Intelligent Data Centres Issue 07 | Page 62

Content supplied by the DCA The data centre sector is rising to the challenge of identifying innovative power and cooling solutions and one such option could be liquid based. Jon Summers, Scientific Leader, RISE North, LuleƄ, SWEDEN, tells us why data centre operators need to consider how to integrate liquid distribution into their facilities to futureproof their operations. ne of the main hardware components of the digital age is the digital processing unit (DPU). Whether central, graphical or otherwise, it consumes a major portion of the energy in the operation of data centres. The ratio of the surface areas of a DPU to the area of a data hall (usually a room within a data centre) in which DPUs are housed, can be as high as 1 to 20 million. O The data centre draws electrical current from the electrical power grid and more than 50% of this current terminates at a distributed array of DPUs, where up to 200 amperes are pumped into an area of approximately 200 square millimetres. It is not difficult therefore to realise that the operational voltage of the DPU combined with the incoming current consumes power, but there are no moving parts inside the DPU to consume this energy at any time rate and so all of this electrical power in a 200 square millimetre area is converted to thermal power. Thermal management of data centres has therefore evolved to become a broad engineering discipline that involves equipment for thermal connections and transfers to carry the thermal power away from the DPUs so that they can continue to perform their tasks without overheating. The transferred thermal power from the DPUs is rejected to the outside environment. Traditional thermal connections used today are heat sinks and heat exchangers with thermal transport being achieved by forced convection of air, however there are limits to this approach of moving the heat from the DPUs due to the low thermal capacity of air and upper limits of practical airflow rates. Historically, DPU heat fluxes have been increasing and are expected to continue to rise, with values greater than 1 MW per square metre for some applications. Jon Summers, Scientific Leader, RISE North, LuleƄ, SWEDEN With these values of heat fluxes, it is not practical to remove the heat totally with air, so there is a growing spectrum of heat removal technologies that employ liquids. One can argue that data centres have already been making use of liquids to remove heat from the data halls with computer room air handling/conditioning (CRAH/CRAC) units, where chilled water or a refrigerant are used respectively to transport thermal energy out of the data hall. However, the term liquid cooling is referring to the use of liquids that come near the information technology racks. Therefore, this requires the data centre to distribute liquids into the data hall, perhaps in the same fashion as electrical Liquid cooling on the rise 62 Issue 07 www.intelligentdatacentres.com