[NewCandle] Getting started with aluminum foil

[Nick Reiter]

Hi Keith and all,

Thanks for the thoughts re: my dad.  I appreciate it.

You wrote:


> Why not? What in my mind is causing runaway in your large
> experiments is the fact that enough heat is being
> generated
> to outstrip the losses of the container. It's then just
> a matter of time before temps rise to boiling.

***********Well, I had informally come to model it as a heat source of a certain total power output ( x calories per cm2 of foil turn, OR conversely x calories per gram of contributing foil.)  As I presume you do too.  However I had simply extended my model of the total system heat dissipation to include the water and plastic bucket material, both of which have a finite thermal conductivity or insulating value.  So in that sense, lets say you have a 10 ohm resistor with 10 amps flowing through it.  The resistor is dissipating 1000 watts, and if suspended in a medium, will come to a terminal temperature X.  If you have 10 of these suspended near each other, they will be kicking out a total of 10kW.  Now if you increase the volume, mass, and dissipative surface area of the vessel these are in proportionally, then they ought not to get much warmer than the single resistor.  However if you pack em into the same vessel as one alone was in, then my prediction
 would be that the resistor pile would have a higher terminal temperature.  Maybe I fell victim to a faulty line of thought.  Regardless of any of this - a vacuum vessel / calorimeter would obviously render any such argument void.  And so thus, you should get some good data.

The other potential mechanism for a greater T rise with increased mass would possibly invoke the annular geometry of the roll turns, and possibly some ill defined (for me sorry to say) focusing and reflection of radiation and conducted energy to the middle of a roll.

Good luck!

n


> 
> I have a small pair of thermos's that I have used for
> calorimetery; I'll try one today. If I _can't_ get this
> to work at small scale we'll know something special is
> happening at large scale. These units are quite small,
> designed for lunch boxes. 
> 
> My safety concern about this is simply the H2 gas. It
> pools
> on the ceilings and can ignite with unfortunate results.
> What I need here is a fume hood. That said, I'm sure I
> could do these small scale experiments in the garage now
> that I've had some experience with them. I was also
> worried
> about free chlorine gas, a big no-no with hydrogen, but
> my nose detected no such problem. That combo will
> spontaneously
> explode. 
> 
> K.
> 
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