

Ask HN: Any Chemistry hackers here? - BrandonWatson

There&#x27;s a project I want to undertake. I want to do it out in the open. I&#x27;ve been inspired by a few Maker projects as of late. I keep hearing &quot;you should file a patent right now&quot; when I have shared this idea with close friends. Which is why I want to do the opposite.<p>I don&#x27;t know enough about the specific domain for the crux move of the solution. I think the solution lies in Chemistry or Chemical Engineering, but I am not certain that the problem is solvable in a cost effective way. My gut tells me that it is.<p>The first step is for me to be able to ask some very specific questions about phase change temperatures and latent heat of fusion of different chemical compounds. Any takers? The background info is too much for an Ask HN post, but I <i>ABSOLUTELY</i> promise that as soon as this enters the realm of &quot;yeah, that&#x27;s probably solvable&quot; I will start posting the whole project and living it the Maker way.
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MrMeker
You can give me a try. I am an amateur chemist. Edit: Email in my profile.

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BrandonWatson
I am looking to identify a material or compound that can dissipate heat
generated by the human body. I want to use this for an athletic textile
application. Specifically a cooling element that is to be placed against the
skin along the forearm, or on the head.

Principle characteristics I need are light weight, self contained reaction,
non-toxic, and can remain cool/cold for as long as possible while dissipating
this heat. Reusable is ideal, but one time use is also OK.

~~~
cake93
Biotechnologist here....As I see it there are three options: 1\. Uptake of the
thermic energy by an endothermic chemical reaction (like
[http://en.wikipedia.org/wiki/Instant_cold_pack](http://en.wikipedia.org/wiki/Instant_cold_pack))
2\. Passive removal of the heat with a heat conducting material (you have to
get rid of the heat somewhere else) 3\. Active removal of the heat (see
[http://en.wikipedia.org/wiki/Cooling_vest](http://en.wikipedia.org/wiki/Cooling_vest))

I think thermoelectric cooling
([http://en.wikipedia.org/wiki/Thermoelectric_cooling](http://en.wikipedia.org/wiki/Thermoelectric_cooling))
would be suitable for your application. It is also compatible with Arduino
technology I think.

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BrandonWatson
Yes, in doing my research the cooling vest was one of the first items I looked
at. The biggest problem for my target customer (triathletes and runners) is
the weight (>4 lbs), the lack of mass security (vests tend to move around a
bit), and the heat blocking nature of the vest when cooling is depleted.

I have been experimenting with saline based solutions to test my theory of
perception of heat reduction. They have worked for the most part, the
challenge has been that they last about :30. I need longer. I have not
experimented with any of the break+mix solutions from the wikipedia article,
though am aware of them.

My preference for an endothermic reaction with a PCM is that in theory the
mechanism is reusable, or easily replaceable, the weight penalty is low, and
the complication of the solution (no pun intended) is also low).

There are some of these "cool materials" on the market right now, and they are
somewhat interesting, though they are not operating as a heat dissipation
level of the endorthermic reactions.

My vision for this product (at this point in time) is a sleeve that houses
chambers with the endothermic reaction solution, and those chambers are either
in an arm sleveve, or inside of a hat (think of the head band of a runner's
hat).

Whether that solution is a one time use, and thus replaceable in the chamber,
or multi use, and thus more permanent, is not really my challenge right now. A
marathoner going to secure their Boston spot would pay $50-$100 for a hat that
is guaranteed to keep them cool on a 90 degree day when their alternative is
to keep throwing ice on themselves at aid stations, or stuffing cold sponges
down their shirts. This is how it is handled today. Same for the age grouper
triathlete who is getting ready for a sprint or Ironman. These folks are
pretty obsessive about gear and kit, and aren't very price discriminating.

~~~
mchannon
The trouble with most endothermic reactions is they involve far less energy
absorbed per kg than exothermic reactions tend to emit (and their reaction
rates much slower than you'd like). As a runner I'd not be too enthused about
lugging around a 500g brick of goo that has the best possible endothermic heat
absorption. You'd lose far more in heat dissipation potential than that brick
could ever absorb, at least if it started at ambient. (Imagine how less
popular ice would be if it never melted but stopped cooling).

A peltier cooler would be right out; they only work when they have an active
cooling mechanism (heat sink and fan usually).

If you wanted to ditch the cooler and put together a hat or other appliance
with a 3V case fan and ultrathin solar cells (CIGS probably), you'd get an
excellent improvement in heat dissipation, and it would work indefinitely as
long as it was daytime (probably a safe bet).

~~~
cake93
Correct me if I'm wrong, but from a thermodynamic point of view the major
problem is the entropy. You can't just convert heat into any other form of
energy (light) without also caring of the entropy. In the case of solving some
salt in water, the entropy is going into the chaos of the solved ions (versus
the low-entropy crystal). With all the other methods you need to get rid of
the heat. With peltier coolers I could imaging "watercooling" the hot side.

On the other hand sweat (evaporation) is already a pretty good cooler and
covering the skin with something else stops that effect. Additionally you
enrich sweat inbetween which does not feel well. Completely absorbing the
sweat also kills the cooling effect..

So maybe, as mchannon suggested, all you have to do is design a nice, flexible
and good-looking sweatband with an integrated fan ;)

