Chandrakant Patel, founder of Hewlett-Packard's Cool Team, continues his conversation -- started here -- on new cooling technologies and the data centre of the future.
Q: You've been experimenting with using ink-jet technology to cool chips. What role will that play? A: We've been working on assisted spray cooling with our ink-jet heads to provision just the right amount of coolant in the right location. We have done a lot of papers and bench-top experiments to show that it's a viable option, but these [ink-jet heads] are not optimised for cooling. We would like to have jets with larger droplets designed for a given array, and that requires us to architect and do a lot of fabrication. We are doing a lot of research work in that, but at this point, we are looking to see if there is a lot of interest.
Q: How does ink-jet spray cooling work? A: Imagine an ink-jet head sitting on top of [a multi-core chip] which sprays drops, and imagine that three of the cores are firing. If one of the cores goes into high-speed mode, the ink jet would apply as much coolant there as needed. What ink-jets do is allow us to put the right amount of fluid that matches the heat that is coming out. The by-product of that is vapour. Water would be ideal.
The vapour will go up into the heat sink, it will condense, and it will get drawn back into the heads. The fluid will never leave the contained system.
Q: Do you see a re-emergence of water cooling for data centres? A: I can cool 15-kilowatt racks rather easily with air. We have done that for customers. When the density of the racks reaches a very high level, we will end up seeing liquid cooling [only] in certain racks. Ideally, I think that is a better way to cool the data centre, because if you start to have every rack liquid cooled, then the piping will result in a pressure drop and energy usage may end up being as much as it is for air.
Q: What will data centres look like in five years? A: Five years from now, data centres will have this flexibility. The idea of having scalability in air conditioning will be there. The scalability in power in the systems will be there, and the data centres will be built in such a way that I can adjust various areas of the data centre separately, in a scalable manner. Five years from now, if we have our way, it will be a rich sensing environment and it will be a smart data centre.