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A pair of water coolers compared

Corsair's Nautilus500 and Zalman's Reserator 1 Plus duke it out
— 12:11 AM on April 19, 2006

FOR YEARS, WATER COOLING has been reserved for the most committed overclocking and silent computing enthusiasts. Piping water around a PC's internals definitely isn't for the faint of heart, and generally only those with supreme confidence in their plumbing skills have been courageous enough to tempt fate. Fortunately, water cooling is slowly becoming more accessible as all-in-one kits that minimize the need for extensive amateur plumbing become more common. These kits are perfect for those looking to get their feet wet without diving into the deep end, so to speak.

Two of the more interesting water cooling kits on the market are Corsair's new Nautilus500 and Zalman's Reserator 1 Plus. Both are second generation kits, and while Zalman's design is a refinement of the original Reserator, the Nautilus500 is all-new for Corsair. Each offers a different take on water cooling, as well. The Reserator targets low noise levels, while the Nautilus aims for ease of installation. But which kit is best for you? And perhaps more importantly, is either significantly superior to traditional air cooling? Let's take a look.

Why water?
Before probing the two water coolers we'll be looking at today, we should take a moment to address some of the motivations behind water cooling itself. After all, if traditional CPU coolers are capable of keeping even Intel's toastiest of space heaters from melting, why bother with the tubes, fittings, water blocks, radiators, reservoirs, and additional costs associated with water cooling?

For the answer, we need to look no further than water's thermal properties, specifically how its specific heat capacity and thermal conductivity compare to that of air. Those properties help determine a material's suitability for cooling applications, and as it turns out, water is far superior to air. A substance's specific heat capacity is the amount of energy required to change the temperature of one unit mass of the substance by one degree. Specific heat capacity is commonly expressed in joules per kilogram Kelvin, with higher values reflecting a greater capacity to absorb and retain heat. Here, water has a sizeable advantage—its specific heat capacity of 4.184 J/gK is more than four times higher than air's 1.005 J/gK. Water looks even better when we consider thermal conductivity, which describes a material's ability to conduct heat. Thermal conductivity is measured in watts per meter Kelvin, and again, higher values are better. Water's 0.6062 W/mK thermal conductivity dwarfs that of air, whose thermal conductivity is only 0.0262 W/mK.

While much of water cooling's appeal coasts on its comparatively attractive thermal properties, where that water flows can also affect system temperatures. Traditional processor coolers blow air around inside an enclosure, relying on exhaust fans or careful ducting to coax hot air from a system. Water cooling can be considerably more direct by using tubing to cleanly pipe water flow from a case. Radiators and reservoirs can be housed in external enclosures where heat transfer won't warm a system's internal components, ideally resulting in lower system temperatures. However, it's important to note that system components can actually depend on the airflow generated by traditional coolers. Some motherboards rely on airflow generated by processor fans to cool voltage circuitry around the CPU socket, and select graphics cards require directed airflow over more than just the GPU.

Water's ability to deliver better cooling performance than traditional air coolers has made it popular among overclockers looking to offset the higher temperatures that come along with mind-numbing clock speeds and core voltages. Overclockers aren't the only ones benefiting, though. The relative efficiency of water cooling has also spawned designs for the quiet computing crowd. These solutions aim to maintain acceptable temperature levels with less forced airflow—and ideally less noise—than traditional air coolers.

In addition to focusing on either lower temperatures or lower noise levels, water cooling systems can also differ when it comes to their makeup. Some are complete kits that include all the necessary parts, fittings, reservoirs, and radiators, while others are custom systems built from individually selected components. We'll be focusing on the former, since building a water cooling system from scratch is generally the domain of only the most seasoned water cooling enthusiasts.

Water cooling has a lot of potential, but there are a few liabilities to keep in mind. Conductivity is probably the most obvious issue, but thankfully it's one that's easily avoided. You see, pure water isn't actually all that conductive. Tap water is, but only because of the minerals and other elements floating around in it. So, instead of using conductive household tap water in a water cooling system, most manufacturers recommend the use of distilled water. Distilled water is much purer than what comes out of the tap, making it less conductive, and also less likely to gum up a water cooling system's internals. Distilled water is cheap, too. Unfortunately, the same can't be said for water cooling systems. Water coolers can cost several times as much as even the most expensive air coolers, setting the bar of expectations rather high for their performance.