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Anisotropic Thermal Conductivity of Silver Sheathed Bi2223 Superconducting Tape | IEEE Journals & Magazine | IEEE Xplore

Anisotropic Thermal Conductivity of Silver Sheathed Bi2223 Superconducting Tape

Publisher: IEEE

Abstract:

Anisotropic thermal conductivity, κ( T ), of a silver sheathed Bi2223 (Bi2223/Ag) tape was determined for three typical directions; the length ( l ), width ( w ), and thi...View more

Abstract:

Anisotropic thermal conductivity, κ( T ), of a silver sheathed Bi2223 (Bi2223/Ag) tape was determined for three typical directions; the length ( l ), width ( w ), and thickness ( t ). κ( T ) of the tape along the l -direction was measured directly and those along the w - and t -directions were estimated by measuring stacked samples in which several Bi2223/Ag tapes were soldered. κ( T ) of the tape along the l - and w -directions was 250 W m -1 K -1 at 77 K and almost coincided with each other. On the other hand, κ( T ) of the tape along the t -direction was about one order of magnitude smaller than those along other directions. The measured κ( T ) curves were analysed using an equivalent heat current circuit. Results show that the applied heat flows through the Ag parts for three directions. The amount of the Ag parts being in the route of the heat current depends on the direction.
Published in: IEEE Transactions on Applied Superconductivity ( Volume: 21, Issue: 3, June 2011)
Page(s): 2828 - 2831
Date of Publication: 22 November 2010

ISSN Information:

Publisher: IEEE

I. Introduction

A SILVER sheathed Bi2223 (Bi2223/Ag) superconducting tape has been developed to achieve a long length cable with higher critical current density . Recently, a Bi2223/Ag tape with high critical current, , over 200 A at 77 K in the self-field was reported [1], [2], which gives us an opportunity to use the tape practically in power applications such as cables and high-field coil magnets. In the applications, it is important to estimate the thermal stability. We can calculate the amount of the heat intrusion and the heat exhaust through the tape, , using the thermal conductivity, , by the following relation,

Here, and are the cross section and the length of the tape and and are the temperatures at both sides of the tape. In a winding coil, the heat might flow both along the length direction of the tape and along the radial direction of the coil, which is perpendicular to the thickness direction of the tape. We measured the anisotropic thermal resistance, , of a double-pancake coil using Bi2223/Ag tape and pointed out that the value of the tape along the thickness direction is important to analyse precisely the thermal transport along the radial direction [3]. However, of the Bi2223/Ag tapes have been usually measured only along the length direction [4]–[6], because the thickness of the tape is too thin to measure by a steady-state heat flow method.

References

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