Question: Is it possible to heat a LARGE metal object with 2

[Gene]

Thanks.

_How_ even?
+ or - 5% would be OK. (~15deg+-)

OK, but since you say it's insulated, How good is the insulation?
At these volts, it's ~ 100% - NP.

"John Fields" <jfields@austininstruments.com> wrote in message
news:48f1k3hsf46ebb8g42b05skl5f6dpjka7o@4ax.com...

On Sun, 18 Nov 2007 13:40:11 -0600, "Gene" <genes@wildblue.net
wrote:

Thanks, Tim.


Direct heating (and the inevitable contact grunge on your sphere)?
Yes, the entire sphere will simply be the heating element. That is,
you connect one wire to one side of the sphere and the other wire
to the opposite side of the sphere & turn on the juice.


Indirect (i.e. can we specify an oven)?

Inductive (this would be a candidate)?

How even do you need the temperature?
We want the entire sphere to have a skin temperature of 300F.
That is, we want VERY even heat.

---
_How_ even?

What's your spec of delta t over the surface?
---

How fast to get up to temperature?
Five minutes would be ideal - just not in hours.

Any current/power limitations?
Yes, we want to use the normally available 220 or 440VAC as
a source to the transformer(s) or whatever.

Can we specify that the sphere has to move?
The sphere will be suspended and insulated.
Think of the sphere as you would the heating element in
a common home electric stove.

We simply want to heat the sphere without having to construct an
oven or other device to supply the heat.

---
OK, but since you say it's insulated, How good is the insulation?


--
JF

 

[Gene]

Thanks.

That was my gut feeling.
However, is it possible to "bring it up slowly"?
That is, use a microprocessor or a timer to apply the
current VERY slowly?






"Nobody" <nobody@nowhere.com> wrote in message
newsan.2007.11.18.21.22.52.931625@nowhere.com...

On Sun, 18 Nov 2007 13:40:11 -0600, Gene wrote:

Direct heating (and the inevitable contact grunge on your sphere)?

Yes, the entire sphere will simply be the heating element. That is,
you connect one wire to one side of the sphere and the other wire
to the opposite side of the sphere & turn on the juice.

How even do you need the temperature?

We want the entire sphere to have a skin temperature of 300F.
That is, we want VERY even heat.

You aren't going to get that using a uniform sphere as a resistive heating
element. The contact points will get hotter than the rest of it. If you
want even heat, you would need to make the metal thinner as you get
further from the contacts.

 

[Gene]

Thanks, Tim.

Direct heating (and the inevitable contact grunge on your sphere)?
Yes, the entire sphere will simply be the heating element. That is,

you connect one wire to one side of the sphere and the other wire
to the opposite side of the sphere & turn on the juice.

Indirect (i.e. can we specify an oven)?

Inductive (this would be a candidate)?

How even do you need the temperature?
We want the entire sphere to have a skin temperature of 300F.

That is, we want VERY even heat.

How fast to get up to temperature?
Five minutes would be ideal - just not in hours.

Any current/power limitations?
Yes, we want to use the normally available 220 or 440VAC as

a source to the transformer(s) or whatever.

Can we specify that the sphere has to move?
The sphere will be suspended and insulated.

Think of the sphere as you would the heating element in
a common home electric stove.

We simply want to heat the sphere without having to construct an
oven or other device to supply the heat.



"Tim Wescott" <tim@seemywebsite.com> wrote in message
news:--6dnb0BV4ZID93anZ2dnUVZ_vLinZ2d@web-ster.com...

On Sun, 18 Nov 2007 13:08:16 -0600, Gene wrote:

Good day, all.

Problem: Cause a sphere that is 6 feet in diameter and made of
0.05 inch thick plate steel (or other metal?) to reach a uniform skin
temperature
of 300F degrees by using 220 or 440VAC as a source?

First, is it possible?
(I'm sure there are better ways of doing this than making the entire
sphere a shorted heating element - but this question relates only to
whether
it's POSSIBLE, not practical.)

"IF" it's possible, what type of transformer would you use?
That is, what would the OUTPUT in volts, amps, watts, etc be -
assuming that you wanted the sphere to reach a uniform skin
temperature of 300F? Basically, we just want to "short-out" the
sphere & cause it to heat to 300F with AC or DC current - so
what's the transformer design

THANKS,
Gene

Your question lacks detail. With your wording, one answer is "Sure! Just
build an oven that runs on 220, takes a 6' diameter sphere, and will heat
to 300F in a few days with the door closed!"

So:

Direct heating (and the inevitable contact grunge on your sphere)?

Indirect (i.e. can we specify an oven)?

Inductive (this would be a candidate)?

How even do you need the temperature?

How fast to get up to temperature?

Any current/power limitations?

Can we specify that the sphere has to move?

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html

 

[Gene]

Good day, all.

Problem: Cause a sphere that is 6 feet in diameter and made of
0.05 inch thick plate steel (or other metal?) to reach a uniform skin
temperature
of 300F degrees by using 220 or 440VAC as a source?

First, is it possible?
(I'm sure there are better ways of doing this than making the entire
sphere a shorted heating element - but this question relates only to whether
it's POSSIBLE, not practical.)

"IF" it's possible, what type of transformer would you use?
That is, what would the OUTPUT in volts, amps, watts, etc be -
assuming that you wanted the sphere to reach a uniform skin
temperature of 300F? Basically, we just want to "short-out" the
sphere & cause it to heat to 300F with AC or DC current - so
what's the transformer design

THANKS,
Gene