If you've ever been in a data center or computer room, you know it's not a fun place. Fans screech so loud you have to shout to have a conversation, and the computer room is kept at a frigid air temperature. That's air cooling for you.
An alternative is slowly, very slowly, creeping into the market. Market research firm IHS says in its new "Data Center Cooling Report—2014" that the market for liquid cooling infrastructure in data centers will grow by 40% this year to $2.3 billion. At that rate, this market will double in size in just two years.
Air cooling is more popular because it's easier to do and if it fails, the worst that happens is the computer shuts down. If liquid cooling fails, you have a mess on your hands. The drawbacks to air cooling are many; you need to build air conditioning into the whole data center with things like a raised floor for piping and HVAC systems. The whole room has to be an ice box so the intake fans can suck in cold air.
If you've never seen liquid cooling, it's pretty much what the name implies. Instead of a heat sink bolted into place over the CPU, a copper-based heat transfer element is bolted down and two tubes are attached. One brings cool liquid in to the heat absorber while the other sucks the hot liquid away from the CPU. The liquid keeps the copper element – copper is used because it transfers heat very efficiently – cool, which in turn keeps the CPU cool. That's known as direct to chip cooling.
In the more extreme cases, the entire electronics are submerged in a coolant. Obviously this is not a pure water coolant but a special formula that won't fry the electronics.
The real benefit of liquid cooling is that it can cut cooling expense by up to half. Liquid cooling occurs at the chip/server level, which means it is as physically close as possible to the heat source. The closer the heat dissipation occurs to a heat source, the more efficient the heat removal is, IHS says. No other heat dispersion method can get this close.
Cooling isn't a total panacea. Water cooling must be contained in a closed environment so no contaminants get into the water or coolant. The up-front costs are much higher for water cooling than for air cooling as well, but it pays off over time if you have the right scenario.
Liquid cooling is popular with hobbyists and overclockers who like to jack their CPU to 5-6Ghz, but in a standard PC, the stock heat sink is usually enough. More and more space is being dedicated to liquid cooling at retail outlets like Fry's Electronics and Micro Center and mail order outfits like NewEgg.com
But those are for consumers. There's a whole separate brand of enterprise-class liquid immersion cooling firms, including Green Revolution Cooling, Icetope and LiquidCool. A few companies that specialize in direct to chip cooling include Asetek, Chilldyne, and CoolIT.
Because liquid cooling can cost as much as five times that of air cooling, rack densities have to exceed the 15 kilowatt+ range before you will see any return on investment from liquid cooling, and servers aren't quite that dense. Because of this, IHS sees liquid cooling only accounting for 2% of total data center cooling revenues. It will be largely a niche practice used in high performance computing and ultra-dense systems.
Still, many technologies that started as a niche has become mainstream, so maybe this will catch on as well.