Over the past few years, CPU speeds have been increasing at a dramatic rate. In order to generate the new speeds, CPUs have more transistors, are drawing more power and have higher clock rates. This leads to greater heat produced by the CPU in the computer. CPU heat sinks have been added to all modern PC CPUs to help try to alleviate some of the heat from the processor into the surrounding environment, but as the fans get louder and larger new solutions are being looked into, namely liquid cooling.
Liquid cooling is essentially a radiator for the CPU inside of the computer. Just like a radiator for a car, a liquid cooling system circulates a liquid through a heat sink attached to the processor inside of the computer. As the liquid passes through the heat sink, heat is transferred from the hot processor to the cooler liquid. The hot liquid then moves out to a radiator at the back of the case and transfers the heat to the ambient air outside of the case. The cooled liquid then travels back through the system to the CPU to continue the process.
What advantage does this bring to cooling a system?
Liquid cooling is a much more efficient system at drawing heat away from the processor and outside of the system. This allows for higher clock speeds in the processor as the ambient temperatures of the CPU core are still within the manufacturer's specifications. This is the prime reason why extreme overclockers tend to favor the use of liquid cooling solutions for their processors. Some people have been able to almost double the processor speed by using very complex liquid cooling solutions.
The other benefit of liquid cooling is the reduction of noise within the computer. Most current heat sink and fan combinations tend to generate a lot of noise for the fans that need to circulate air over the CPU and through the system. Many high performance CPUs require fan speeds in excess of 7000 rpm that generate noise of 60+ decibels of noise. Over clocking a CPU requires even more airflow over the CPU, but when a liquid cooling solution, there is much less noise.
Generally there are two moving parts to a liquid cooling system. The first is the impeller which is a fan immersed in the liquid to circulate the liquid through the system. These are generally fairly low in noise because the liquid acts as a noise insulator. The second is a fan at the exterior of the case to help pull air over the cooling tubes of the radiator. Both of these do not need to run at very high speeds which reduces the amount of noise by the system.
What disadvantages are there to using a liquid cooling system?
Unfortunately there are a large number of disadvantages to liquid cooling in computer systems these days. Some of the most prominent disadvantages are size and technical skills required to install a kit.
Liquid cooling kits require a large amount of space within the computer case to work effectively. In order for the system to work properly, there must be space for items such as the impeller, the fluid reservoir, the tubing, fan and power supplies. This has a tendency to require larger desktop system cases to fit all of these parts within the computer case itself. It is possible to have much of the system outside of the case, but then it would take up space in or around the desktop.
Since liquid cooling is a fairly new technology to PC computers, its still requires a significant level of technical knowledge to install. While there are kits to purchase from some of the cooling manufacturer's out there they still need to be custom installed into the PC case. Each case has a different layout so the tubes must be cut and routed specific to make use of the room within the system. Also, if the system is not properly installed, leaks could cause severe damage to the components inside of the system. There is also the possibility of injuring to the individual installing the system into the computer.
So is liquid cooling worth the trouble?
At this stage of the market, liquid cooling is still only really effective for those people who are interested in over clocking their computers well beyond what air cooling will allow. Due to the size and difficulty of the installations for liquid cooling, it is not advised for general system use. There are many effective heat pipe designs being developed now that will cool off the current CPUs on the market without the noise from a large number of high speed fans.
If CPU speeds continue to increase and no new thermal breakthroughs are discovered in regards to CPU construction, I believe that liquid cooling will begin to become more common in standard system construction. This is going to be particularly true if PC systems are going to be integrated into consumer electronics such as home theater. People are sensitive to noise when watching movies or listening to music, so any system integrated into this environment must be able to run as quietly as possible.