Among today’s computer users an increasing number takes interest in water cooling. There are more and more complete kits requiring no experience from the user, which allows water cooling to spread to larger and larger groups of people. As part two in the “article series” concerning different solutions of computer coolance we will present water-cooling and explain it’s theory…
Among today’s computer users an increasing number takes interest in water cooling. There are more and more complete kits requiring no experience from the user, which allows water cooling to spread to larger and larger groups of people. As part two in the “article series” concerning different solutions of computer coolance we will present water-cooling and explain it’s theory. The main part of the article will deal with the parts needed – as that is the most important – as well as common problems. A lot of people are concerned about leakage etc, as there are several that have gotten a scenario of “mass destruction” in their systems. However, if you are careful, there is no need to worry. To get a deeper insight in the world of water cooling, I suggest that you click the small blue text on the bottom right hand corner.
Water cooling and air cooling has much more in common than what is generally thought, the big difference is of course that water cooling use water as cooling medium. It has many practical disadvantages, but the theoretical advantages weigh far heavier. In the air cooling article I went through two basic concepts, heat capacity and heat conductivity. We are going to compare these variables between air and water.
As we can see water has far better properties, and conducts heat 25 times better than air. It also holds a lot more heat, but that just makes it take longer before the water reaches its working temperature. The important thing is the heat conductivity; since it conducts heat as good as shown, almost all heat from the block will transfer to the water.
The general principle of water cooling is that you heat water instead of air. The air is not in need of cooling, since there is a lot of it available – you can just get new air all the time. The water, though, is limited, so it needs somewhere to be cooled. This can be done in several ways (we will take a look at the most common methods later). The optimal cooling device cools the water to be at exactly room temperature, and since you almost always cool with the surrounding air it is impossible to get below that. It might seem stupid to use air cooling in a water cooling system, but the water is actually in need of cooling too.
There are lots of rumours proclaiming the protruding water from a water block to be hot, so that you absolutely shouldn’t put a video card block after a CPU block. This is just a myth though, and can easily be shown with a small calculation. There is a formula which looks like this: E=C*m*DT where E=provided energy, C=the materials specific heat capacity, m=the mass of water used and DT=the increase in heat. One can use this formula to calculate how much warmer a material gets after a certain amount of energy is provided. We also know that E=Pt, in other terms that energy is power times time. By combining them we get P*t=C*m*DT, and with some algebra P*t/(C*m)=DT. If we say that the CPU generates 80 Watts of heat, and that the pump has a flow of 1 litre per minute, then we get P=80W, t=60s and m=1kg. C has a tabular value of 4190 J/(kg*K). By putting that into the formula we get 80*60/(4190)=DT=1.15. The water that comes out from the block is theoretically 1.15 degrees (Celsius) warmer than that which is going in. Even though the water gets hotter, we aren’t speaking in any huge numbers here.
For air cooling you only need a heat sink and a fan, but when it comes to water cooling there are several parts required. First and foremost you something that transports the heat from the CPU to the water: a water block. The water block has the same function as the heat sink, and that is to be the connection between cooling medium and heat source.
There are endless models of water blocks; the most important is how the inner construction is designed. As said before water is far better than air when it comes to conducting heat, but it is still a lousy conductor compared to aluminium or copper. This means that the water is only heated in the area closest to the water block, and therefore the water must circulate inside the block. There are several solutions on that problem, the most common being a labyrinth with some irregularities. There are more advanced solutions: Swiftec has a patented flowing chamber with a ribbed base for maximum water turbulence. Moreover the total area of contact between block and water should be as large as possible. There the classic labyrinth is a very good option, since the water has a long way to go through the water block.
Dangerden’s construction |
|
Swiftec’s construction |
|
Usually there is only a water block on the CPU, but there is of course possibilities of extending the system to cool your video card and North Bridge as well as other sources of heat in you computer. There are also certain water blocks with room for one or two peltier elements, but I will not write about that in this article.
Chipset cooler |
|
Video card cooler |
|
Since the water is constantly in need of circulation there is the logical need of a pump. The pump is not a part you should spare your cash on. If it brakes there’s a risk that everything you cool might overheat. A high quality pump simply allows you to sleep better at night. When it comes to pumps there are many different kinds; the most important division is whether the pump is run saturated or dry. A satiable pump has only got one nipple (one exit). It sucks water from its surroundings, so it has to be placed in a water tank. The other type is the circulation pump that can be run dry. It has two nipples: one entry and one exit. Most often you can run your circulation pump saturated if you like, but it is usually better to run it dry. The pump has three factors that are important to look at: pump capacity (water flow), maximum lift and sound level.
Satiable pump |
|
Circulation pump |
|
Of course one wants as high a pump capacity as possible, but the water flows in the pump specifications are at best exaggerated, and are specified when there is no flow resistance. As soon as you put a water block in the system or let the pump press water upwards then the flow will decrease radically. The measurement of maximum lift is a good way of checking the decrease in flow as flow resistance increase. Therefore a higher maximum lift is often better than a higher flow. Of course a higher flow gives better or in worst case equal cooling. The sensitivity of the system when looking at water flows depends a lot on which components you’ve got and how many heat sources you cool. The best way is most often to try and see. Not everyone has access to ranges of different pumps, but remember to try finding an even line. A bit too much flow is better than a bit too little, but with increased flow comes increased pressure and with increased pressure comes an increased risk of leakage. Moreover a more powerful pump generates more heat that heats the system, so it might be hard to decide which pump to actually choose.
All pumps need a power supply in one way or another. The most common way is to connect it to your standard 230V or 100V via a separate cord. There are specially designed computer pumps that work on the computers own +12V or +5V though. These are connected either to the motherboard by a 3-pin contact or directly onto a Molex. There are Eheim-pumps that can get a +12V connection by modification and ThermalTake’s Aquarius II also runs at +12V. The advantage with this is that the pump starts running at the same time as the computer. In any other case you would have to hit the pumps “ON”-button separately or have a circuit with a relay that turns the pump’s power supply on simultaneously as the computer.
Time has come to take a look at the radiator, without it no watercooling system will work very well. The radiator cools the heated water. The goal is to keep the water as close to room temperature (air temperature) as possible. If you use a processor that produces a lot of heat or if you are using peltier it takes a fairely potent radiator to handle the job. There are, however, alternatives to the radiator. If you only use the computer for short periods at the time a large water reservoir will suffice. But then again, time becomes a limiting factor. The water constantly heats up and eventually you might reach unwanted temperatures. But with shorter sessions it’s probably going to be enough. This time varies with the amount of water in the reservoir of course. Using say, a 500 litre reservoir, you could manage for long stretches of time but you probably don’t want half a ton of water next to your computer. Another alternative to radiator is using a so called ‘bongo cooler’, we will bring this up in a comming article so stay tuned for that one. Just as it did when it comes to choosing pump there are a lot of different radiators to choose from. This poses the question, what should one think of when choosing radiator?
This is a time to think things through. What’s an acceptable sound level? Does it have to be inside the case or can it reside outside it? The need for airflow decreases with the size and efficiency of the radiator and less airflow means less noise from fans. If one should use a radiator that was really big and efficient you wouldn’t need fans at all. To manage totally without fans could be hard if you have a system that develops a lot of heat (say approx. 150W+). Those who have these kinds of systems are probably hardened overclockers that use a substantially overclocked cpu and high voltages or maybe a peltier. Peltiers result in a lot of access heat to manage, another issue covered in a forthcoming article. These people probably didn’t have low sound levels set as their top priority.
If we sort roughly amongst the radiators you could say that there are basically two kinds of occuring types. Let’s look at this picture: (pictures says as you might have heard more than a thousand words;))
Radiator, pipes with lamellae |
|
This type of radiator is the least effective of the two kinds we examine here (this is not said to indicate that the radiator seen here is in any way bad, it’s to illustrate that the construction isn’t the most effective). Like when we were talking about waterblocks the main aim is to acheive maximum contact surface for the water. A pipe doesn’t give the maximum surface coverage. The thin lamellae attached against the pipe also need to have close to perfect contact in order to make this type of radiator somewhat efficient.
To buy a radiator in Sweden is not the simplest of things if you want a really good one. That is if you want to buy it from a computerstore! For my own watercooling system I bought my radiator from the local car demolisher. This is a good place to find really potent radiators at a very resonable price compared to what computerstores charge. For only one or two hundered kronor (SEK) you could get a radiator that’s better than those found in computer stores. Recently it has started to show up radiators on the market which use the very same technique as car radiators do, the only differance is that they are slightly smaller. A disadvantage with many of these radiators is their size since they most of the time originate from cars. Fitting them into your case could prove to be a problem. Smaller ones are avaliable though and if your lucky you could find a nice oilcooler, which are much smaller. For me on the other hand, I wanted something robust.
The intire radiator |
|
Waterchannels |
|
As you might notice the radiator is quite large and nothing you easily mount into the case. I got it for about 400kr (SEK) at the local car demolisher’s. This particular one was overly expensive since it came out of a brand new Mercedes (Obviously easily sold and popular radiators!?), the other radiators were somewhere between 100 and 200 kr (SEK). Remember to check the radiator for leakage before you buy it! Here we see that the water channels are constructed in a different way. It has more and thinner channels, ergo it has a greater contact suface. It’s a total of 76 channels in this perticular radiator. Let’s look at a cross cut visualisation of the two radiators.
Radiator with pipes |
|
Radiator with thin channels |
|
As you can see here the right side radiator has a bigger contact surface for the water. This means that it will be much more effective. It doesn’t have to look exactly as the picture with two rows of channels, it could just as well be one or three or whatever the number. But the principle of cooling is the same, many tiny thin channels.
A minor summation:
The later type (car radiator type) is more efficient that an ordinary radiator with pipes. They are also more expensive and not very easy to come by in Sweden if you want to buy from a computer/cooling store. But if you want an efficiant and adequately sized radiator for mounting inside the case it’s worth both the money and the hassle. If you could consider some modifications and possibly have it outside the case finding one at your local car demolisher’s shouldn’t be a problem (with some luck you could find one not to big like an oilcooler). Alternatively you could buy a brand new car radiator but then the price gets much higher of course. For those who don’t have maximum performance in mind a radiator with pipes will do just nicely. There are many at hand in different sizes and not to expensive. Make sure to check if the pipes have good contact with the lamellae before you buy one though.
Enough about the radiators, moving on!
Something vital is missing, namely the hose. Without hosing, moving the water amongst the components will be very difficult. The choice of hose is more important than you might think. A cheaper hose isn’t as bendable as the more expensive alternatives but since the other parts aren’t exactly free, spending lots of money on hose is something that you probably don’t want to do. Hose made from PVC plastic is the cheapest alternative that you can use with a watercooled system, you can get that for approx. 15 to 30 kr/m (SEK). Next step is hose made from silicone, thats about 100 to 150 kr/m (SEK). Good silicone hose is avaliable at Overclockers. An alternative to silicone is tygon hosing. Tygon hose is not as bendable but it’s more dense than a silicone hose. This means that the water will not evaporate through the hose, this is not a problem really no matter what type of hose you choose. Tygon hose is about as expensive as the silicone kind but it’s much harder to come by.
Two kinds of PVC-hose |
|
Tygon hose |
|
For the hose you need clamps. These are used to create extra pressure between the hose and the nibble, this reduces the risk of leakage. There are several kinds of clamps, plastic ones are often avaliable through computer stores. The plastic kind is gentler to the hose than one made from metal but they are a lot harder to open. The metal clamps are adjusted with a screw while the plastic ones are snapped together.
Metal clamps |
|
Plastic clamps |
|
There are a lot of other components you can ad to a watercooling system but none are vital to the essential function of the system. One good example is the tank. A tank makes it a lot easier to fill or empty the system of water and it’s also a good spot for evening out pressure. If you get bacterial growth it could cause an overpressure and that’s never good. Simply opening the tank would release redundant pressure. A tank slightly lowers the temperature if the system too since the water gets more contact with the air. Another thing you could do is to dye the water with uv-sensitive dye that when litt by a UV-CCFL produce a cool effect in the dark. And we have flow sensors that warn if waterflow stops and so on…
Watertank |
|
Flow sensor |
|
Apart from all this you need water. Ordinary ionised water (drinking water) can be directly harmful to the system. If the water is hard calcium oxide can be formed in the radiator and the block, which diminishes the contact area and the performance. This can be set right by adding a little vinegar to the water (the key word is ‘a little’, a tablespoon per litre is enough).
In addition, all different ions conducts electricity, and ionised water means that there is ions in it. If a leak would come up somewhere in the system it could short circuit the components, thus making a big damage to it. By using distilled water you bypass most of the problems, but even distilled water conducts a little electricity. This is due to the waters hydrolysis, H20 + H20 <=> H30+ + OH-. I’ve never experienced any leakage during all my crazy watercooling experiments, but the risk is always there so be sure to use distilled water. Distilled water, also known as battery water, can be found at your nearest gas station.
The last thing you have to think about is that the components need to be compatible with eachother. You might think that all you have to do is buy everything needed, connect the stuff and then everything will be fine, but unfortunately that’s not the truth. First of all there are different diameters of the tubes, 3/8″ and 1/2″ are the most common ones. It makes it easier if all components in the system have the same size of the fittings so you don’t have to convert different thick tubes.
Fittings of different sizes: 1/2″, 3/8″ and 1/4″ |
|
Furthermore it’s important that all blocks and the radiator are made of the same metal, a mixture is never good. This is due to different metals has different electric potentials, which means that a galvanic cell forms if you mix different metalls. If you have, as an example, an aluminium block and a copper radiator, the copper will dissolve gradually and the copper ions will travel to the aluminium block. There, copperions will become metallic copper and simultaneously dissolve some aluminium. In time this continues, more and more of the block will dissolve, and more and more copper will become an obstacle which prevents the water flow. There are anti-corrosion substances which can be solved in the water, but the best thing is always to use the same metal of the parts in the system.
Anti-corrosion substance |
|
Lately, a lots of complete water cooling packages has been released, so you don’t have to think about all you need by yourself. The price for them are from 180$ and above, and can be a good alternative for the novice. All parts are guaranteed compatible with eachother, and often a liquid you solve in distilled water, which prevents the problems with corrosion and so on, is included. The disadvantage of these complete packages is that the performance almost never can challenge a hand picked system. This is due to the fact that it’s cheaper to buy a complete system, and the parts simply are not as good. Another disadvantage with a complete system is that you can’t chose what components you want. If you build your own system you can chose a radiator which fits perfectly in your case, or the water block you think is most beautiful. In short, complete packages are good for the doubtful user who wants to try water cooling, but don’t dare or can’t build anything by him/herself.
Complete package from asatek |
|
Complete package á la Swiftec |
|
Altought that water cooling is in no way as easy to handle as air cooling, it isn’t as complicated as many expect it to be. Of course it does require a little more work to bring the case wherever you want, but the performance is a lot better. Water cooling is a good stage for the pretty experienced user who knows pretty much about hardware. Of course novices can use water cooling too, but there is a risk that the extra performance won’t be used. Also to make a water cooling system is a fun project, and if nothing else, a good reason to spend a lot of money. A home made system has huge expansion possibilities, and is also a long term investment. If you buy a new video card you can almost always use the same water block as you did with the old card, so even if the price is high when you buy it, the system works for a long time without any performance loss, which makes it a really good investment. In the next article we’ll look into the myth about the peltier elements and to see how they really works, stay tuned!
