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

[Patrick Giagnocavo]

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

Cordiall

Patrick Giagnocav
***@zill.ne

[m***@bt.com]

> My guess is that someone will come up with an inexpensive,=2
> reliable way to put a heat collector, which will basically=2
> look like a car radiator the size of a rear rack door,=2
> directly behind the hot air coming from the systems in the rack

> b) air is a lousy way to transfer heat away=2
> from where you want it to be compared to other materials

So how did you propose to get the heat from the equipmen
to the car-radiator door

The idea of making the entire room into a refrigerator b
bringing coolant to the racks is a good one, but I thin
that for this to be successful, more attention needs to b
paid to physical placement of things, and the chillers nee
to be broken open. By that I mean that chillers cease to b
a big box at the edge of the room because they are now par
of the room itself. Think of a flat chiller attached to th
ceiling with spaces for racks to be inserted into it

--Michael Dillo

[Marshall Eubanks]

On Apr 4, 2008, at 5:14 AM, <***@bt.com> wrote

>> My guess is that someone will come up with an inexpensive
>> reliable way to put a heat collector, which will basicall
>> look like a car radiator the size of a rear rack door
>> directly behind the hot air coming from the systems in the rack

>> b) air is a lousy way to transfer heat awa
>> from where you want it to be compared to other materials

> So how did you propose to get the heat from the equipmen
> to the car-radiator door

> The idea of making the entire room into a refrigerator b
> bringing coolant to the racks is a good one, but I thin
> that for this to be successful, more attention needs to b
> paid to physical placement of things, and the chillers nee
> to be broken open. By that I mean that chillers cease to b
> a big box at the edge of the room because they are now par
> of the room itself. Think of a flat chiller attached to th
> ceiling with spaces for racks to be inserted into it


Dealing with heat transport is an important part of the design of
spaceflight hardware, with n
convenient gases to extract heat in most cases. Heat pipes, which
can have thermal conductivities muc
higher than solid copper, are commonly used to transport heat t
outside radiators, but more important is that the entire system is
engineered to remove the heat of operation from where it is created
to where it can be radiated away

It sounds to me that blade systems are reaching the point where heat
transport will also have to be designed into the rack system, and
maybe also into the room system. A set of heat pipes could, for
example, remove heat from blades and bring it to the floor of the
rack, say to a radiator directly into the plenum of the airflow

The working fluid inside heat pipes is unlikely to leak, and
typically contains very little fluid, but in any case could be chosen
to be something that would be fairly benign if the pipe was breached,
say methanol

There might be a business model here..

Regard
Marshal

> --Michael Dillo

[V***@vt.edu]

[Robert E. Seastrom]

Patrick Giagnocavo <***@zill.net> writes

> For fire suppression, an alarm would sound and only when it can i
> some fashion be "proven" that no humans are inside the area, CO2 i
> flooded into the area and the fire goes out. Some form of ductin
> which mixes the CO2 with regular air and exhausts it is needed afte
> the fire is out. Firemen go in with oxygen if they need to ente
> before this is done. (obviously there would be an entire teste
> procedure for how this is done, probably including a small oxygen mas
> with ~4 minutes of O2 placed beside each fire extinguisher and withi
> easy reach)

You'll never get your insurance company to sign off on this. The U
Navy loses people to CO2 fire suppression systems from time to time
acceptable risk on a warship and acceptable risk in a data center ar
not even on the same page. This includes dumps that are unintentiona
- having enough CO2 around to do meaningful fire suppression in
moderate size datacenter has its own hazards associated with it

http://gcaptain.com/maritime/blog/the-dangers-of-co2-use-in-firefighting-videos

Being in the same room as a halon or fm200 dump is bad enough.
don't think I'd be willing to work at (or make my employees work at)
datacenter that had CO2 fire suppression installed, no matter ho
strenuous the assurances were that there were interlocks in place

---Ro

[Kevin Blackham]

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

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

"CO2 has the additional benefit that should a leak occur, it i
electrically benign. Imagine the consequences of a leak of water o
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 <***@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
> > ***@zill.net
> >
>
>