What is liquid cooling? - Definition from WhatIs.com
Part of the Personal computing glossary:

Liquid cooling is the reduction of heat in electronic and mechanical devices through exploiting the properties of liquids.

Liquid cooling is a firmly established cooling method in many current technologies. Automobiles, mainframes and the systems of computer enthusiasts have used water cooling for many years. The methods and coolants can differ between and within these categories.

In computer cooling, the most common form of liquid cooling involves a closed system of tubes that carries the liquid from one component involved in cooling to another. These systems are generally referred to as loops. There are some parts common to all liquid cooling loops:  pumps, tubing, water blocks, and radiators.

The pump pushes the liquid though a loop and must be primed in order to start circulating the liquid. Pumps burn out when spinning empty as they too rely on the fluid they circulate for cooling. The tubing is most commonly flexible plastic, often clear but sometimes colored and even UV reactive. Some users have used hard plastic or copper pipe with bend fittings or formed soft copper piping. After the pump, the tubing typically carries the liquid to the radiator where it is cooled of the pumps heat load. Then the liquid moves on to the components that need cooling. The liquid is run through water blocks. A water block is similar in function to a heat sink but the cooled surface area is enclosed within the block.  Thermal contact with components is enhanced by thermal compound. Due to the liquid’s thermal capacity (about 30 times that of air), the surface area inside is much smaller than today’s typically large high-end air cooling heat sinks. Water blocks exist for many computer components besides the CPU and the GPU. There are blocks for motherboards, northbridge, southbridge, chips and power uptake circuitry such as MOSFETs, RAM and hard drives.

 The liquid used in cooling may be deionised water or an electrically nonconductive and non-capacitive engineered fluid, of which there are a number of patented formulations. You can’t use tap water as the ions dissolved in it are likely to corrode the water blocks. For the same reason it’s inadvisable to mix metals in a cooling loop. You also have to consider algae and bacteria growth that could clog a system, so some biocidal agents should be included. A coil of silver may be used for a biocidal, although it has to be very pure for corrosion prevention. Often enthusiasts choose de-ionised water because of its performance, ready availability and low cost.

 There are other optional parts as well. A loop may use a reservoir (a tank of liquid) or a three way adapted T-line with a fill port. It may have water blocks for hard drives and ram as well. The liquid may also be actively cooled by thermo-electric- or phase change-based water chillers in extreme cases. In these extremes, there are additional considerations beyond leaks, like the possibilities of condensation or freezing the liquid.

Liquid cooling supports greater running speeds and quieter running. Among enthusiasts, there is a certain pride in the appearance and prestige of ones cooling solution as well. Liquid cooling used to be the near exclusive domain of the computer enthusiast and overclockers. Because current CPUs and GPUs run at higher speeds, they produce more heat than ever. Pre-packaged closed liquid cooling comes with some high-end CPUs and GPUs. This can be a comfort to those who still are wary of the idea of constructing their own cooling loops.

Liquid cooling is becoming more mainstream for personal computing. The densities of datacenter systems have driven this sector, which is more concerned with stability, to look at its benefits. In this sector, the most common method of liquid cooling is liquid immersion cooling: cooling by submersion in an electrically nonconductive and noncapacitive liquid that is thermally conductive. Some solutions boast as much as 99 percent savings in cooling-related electrical costs for a green data center.

See a video guide to water cooling your computer:

This was last updated in October 2014
Contributor(s): Matthew Haughn
Posted by: Margaret Rouse

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