Topic: Water or air cooling? (Read 5012 times)

Sorry about taking so long, work got really hectic, and I haven't had the energy.

This will be light on the math since I couldn't find my textbooks.  This is also why i haven't made a diagram; I've been really busy and making one from scratch with no references would probably be less than totally effective.

Think of a radiator as a piece of finned tube (baseboard radiation).  I'm not saying its exactly the same, but similar enough for this purpose.  So, just a piece of pipe with fins on it.  Consider the fluid flowing through the pipe; as the fluid proceeds down the pipe it will lose energy, decreasing in temperature.  Heat transfer is a function of temperature differential.  As the temperature of the fluid decreases, so does the heat transfer, assuming a constant ambient temperature.  Therefore the most effective length of pipe is the very first part.  If you have a really long pipe, the fluid will approach ambient temperature.  Really slow flow would also allow your fluid to reach ambient temperature, but that would require a similarly low flow in your block, allowing the component in question to get much hotter.

Higher flow will increase the effectiveness of the finned tube (or radiator, or block) by increasing the distance the fluid has to travel to cool down.  However, this will serve to decrease your outlet temperature relative to your inlet temperature.  This seems wrong, but isn't.  If you change anything in the system you change everything.  You also don't really care what the temperature difference across the radiator is.  What you care about is the energy transfer, which is constant.  What you care about is the leaving water temperature.  Even though you have reduced the delta T across the radiator, you will have lowered the average temperature of your system, so the temperature at the inlet of your radiator will have decreased as well.

Finally, this is something of an ideal situation.  Having a huge pump that is trying to force way to much fluid through a relatively small tube will have a huge pressure loss. This will effectively cause your pump to heat your fluid.  I'm not saying that you want to boost your flow as much as possible no matter what, I'm saying that your fluid is constantly moving through the system so it doesn't need to take time to cool down.  Your radiator is transferring the most energy when it has the hottest fluid in it.

Hmmm...thanks for clearing this up, but I guess the Laing is not able to produce the pressures that friction will have any effect.
My english is not that good to understand all you have written.
The needed flow rate for effective cooling is a controverse discussion, my expierience is, that there is nearly no difference between 60 Li/h or 80 Li/h or even more. But this may vary from the chosen radiator and blocks, some will work better  some not. The lower flow rate should be not under 30 Li/h.
Maybe your diagram will be helpful!

Correct conclusion, incorrect reasoning.

The idea that the fluid needs time to cool down is common, and is a result of thinking of the heat transfer fluid in individual parts rather than a closed system.  Heat transfer is dependent on your delta T.  Your delta T will decrease across the length of your radiator as a function of fluid velocity.  If your fluid was moving infinitely fast, your radiator would be transferring the maximum amount of heat since it wouldn't have a temperature gradient.  The same would hold true across your water block.

However, I will believe that people have tested much larger pumps then they need and found that they are running higher temperatures with the higher flow.  Really high flow will have really high pressure loss through tubing, radiators, blocks etc...  Your pump has a certain flow rate for a given head loss.  The higher your head the lower your flow.  Think of head loss as friction, which basically increases your fluid temperature.  So the higher your flow the more energy your pump is heating the fluid with.

If this isn't making sense I'll try to put together a diagram or something tonight after I get off work, maybe with some of the math if I'm feeling ambitious and dig out my old textbooks.

I am watercooling for now about 5 Years with changing equipment, only the pump is the same.
 I personally do not like the laing-style pumps, my favourite is the aquastream xt, based  on the good old Eheim-Aquarium pump, but modded. My pump is running now for the whole time without any failure.
The Laing-pump is not that stable, Eheim is a good brand for reliable systems.
Besides: there is lots of equipment avaiable tho watch over the system and shut the computer down if a failure occurs. All you can buy for money is there  .

 And it is a myth that a big waterflow is necessary, several tests have prooven that this is not the case. The water needs some time inside the radiator to cool effectivily down. Maiboard blocks are in fact very expensive, I bought some standard-blocks witch are compatible on other mainboards also, the pain is the grafik-block, beeing expensive and most times not compatible (Don`t buy cheap blocks just cooling the gpu, this is crap).

 Without CPU-fan you willget trouble with the mainboard temperature, thats why I have it under water also (some fans will do the same job). RAM-watercooling is very good also if the airflow is missing, mine are compatible and I have them for serveral years from DDR1 to DDR2, they will fit for DDR3 too.
 You have to look out for stuff that lasts long and is compatible for future, otherwise the stuff is a waste of money.

The loudest part on mine is the fan, which can be turned to a low setting. It's not very loud, more like background noise. But it's not as quiet as a liquid cooling system, or even a computer fan.

Wow, thanks for the info Nebiki!

are these a/c's loud?


you have to do it yourself. there are some kits out there, but they usually suck (and i don't know of any which cool the gfx card). get a nice pump (eheim 1046 = great) with some 1/4" fittings, some adapters 1/4" -> whatever tube you want to use and a radiator. a cheap triple radiator is enough for 1 card + cpu. if you use a dual gpu or two or more cards, i'd recommend an expensive quad (420 or 480) or even a 9x radiator. as i've said somewhere, it's pretty easy to get quality stuff in germany from about 3 different online shops.

an estimate:

40€ pump
70€ gpu block
40€ cpu block
50€ triple radiator
20€ fittings
10€ tube
40€ high quality fans (! must be high quality, you'll regret buying low quality ones)
-------------------
270€ = ~$390

things you can add: temp sensors, bigger radiator, motherboard blocks (i highly recommend not buying these. they are way too expensive and yield no benefits). some people even cool their hdds and ram, but again, not necessary (although some hdd blocks are combined with noise dampening, really neat feature because your hdds will be the only thing you might be able to hear. i use ssd only, though).

it's pretty easy to install the components and i doubt anyone would have to deal with leakages, which many who are not familiar with watercooling are afraid of. only downside of it is the cost if you upgrade your graphics card. it's usually 70€ for each new gfx card, because they won't be compatible with the next generations. once you've switched to watercooling, especially with highend graphic cards, you probably will never want to switch back to air. you won't hear a damn thing. ever (be sure to use some good decoupling on your pump, though).

Yeah, note that it does this via a heat pump so it takes much less than 1400W to move the heat. I have a 10k BTU window a/c and it's about 400W (that's just for a/c, not for miner cooling).

Also since you know that 5000BTUs are displaced you know that it can cool 1400W of energy lost from the cards as heat. Assuming the 80% efficiency, 20% loss, that means you can cool 7000W of equipment for about 250W. In reality it's probably more because you don't have to seal the box.

Do they make water cooling kits specifically for GPUs?  or is it sort of a "piece it together yourself" kind of thing?

BTU is a measurement of heat/energy
Watt is a measurement of power (energy/time)
A BTU is similar to a joule, a BTU/hour is similar to a watt.

When an AC unit says 5000 BTU it means that the unit will remove 5000BTU/hour from a space, though this depends on the temperature difference.  It is not a measurement of how much power the unit is drawing.  That would depend on the specific unit you are looking at.

never heard of btu before, the british have some really weird units.


so i guess that's what you mean. 1400W is not exactly cost efficient i would say. active cooling requires a lot of power consumption, it's not recommended unless you don't have any means left to get rid of the produced heat.

Get a 5000btu a/c unit and box it to your unit so that cold air is forced onto the cards. Forget the watercooling.

well, a waterblock is about 70€ (new, ~50€ used). you're on 6870s which cost about 130€. i wouldn't buy waterblocks for these cards. but it's up to you. if you don't plan to swap your cards anytime soon, it might still be a good investment (given that noise can be really annoying).

here's the waterblock: http://www.ekwaterblocks.com/shop/EK-PSS/EK-PSS-3831109835210.pdf

i don't know about any watercooling resellers in the US, but there should be some decent ones out there (we have about 3 huge ones in germany).

Sure. Given that it makes sense to go this route, what are your recommendations, though? Is there an obvious choice for some of these components? I'm using 6870's. Is there a good selection on blocks?

I'm trying to search for this stuff myself but it's not easy going so far...

Well again, water cooling is awful if you plan to make money. If this is your gaming rig that you're just mining casually then it might be ok.

Replacing the stock cooling is simple, just unscrew the fan shroud, pop it off, and pop off the heatsinks/fan like you would a normal chip. Clean off any crap with high grade isopropryl alcohol and you're ready to go. A little force may be necessary, but if you are really straining you are doing it wrong.

The 'best system' is a misnomer, there's the best for your needs which you can decide. The waterblock will need to be custom designed for whatever graphics card you own (the layout is different for lots of card types). The BlackICE GTX rads are amazing, but expensive, XSPC Rasa makes decent rads that are cheaper. Just make sure you have a large enough radiator setup to handle the power you are putting into it. A reservoir helps stabilize temps, fans are your choice but obviously the bigger the better. Pump will depend on your setup, need enough power to push through your entire loop with steady flow. That's pretty much all you need other than barbs/fittings and kill coils and liquid and whatnot.

for dedicated mining rigs watercooling is a waste. i, however, have made the best decision to buy a waterblock for my 6950 as it was running on 50% fan which is like living next to an airport. usually gaming rigs are idle most of the time except when you play games. that's when you don't mind the loud cooler at all. with mining however you get the noise all the time. a good 3rd party cooler would do, too, but in my case i've already had a set up watercooling loop, so it was like 50eur vs 30eur.

edit:


a laing dcc pump, an ek waterblock for each card, some cpu block and for each 100W of heat i'd say 1 120x120 radiator. my watercooling loop has 2 cards (6950 for mining, old gtx460 for everything else) and cpu which eat about 300W (when mining, no cpu load). i have a triple radiator which can keep the water temperatur at 10K above room temperature. if i decided to buy a 2nd 6950, i'd probably have to go for a bigger radiator or a more efficient one.

replacing the stock coolers is pretty easy, you just have to be careful (on ek waterblocks) to place the thermal pads so that each vrm has good contact. otherwise you might burn your card. my gtx460 has a gpu only waterblock which i would not recommend. i had to lower the voltage, otherwise the voltage regulators would go above 100°C on load.

For those of us who do require a good watercooling setup, what's the best system to get? How delicate a job is replacing the stock cooling setups on these cards?

First off ensure that you have a nice gap between the cards. What you can do is put some plastic piece or something there to open up a gap between the cards.

It's the front intake fans that matter the most, so if the stock fans aren't pushing enough CFMs then get higher speed ones or maybe one of those "Silverstone Air Penetrator" fans.  Direct them at the graphic card's intake vents at the far end of the card.

I picked up 2 HAF series cases, and since the reference coolers are almost entirely shrouded, the high case flow provides almost no benefit, so I'd almost welcome a reason to have invested in the case 

Another vote for the Twin turbo pro. I replaced the stock hsf on my 5850 Xtreme because it was too loud for me......im mining at a constant 48C at 28% fan speed with it. Definitely worth the $30 i paid for it.