338 Ë 9 HTS Maglev bearing and flywheel energy storage system
inner tank and outer tank. While support between the inner and outer tanks is a
problem, a HTSB can be used in this case to reduce the conductive heat. A RSB is
applicable, because the exterior tank is more compact than the planar design of
a superconducting bearing. When two RSBs with inner PM rotors were designed
to support the inner tank of a liquid hydrogen tank, the heat leakage was reduced
from 2.7 W with a conventional support to 0.3 W with a RSB. The PM rotors were
fixed to the outer tank. Outer HTS stators with YBCO rings and BSCCO rings were
fixed to the inner tank and cooled by 20 K liquid hydrogen. The advantage of this
design was that there was no need for extra cooling device.- Non-contact mixer [41–43]: Most pharmaceutical solutions on an industrial scale
require highly controlled, thorough mixing to achieve a satisfactory yield and
a uniform distribution of ingredients in the final product. Agitator tanks are
frequently used to complete the mixing process, and a large proportion of conven-
tional mixing technologies are normally achieved by using a mechanical stirrer.
However, a significant shortcoming of such an arrangement is the danger of con-
tamination or leakage during mixing, and the contamination is unavoidable. For
superconducting mixers, the proposal for stirring fluids under sterile conditions is
to use a magnetic coupling with a combination of PMs and HTS bulks. At the top of
the agitator vessel, a rotating PM bar is levitated by magnetic coupling between
PMs and HTS bulks coupled with flux pinning. It is rotated by a driving motor
positioned external to the vessel. In the agitator vessel, another rotating PM bar
attached to the mixer wing is suspended by magnetic coupling between PMs and
HTS bulks based on similar principles. The two magnetic bars are coupled by HTS
bulks. At the bottom of the agitator vessel, a radial PM bearing is applied for the
compensation of lateral stiffness and to enhance the stability of the mixer wing.
The use of such an externally driven magnet bar avoids the need for a dynamic
bearing in the vessel to transfer the rotational forces from the driving magnet to
the stirring magnet. Therefore, a completely enclosed system is provided which
is able to prevent leakage and possible contamination from mechanical bearings.
The cleanup and sterilization are also easy. Experimentally, this superconducting
mixer has provided a rotational force strong enough to stir a 30-L solution [43].
9.3.2Liquid nitrogen pump
In this section, a liquid nitrogen pump and a related prototype are introduced as
interesting cryogenic applications beyond the above-mentioned hot applications of
HTSB (Q. X. Lin, D. H. Jiang, Z. G. Deng, X. Chen, H. L. Jing, Y. Y. Xu, R. B. Wang,
G. T. Ma, J. S. Wang, J. Zheng, and S. Y. Wang. Operation of liquid nitrogen pump with
radial high temperature superconducting magnetic bearing, unpublished data) [44].
As one kind of cryogenic pump, a liquid helium circulation pump can be used
for cooling of the superconducting magnets in a Tokamak reactor. First, the cryogenic