Herb Zien is CEO of LiquidCool Solutions, a technology development firm with patents surrounding cooling electronics by total immersion in a dielectric fluid.
Today, virtually all data centers circulate conditioned air around the data processing room and through the racks to cool IT equipment. Separate hot and cold aisles are maintained to conserve energy, and blanks are inserted to prevent short circuiting through empty slots in the racks. In most installations cold air is forced up through holes in the floor. Humidity control is critical to avoid condensation on IT equipment if too high or electrostatic discharge if too low.
Get Rid of the Horse!
None of this makes sense. Air is a thermal insulator with an extremely low heat capacity and virtually no thermal mass. Cold air sinks. Contact between air and electronics promotes oxidation and corrosion. Pollutants in the air can cause additional damage. Fans can fail, affecting reliability. Earplugs are required in some data centers due to excessive fan noise. Heat generation at the device level is bumping up against the thermodynamic limit.
Some engineers argue that the day for liquid cooling will come when racks reach 25 kilowatts or hell freezes over, whichever comes first. But the ability to accommodate high power densities is among the least important benefits of liquid cooling. My great grandparents did not trade up from a horse and carriage to a horseless carriage because they wanted to go 30 miles per hour; they did it to get rid of the horse! The horse wasted energy, took up space and had a negative environmental impact, sort of like fans in a data center. Data center owners and operators should want to get rid of the fans regardless of power density.
But Why Are Fans a Problem?
- Fans are inefficient and add to the heat load that must be dissipated: 15 percent of data center energy is used to move air and onboard fans in the chassis can use up to 20 percent of the energy at the device level when servers are operated at full load.
- Fans waste space because racks need room to breathe and CRAC units and in-row coolers take up expensive floor space.
- Fans reduce reliability because they are prone to failure, electronics are exposed to air, and thermal fluctuations and vibration drive solder joint failure.
- Fans are noisy, blow dust around and generally create environmental issues for equipment operators.
So the issue has nothing to do with liquid cooling, it is all about getting rid of fans. The engineering problem is how to replace fan-based cooling with a cost efficient platform that is scalable and provides quick and easy access for maintenance.
There are companies that offer technologies that eliminate fans. These technologies travel different paths to reach the objective of getting rid of fans, but they all isolate electronics from air, significantly reduce or eliminate the need for mechanical refrigeration, save space, reduce thermal fluctuations, reduce noise, eliminate the need for humidity control, eliminate raised floors or high ceilings, and facilitate energy recovery. As icing on the cake they also can dissipate heat from high density racks. Some are more practical than others, but my guess is that all of these technologies are more cost efficient than current data center cooling practice.
Industry Perspectives is a content channel at Data Center Knowledge highlighting thought leadership in the data center arena. See our guidelines and submission processfor information on participating. View previously published Industry Perspectives in our Knowledge Library.