short burst heater?

[ivymike]

hey, anyone have any suggestions about how one might provide periodic short bursts of intense localised heating, with no nearby combustion, without requiring a high electrical current draw?

 

[MikeHalloran]

Steam?

Lasers?

Flash lamps? ( Google "Edgerton" )

Arc lamps?

Gamma rays?

Neutrons?

It depends on what you want to heat, and what you mean by 'short' and 'intense'.



Mike Halloran
NOT speaking for
DeAngelo Marine Exhaust Inc.
Ft. Lauderdale, FL, USA

 

[GenB]

you must post temp, and details. air heaters, steam heaters,
hi-temp water or oil heater ; again all depend on the temp you are trying to throw,
maybe an induction heater who knows. POST IT...

ER

 

[IRstuff]

AND what you mean by "without requiring a high electrical current draw."

What is the basis for comparison on current draw? How much lower do you need? Even an arc welder could potentially fit the description.

TTFN

 

[ivymike]

yeah, it occurred to me after I'd posted that I was being too vague. I can't give too many specifics about the application. I can say that the peak temperature should be about 700degF. The space to be heated is approximately 1 inch diameter by 8 inches long. The space is continually cooled (internally) by airflow, and is approximately 20% filled by steel mesh. The temperature should be achieved in under 10 seconds, and should be sustained for approximately 30 seconds. A current draw of less than 15amps@12V would be acceptable (wiring requirements seem to prohibit greater draw). The entire thing is enclosed within a small steel enclosure and mounted on a moving vehicle, which will operate in the presence of the general public in a variety of settings (out of reach).

I wonder whether the "flash lamp" circuitry could be revised to operate a small heater, thus limiting the sustained current draw to an acceptable level, while allowing a very high local current?

I was also wondering whether there is a chemical mixture which could be used as a small "thermal battery," allowing slow accumulation of heat (endothermic reactions) and rapid release (exothermic), over and over again, within a closed volume (skinny steel tube, perhaps)? Like these but reversible?

http://micro.magnet.fsu.edu/electromag/electricity/batteries/thermal.html

 

[ivymike]

maybe like these, but more intense:

http://www.bodyheaters.com/store/pr...id=35&osCsid=616da607e4c0a178c8ed9cab2e95acc6

 

[IRstuff]

I can't see anything other than a nichrome heater providing the desired energy. At 15A@12V, that's 180 W for 40s = 7200 J.

If you want more energy, you'll need to have a a long charging time to provide more energy prior to release.

You say you have airflow; how much and what is the effective HTC at 700ºF. This is lost energy that must be provided by your heater element.

While 50 gm of sodium acetate could provide up to 9000 J, it's unclear that all of it could be released within 40 s.

TTFN

 

[ivymike]

I suppose I should add that the period between heating events can be very long compared to the events themselves - say perhaps 3 days.

 

[IRstuff]

Well, you'll need to figure out how many joules you need and the configuration will be dictated by the requirements.

TTFN