
Your Future iPhone May Be Stuffed With Wax - Libertatea
http://www.wired.com/wiredenterprise/2013/08/sprinting/
======
ctdonath
The point is taking advantage of matter phase transitions: a lot of energy
goes into converting a solid into a liquid, without changing the temperature.
Ergo, you can dump a lot of heat into something without then having to move
the something away fast to keep the heat source cool. Only works insofar as it
only takes so much energy to melt the solid (wax, ice, whatever), after which
you need to either resume a classic moving-coolant process or otherwise stop
generating so much heat and let the now-melted substance cool via ambient
surroundings and re-solidify.

An interesting variant on this is Coffee Joulies
[http://www.joulies.com](http://www.joulies.com) which are metal balls you
drop in your too-hot coffee to rapidly cool it to a desirable temperature,
then keep it at that temperature much longer than it normally would stay. The
initial heat is absorbed to melt the ball's contents, then is re-released back
during the reversed phase transition. Kinda neat.

A limited solution, but easily quantified and quite applicable to a narrow but
popular range of use.

I first thought the title's point was Apple would be stuffing the phone's
interior with wax to either make it waterproof or further frustrate reverse-
engeineering attempts.

~~~
samatman
Joulies do not in fact work:

[http://en.wikipedia.org/wiki/Coffee_Joulies](http://en.wikipedia.org/wiki/Coffee_Joulies)

Basically, if your vessel isn't insulated, you lose the same amount of heat to
the walls and air. The part where they cool your beverage to a certain
temperature and then stop cooling it works fine. The part where they retain
heat is thermodynamically senseless.

Fortunately, when you replace "beverage" with "chip", you have something that
cools the chip for awhile and then stops. Hence the article.

~~~
Retric
In a 30c room a cup of 80C coffee loses heat energy a lot faster than 60C
coffee so there is a faire amount of free energy when the coffie is to hot to
drink. Phase changes store and release identical amounts of energy. So, while
the increased drinking time may not be significant it is there assuming that
increasing the liquids volume does not overly increase the heat loss.

Edit: look at the graph on page 2 of this PDF.
[http://web.eecs.umich.edu/~martinjs/math115/coffee_expl.pdf](http://web.eecs.umich.edu/~martinjs/math115/coffee_expl.pdf)

~~~
samatman
The former point is correct as far as it goes. The latter is not. A cup of
coffee loses heat around the perimeter, not the middle, and the rate of heat
loss is entirely determined by that perimeter. The only thing the Joulies can
keep warmer than that equilibrium is themselves.

If they start warmer than the coffee, they may contribute to slowing the rate
of heat loss. If they do not, they cannot.

I have come to think of this as the Monty Hall problem of thermodynamics.
People with degrees similar to my own disagree with me all the time.

~~~
Retric
_If they start warmer than the coffee, they may contribute to slowing the rate
of heat loss. If they do not, they cannot._ Except people don't drink 80C
coffie so the absolute time it takes to reach 30C is less important than how
long it spends in the drinkable range.

Now I don't know what wax there using or how much, but Paraffin wax for
example has about 1/2 the heat of fusion of water. So it would store enough
energy to keep ~35 times as much water at a constant temperature rather than
failing one degree c at which point the was would freeze and provide
negligible benifit. On the other hand if the wax water ratio was 1:5 then the
temperature would stabilize though 7 degrees worth of cooling when the coffie
was 80C and then 7C of warming when the coffie was 37C which would be
noticeable. Granted, 37C is a little to cold for coffie, other waxes have a
higher melting point.

PS: I still don't think this would be all that useful in practice. I am just
pointing out it's not physically impossible.

~~~
samatman
That's why this is a Monty Hall problem. If you put the phase change material
between the coffee and the insulation, it works. If you don't, it _does not_ ,
because we are forgetting that the definition of heat is of a system, and heat
exchange is on the interface. Coffee exchanges with a certain efficiency that
is _unaffected_ by the presence of a more efficient heat transfer material
holding a reservoir of heat, _unless_ that reservoir _begins_ at a higher
temperature.

You may need to go all the way back to definitions on this one, but it works
out, and it predicts, correctly, that the effect is insignificant, per volume
of coffee.

Yes, you can keep less coffee warmer longer by putting a volume inside it.
That's not impressive. Can you keep the _same_ amount of coffee warmer longer?
You cannot.

~~~
samatman
The reason is that that Joulies, or anything else you put inside the system,
displaces coffee out to a larger surface of interaction with the outside
system. All other things being equal (basically, with a lid), it cancels out.

Without a lid, convection is primary over any other factor, and the entire
system will tend to reach equilibrium at about the same rate.

Unless you a) add heat or b) reduce the rate of heat transfer at a surface,
you cannot slow thermodynamic equlibrium.

~~~
Retric
If the heat transfer material is inside the coffee then the heat transfer is
not just with the outside material but also with the phase change material.
Also, even if the phase change material is the same temperature at the start,
it becomes warmer at the point the phase change occurs. Now, increasing heat
loss to the outside world is possible as the coffee surface area increases.
However, that's vary much a question of cup design as a matalic vacuum thermos
generally heats up the internal metallic part reasonobly evenly almost
regardless of fluid level.

PS: And if you don't believe me actually model the equations it works out
after you realize _drinking time only starts below an acceptable temperature._

------
annnnd
Interesting - one of the few links where the article delivers more than the
title promises. How about "dissipating short bursts of heat in mobile CPUs"?
Just for HN, of course, where people are genuinely interested in such topics.
/2cents

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susi22
I'm slightly disappointed by the article. It's a novel and interesting topic
but wired fails to explain the details of how this works and doesn't even try
to explain the physics behind it. IMO it wouldn't be too difficult, since the
idea is actually quite simple and can probably explained to a non-technical
reader in a few sentences.

In my opinion the Figure A in this PDF really explains it well:

[http://acg.cis.upenn.edu/papers/ieeemicro13_responsiveness.p...](http://acg.cis.upenn.edu/papers/ieeemicro13_responsiveness.pdf)

(page 3 of pdf)

------
nwh
A similar idea is used in practice in a building I'm frequently in. Beads of
wax in the concrete floor keep it cool in summer by melting when the
temperature rises, and recover overnight when the windows are open and
resolidify.

~~~
joezydeco
Some of the larger skyscrapers in my city are cooled using a phase-change
material as well: water.

A local facility makes ice overnight when energy is cheaper and then pumps the
melting cold water into the buildings to assist the air conditioning units.

------
btilly
My first thought at the title was that this would result in the ability for
them not to be damaged by water. But it also makes sense as a coolant system.

~~~
mikeash
Same here. Fill every empty space inside the thing with wax, and you have a
waterproof phone! Wonder if that would really work.

~~~
nknighthb
Not the way you'd hope. Without some way to seal it off, you'd have wax
dripping out of your phone every time you use it... or charge it. If you do
have some way to seal it in, then you've probably solved the waterproofing
problem anyway.

If you do want a waterproofed iPhone, there are cases out there that claim to
be waterproof, e.g. LifeProof. I've not used or tested one yet, though...

------
6ren
I love approaches like this: instead of butting your head against the same
limits, look at the whole problem, find a re-frame the problem with a new
trade-off that actually the whole problem.

Arguably, this is what Clayton Christensen is talking about with "over-
shooting": making your product better than it needs to be in some particular
dimension, just because that's the way you've always been making it better.
But like doing your shopping in a Ferrari, maybe increased horsepower isn't
what's really needed.

Here, they'll saying that bursty usage (they call it "sprinting") is what is
actually needed. I noted this with word-processors - most of the time the PC
is idle - and wondered how those cycles could be harnessed. Instead, they say,
turn it off.

This might be an alternative to many-core - just boost it x100 faster. It can
also go the other way, having a much _less_ powerful processor, just super-
boosted for when needed. Cheetah would be a good code name for this project.

~~~
nknighthb
It doesn't solve "the whole problem". It won't help with any sort of batch
processing, nor with the latest game trying to squeeze every bit of
performance out of the hardware.

Worse, it may actually encourage bad behavior by applications. We already have
problems with applications draining batteries unreasonably fast on mobile
devices because they implement features in ways that look "fast enough"
interactively, but under the hood are an unnecessary power drain. Now such
inefficiencies can be even _less_ obvious!

There's a lot more to practical application of this than tossing some wax on a
chip.

~~~
6ren
The "whole problem" doesn't mean "every problem". It means taking a step back
and seeing what the user is really trying to accomplish, and everything that
is needed for _that_ problem to be solved - as opposed to myopically seeing
just one aspect of that problem. Some extreme examples of whole solutions:
Edison establishing a power generator and power line infrastructure, not just
a light bulb (Musk's Tesla is doing similar now); Birdseye establishing
freezers in supermarkets, not just selling frozen fish. Sometimes, you'll
focus on one specific user problem, which can even mean removing features.
BTW: I'm taking the term from _Crossing the Chasm_ (Geoffrey Moore).

Of course, what you say is true about continuous loads, and also battery
drainage for bursty loads. It's not a solution to every usage pattern, and as
the article mentions, it's around 10 years away.

I love changing problems to see unexpected ways of solving them - even if it
does take years to realise the vision.

------
Pxtl
I'm curious how this works long-term. Old computers already have coolant
systems that degrade - thermoconductive paste gets brittle and cracks, fans
get gummed up. How will this wax work long-term?

[http://www.youtube.com/watch?v=OpCJzdWxEbQ](http://www.youtube.com/watch?v=OpCJzdWxEbQ)

~~~
GFischer
I believe paste and fans work longer than the average useful lifetime of a PC,
I guess planned obsolesence is at work here too...

------
jnbiche
And I was so hopeful from the headline that Apple was adopting the Lua Wax SDK
as an official API.

