Heat exchangers

Discuss the technical details of an "open source" community-driven design of a polywell reactor.

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eros
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Post by eros »

MSimon wrote:Permanent Magnets won't work. The field lines are in the wrong place. Electromagnets are the only way.

This has been discussed extensively on this board. Look around.
Uh, not find yet, there are so much text it take month ore more to read all.

However I can't yet imagine why they can't magnetize like coils. Of shelf magnetizations don't work, but remagnetizations is posible.
Even use Nd insert inside coil can grow field much.

Any magnet used would have to be custom designed due to the necessity of dealing with high voltage. LN2 Cu would be the quickest. The Bitter design is my preference because of mechanical stability and cooling. Mechanical stability is important if you are going to pulse them.

I did some Cu LN2 calculations at:

http://iecfusiontech.blogspot.com/

Have a look around.

I also have a spread sheet I could dig up if you were interested.
Hmm, this is missing
http://theory.physics.helsinki.fi/~plas ... iption.pdf

I quite fast search, but not find exact power needs + size. Some your recipes for needed supply are in blogspot.
LN2 cooling drops only 50% copper resistance. Previous I calculated at 1m machine with 30cm coils 0.13T use 400kw coil power. -50% resistanse do -50% power. Still lot of and fusion power ~1W.
(edit:CNT drops resistivity 50%, 70K drops ~7.9x)

Is it that sheet?
http://www.mediafire.com/?0xvmsrumy8x

400cm coil and 0.45T ? Uh, what is coil crossection area?

my sheet at 40cm thicness give ~166MW coil power, say 200turns per coil it needs 22.5KA and 7.4KV (over six coils) (28.86A/mm²)
If put LN2 cooling it drops volts ~50%.
My sheet says ~9kw DD fusion power.
Your sheet 7.33 x10^9W pB11 fusion power..
My sheet power is based WB6 power..

How realistic is that pB11 power?
Last edited by eros on Tue Nov 18, 2008 6:34 pm, edited 1 time in total.
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MSimon
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Post by MSimon »

It is where the field lines converge. In an electromagnet they converge in "empty" space. In a permanent magnet they converge on the face of the magnet.

Draw a picture - it will be obvious. In an electromagnet the field lines go around the coil. In a permanent magnet they enter one face and exit the other.

If it is not clear to you just take my word for it or wait until some one else is willing to explain it in detail. I spent two weeks on this and I'm not currently interested in doing it again.

BTW try using the search function. "permanent magnet" might be a good place to start.

LN2 drops the coil resistance by a factor of about 7 from room temp. The number I got was about 100KW total coil power.
Engineering is the art of making what you want from what you can get at a profit.

MSimon
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Post by MSimon »

Give me your e-mail and I will send you my spread sheet. If you don't want your e-mail public - send me a PM.
Engineering is the art of making what you want from what you can get at a profit.

KitemanSA
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Post by KitemanSA »

MSimon wrote:
KitemanSA wrote:Would someone explain to me why a Bitter magnet, which is a stack of flat rings, is better than a coil of flat plate? The number of turns and x-section can be identical, and the coil seems so much easier to build.

The bolt holes and coolant holes can be effectively identical. Why so Bitter?
The Bitter can be made from stampings. Winding a wide flat spiral is a tougher manufacturing problem.
How can winding a ribbon around a spool be a harder problem than assembling a bunch of stampings?

MSimon
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Post by MSimon »

KitemanSA wrote:
MSimon wrote:
KitemanSA wrote:Would someone explain to me why a Bitter magnet, which is a stack of flat rings, is better than a coil of flat plate? The number of turns and x-section can be identical, and the coil seems so much easier to build.

The bolt holes and coolant holes can be effectively identical. Why so Bitter?
The Bitter can be made from stampings. Winding a wide flat spiral is a tougher manufacturing problem.
How can winding a ribbon around a spool be a harder problem than assembling a bunch of stampings?
There is the problem of drilling the cooling holes and bolt holes without shorting turns.

You have to look at why Bitter did what he did. Why didn't he just wind a ribbon on a spool?
Engineering is the art of making what you want from what you can get at a profit.

KitemanSA
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Post by KitemanSA »

MSimon wrote: There is the problem of drilling the cooling holes and bolt holes without shorting turns.

You have to look at why Bitter did what he did. Why didn't he just wind a ribbon on a spool?
I don't know why he did it, that is why I am asking. Is it not plausible that technology has improved to a point where his reasons no longer pertain?

To me, it seems better to use a ribbon (Cu or superconductive) with a gap-wound spiral insulator, layed up on a mandrel then clamped rather than bolted. The overlayed cross-hatch spirals would the create an almost perfect "plate and frame" type microchannel heat exchanger running ACROSS the ribbons.

If you absolutely need to have cooling holes or bolt holes running radially thru the ribbon stack, I'm pretty sure that NC machines can place them wherever they would be needed, no drilling in the stack.

Are there other reasons?

MSimon
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Post by MSimon »

Kiteman,

It is very difficult to place the holes correctly unless you can hold the thickness of the materials to extremely tight tolerances. And that goes for the temperature of the winding during winding.

Flat plates laid on top of each other are easier with reasonable tolerances. That influences cost.

So yeah. If you could hold thickness to 1 part in 10,000 or better and place the holes similarly accurately or better no problem.

One mistake and you wipe out a whole roll of Cu.

The Bitter design absorbs the manufacturing tolerances.
Engineering is the art of making what you want from what you can get at a profit.

tombo
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Post by tombo »

Try assembling a paper model.
That should make the assembly issues clear.

I can't visualize your micro-channel heat exchanger. Gap-wound spiral insulator?
Can you do what johnshearing did in his 11/13/08 post to "spherical electromagnet".
Then we can see exactly what you propose.

Text is a horrible format for trying to put across 3D concepts.
The old saw about a picture being worth 1000 words is a fact of engineering life.

The configuration must also accommodate thermal expansion cycling.
-Tom Boydston-
"If we knew what we were doing, it wouldn’t be called research, would it?" ~Albert Einstein

KitemanSA
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Post by KitemanSA »

tombo wrote: I can't visualize your micro-channel heat exchanger. Gap-wound spiral insulator?
I have a simple graphic of the idea, but I don't know where to post it so that I can use the "img" tag. Any suggestions?

MSimon
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Post by MSimon »

KitemanSA wrote:
tombo wrote: I can't visualize your micro-channel heat exchanger. Gap-wound spiral insulator?
I have a simple graphic of the idea, but I don't know where to post it so that I can use the "img" tag. Any suggestions?
Try Photobucket. The price is right.
Engineering is the art of making what you want from what you can get at a profit.

eros
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Post by eros »

MSimon wrote:It is where the field lines converge. In an electromagnet they converge in "empty" space. In a permanent magnet they converge on the face of the magnet.

Draw a picture - it will be obvious. In an electromagnet the field lines go around the coil. In a permanent magnet they enter one face and exit the other.
Ah you mean that broblem. I just say that factory magnetized magnets have that kind of magnetization.
But magnet spins are posible to order like in electric coil. Normally that kind of magnet is quite useless and they don't manufacture our special magnetization.
Think normal long bar magnet and twist it 360degree to ring. It have correct field.
In reality twist is not posible, but you need special magnetization device, two half round coils inside empty, just enough room to put permanent ring and close coil halves together. Then load your capasitor bank to coils..

In industry that kind of magnetization device is quite difficult. Need build new coils for every new magnet size..

But coils inside is correct circular fiel and permanent magnet come magnetized correctly.
(this is only what I think, limited knownledege yet, but like to build something)
If it is not clear to you just take my word for it or wait until some one else is willing to explain it in detail. I spent two weeks on this and I'm not currently interested in doing it again.
Instead I try do some test. Magnet show plastics are available:
http://www.supermagnete.de/eng/magnets. ... =M-04#M-04

Trying to read ofcourse what other are writed, just find serch function, google don't give good hits.
BTW try using the search function. "permanent magnet" might be a good place to start.

LN2 drops the coil resistance by a factor of about 7 from room temp. The number I got was about 100KW total coil power.
Hmm, you are correct, this page says same (check table link):
http://hypertextbook.com/facts/2004/BridgetRitter.shtml
(edit: I just confuses CNT resistivy)

80K 0.215 ohm/mm² drops resistivy at factor 7.9. it means same amount power saving.
100kw are in range, almost megawatt without that 7.9x drop. So my calculations and yours show that copper coils are giant energy hugs..
Please give coil dimensions and used resistivy so I can cross check my sheet.. (no needs for your secret dimension, but something simple)
Last edited by eros on Tue Nov 18, 2008 6:33 pm, edited 3 times in total.
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eros
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Post by eros »

MSimon wrote:Give me your e-mail and I will send you my spread sheet. If you don't want your e-mail public - send me a PM.
Why hide, spammers maybe, but try

eerin xylogas period fi
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eros
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Post by eros »

KitemanSA wrote:
How can winding a ribbon around a spool be a harder problem than assembling a bunch of stampings?
I think Bitter idea is resist magnet forces, so windins need to be disks that carry expansion better and are bolted with end plates together to keep plates not expoloding away.
Cooling is also quite easy and insulation is minimal.

Maybe ribbon is hard to get enough pre tension or something. Bitter coils have many times higher B values than others.

Anyway BFR don't need that high teslas so bitter is not needed for resist high teslas, but its cooling seems to be good and it is quite easy to do. Order suitable copper rings from laser cut industry and bolt them together. (and put insulation spray paint every plate before bolting.)

circular is hard for bitter, corners capture electrons so it need casing and maybe standard coil performs better because you can fit little more copper. Who knows?
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KitemanSA
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Post by KitemanSA »

Thanks for all your replies. Can someone suggest a "Electro-Magnets for Dummies" level book?

MSimon
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Post by MSimon »

eros wrote:
MSimon wrote:Give me your e-mail and I will send you my spread sheet. If you don't want your e-mail public - send me a PM.
Why hide, spammers maybe, but try

eerin xylogas period fi
Where do I put the at sign?

Here:

msimon6808

at

yahoo

dot

com
Engineering is the art of making what you want from what you can get at a profit.

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