Re: steam power

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>



Tesla list wrote:
> 
> Original poster: "davep by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<davep-at-quik-dot-com>
> 
> Tesla list wrote:
> 
> > Original poster: "bob golding by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <yubba-at-clara-dot-net>
> 
> > Hi All,
> >     Ran my big coil at the museum this weekend to an appreciative
> > audience. I ran it for 5 minutes at a time once an hour though out the
> > day. I gave a brief introduction then let her rip. The audience was
> > underneath the coil behind a metal screen. I don't think we lost anybody
> > ;-).
> 
> >At the end someone suggested that we try blasting steam at the coil
> >to see what would happen! After reading about someone running there coil
> > in the rain I thought we would give it a go. Besides I wasn't the one
> > holding the steam pipe :-) The results were spectacular. The sparks were
> > a lot longer than  normal and ran all round the toriod.
> 
>         There is an extensive literature on the effect of humidity (and
>         temperature, and pressure and etc) on the dielectric properties of
>         air.  Humidity lowers the breakdown voltage.  So do added particles
>         eg water droplets...

Actually, humidity INCREASES the breakdown voltage.  See, for instance,
p182-184 in Naidu & Kamaraju, "High Voltage Engineering". Their summary:
increase in voltage of up to 2-3% as humidity varies from 8 to 15 g/cu
meter; effect is biggest in uniform field, (meaning almost no effect for a
TC, since the field is anything but uniform); and for a given humidity, the
change in voltage is largest for long gaps.  They cite work by Bruce,
actually cited in Craggs, et. al. and Kuffel, et al.

For Rod Gaps, Naidu gives corrections for -16.5% for a H2O vapor pressure
of 2.54 torr all the way up to 10.1% for a vapor pressure of 10.1 torr

That said, surface flashover voltages are DECREASED with increasing
humidity, and, as anyone who has worked with static electricity machines is
aware, incrasing humidity greatly increases the surface leakage.

And, Dave's point about particles is well taken.  They GREATLY decrease the
breakdown voltage by creating localized field concentrations (because the
dielectric constant of the particle is different than that of air).

This is particularly important in the case of your steam effect, since what
you've really got is probably not steam (which is technically a gas with no
condensed particles) but a warm fog made from partially condensed steam.
LN2 or DryIce fog would probably work the same.

For an interesting experiment, you might try rain, as well.  Sprinklers
suspended above will make a nice rain, or, if you want to insure grounding,
you can just use a high pressure nozzle on the ground and shoot up.


> 
>         Lookout for strokes coming back down the spray...
>         Firemen working near energized HV lines use explicit grounds
>         on the nozzles to reduce risks.
> 
>         best
>         dwp
> 
>         best
>         dwp