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i'm trying to build a dodecahedron polywell reactor
Posted: Fri Mar 02, 2012 5:42 am
by vnbt4
i've dreamed of space travel for as long as i can remember and i think polywell is the first step in achieving my dream.
i am planing to use a water cooled copper magnet wire for my 1 meter(coil size) for my reactor. i intend to have the reactor generate power
thoughts?
thank you for reading
Posted: Fri Mar 02, 2012 7:50 am
by DeltaV
viewtopic.php?p=43531&highlight=#43531
The electrical resistance of high purity aluminum or copper near liquid hydrogen temperature can be 1/100th or less of the room temperature resistance.
Liquid Hydrogen might be a bit tough to deal with for the home experimenter. Liquid Nitrogen won't improve conductivity as much, but might be worth trying.
Heh. The link to the NASA paper above has gone dead. Google is also silent.
Hit a nerve? Subject matter gone to the Dark Side, reserved for the "elite" and hidden from the "cattle"? Or maybe my Google-Fu is just on the fritz.
Posted: Fri Mar 02, 2012 7:55 am
by DeltaV
Ah, here's a related paper at least:
http://ntrs.nasa.gov/archive/nasa/casi. ... 025905.pdf
HIGH SPECIFIC POWER MOTORS IN LN2 AND LH2
TABLE 1. Copper and fluid properties at room, LN2 and LH2 temperatures
Property Unit (300K) LN2 (77K) LH2 (20.4K)
Cu resistivity* μΩ-cm 1.7 0.23 0.017*
Cu thermal conductivity* W/cm-K 4 5 10*
Cu heat capacity (ΘD = 396K) J/g-K 0.38 0.20 0.009
Cu thermal diffusivity* cm2/sec 1.2 2.8 124*
critical nucleate pool boiling heat flux W/cm2 -- 20 10
superheat at critical heat flux K -- 12 3.3
heat of vaporization per mass J/g -- 199 446
heat of vaporization per liquid volume J/liq-cm3 -- 161 32
heat of vaporization per gas volume J/gas-cm3 -- 0.91 0.58
gas density at normal b.p. g/cm3 -- 0.0046 0.0013
liquid density g/cm3 -- 0.81 0.071
gas to liquid molar volume ratio at b.p. -- -- 176 55
*N.B. Cu transport properties are approximate. A round number of 100 is used for the ratio of Cu
resistivity at room temperature to resistivity at LH2 temperature because the latter resistivity depends so
strongly on purity, work hardening and even magnetic field.
So about 1/7 the resistivity in LN2 (vs. room temp) for copper.
Posted: Fri Mar 02, 2012 12:35 pm
by KitemanSA
I would suggest that you consider copper tubing carrying LN to improve the conductivity of your unit. Square tubing will allow a maximum packing factor.
Posted: Fri Mar 02, 2012 12:38 pm
by KitemanSA
Oh, and if you really want to get with it, a LOx/LN eutectic will permit a lower operating temperature and a greater span between melt and boil (lower flow rate required).
Posted: Fri Mar 02, 2012 6:45 pm
by vnbt4
wow thanks for the responses
if i use LN would it be possible switch to another coolant like water? Also i was planing to us cryogen as a way to store extra energy. My biggest problem is how much power i need to generate to start the reactor?
Posted: Fri Mar 02, 2012 7:46 pm
by ladajo
You will also have power needs for the coolant pump(s), and vacuum pumps.
Are you planning to run continuous? Or will you cool, charge, pulse?
This is not something you are going to do in a garage. You will need some space, and something more than a 200amp service to drive your 1 meter rig. When you say 1 meter, are you thinking 1 meter diameter coils for 12 coils? (So .5 meter radius coils), or are you thinking 1 meter total device diameter for about 30cm diameter coils?
Either way, you are talking about a big power supply.
Posted: Fri Mar 02, 2012 8:17 pm
by vnbt4
the coils themselves have a radius of .5 meters and I'm working on getting a space but it will be a tight fit. I plan on having it steady state not pulsed
Posted: Fri Mar 02, 2012 8:37 pm
by ladajo
What will you use for a chamber?
Also, if you are going steady state, you are talking about lots of juice. That is going to be a big feeder (not impossible), and a bigger power bill.
How are you funding?
Posted: Fri Mar 02, 2012 10:25 pm
by vnbt4
funding close to zip as for the chamber i am going to build one and i am looking for a pump.
i am a tempting to build the reactor for a maximum of 15,000 dollars. I started this to gain the insights to make this work under suck a money constraint
as for copper tubing doesn't need to be insulated to avoid arcing and if so how would i go about insulating the tube
Posted: Sat Mar 03, 2012 12:12 am
by ladajo
you need to get it dipped and baked. You could try to wrap it by hand, but you will end up with no turns. No turns means you would have to slam it with current to get any kind of field.
Posted: Sat Mar 03, 2012 12:26 am
by vnbt4
what should i use for the insulation
Posted: Sat Mar 03, 2012 12:50 am
by ladajo
if you want to hand wrap (not recommended), then you will need Cambric tape, rubber HV tape, electrical tape. The problem with hand wrap, besides the bulk issue, is the outgassing. For your application, you could consider using Kapton tape, then go over it with Silicon Rubber tape.
I always liked to finish with regular electrical tape, but with the right grade rubber, you don't actually need to. It is just insurance if you expect to be bumping around on the rubber wrap job with tools and such later.
If you hand wrap, outgassing is going to be a problem.
Posted: Sat Mar 03, 2012 12:51 am
by ladajo
I really think you should get the coils dipped and baked.
Posted: Sat Mar 03, 2012 2:15 am
by vnbt4
what do you mean dipped and baked? What would be the best power supply?