Refrigeration – Gas compression – heat regeneration and expansion – e.g.,...
Reexamination Certificate
2001-03-22
2002-10-08
Doerrler, William C. (Department: 3744)
Refrigeration
Gas compression, heat regeneration and expansion, e.g.,...
Reexamination Certificate
active
06460348
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a regenerator (cold accumulating unit) filled with a cold accumulating material and a cold accumulating type refrigerator using the regenerator, and more particularly to a regenerator of which cold accumulating material is free from the risk of being pulverized into fine particles, and is excellent in workability and durability, and exhibits significant refrigerating performance at a low temperature region, and relates to a cold accumulation refrigerator using the regenerator (cold accumulating unit).
2. Description of the Related Art
Recently, superconductivity technology has been progressed remarkably and with an expanding application field thereof, development of a small, high performance refrigerator has become indispensable. For such a refrigerator, light weight, small size and high heat efficiency are demanded, and a small-sized refrigerator has been practically applied to various industrial fields.
For example in a super-conductive MRI apparatus, cryopump and the like, a refrigerator based on such refrigerating cycle as Gifford MacMahon type (GM refrigerator), Starling method, pulse-tube type refrigerator has been used. Further, a magnetic floating (levitating) train absolutely needs a high performance refrigerator for generating magnetic force by using a super-conductive magnet. Further, in recent years, a super-conductive power storage apparatus (SMES) or an in-magnetic-field single crystal pull-up apparatus (magnetic field applied Czochralski) has been provided with a high performance refrigerator as a main component thereof.
In the above described refrigerator, the operating medium such as compressed He gas or the like flows in a specified direction in a regenerator (cold accumulating unit) filled with cold accumulating materials so that the heat energy thereof is supplied to the cold accumulating material. Then, the operating medium expanded here flows in an opposite direction and receives heat energy from the cold accumulating material. As the recuperation effect is improved in this process, the heat efficiency in the operating medium cycle is improved so that a further lower temperature can be realized.
As a cold accumulating material for use in the above-described refrigerator, conventionally Cu, Pb and the like have been used. However, these cold accumulating materials have a very small specific heat in extremely low temperatures below 20K. Therefore, the aforementioned recuperation effect is not exerted sufficiently, so that even if the refrigerator is cyclically operated under an extremely low temperature, the cold accumulating material cannot accumulate sufficient heat energy, and it becomes impossible for the operating medium to receive the sufficient heat energy. As a result, there is posed a problem of that the refrigerator in which the regenerator (cold accumulating unit) filled with aforementioned cold accumulating material is assembled cannot realize the extremely low temperatures.
For the reason, recently to improve the recuperation effect of the regenerator at extremely low temperature and to realize temperatures nearer absolute zero, use of magnetic cold accumulating material made of intermetallic compound formed from a rare earth element and transition metal element such as Er
3
Ni, ErNi, ErNi
2
, HoCu
2
having a local maximum value of volumetric specific heat and indicating a large volumetric specific heat in an extremely low temperature range of 20K or less has been considered. By applying the magnetic cold accumulating material t o the GM refrigerator, a refrigerating operation to produce an arrival lowest temperature of 4k is realized.
The magnetic cold accumulating material described above is normally worked and used in a form of spherical-shape having a diameter of about 0.1-0.5 mm for the purpose of effectively performing the heat exchange with He gas as cooling medium in the refrigerator. In particular, in a case where the magnetic cold accumulating material (particulate cold accumulating substance) is intermetallic compound containing rare earth element, the particulate cold accumulating substance is worked so as to have a spherical-shape in accordance with working methods such as centrifugal atomizing method.
However, in a Starling-type refrigerator and a pulse-tube type refrigerator or the like to be operated with a high speed, there has been posed a problem that a pressure loss at the regenerator packed with spherical magnetic cold accumulating particles is disadvantageously increased, so that a sufficient refrigerating capacity cannot be realized. Further, in the GM refrigerator or the like, there has been liable to cause the following disadvantages. Namely, vibration and impact force are applied to the magnetic body particles (magnetic cold accumulating particles) during the operation of the refrigerator and the magnetic particles were liable to be further finely pulverized, so that a flow resistance of the cooling medium gas is increased thereby to abruptly lower the heat exchange efficiency.
To cope with these problems, as samples of structure of cold accumulating material for lowering the pressure loss of the cooling medium gas, there has been proposed: a cold accumulating material composed of a punching plate formed by punching a magnetic material plate so as to form a number of through holes through which the cooling medium gas flows; a cold accumulating material composed of a rolled ribbon formed by winding a magnetic material ribbon; and a cold accumulating material composed of a screen formed by laminating a plurality of net-shaped magnetic materials.
However, since the cold accumulating materials described above exhibit a brittleness peculiar to the intermetallic compound, there had been raised a problem such that it was difficult to punch, bend or drill the materials, and it was extremely difficult to work the materials to have the above shapes, and the materials required an enormous large amount of working cost.
SUMMARY OF THE INVENTION
The present invention has been achieved to solve the above described problems and an object of the invention is to provide a regenerator (cold accumulating unit) filled with cold accumulating material which is free from the fear of being finely pulverized, and is excellent in workability and durability, and capable of exhibiting a significant refrigerating performance at an extremely low temperature range for a long period of time in a stable condition, and provide a cold accumulation refrigerator using the same.
In addition, another object of the present invention is to provide an MRI apparatus, a super-conducting magnet for magnetic floating train, a cryopump and an in-magnetic field single crystal pull-up apparatus capable of exerting an excellent performance for a long period of time by using the aforementioned cold accumulation refrigerator.
To achieve the above objects, the regenerator (cold accumulating unit) of the present invention comprises a regenerator body and cold accumulating material packed in the regenerator body in which cooling medium gas flows from one end portion of the regenerator body to the other end portion of the regenerator body so as to obtain a lower temperature, wherein at least part of the cold accumulating material is a plate-shaped cold accumulating material having a thickness of 0.03-2 mm.
Further, in the above structure, it is preferable that the cold accumulating material is composed of an alloy containing 10 at % or more of rare earth element, and that a length of the plate-shaped cold accumulating material in a flowing direction of the cooling medium gas is set to 1-100 mm. In addition, it is also preferable that a plurality of the plate-shaped cold accumulating material are arranged in a direction normal to the cooling medium gas flowing direction so as to form gaps therebetween, and a width of the gap is 0.01-1 mm.
Furthermore, in the above regenerator (cold accumulating unit), it is preferable to constitute the regenerator so that grooves are formed to an inner su
Arai Tomohisa
Okamura Masami
Doerrler William C.
Drake Malik N.
Foley & Lardner
Kabushiki Kaisha Toshiba
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