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Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Chobrutsky wrote ...
That's not a bad idea. Is there something better than teflon to bridge the two? Teflon, while it can withstand high heat, to my known has terrible conductive properties. Do you think that'd be a problem? Do you really think I'd need 50ft of nichrome to pull that off? I think I need about 1600W. But I'm not sure how that translates into nichrome length/current/power/etc.
The best idea I could come up with when I was designing a 12V water heating system for a boat 15 years ago was to wrap it in glass fibre tape, then wrap the nichrome wire around that. You only need enough to electrically insulate it, then you can wrap more glass fibre over the top to thermally insulate it.
(just my 2 cents worth)
EDIT: stainless steel rigging wire, unwound into single strands, is a cheap alternative to nichrome wire if you have access to a boatyard skip/dumpster where they dump the old stuff after the end of the season. Also a good source of glass fibre offcuts.
Registered Member #2529
Joined: Thu Dec 10 2009, 02:43AM
Location:
Posts: 600
Chobrutsky wrote ...
From what I've read about induction heating, since my "work piece" is so small (.405" OD) to heat it efficiently i need to be over 100khz.
Off hand I don't think that's right at all, provided your object is bigger than a skin depth you can generate some pretty mammoth eddy currents, which would heat up the piece just fine.
A centimetre (0.405") is bigger than one skin depth even at 50hz.
The trick is to induce the currents in the plane of the surface, rather than the thickness; if you present a pole size that is above one skin depth it will induce eddies just fine.
Registered Member #2901
Joined: Thu Jun 03 2010, 01:25PM
Location:
Posts: 837
wrote ... Do you think that'd be a problem?
No, idea ... but the glass fibre thing doesn't sound bad either.
wrote ... Do you really think I'd need 50ft of nichrome to pull that off?
Not really, it's just a unit in which nichrome wire seems to be sold ... if you use less wire you should thinner wire. I dunno how little you can get away with, depends on the thermal resistance between the wire and the copper pipe and the peak nichrome wire temperature you want to allow.
As for resistance that is simply about V^2/R, assuming you want peak power to be at near 100% duty cycle R should be less than V^2/P.
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Induction heating - inline water heating
