Re: [TCML] Arc Temperature

[Jim Lux <jimlux@xxxxxxxxxxxxx>]

-----Original Message-----
>From: "nnanred1@xxxxxxxxxxx" <nnanred1@xxxxxxxxxxx>
>Sent: Dec 3, 2007 9:47 PM
>To: tesla@xxxxxxxxxx
>Subject: Re: [TCML] Arc Temperature
>
>hi,
>this is just something to work with.  i dont have any books with me but get a thermo book and a sophmore physics book on electricity and then cobble this mess together:

<sniip>
>so now as the smoke clears, u see that u can solve for the temperature (say degrees centigrade) of an electron that has fallen thru 15 kv.  and subtract a little off for collisions in the plasma..
>anyway that's the idea.  its good to poke around a bit in Boltzmanns stuff cus the difference between him and einstein is that he really was smart.

except that this will give you the wrong answer.  There's a significant amount of radiative and conductive heat transfer among the ions and unionized atoms in the gas.  Turns out that the temperature tends to sit right around that where the big transition in ion density occurs (see, e.g., the Saha equation), which is around 7000K...


If it gets much hotter, then the arc tends to expand (by radiation and conduction) until the current density decreases to where the thermodynamic balance is established again.

To a first order, the radiative/conductive losses are proportional to the diameter of the arc (where arc means the highly conductive plasma), but the resistance of the arc is inversely proportional to the square of the diameter.



BTW.. 1 eV = 11000K.. give or take..
20 keV = 220,000,000K 

This is how they get those "fusion requires hundreds of millions of degrees" sorts of statements...

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