big, i'd just suggest a large amount of intake radiators on the bottom and front, then no radiators on your top and back exhausts

to the guy above, i agree with the 4 and 3 card statements, usually just go with 2 of the currents flagships. That being said though, both mantle and direct x 12 greatly increase multiple card performance (direct x 12 is the response to mantle, not yet out, but will work on same principle.

as far as radiators, you really only need 1x120mm radiator per unit being cooled, and any more than this quickly hits diminishing returns. 1 480 would very well be enough, but who would want just one radiator? and even still you will still get noticably better performance with up to 720mm worth of radiator space. after that, you tend to hit a wall as far as cooling even with this many components

and just because a radiator is rated for 300 watts doesnt mean if will give the desired levels of temps after overclocking (a flashed bios 780 can use up to and over 400 watts alone btw). if he has been saving up, and wants to make a beast system, the best is to tell him what is the max he can do without downright wasting money. i have given my input, and i believe navysealbrian has some good suggestions, but his final one is just not right (well it's right, but you do want radiators as intakes for maximum component cooling, but still have a good amount of exhausts in your system)
 
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navysealbrian

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I don't under stand your point about the 300W dissipation. It's still dissipating 300W whether or not you have something overclocked. If your system is using 750W total, and each 120mm radiator can dissipate 300W, you'll need at least 3 of them (900W), getting a 4th would be okay too, getting more would just be pointless as they wouldn't decrease the temperature by much.
The placement of the radiator at the top or bottom doesn't matter. The ambient temperature above or below the case is practically the same. The only way the temperature will vary drastically is if you have the computer sitting out in the sun, or you have a radiator/air conditioner/desk fan blowing onto the computer. If that is not the case, then it doesn't matter where you put the radiator. In fact, the best place to put the radiator is where it's closes to the rest of your loop. For example, in my case, I have my resevior and pump in my 5.25" bay which is at the top of the case, I put 2x140 radiators at the top just behind it, and have it it going to my CPU block. In my case, it wouldn't make sense to put the radiator at the bottom since I'd have to run an extra foot or so of tubing for no extra benefit.
 
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Brantyn Gerik

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the reason you have intakes on the bottom as radiators is that heat already passively radiates up, yes it does not matter, but say with an h100i, you will get better temps as an intake on the bottom than you will as an intake or exhaust on the top simply due to the way heat moves.
 
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Brantyn Gerik

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You can argue with the above statement all you want, but you cannot prove it false as it is not false. heat rises, and so any radiator higher than the lowest place in the case will give ever so slightly worse temps than an intake radiator at the bottom of the case blowing upwards
 
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navysealbrian

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Convection plays practically no role in a circulated environment. Heat doesn't rise if there is air blowing down. Maybe you'll see a 1 C difference if you run Prime95 or Furmark. Case in point, your suggestion about using the radiator fans as exhausts has a much bigger impact, and you were right about it being cooler as using the fans as intakes. Someone tested intake vs exhaust, they stated an 8C increase with an exhaust setup using Prime95. Prime95 is never a typical load on a computer, even in heavy gaming you won't get anywhere near those levels. Placing the radiator at top or bottom will make practically no difference in cooling. However, using the fans as exhaust vs intake will increase temperatures by single digits. So you're arguing over reducing a few points of degrees under typical usage. So instead of running at 40C while gaming, you'll be instead running 45C. Regardless of where you place the radiator and how you orient the fans, the temperatures will be significantly lower than air cooling. If you want to shave off 5-10C on heavy/extreme loads, then change the exhaust fans into intake fans. Otherwise, it doesn't really matter since your computer will still be running far cooler than under air.
 
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Brantyn Gerik

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Yes, i am arguing a few degrees because to some people every degree counts, and he asked for the best, and i told him the best. You arent even making a point of argumentation. Convection does play a role and if you have air blowing down, the air becomes relatively centralized around the parts expelling heat. A radiator as an intake at the bottom gives better temperatures (marginally of course) than a radiator as an intake at the top. End of story, there is nothing else to say, I don't even know why you are still commenting on this thread. Yes it doesnt really matter all to much, but there are individuals who wish to get the lowest possible temperatures, and this is how they do it. (of course they use more radiators too, but i have made my point)
 
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