A rapid, semiempirical method of calculating the stability margins of superconductors cooled with subcooled He-II: (Final report) Page: 4 of 4
4 pagesView a full description of this article.
Extracted Text
The following text was automatically extracted from the image on this page using optical character recognition software:
Liit of symt>oi«
E0'1.43 J/cm2
w * 1.65 mm
L * 50 mm
* d, * 25 mm
o d i = 0.7 mm
q (W/cm2)
J
Figure 7. The experimental points of Pfotenhauer and
van Sciver (ref. 3) and the various theoretical curves
described in the text.
experimental points to lie slightly- to the right of the
theoretical curve of Pig. 2. In Pig. 7, 1 have nor-
malised q^ eo that the asymptote E - Cq^ 3 passes
through the cluster of experimental points near E/E
o
• 0.1. Also shown in Fig. 7 are the asymptotes E
3 -3
• C(v/d) q^ for both sets of points and the corre-
sponding values of E ■ (d/L)EQ (shown as horizontal
line segments) . Both sets of points seem to behave as
described in the previous paragraph.
It might be argued that the sharp drop in the
solid points near ■ 6 w/cm2 signifies approach to
the Kapitza limit. The corresponding limit for the
open points would be « (2.5/0.7)6 « 21.4 W/cm2.
Thus the open points would be unaffected by the Kapitza
limit in any case.
References
1. P. seyfert, J. Lafferranderie, and G. Claudet,
•Time-Dependent Beat Transport in Subcooled
Superfluid Helium," Cryogenics, 22, 401-408, 1982.
2. C. Meuris, "Experimental Study of the Stability of
a Superconductor Cooled by a Limited Volume of
Superfluid Helium," IEEE Trans. Magn., MAG-19(3),
272-275, 1983.
3. J. Pfotenhauer and S. W. van Sciver, "Stability
Measurements of a Superconductor Cooled by a
Two-Dimensional Channel of He-II," Paper DA-4,
1985 CEC/ICMC Conference, Cambridge, Mass.,
August 12-16, 1985.
a proportionality constant in Kipotze'a law of
lnterfacini heat transport, Eq 5 (W m*2 Jt”n)
Cp specific heat at constant pressure [J kg-1 It”1)
C abbreviation for E3S (Ij - Tb)2/4
d width of the two-dimensional channel [m)
E heat pulse energy per unit area [J m”2)
Eq available enthalpy of He-II per ur.il area, cf.
Eq 2 [J m”2)
h enthalpy per unit volume of helium [J m”3)
i ratio of the transport current to the critical
current
K Gorter-Hellink conductance [W a”5/3 n”i/3]
L length of the channel [m]
n exponent in Kapitza'( law of interfacial haat
transport, Eq 5
9j Joule heat flux down the length of the channel
tw m”2]
q^ Kapitsa heat flux, cf. Eq 5 [w n”2J
qs Joule power per unit heated aurface [W m”2]
q, a fiducial haat flux defined by Eq 3 [W m”2]
S pcp, the heat capacity per unit volume (J m”3 K*1}
T> temperature IK]
Tfa ambient helium temperature [K]
T critical temperature IK)
T current-sharing threshold temperature [K]
TBe helium taperature frj
T metal temperature (K)
B
Te temperature of tangency, cf. rig. 4c [K)
T the (lambda) temperature of phaae change from
He-II to He-I [K]
w the width of the heater in the two-dimensional
channel (ml
-3
p density [kg m ]
4. L. Dresner, "Transient Heat Transfer in Superfluid
Helium - Part II," Adv. Cryog. Eng., 29, 323-333,
1984.
DISCLAIMER
(his report was prepared as an account of work sponsored by an agency of the United Slates
Government. Neither the United States Government nor any agency thereof, nor any of their
employees, makes any warranty, express or implied, or assumes any legal liability or responsi-
b.lity for the accuracy, completeness, or usefulness of any information, apparatus, product, or
process disclosed, or represents that its use would not infringe privately owned rights. Refer-
ence herein to any specific commercial product, process, or service by trade name, trademark,
manufacturer, or otherwise does not necessarily constitute or imply its endorsement recom-
mendation, nr favoring by the United Slates Government or any agency thereof. The views
and opinions of authors expressed herein do not necessarily state or reflect those of the
United States Government or any agency thereof.
Search Inside
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
Dresner, L. A rapid, semiempirical method of calculating the stability margins of superconductors cooled with subcooled He-II: (Final report), article, January 1, 1986; Tennessee. (https://digital.library.unt.edu/ark:/67531/metadc1069622/m1/4/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.