Re: rack power question, and a prediction about "direct heat removal" (DHR)

["Kevin Blackham" <blackham () gmail com>]

Forgive if this is duplicate.  Too many posts in the various forks of
this thread to dig through them all.

http://www.troxaitcs.com/aitcs/products/co2_mcc/index.jsp
http://www.modbs.co.uk/news/fullstory.php/aid/1735/The_next_generation_of_cooling__for_computer_rooms.html

"CO2 has the additional benefit that should a leak occur, it is
electrically benign. Imagine the consequences of a leak of water or
refrigerant. While a leak of CO2 could be a health-and-safety hazard,
the risk is minimised by CO2 detection as part of the system."

> On Thu, Apr 3, 2008 at 11:58 PM, Patrick Giagnocavo <patrick () zill net> wrote:
>
> > First, I would like to thank everyone who responded to my initial query.
> >
> > It seems that power and how to remove the resulting heat, is certainly on a lot of people's minds.
> >
> > Clearly the days of "including" power are past in all but sales and marketing materials.
> >
> > There is a cost to each component and markup is applied (if internally and not broken out to the customer) on each 
> > rack, each power circuit, etc. with covering the overhead of UPS, diesel generator, chillers, etc.  being a big 
> > priority.
> >
> > After some thought, I believe, to coin a term, that "DHR" or direct heat removal, in some fashion will be the "new" 
> > thing for the datacenter.
> >
> > Somewhat counter-intuitively, the focus will be to remove the heat that comes out the back of the rack rather than 
> > worrying so much about the temperature of the air going in the front as long as it falls in a generally acceptable 
> > range of say, 68-75F.
> >
> > My guess is that someone will come up with an inexpensive, reliable way to put a heat collector, which will 
> > basically look like a car radiator the size of a rear rack door, directly behind the hot air coming from the 
> > systems in the rack.
> >
> > Hot air flows past the cooling fins and is quickly cooled back to 68F; the heated refrigerant is immediately piped 
> > away, out of the room and to the chiller, so that the evil BTUs do not spread out and contaminate other areas of 
> > the room.
> >
> > It might involve a phase change material, or might involve a more traditional refrigerant.
> >
> > My money would be on R744, also known as CO2, as it is not polluting and can serve double duty as fire suppression 
> > (provided you have enough on hand to flood the area/room).
> >
> > Detectors for leaks are very inexpensive and the technology  for the closed-loop of the refrigerant cycle is 
> > already here.
> >
> > It is not caustic the way any of the salts-based variants would be, is not explosive, and is heavier than regular 
> > air, meaning it will sink below the area that most people breathe at should there be a small leak.
> >
> > With the heat being removed within a few inches of where it is generated, less CRAC units will be needed to keep 
> > the rest of the air cooled; and possibly, no separate unit would be needed if enough heat can be removed to drop 
> > the temperature below 68F.
> >
> > For fire suppression, an alarm would sound and only when it can in some fashion be "proven" that no humans are 
> > inside the area, CO2 is flooded into the area and the fire goes out.  Some form of ducting which mixes the CO2 with 
> > regular air and exhausts it is needed after the fire is out.  Firemen go in with oxygen if they need to enter 
> > before this is done.  (obviously there would be an entire tested procedure for how this is done, probably including 
> > a small oxygen mask with ~4 minutes of O2 placed beside each fire extinguisher and within easy reach).
> >
> > (For racks with less than say 4KW of power use, network and power is fed from overhead with a few feet of slack in 
> > the cables, as well as a portion of the DHR piping being flexible tubing.  This allows them to be  placed more 
> > closely together than normal, almost front to back to front to back, with enough slack to pulled the wheeled racks 
> > "out" from the stack so it can be worked on (sort of like pulling a book out of a bookshelf). They use far less 
> > space and are sold a little cheaper by the colo facility.)
> >
> > Surely there is a limit as to how much air can be moved around, even with the use of best practices, there are hot 
> > spots.
> >
> > Simple physics dictates that this is a less energy intensive cooling method as a) moving a lot of air around 
> > requires a lot of energy b) air is a lousy way to transfer heat away from where you want it to be compared to other 
> > materials.
> >
> > Cordially
> >
> > Patrick Giagnocavo
> > patrick () zill net