
The fanless spinning heatsink: more efficient, and immune to dust and detritus - lmathews
http://www.extremetech.com/extreme/89710-the-fanless-spinning-heatsink-the-heatsink-is-the-fan
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sbierwagen
I've read the paper now, so I can chime in on an informed basis.

They _claim_ a 0.2°C/W, which would be really something. You can get down to
0.37°C/W[1] with air cooling, using heroic measures, and blisteringly awful
efficiency. Doing 0.2°C/W would be a real step up.

I don't really think they've done it, here. Their experimental setup used six
1"x1" 10 watt heating elements. This is because their heatsink needs a very
large cross-section to overcome the lousy thermal conductivity of the air gap
between the impeller and the base plate.[2] Total area, 38.7cm^2, total power,
60W.

The Intel Core i7's heatspreader has a surface area of ~20.25cm^2, and a
thermal design power of 130W. 52% smaller, 216% times the heat output. That's
about four times more heat per square centimetre.

The smaller the heat source, the longer the average thermal path between the
source and the air/heatsink boundry, the worse the C/W, and the less effective
the heatsink will be. If they had actually used a computer processor, rather
than a bunch of heating elements, then my WAG is that they would have done
0.35°C/W.

It's a beautiful idea, but their setup looks nothing like reality.

1: <http://www.dansdata.com/quickshot012.htm>

2: They say that, due to the high sheer speed, there's no boundary layer,
which "increases thermal conductivity several-fold". Well that's a cool story,
bro, but air (0.025 W/(mxk)) is still _sixteen thousand times_ less thermally
conductive than copper! (401.0 W/mxk)) If you increased the thermal
conductivity of air by 6.4 times, then it would be as conductive as... rubber,
something which is not world renowned as a good conductor of heat!

~~~
miahi
Dan's article is very old (2003). At that time is was not easy to mount a big
cooler on a motherboard. The heatpipes were not widely used.

These days you can find huge coolers with (or at least claimed[1]) less than
0.2°C/W. Most of the lower power CPUs (40-50W) can run fanless at decent
temperatures with half a kilo of metal fins + some heatpipes, and you can
mount that kind of heat spreader easily with bolt-through screws.

Also, that metal fan is dangerous! If you ever touched even a slow-spinning
plastic fan's blades, you know how painful (or bloody) it can be. And that was
only a very light plastic blade, probably less than 30 grams. Now think about
the momentum of a 200 gram metal thingie spinning with more than 1000rpm (as I
understand, they tested it to 7-8000 rpm). You really want to be sure you will
not touch it while spinning. But if you enclose it, even in a wire cage, the
performance will decrease.

1: [http://www.scythe-
usa.com/support/cpu/006/scmn1000_scnj1000p...](http://www.scythe-
usa.com/support/cpu/006/scmn1000_scnj1000p.html)

~~~
sbierwagen
I would hesitate twice and then hesitate one more time before placing any
confidence at all in a manufacturer supplied number for a statistic like C/W,
which can be so easily fudged, as we have seen.

But yeah, I've been out of the overclocking scene for a couple years, now. I
have no idea how well heatpipe heatsinks perform, other than "better".

As for the danger of a large piece of metal spinning at kRPM, I agree. This is
bad enough that there probably would have to be an safety interlock on
computer case access panels that reverses the impeller to a halt when the
enclosure is opened.

~~~
jarek
SPCR is a review site pretty serious about their methology; their newest
heatsink reviews don't have °C/W figures due to difficulty measuring the power
output of socket 1366 CPUs, but here's a mid-2009 review of a huge
heatpipe/tower heatsink: <http://www.silentpcreview.com/scythe-mugen2>

Page 6 states °C/W values of 0.29 down to 0.14 depending on the amount of air
pushed with the fans. SPCR's test fans are pretty low-flow to begin with (47
CFM/1080 RPM at 12 V), so you could probably go slightly lower by using real
screamers.

------
nathanb
Two points of confusion (for me, at least) which the article doesn't
satisfactorily alleviate: first, how can something dissipate heat effectively
when there is an air cushion between the base plate and the cooling vanes? And
second, how is this device "immune to dust and detritus"? For instance, it
seems like dust could easily enter the thin air cushion layer and cause all
kinds of problems.

Can anyone help me overcome my ignorance and understand these points?

~~~
joejohnson
I can't answer your questions, but I was wondering the same things. Also, what
makes this design quieter than a traditional fan/heatsink? Isn't this still
basically a fan?

~~~
riffraff
from what I understand, the point is that lower spinning speed and better
mechanical efficiency should cause less noise

~~~
acqq
their lowest speed was 3000 rpm, target 5000 rpm.

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jws
_…if these heat exchangers can find windespread adoption in computers and air
conditioning units, Koplow estimates that the total US electricity consumption
could drop by 7%._

Wikipedia says 11% of US electricity goes to air conditioning and 5% to all
electronics combined. That about half of that is cooling fans does not survive
the sniff test.

~~~
barkingllama
I don't disagree with you that the numbers may be off, but consider the fact
that the compressors in an A/C unit don't have to work as hard if the heat
exchange is more efficient. That's saving electricity from the cooling fan AND
the compressor.

~~~
SoftwareMaven
Furthermore, put a very large one in place of the fan in the A/C condensor and
save more.

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zck
I wonder what the production cost of this is compared to a "traditional"
heatsink. It looks like it would require more metal, but I'm not sure. I don't
know if it would require more precision in the construction process, but this
smells like it will be more expensive. It might not replace stock CPU coolers,
just high-end ones. Certainly at first that'll be the case.

It looks like the benefit of this over other high-end coolers (i.e., water
cooling) is that it can be a _drop-in replacement_ for them. It doesn't seem
to require special parts, knowledge, or tools to install. It could be
installed as easily as a normal CPU cooler. The reduction in electricity costs
is exciting for businesses (consumers don't care about a 7% electricity
reduction). That it doesn't get clogged with dust is also very useful in the
long run: less maintenance.

I'll be more excited when this is in production, even at a high cost. Let's
hope it gets there.

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rytis
"The cooler consists of a static metal baseplate [...A HEATSINK...], which is
connected to the CPU, GPU, or other hot object, and a finned, rotating heat
exchanger [...A FAN...] that are cushioned by a thin (0.001-inch) layer of
air."

OK, there's only 0.001-inch between them, but still a heatsink + a fan, no?

~~~
Pfiffer
The article should probably be re-titled "Metal Fans Replace Plastic Fans as
Industry Standard Cooling Solutions".

~~~
reitzensteinm
How about "combining fan and heatsink yields efficiency gains"? It's clearly
not (just) a metal fan, since it has thermal mass and will likely be optimised
for surface area just like a heatsink would be.

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jcromartie
"Fanless" in that it is a fan itself.

~~~
ajb
It is fanless in an important sense. The job of a fan is to move the air, for
which small fans are inefficient. Then, the relative motion of the air vs the
heatsink allows cooling. But in this device, as the report says, the relative
motion of the air vs the fins is obtained directly - and much more
efficiently. The fact that the device also serves to move the air - as a fan -
is irrelevant.

~~~
tantalor
Semantics.

~~~
CPlatypus
Semantics matter. Would you rather argue about syntax?

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stcredzero
Do away with the air bearing. Just put the whole computer in the base of the
rotating heatsink/fan. Get power and data on/off of the thing using brushes.
Implement an emergency mode where the CPU slows the clock if the motor fails,
so that the heatsink still provides enough cooling without rotating.

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dexen
There is one existing technology that could perhaps do away with the problem
of the air gap (if that's a significant problem at all): heatpipe.

The good old heatpipe could extend from the stationary baseplate, as an
axle/shaft of the impeller, well into the spinning part and here flange out
internally. The seal/bearing would have to be quite gas-tight, but if that's
achieved, heat transfer could be great.

~~~
sbierwagen
It would have to be gas tight, _and_ resist a pressure differential. (HSF
heatpipes contain water in a partial vacuum)

It must also not leak at _all_ over the course of several years at elevated
temperature, while spinning at several thousand RPM, or else the heat pipe
will stop working.

It also must be cheap enough to compete commercially with a solid piece of
metal.

The design constraints are... loosely possible. But it sure as hell won't be
_cheap._

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thinkcomp
I hope to see this in systems soon.. It would be really nice not to risk
hearing loss every time I walk into the data center!

~~~
JonnieCache
Isn't most of the noise in a datacenter the compressors in the aircon units?

~~~
calloc
No, it is all of the fans sucking air in the front and dumping it out the
back. Fire up a 2U server in an otherwise quiet room and it will sound like
someone just fired up an vacuum cleaner...

~~~
MostAwesomeDude
I have two Dell PowerEdges in my living room and they make a sound not unlike
an airplane revving up for takeoff.

------
JohnLBevan
This gives me a thought. . . could Dyson Air Multiplier technology be scaled
down to be used in computers?

[http://www.dyson.co.uk/technology/airmultiplier.asp#HowItWor...](http://www.dyson.co.uk/technology/airmultiplier.asp#HowItWorks)

~~~
jarek
If it can, I'm not sure what the benefits might be for use in computer
cooling.

------
JohnLBevan
Another thought. . . could you take advantage of the thermoelectric effect to
cool a system and make it more efficient in the process?

~~~
jarek
Yes, to the first part. The computer applications are usually known as
"Peltier coolers". Due to a variety of factors, current implementations are a
fair bit less suitable to cooling most computer components than traditional
heatsinks/fans. I've mostly seen them used in extreme overclocking situations.

------
chopsueyar
What about submerging it in mineral oil?

~~~
chadgeidel
The specific heat of mineral oil (1.67 kJ/kg.K) [1] isn't much better than air
(1.0 kJ/kg.K) [2] when considering the difficulty of using a liquid. If you
are going to use a liquid - water is a much better heat transfer medium (3.93
kJ/kg.K) [3].

1: [http://www.engineeringtoolbox.com/specific-heat-fluids-
d_151...](http://www.engineeringtoolbox.com/specific-heat-fluids-d_151.html)
(search for "mineral")

2: [http://www.engineeringtoolbox.com/air-specific-heat-
capacity...](http://www.engineeringtoolbox.com/air-specific-heat-capacity-
d_705.html)

3: <http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/spht.html>

~~~
biot
Water may be better at transferring heat, but there is the slightly
undesirable effect that it shorts out your electronics and causes corrosion.

Don't try this using water: <http://youtu.be/PtufuXLvOok?t=2m10s>

~~~
chadgeidel
Although I can't watch the video at work - I assume it's one of the many
videos where the entire motherboard is submerged in mineral oil. Certainly
that's the case, and it's why overclockers have been trying this for over a
decade. It's just a problem with moving the heat away from a very concentrated
area of the die. As lutorm observed, the viscosity (combined with the
inability to transfer heat quickly) ends up preventing an efficient mineral
oil based cooling solution.

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AlexC04
So where do I buy them?

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SaltwaterC
"Moving beyond 3GHz". Really?

~~~
seabee
How many 4GHz chips have been produced that don't need watercooling to operate
at load?

~~~
jconnop
Pretty much every intel desktop chip of the last few years will do 4ghz+ with
good air cooling. I have an i7 930 @ 4.2ghz on air, my flatmate has a 2600K @
4.8ghz on air.

~~~
juiceandjuice
Lots of things can run faster than they are supposed to, but that doesn't mean
they _should_ or that people are going to like the solution. Often times the
bleeding edge processors are clocked according to MTTF based on a reference
implementation (which would include some standard of heat dissipation and a
processor's TDP and probably not exotic copper heatsinks and high speed fans.
If this fan can more efficiently transfer heat out of the processor and
dissipate it with a lower total energy consumption, then it could be very
useful, especially when you are talking about things like datacenters where
total energy consumption and MTTF are things that really matter.

~~~
stcredzero
If you can improve the MTTF by leveraging this technology to make the entire
server highly resistant to dust fouling, then there might be another
tremendous benefit for datacenters.

