Most standard heatsinks are made of aluminum. Aluminum is inexpensive, lightweight, and easy to work with. These attributes make it a popular material with most system builders. The problem is that aluminum can effectively remove only a relatively low amount of heat compared to other materials, such as copper. Heatsinks made of copper do a far better job of moving heat away from your processor, but copper is much more expensive than aluminum. Most companies handle this dilemma by using a hybrid heatsink made of a copper core or heatplate, bonded to aluminum fins. Many of the high-end coolers are traditionally made completely of copper but are very expensive, with the heatsink alone easily costing $50 or more.

Regardless of which heatsink you decide on, you'll still need to choose the proper fan for your new heatsink. It's important to note that just because a heatsink comes with a fan, that doesn't mean the stock fan is the best one for the job. Research your fan selection carefully and remember that very high rpm fans provide the best cooling, but also produce an enormous racket. Balancing the airflow with an acceptable noise level will require a little research.

It is always important to check the mating surface of both your CPU and your heatsink to ensure that the mating surfaces are as flat as possible so that proper contact can be made between both the heatsink and CPU.



Watercooling

Circulated liquid cooling, known simply as watercooling to most of us, is an effective way to remove heat from your computer components. This is because water is denser than air. A typical watercooling system consists of a pump, CPU/chipset, water blocks, radiator, fan, and reservoir. A watercooling kit for your PC is much like a cooling system found in most of today's automobiles, so it's no wonder that many of the same additives are used to prevent corrosion and electrolysis. Propylene glycol, also known as antifreeze, is the most common additive used in watercooling kits to prevent corrosion, and a small bottle of propylene glycol is often included with retail watercooling units as part of the kit.

As we've said, a basic watercooling kit works in much the same way as an automobile cooling system. A water pump is used to circulate coolant through a water block attached to your CPU in the place of a standard heatsink. The liquid absorbs the heat generated by the CPU and carries it away to the radiator (also called a heat exchanger). The heated coolant transfers its heat energy to the radiator when the coolant in the radiator is run through a series of small pipes or passageways connected by a series of metal fins. The metal fins are cooled by moving cool, ambient air through the radiator with a large fan. The cooled fluid is then collected in the reservoir, where it is stored for a short period of time before traveling through the pump and completing the cycle again. It's important to remember that, although it is far more efficient than air cooling, watercooling can theoretically only cool your processor to a temperature as low as whatever the ambient temperature happens to be. Later we'll discuss other methods that can be used in conjunction with watercooling to achieve subambient temperatures.

There are two types of watercooling kits currently on the market; one type is geared more toward the novice user, the other toward the performance enthusiast.

Self-contained external kits. Targeted at the novice user, these kits require no additional modifications to your existing PC, and almost anyone can set one up in a matter of minutes. With an external kit, the manufacturer has taken every component of a full-fledged watercooling kit and fit them neatly into a self-contained unit. This allows anyone to purchase an external kit and basically set it next to any system they're currently running; within minutes you can have a complete water-cooled PC without a single permanent modification to your current case. When the time comes to move on to a different case or PC, you can take your watercooling system with you.

Some of these kits fit neatly on the top of your computer case. Others sit next to your case, which requires additional desk space. The hoses that carry the coolant to your CPU's water block are routed through a special bracket that installs into an open PCI slot in the back of your case. These systems are powered by your computer's power supply and power up when your system is started. Most kits of this nature use a low volume water pump and hardware-controlled temperature settings that allow for automatic overheat protection. Many include turbo or accelerated modes that operate the system's cooling fan at a higher speed for high cooling efficiency. While the ease of setup and low maintenance make this a popular option for novice computer users, these kits do not allow for much variation and they lack the overall performance that more sophisticated enthusiasts may require.

Build it yourself. Your second watercooling option is to assemble an internal watercooling system yourself, either from scratch or from a kit. High-performance watercooling products have become so popular that many kits can be purchased from large online retailers and computer outlet stores. These kits consist of custom water blocks, large radiators, water pumps with a 300GPH rating, and hose sizes up to 0.5-inch inside diameter.

If you choose this option for your watercooling needs, we certainly recommend buying your components as a complete kit to avoid compatibility issues. The components you purchase in a kit are designed specifically to work together to produce the best possible performance.

Deciding how the kit will fit inside your case isn't always as easy as it sounds. Once you've decided on a layout, decide on a kit (or a selection of components) that has the best design for your needs. Most of the major watercooling suppliers offer complete kits to fit most users' needs, but there is still a good deal of planning that goes into choosing a performance kit that is right for you. Planning the layout and component placement of your kit in advance will save you time, effort, and money.

The amount of time spent outlining your system's needs and component layout will directly determine the quality of your overall experience with watercooling.



Peltier Cooling

Peltiers (also known as TECs) are named for the Peltier Effect, discovered in 1834 by J.C.A. Peltier, who noted that when DC current is applied across two dissimilar materials, a temperature differential results. Thermoelectric cooling is based on this phenomenon. Peltier cooling involves the heating or cooling of the junction of two thermoelectric materials by passing current through the junction. During operation, direct current flows through the thermoelectric device, causing heat to be transferred from one side to the other, creating a cold side and a hot side.

A typical TEC is made using two thin, ceramic wafers with a series of positive- and negative-doped bismuth-telluride semiconductor materials sandwiched between them. The ceramic material on both sides of the thermoelectric makes the unit rigid and adds the necessary electrical insulation. When electrical current is applied, the negative type material has an excess of electrons, while the positive type material has a deficit of electrons. A thermoelectric couple consists of one positively charged and one negatively charged material, and a single peltier module can contain anywhere from one to hundreds of such thermoelectric couples, which are connected electrically in series and thermally in parallel.

The electrons jump to a higher energy state, absorbing thermal energy (the cold side) as the electrons move from the positive material to the negative material through an electrical connector. Continuing through the checkerboard of material, electrons flowing from the negative material to the positive material through the electrical connector drop to a lower energy state and release energy as heat (the hot side). The cold side of the peltier is placed against the CPU, usually through a cold plate to better distribute the cooling, while a water block cools the hot side of the peltier unit. Because the peltier is able to cool your system to temperatures below ambient, it's extremely important to insulate the processor to prevent condensation. Closed cell foam material is generally preferred as an insulator, because it comes in many varieties and is easy to work with. You must insulate around the socket area, as well as around the TEC itself.

Using a peltier to cool your processor is somewhat labor intensive because it requires a good deal of maintenance and constant monitoring. In addition, there's a downside to using a peltier that makes it unique from any other cooling solution: If the fan on a heatsink dies, or if a water pump fails in a water-cooled environment, the processor will overheat until it either fails or the system shuts down. But in a system that utilizes a peltier, if the thermoelectric cooler goes bad, instead of cooling, it can actually pump heat onto your processor, almost certainly killing your processor and damaging other components.



Phase-Change Cooling

Phase-change cooling (also known as vapor-phase cooling) uses a system similar to that in your home freezer and actually produces subzero temperatures. The system basically consists of the following components that work in a constant cycle to produce these extremely low temperatures: R134A refrigerant (the commercially available HFC [hydrofluorocarbon] refrigerant that is commonly used for automotive air conditioning), compressor, condenser, expansion valve, and evaporator.

The cycle is essentially divided into two sections: hot and cold. The starting point is when the refrigerant is compressed to a high pressure in the compressor. The refrigerant then passes through the air-cooled condenser in which it is condensed to saturated liquid at high pressure. During condensation, heat-exchanging coils dissipate the heat of pressurization and then exhaust it into the air. The refrigerant then passes from the condenser through an expansion valve that reduces the pressure of the refrigerant, allowing it to expand and evaporate. The evaporation process absorbs heat, making it extremely cold in the evaporator. The system then repeats this energy exchange cycle over and over.

Complete vapor-phase cooling systems are available, but are currently very expensive; only the truly hardcore need apply.



Liquid Nitrogen: LN2

LN2 cooling is expensive and dangerous, but there are a handful of people who use this method to cool their PCs. The technique is used mainly by extreme cooling gurus for what can only be described as "benchmark drag races."

High school chemistry tells us that nitrogen is by far the most common gas in our atmosphere. Liquid nitrogen is the liquid form of nitrogen gas, and it is this form of nitrogen that's sometimes used to cool a PC.

To use liquid nitrogen to cool a PC, you need to make a large pipe or cup-shaped container that will sit directly on top of your CPU. The container should be in the shape of a large top hat (think Abe Lincoln's hat), flat on one end with a high rising pipe or chimney. The LN2 is poured directly into this container. Liquid nitrogen has an extremely low boiling point (-320 F) so as the LN2 boils it instantly begins to freeze the metal container strapped to your CPU. While this produces insanely low temperatures, it also causes extremely large amounts of condensation on the LN2 receptacle. The super-cooling only lasts for the short periods of time it takes the LN2 to evaporate, making it impractical for use for anything other than a few benchmark drag races.



Take Your Pick

In the end, your cooling options are limited only by the amount of time, energy, and money you wish to spend on your system. Overall, watercooling provides the best performance for the dollar, while standalone kits provide ease of use and performance that is unattainable by air cooling alone. Choose wisely and do your homework, and you'll be more than happy with your cooling choice, regardless of which system you end up using. So let's get cooling.

by Steven Lynch