Re: Fair Radio Sales HV cap---cool with liquid N2?

To: tesla-at-pupman-dot-com
Subject: Re: Fair Radio Sales HV cap---cool with liquid N2?
From: Jim Lux <jimlux-at-jpl.nasa.gov> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Tue, 29 Dec 1998 12:06:52 -0700
Approved: twf-at-verinet-dot-com

Tesla List wrote:
> 
> Original Poster: Doug Brunner <dabrunner-at-earthlink-dot-net>
> 
> I'd like to be able to use one of these caps in my next coil, but I'm
> concerned about the dielectric heating. I had the idea of immersing it
> in liquid nitrogen. Do you think it would work?
> 
> --
>            --Mr. Postman (Doug Brunner)
>                 <dabrunner-at-earthlink-dot-net>
No need to cool it in LN2, which although very cold, is actually not a
very good coolant. Oil or deionized water would be better choices as
coolants. 

HOWEVER, that isn't really the problem. The real problem is that the
rate of heat transfer out of the cap isn't all that great, and, so,
while the outside is nice and cool, the inside is really hot and the
dielectric is getting soft. Mylar (and plastic in general), while
serving as a nice dielectric (i.e. high resistivity for electron flow),
is also a nice heat insulator (i.e. high resistivity for thermal flow).

-- 
Jim Lux                               Jet Propulsion Laboratory
ofc: 818/354-2075     114-B16         Mail Stop 161-213
lab: 818/354-2954     161-110         4800 Oak Grove Drive
fax: 818/393-6875                     Pasadena CA 91109