[TheForge] Chip forge

[Jerry Frost]

Yes, radiative heat transfer is what's happening along with a very small 
percentage of conduction.

Least first. Conduction is dependant on physical contact, there'll be little 
actual physical contact between the chips and work so it's not much of a 
factor.

I suppose if you used a small gradation of chips, say passing a -20 seive, 
conduction would become the significant transfer. (vehicle?) The problem 
with using fines as chips is forcing the flame through it without blowing it 
out of the forge. Not impossible I supppose but I'll bet it'd be really 
finicky to set up and use. Every time you put a piece of steel in it it'd 
change the flow patterns and some media would fall out of suspension and 
some would get blown out of the fire.

Radiation on the other hand is what's going to do all the serious work and 
surface area really matters. IR is radiated from the surface only so the 
higher the ratio of surface area to volume the faster the IR radiates.

I don't know the mechanics of how the media will pick up heat from the flame 
but convection doesn't enter into it. The flame is being forced through the 
media rather than circulating via convection. What I do know is the media 
picks up heat from contact with the flame or it's radiated IR, so the higher 
the ratio of surface area to volume the faster heat will transfer.

I would not use different sizes of chip as they'll fill in gaps and make it 
less flame flow friendly. My experiments will be with 1/4"-1/2" size chips.

I got to thinking about chips again this morning over coffee and think if I 
punch a hole through slightly rounded cubes I'll get much better heat 
transfer rates. The chips will also be lighter and easier on the work.

Frosty
-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.

http://www.artmetalradio.com/

From: "Steve Smith" <sos at alum.mit.edu>


>
>
>
> Frosty, I've always heard that at these temps heat transfer was mostly 
> radiative. Now that may be in relation to convection rather than 
> conduction, I don't know. If it is radiative, shape and surface area 
> doesn't matter (to heat transfer). I think maybe some experimentation is 
> in order (not that I'll actually manage any...).
>
> Steve