Re: On Superconductors, Superfluids and Heat Transfer

From: greywolf42 (mingstb_at_marssim-ss.com)
Date: 12/22/04 

Date: Wed, 22 Dec 2004 01:22:46 GMT

Thomas Clarke <tclarke@ist.ucf.edu> wrote in message
news:714dc636e5a2f50067dfd6d468b95e93.128340@mygate.mailgate.org...
> With regard to the thermal conductivity of electrical superconductors I
> finally found a clear for the non-specialist statement of the situation
> at
> www.physique.usherbrooke.ca/ taillefer/publication/FINAL-published.ps
> "Heat Transport in High-Temperature Superconductors"
> by L. Taillefer and R.W. Hill
>
> "Superconductors are perfect conductors of electric charge but
> very bad conductors of heat. This is because electric currents
> are carried by the Cooper pairs that form the superconducting
> condensate, which has zero entropy, while heat (or entropy)
> is carried by the elementary excitations out of the ground state,
> or 'quasiparticles'."
>
> So my argument that an electrical superconductor should
> also be a thermal superconductor by analogy to metals where
> the heat is largely transported by the charge carriers is wrong.

Thank you for your honesty. I'm sorry I didn't see your post, before
posting my responses to your earlier efforts, this morning.

> But this still leaves the issue which led to this thread: the
> thermal conductivity of a superfluid. So far I have not seen
> anything to contradict these references I found.
>
> http://www.tau.ac.il/~lab3/LOWTEMP/lowtemp.html
> "SUPERFLUIDITY occurs in liquid helium (LHe) below the lambda point,
> a temperature, where the viscosity becomes zero and the heat
> conductivity infinite."
>
> and
>
> http://hypertextbook.com/physics/thermal/conduction/
> "The material with the greatest thermal conductivity is a
> superfluid form of liquid helium"
> ----- A table shows: He II conductivity W/m/K ~100,000

Great! Now we can focus on the direct discussion of the assertions
contained in your references. I think we should focus on the first one --
since the second one indicates a finite thermal conductivity.

The only support given on the first website for the statement above is the
very next sentence: "In that case no local overheating is possible which can
be seen in the absence of bubbles." As noted earlier, this is a very
slender thread of resoning: "No bubbles are seen, therefore the heat
transfer is infinite."

On the first site, there are no direct links to any references, and the
links to the experimental description seems to result in a .pdf file written
in arabic. However, the paper references are in English. These are
introductory textbooks. I have a copy of the following reference used:

C. Kittel, Introduction to Solid State Physics, 5th ed., pp. 337-57. Though
I have the Fourth edition. There is no mention of superfluidity at all
(which is not surprising, given the title).

So, I'm still looking for some substantiation of the basic claim.

When I search the web, I find the following links:

1) http://www.iop.org/EJ/abstract/0022-3727/28/1/006
"Measurement of steady state heat transfer in a bath of sub-cooled
superfluid helium," Wang Rhuzu, 1995, 1995 J. Phys. D: Appl. Phys. 28 25-30
{Unfortunately, not available online to non-subscribers.}

But the title implies that finite heat conductivity is experimentally
measured.

2) http://prola.aps.org/abstract/PR/v60/i4/p354_1
"Heat Transfer and Superfluidity of Helium II", P. Kapitza, Phys. Rev. 60,
354-355 (1941), {Unfortunately, not available online to non-subscribers.}

" IN our recent researches, when studying the. heat transfer of helium II in
capillaries,
we. ... SUPERFLUIDITY OF HELIUM. ... is a superfluid and a poor heat
conductor. ... "

3) http://www.pe.energy.kyoto-u.ac.jp/English/

"Superfluid helium (He II) has excellent cooling properties and therefore is
expected as a coolant for large scale superconducting magnets for nuclear
fusion facilities, accelerators and magnetic energy storage systems. Steady
and transient heat transfer from various shaped heated surface in He II is
studied experimentally and theoretically to establish a database for the
magnet design and to clarify the heat tranfser model."

Again, it seems that experiments measure finite heat transfer rates.

So, what support (other than the bald assertion in the above link) can we
find to support the view that superfluids must be perfect conductors of
heat?

I suspect that it is simply a myth that originally resulted from sloppy use
of the term "superconductor" to apply to electrical and heat transfer. And
that it got morphed into superfluids, as well. 

--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}

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