Cooling of data centers is one of the US Department of Energy’s challenges and poses a real challenge for HVAC design engineers. Traditionally, this has been done by blowing large volumes of cold air through the building. Directing the air through the racks to pass over cooling fins to dedicated return air aisles behind the racks is common place. But as electronics are packed into smaller packages and densities increase, air cooling is simply not got enough. Add to this the very high cost of providing mechanical cooling – roughly 20-25% of total energy cost assuming a COP of 4-5 in the cooling season. So data center cooling is something worthy of research in light of efforts to reduce carbon.
A partnership between Intel, one of the largest chip manufacturers in the world, and Green Revolution Cooling was created to design the next generation of computer rack cooling – immersion cooling. In immersion cooling, the electronics are cooled by immersing it in a non-conductive liquid. This liquid can be circulated or it can boil like a refrigerant. Temperatures can be controlled by fluid flow rates or controlling pressure (which determines evaporation temperature).
Heat can be removed near the chip desired operating temperatures – say 40-70°C (104-158°F). At these temperatures, heat can more easily be rejected to the environment through a cooling tower or even in an air cooled condenser, than if we cool large volumes of air to 15°C (59°F) or less to blow through the room.
Transferring heat from a hot surface to cold air, as is done now, is very inefficient, but the heat transfer from a hot surface to a liquid is far more efficient (and if phase change is used, even better). The trick is finding the right fluid and system that can operate with the sophisticated electronic components. It is hoped that research will improve the energy use of data centers and allow for the creation of even higher density data centers. –– Steve Terry, DTC HVAC & Refrigeration Instructor
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