Introduction to Water Cooling

The first law of thermodynamics is the law of conservation of energy; energy is neither created nor destroyed. The second law of thermodynamics is that energy can never pass from a body of lower energy to a body of higher energy spontaneously. Entropy (or disorder) must increase with time in an isolated system. From these two laws come the commonly used phrase "no energy transfer is ever complete." Due to increasing entropy, some energy must be lost in a process, be it mechanical, electrical, natural or otherwise. This is the major cause of the immense heat that is generated with a CPU; the more transistors and leads present in a finite space, the more heat it will generate.

Specific heat is a measurement of the amount of energy needed to increase the temperature of a substance by 1 degree (for one gram of the substance.) Air has a specific heat capacity of 1.004 J/g°C, whereas water has a specific heat capacity of 4.184 J/g°C. Specific heat capacity is a measurement of the amount of Joules (a measurement of energy) that it takes for an increase in temperature of 1 degree. Therefore it takes more heat to raise the temperature of a substance with a higher specific heat capacity than one with a lower. In this case, the same amount of energy is required to raise the temperature of air 4 degrees, and water 1 degree (aproximately, as the temperature raise is not EXACTLY 1 degree).

Based on the above theory, as well as the fact that the water in the cooling system is cycling faster than air, and the increased density of water, a water cooling system can quite simply remove the heat from a processor at a much quicker rate than air cooling can, which is why so many people have used water cooling. Corsair has a large share in the memory market, but didn't see a whole lot of options for the home user who wants to water cool without having to deal with the hassle of possible leaks and designing their own system. In conjunction with Delphi, Corsair has created the HydroCool 200, and hopes to capture the market with their sleek and unique design.

Until recently (within the last year or so,) there hasn't been much for the average home user in respect to water cooling - it was an extreme solution that was best left to the crazy hardcore enthusiasts. Who in their right mind would ever dream to voluntarily use water and electronics, let alone a computer, within the same enclosure? It's not hard to figure out that electronics and water mix just as well as oil and water; water is a conductor and short circuits everything that isn't explicitly waterproofed because it becomes the path of least resistance, thereby destroying pretty much everything it touches... or so many people have been led to believe.

It is a misconception that water is a conductor; in fact it doesn't conduct well at all. Let me rephrase that, H2O doesn't conduct well at all. Pure H2O (distilled water) is a very poor conductor for reasons that are beyond the scope of this article, so I hope you will take this fact as faith.

So why do you see "do not submerse in water" (or something similar) on your hair dryer or electric shaver? Because non-distilled water (ie: tap, bottled, etc.) is not pure H2O, it has minerals and vitamins dissolved in it, which gives the water a conductive property. This is the reason that people don't just submerse their computers in distilled water, since water is a solvent, most things will dissolve into it and thereby contaminate the water, giving it conductive properties and killing the system.

For this reason it is quite hard to use water as the only method of removing heat from a processor. I have seen it done successfully (no HSF at all, simply water running over the CPU die, however without a HSF there was no suitable way to generate turbulence near the die, which hurts performance,) but the CPU ended up being permanently bound to the shroud (which was created to interface the water with the die.) I do not believe that most people would be willing to permanently bind something to their CPU (especially since the shroud is a homebrew concoction.)

So, people have done the next best thing: they have water cooled the metal heatsink on the processor, instead of adding a fan and air cooling the heatsink. To prevent the water from heating up too much, the water itself is air cooled. The water is run through a radiator, which is essentially a specialized heatsink. Radiators consist of many small fins which need to be in the pathway of air; the water heats up the radiator (ergo the water gets cooler,) and the fan dissipates the heat from the radiator into the air. Most water cooling setups consist of four things: a pump, radiator, water block (heat sink) and reservoir.

The advantage to doing something as extreme as water cooling is the ability to cool the processor more efficiently than if it were air cooled, as well as the ability to completely remove a fan from your system (or at least move it out of your system.)

Let's get onto the Hydrocool 200 itself and see how Corsair and Delphi have created their home watercooling setup.

Corsair Hydrocool 200

Unfortunately there are no specs for the Hydrocool that I could find, other than its features.

Real time temperature display (both Fahrenheit and Celsius)
Programmable alarms and emergency shutdown
High efficiency water block and heat exchanger gives RSA rating of 0.13
Included water block fits both K7 (Athlon) and P4
Extremely low noise
Visual flow meter confirms water flow
Non-drip quick connect hoses allow system to be easily separated from PC with no leaks
Extracts up to 200W of heat from a PC CPU
Rugged high reliability 12V inline pump

The Hydrocool unit is self-contained in a plexiglas enclosure that measures 13.5"x6.25"x6.5" (LxWxH). It's really not that big, but neatly packed away inside is a pump, radiator, reservoir, water flow meter, a user interface, and connectors for the water block tubes and pc connection.

Included in the package is everything you need to set up your Hydrocool:

Waterblock with hoses attached
PC connector cable
PC interface
Hydrocool unit
P4 retention mechanism and clips
K7 retention clip
Funnel
Thermal paste
Hydrocool additive
4 Plastic hose clamps
2 90° adapters/connectors
2 Hose shrouds
2 Metal clips

Just a little note, the hose "shrouds" are there for cosmetics only - they cover the hoses where they enter the PC in the back.

The buttons you see on the front of the Hydrocool are (clockwise,) temperature in Celsius (black), temperature in Fahrenheit (black), turbo (red), and set (black.) The turbo button is interesting, it will speed up the fan from its normal running speed, and of course thereby create more noise. Turbo is automatically selected when the temperature measured by the water sensor rises above 43.3°C/110°F.

The PC cable is (as far as I can tell) a DB15 connection, and is used for communication between the power circuit inside the PC and the Hydrocool unit itself. The PC interface has three connections: power (Molex), temperature sensor, and power on switch.

The molex connector is simple enough - it draws power from the PSU to power the Hydrocool unit.

The temperature sensor connection is there for the thermal probe that is connected to the water block, and used to measure water temperature (not CPU temperature.)

Finally, there is a connector that connects to your power switch in series. The Hydrocool doesn't turn on due to the power button being pushed, it actually turns on whenever there's a live power feed. The power switch tap is there so that if the temperatures get extremely high, the Hydrocool can automatically shut down the computer and save it from possible damage.