How to remove heat from a copper wire magnet?

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

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tobiwan
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Joined: Wed Jul 22, 2009 12:37 pm

Post by tobiwan »

We take drinking water from the street ,run it thru a reverse osmosis unit and finally thru mixed resin bed water purification bottles and you have ultra pure demineralized water. Don't drink it it will pull minerals from our body and make you sick!!

KitemanSA
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Location: OlyPen WA

Post by KitemanSA »

Have you considered 3M Fluorinert? There seems to be a sale going on.

http://www.mdssys.com/clearance

Mattasmack
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Joined: Sat Jun 07, 2008 4:44 am
Location: Minnesota, USA

Post by Mattasmack »

KitemanSA wrote:Have you considered 3M Fluorinert? There seems to be a sale going on.

http://www.mdssys.com/clearance
Hi all, long-time lurker, first-time poster here. I'm a grad student studying heat transfer and sometimes use Fluorinert liquids in the lab (FC-72 specifically). I must say, they can be quite the PITA. If you're planning to use some in any sort of flow loop, make sure to get plenty of extra -- the stuff will find the tiniest of leaks and just disappear. Fluorinerts also have compatibility problems with some elastomers and polymers.

Unless one of the special properties of Fluorinert liquids is important to you (boiling point, compatibility with electronics, low pour point, etc), just sticking with water with save you lots of headaches. Water's heat transfer properties are generally much better anyway.

Nik
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Joined: Thu Mar 12, 2009 8:14 pm
Location: UK

Boiling water...

Post by Nik »

Um, can your coil tolerate temperatures ~120C ?

Co-winding 316 stainless steel capilliary tubing as used for HPLC (High Pressure / High Performance Liquid Chromatography) analysis hook-ups might do the trick. They'll take daft pressure ~ 200 Bar barely beyond finger-tight. Complex s/steel Ts & feed-throughs etc are 'off the shelf', connectors are easily made / released/ renewed etc with finger-sized spanners...

A couple of ml /min water pumped through should remove much of the heat, and will stay liquid beyond 100C due over-pressure. Think 'flash steam'...

Um, you may be able to re-purpose car fuel-injector tech...

DustyStyx
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Post by DustyStyx »

This is probably out of the realms of remote possibility, but the question reminded me of the "Thermal Ground Plane", copper diamond compost they are working on at Georgia Tech.

Would it be possible to fashion an electromagnet out of the composite, and would such a magnet be ideal for situations described above?

I apologies if the idea has been floated elsewhere on the forum.

Jccarlton
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Joined: Thu Jun 28, 2007 6:14 pm
Location: Southern Ct

Low Conductivity Water

Post by Jccarlton »

If anyone is an IEEE member or has access to a University library this migh tbe useful:
http://ieeexplore.ieee.org/Xplore/login ... ision=-203

I designed a LCW system for the Jefferson Lab FEL and we got quite a bit of cooling just by running LCW through the center of the conductors.

MSimon
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Post by MSimon »

LCW has been used for cooling high power vacuum tubes for a very long time. Radio amateurs have done work in the area. So it is not extremely high tech.
Engineering is the art of making what you want from what you can get at a profit.

Jccarlton
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Joined: Thu Jun 28, 2007 6:14 pm
Location: Southern Ct

Post by Jccarlton »

MSimon wrote:LCW has been used for cooling high power vacuum tubes for a very long time. Radio amateurs have done work in the area. So it is not extremely high tech.
It's still a possible solution. I know that in the system that I designed the plumbing for, we used diesel locomotive cable to hook up magnets that had 1/4 in rectangular conductors. figure 600 or more amps at 600V

BenTC
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Joined: Tue Jun 09, 2009 4:54 am

Post by BenTC »

MitchellJames wrote: I searched around last night and came up with one place that sells 4 oz jars of silver doped vacuum grease for $275 a jar. A little steep for my budget. But the same concept could be used with any thermal conductive material so I am trying to see if I can obtain bulk amounts of powdered diamond or beryllium oxide. I am also going to stick a highly rated computer thermal paste in a vacuum chamber to see how much it out gases. I would like a non electrically conductive thermal grease.
Someone's homemade non-conducting DIY Diamond Thermal Paste for around $40, compares favourably with traditional conducting silver based thermal paste.

[Edit: Actually thats $40 for about 1/2 oz, so $320 for 4oz]
Last edited by BenTC on Thu Aug 20, 2009 1:25 pm, edited 1 time in total.
In theory there is no difference between theory and practice, but in practice there is.

MSimon
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Post by MSimon »

vankirkc wrote:Starting off with usual caveat...not an engineer, so please forgive if my question is silly.

I read somewhere that some species of carbon fiber are highly conductive. Can you wind them into an electromagnet? They are supposed to have very high thermal tolerance (I saw 2500k somewhere?).
This is true. About 5X more electrically conductive than copper.

http://powerandcontrol.blogspot.com/200 ... ctors.html

The difficulty right now is that production volumes are low and the costs are high. That should change over time.
Engineering is the art of making what you want from what you can get at a profit.

D Tibbets
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Post by D Tibbets »

MSimon wrote:
vankirkc wrote:Starting off with usual caveat...not an engineer, so please forgive if my question is silly.

I read somewhere that some species of carbon fiber are highly conductive. Can you wind them into an electromagnet? They are supposed to have very high thermal tolerance (I saw 2500k somewhere?).
This is true. About 5X more electrically conductive than copper.

http://powerandcontrol.blogspot.com/200 ... ctors.html

The difficulty right now is that production volumes are low and the costs are high. That should change over time.
"Carbon nanotubes 5X better than copper at room temperature." What is the ratio at liquid nitrogen temperatures? Copper is 8 times better. Is there any information on the carbon nanotube's conductivity at different temperatures?
I imagine that the magnet wires will have to be cooled irregardless of the material. Certainly, maintaining a temperature of perhaps a 100 degrees C would with circulating water would be less challenging than maintaining cryogenic temperatures against the ohmic heating and bombardment heating (with D-D fusion).

Some numbers I have made up (I don't know if they are realistic).
Assume you can force some cooling water through a WB6 size magrid with copper wire so that you can maintain a steady state magnetic field of 500 Gauss (0.05 T). Now increase the minor radius of the coils so that the coil makes up 20% of the major radius instead of the current 10% (WB 4 was ~ 25%, based on pictures). This increases the volume inside the coil can by a factor of 4. Assume 1/4th of that increased volume is dedicated to cooling/structure , the remaining is used to increase the wire windings 3X. If the size of the machine is increased to 3 meters, the volume aviable for windings increases an additional 100x while the wire length would increase by a factor of 10 (circumfrence), yielding in a 10x gain in effective windings (adjusting for equivalent heat loads(?)).
This adds up to a 30x gain in magnetic field strength (same amps with 30x as many turns). Multiply this by 5x for carbon nanotubes (smaller wires allowing more turns) yields a 150x increase to ~ 7.5 Tesla in this made up example. Liquid nitrogen cooled copper would be ~ 10.5 Tesla.
Of course I neglect to figure the actual cooling volume needed beyond my flimsy assumption. But, I'm guessing this grossly demonstrates the magnetic fields that can be obtained without resorting to superconductors.


Dan Tibbets
To error is human... and I'm very human.

vankirkc
Posts: 163
Joined: Fri May 01, 2009 12:08 pm

Post by vankirkc »

MSimon wrote:
vankirkc wrote:Starting off with usual caveat...not an engineer, so please forgive if my question is silly.

I read somewhere that some species of carbon fiber are highly conductive. Can you wind them into an electromagnet? They are supposed to have very high thermal tolerance (I saw 2500k somewhere?).
This is true. About 5X more electrically conductive than copper.

http://powerandcontrol.blogspot.com/200 ... ctors.html

The difficulty right now is that production volumes are low and the costs are high. That should change over time.
That's funny. I deleted the post because I thought it was a stupid question.

chrismb
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Joined: Sat Dec 13, 2008 6:00 pm

Post by chrismb »

BenTC wrote:
MitchellJames wrote: I searched around last night and came up with one place that sells 4 oz jars of silver doped vacuum grease for $275 a jar. A little steep for my budget. But the same concept could be used with any thermal conductive material so I am trying to see if I can obtain bulk amounts of powdered diamond or beryllium oxide. I am also going to stick a highly rated computer thermal paste in a vacuum chamber to see how much it out gases. I would like a non electrically conductive thermal grease.
Someone's homemade non-conducting DIY Diamond Thermal Paste for around $40, compares favourably with traditional conducting silver based thermal paste.
Commercial diamond thermal compund is remarkable. Diamond has a thermal conductivity 10 times better than copper or silver.

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