Watercooling advice please :)

Discussion in 'Cooling / Overclocking' started by ipood, Jul 4, 2006.

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  1. ipood

    ipood Registered User

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    Hi everybody!

    I'm looking to upgrade my setup from air cooling to watercooling and as my current case is just not big enough to cope and I'm new to watercooling, I would like some advice from the people in the know. I am looking at Lian Li G70B Black / Evo 360 Kit Pre-Fitted with 1 x Aquacomputer Cuplex XT Block Athon64 & 2 x Aquacomputer AquagraFX6800LE / 7800GTGS / 7900GT Block.

    What I would really like to know is am I making a good choice? I would like to overclock my CPU & GPU'S and make the whole thing quieter than my current aircooled setup :D and will i need any other bits to go with it? I would really like to get this spot on and i have a budget of about £1000 all in (including the parts listed above)

    Here are the specs:
    skt 939 X2 4200+ CPU
    ABIT A8V Fatality SLi
    Corsair 2GB DDR XMS4400 Pro TwinX
    2 x XFX 7800GT's
    Tagan 480w SLi PSU

    Any input would be most welcome :)
     
  2. pdf27

    pdf27 Homicidal Pacifist

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    This may be rather a lengthy post (or set of posts) as I'm bored to tears sitting in the lab at work trying to persuade a mass flow controller to talk to the PC it's attached to by an RS-232 line. It listens to what I say about half the time, but never replies :mad:
    Anyway....

    A lot depends on what you're after.
    - If you're after absolute silence it's a pretty good system, but you would probably want to change the fans and possibly replace the radiator with a different model (e.g. Thermochill PA series) before you were absolutely happy with it. It all depends on your standards - to me, my system is still a little bit loud, and the only part I can hear is the fan on my Seasonic S12 (just about the quietest fanned PSU you can get).
    - For max overclock it's reasonable. I'm not sure on exact performance of the system because I can't find pressure/flowrate/waterair temperature difference curves for the block on a decent testbed, but it doesn't look too bad. Conceptually it looks somewhat similar to the Swiftech Apogee block (if rather more restrictive and hence probably lower performing) - and it should be noted here that the Swiftech Apogee is about the best CPU block out there right now. Many chips will stop overclocking for other reasons before they hit the thermal limit when you're watercooling them, and it may be true for this system. Can't tell without lots more data.
    - If you're after a well built system of reasonable performance and don't feel comfortable building it yourself (and particularly if you like shiny things!) go for it.

    My system (which incidentally was both the first PC I built myself and my first attempt at watercooling) has got the following bits in it:

    Eheim 1048 pump: in performance terms much the same as the pump in the rig you're thinking about. The Eheim pumps are very quiet indeed, but suffer from a low maximum pressure difference. As my setup is designed primarily for silence and I've put a fair bit of effort into avoiding pressure losses elsewhere in the system, this is acceptable to me.
    Danger Den Maze 4 graphics card block: GPUs can generally run a lot hotter than CPUs, and most video RAM doesn't really need watercooling (ramskinks and at least some air flow over it are usually enough). As such you want a block that causes minimal pressure drop (as a rule of thumb, for a well designed block increased pressure drop = improved cooling performance) on your graphics card. The Maze 4 looks ideal to me, although the barbs Danger-Den use are IMHO badly designed (and resulted in me soaking my graphics card then damaging it by whacking it with a spanner :eek: ).
    Little River Storm G4 CPU block: Now license produced by Swiftech, mine is one of the original blocks made by Cathar. My A64 3000+ Venice is currently at 4000+ speeds, and I've only just started to properly overclock it in the last couple of days so it will almost certainly go faster still.
    Thermochill PA.160 radiator: Heavily optimised to cool well with silent fans, and single pass as well (water enters at one end and leaves at the other) so will have minimal pressure drop.
    I'm using 1/2"ID tubing, so the whole thing takes up a LOT of room in my case (Silverstone TJ-06, with the insides fairly heavily cut up).

    In all, I think my setup will probably give a better overclock and I'm certain it will be a lot quieter than this one you're looking at. However it isn't as blingy, took a hell of a lot more effort/time and involves more risk (I damaged my graphics card fitting the waterblock).

    I'll post something on the theory behind why high pressure drop is good, temperature differences within water loops and the like later this afternoon if I'm still having no joy setting up this RS-232 link. Anyone with experience of MKS PR-4000 flow controllers please let me know!
     
  3. ipood

    ipood Registered User

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    Thank you so much for the detailed reply :D

    I'm quite happy to build the thing myself, but I just want to make sure I'm getting something thats gonna do the business. I know my hardware but I don't know much about watercooling parts.

    If you had the money would you buy the same parts again ? I just want to get the mutts nuts i guess!

    will the parts you suggest be suitable for sli? and im not too bothered about it being totally silent just quieter than my aircooled setup.
     
  4. pdf27

    pdf27 Homicidal Pacifist

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    One or two modifications, nothing major. I'll do a detailed version of how I would design a setup for what you're planning with numbers later as I'm kind of busy tonight. Probably late tonight or tomorrow at some point.
     
  5. Fat Jez

    Fat Jez Master of the High Five!

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    You may want to take a look at this thread, which has been running for the last week or so.

    Cheers,
    Stephen
     
  6. pdf27

    pdf27 Homicidal Pacifist

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    Apologies if some of this is a bit simplistic, I don't know how good you are at thermodynamics and the like...

    OK, first of all the air side. Contrary to what some people seem to think, water isn't a magic way of destroying heat - what it does do however is provide an easy way to move heat about. You've still got to dump the heat to atmosphere through a radiator.
    To work out what size radiator you want, you need to know how much heat you want to dump, and hence how much air flow you need. The starting point for this is the equation:

    dh = mdot x Cp x dT

    This says that the total amount of heat dumped to air is the mass flow of air multiplied by the specific heat capacity of air multiplied by the temperature difference of the air. Thus for a system dumping 250W into the water loop (which should cover what you're looking at easily I would guess) and a water temperature 10 deg C warmer than ambient (quite a lot) you would get:

    250 = mdot x 1010 x 10

    thus mdot is 0.025 kg/sec, or 43 CFM. That's just about right for a pair of silent fans on a double radiator.

    Gotta do some work now, I'll finish this later.
     
  7. brumster

    brumster Midland Muppet

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    (All the n00bies run for miles.....) :p
     
  8. pdf27

    pdf27 Homicidal Pacifist

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    Heh. I'm just waiting to get on to how waterblocks work and why higher flows are always good. Someone is sure to come up with that "but X waterblock is better because it is designed for low flow so high flow is bad". :eek:

    Besides, weren't you the one telling me to write something like this for a sticky some time last year? :p
     
  9. ipood

    ipood Registered User

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    That all makes sence to me :) im gonna put a spec together and will post my results :)

    thank you so much for your advice :D
     
  10. brumster

    brumster Midland Muppet

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    LOL, probably, although not sure it needed to drop into A-Level mathematics and fluid thermodynamics at any point...!

    The crux of it - and this is my own personal opinion - is that there's a lot of people who want to go water cooling without really needing it. Some think it'll give them the ability to massively overclock their PC, but the latest whizz-bang cooling blocks and pumps, then sit their PC in a small, centrally-heated room that's absolutely roasting, with poor PC location and ventilation, and whinge and moan when someone comes along with a £100 Innovatek kit and gets lower temps than them. Some do it purely for silence (this is why my main rig is watercooled, really) and then waste all their effort by putting cheapy power supplies or too many fans in place.

    The rest do it purely for the bling factor, buying the latest whizz-bang blocks purely because they're the latest whizz-bang blocks. Somehow, I think there's more people out there who fit in this last category but who pretend they're in the former two... :rolleyes:

    The way some of these high-end water cooling systems are going, I don't know why people don't just bother with phase change...
     
  11. pdf27

    pdf27 Homicidal Pacifist

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    No problem. There's quite a bit more to come when I get around to it.

    OK, so we've got so far as saying that the water will be roughly 10 deg C above ambient for a pair of silent fans on a double radiator. I'm assuming Thermochill PA series radiators here, as price doesn't seem to be a major driver for you and the test data I've seen indicates that these are the best radiators out there when paired with non-screaming fans.
    Now, 10 deg C is maybe a bit on the high side, as there will also be a temperature difference between the water and the CPU itself. If you used middling fans (say one of these as a random example) you could probably get the same performance from a single 120mm radiator (just about) or get the water-air temperature difference down to maybe 5 deg C for a double radiator, 3 deg C for a triple radiator. Notice the diminishing returns here - IMHO triple radiators are really only useful if you're playing with Peltiers or are going for extreme silence on a very hot system.
    Alternatively, if you wanted to stick with silent fans (e.g. the Nexus ones) and went to a triple radiator you could get the temperature difference down to 6 or 7 deg C.

    (multipart post as for some reason the system is eating long posts of mine right now)
     
  12. pdf27

    pdf27 Homicidal Pacifist

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    Now we get on to the water loop. This is simply a way to transfer heat from the hot bits (graphics cards, CPU) to the cold bit (radiator). Because water has such a high thermal capacity and is actually pretty heavy, the speed at which it moves through the loop and the amount of time it spends in the radiator is pretty irrelevant. There is this persistent myth that water should spend a long time in the radiator to cool it down, but as the loop is closed then no matter what the radiator design water will be spending the same fraction of it's time in the radiator.

    However, this does NOT mean that the pump is unimportant, or that water speed is never important. To do this I've got to explain a bit about fluid mechanics.
    Between all fluids (i.e. liquids or gases) and solids there is what is called a boundary layer. This is the layer of fluid nearest to the surface that sticks to the surface and doesn't move. You can try this out for yourself if you like - go outside on a windy day, and feel the strength of the wind standing up and then lying down. The air is virtually still next to the ground, where the rough surface is slowing it down almost to a halt.
    The same happens inside a water block, where a layer of water sticks next to the surface of the metal. This warms up and acts like a blanket over the metal, stopping heat from transferring out and so making your CPU/GPU warmer.
    Some of the better designs of water block (like the Danger-Den TDX or the Storm) use a method called "impingement" to get rid of most of this boundary layer. This basically consists of pointing a nozzle straight at the copper above the chip and blasting water out at it. The faster and harder you blast water at the boundary layer, the thinner it becomes and the smaller the temperature difference across it. This effect actually happens with all water blocks ever built, but works best in those using the impingement process.

    We've got to be a bit careful here, as if you put too big a pump (say a 1,000 watt pond pump) in your system all the power will be used to heat up the water and your radiator won't be able to cope. However most modern PC watercooling pumps are actually pretty good, producing a lot of pressure (which can be used to drive water through restrictive impingement waterblocks) without consuming a lot of power.
     
  13. pdf27

    pdf27 Homicidal Pacifist

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    While the explanation didn't really need it, if you're going to design a system it helps to have hard numbers to base that design on. I'm an engineer (about half way to being Chartered) so I tend to give numbers wherever possible.

    Yeah. I'm a bit of all of them to be honest. The design was based on silence as a "must have" and ability to overclock in hot conditions a "nice to have" if possible. Fluid mechanics/thermodynamics interests me quite a lot anyway (I did my degree in them) so that was a major driver - probably the biggest one of all in getting me to go water rather than air in fact.

    That's largely who these posts are aimed at, rather than ipood. While he seems to be finding them useful and helpful, I'm going into far greater depth than he really needs for what he's doing.
    Besides, I need to let the geek in me out sometimes ;)
     
  14. seanyc5

    seanyc5 Silent Assassin.....

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    lol this is the most complicated thread ive ever read !!! the rad's in my house warm up not cool down. i think you mean fridge !!!! :D :D easy mistake lmao
    ________
    WEB SHOWS
     
  15. pdf27

    pdf27 Homicidal Pacifist

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    Umm... nope. I'm referring to the water circuit, and the radiators are there to transfer heat energy from the water to the air - whether in a computer cooling circuit like I was describing or in your central heating. In doing so, they cool the water.
     
  16. brumster

    brumster Midland Muppet

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    Good post ;)
     
  17. Tami

    Tami Old Sod Mod

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    1 correction

    you cannot "cool" anything, you can only remove heat.

    Physics 101 :) :)

    added smileys to show light hearted nature
     
  18. pdf27

    pdf27 Homicidal Pacifist

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    True enough - you can indeed only move heat from a hotter object to a cooler object (unless Rankine's demon is lurking somewhere nearby). That would be the zeroth law of Thermodynamics.
    I'm trying to keep my language relatively simple, since I'm pretty sure nobody wants me to throw in the TdS equations or other rubbish like S = k ln(omega).

    "Cool" is a convenient colloquialism for "transfer heat from the body in question to another body".

    I'll try to do a bit on component selection, tubing size and the like later on today.
     
  19. brumster

    brumster Midland Muppet

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    :confused:

    I like pees, me :eek: ;)
     
  20. ipood

    ipood Registered User

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    I think this post is awesome! Can't thank you enough! Its all very well people saying you need this kit because Custompc mag gave it a shiney badge to say its awesome, but that doesn't mean it's gonna be any good on my setup. I want to make the most out of the kit that i have busted my gut to buy, and using these calulations i can make sure the kit i buy will give me the maxiumum performance and scope for now and the future. I am very lucky to have the parts to make a great PC and when I do something I like to get it right, so this is just great!