CONTROLLABLE PHASE SEPARATOR FOR
SEALING CONTAINERS FILLED WITH
SUPERFLUID HELIUM
The present invention relates to controllable phase separators for containers filled with helium in its superfluid state.
BACKGROUND AND PRIOR ART
Superfluid helium is used, for example, during space travel for cooling of equipment. Superfluid helium is in a one phase state and there are no difficulties at the orifice of the container concerning the phase boundary liquid/gas (two phases). There is always a superfluid helium film of finite thickness at the wall of the container and so at the orifice. Only the thickness of this film is affected by the direction and magnitude of the applied force of gravity.
In known systems, such phase separators consist of plugs of a porous ceramic material or of sintered metals. Rolled, contracted foils can also be used. The mass flow then takes place through the capillaries of the plug. All of the abovementioned phase separators are passive systems in which the mass flow of helium and therefore the cooling power cannot be regulated to the required extent. An exact regulation is, however, essential when the heating losses of the equipment to be cooled vary greatly during operation.
SUMMARY OF THE INVENTION
It is an object of the present invention to furnish a phase separator of the above-described type which does not require fine positioning apparatus and which allows regulation over a wide range with relatively simple, inexpensive equipment.
In accordance with the present invention, the phase separator comprises a first and second disk having highly polished mating surfaces and mounted for rotation relative to one another. Each of the disks has at least one axial through passage, at least one of the through passages being eccentric to the axis of rotation of the disks. In a particularly preferred embodiment, the rotation of one disk relative to the other is carried out by a motor. If the motor is a step motor, the positioning can take place in very accurate, small steps without requiring more than a counter to determine the actual position.
In embodiments of the invention wherein the roughness of the surface of the two polished disks is in the order of 10 fim, this gap between the two disks permits the flow of helium, i.e. the superfluid helium then flows out of the container through a through passage in one disk, the gap, and the through passage in the other disk.
In embodiments of the present invention where the roughness of the highly polished surfaces is less than 2 u-m, the two mating surfaces can be used to seal the container. For improved control of helium flow, one of the disks has capillary grooves which extend from its through passage. Rotation of the disks relative to each other with attendant differences in distance between the two through passages results in a control of the mass flow of helium.
The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof will best
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be understood from the following description of specific embodiments when read in connection with the accompanying drawing.
FIG. 1 is a perspective view of the basic arrangement 5 of the two disks according to the present invention;
FIG. 2 is an axial sectional view of the two disks of FIG. 1;
FIG. 3 is a variation of the sectional view of FIG. 2; FIGS. 4-6 are schematic top views illustrating differ10 ent through passage arrangements;
FIGS. 7-9 are schematic top views of various arrangements of capillary grooves.
DESCRIPTION OF THE PREFERRED 15 EMBODIMENT
The basic principle of the invention will first be explained with reference to FIGS. 1 and 2, without taking dimensions and actual construction into consideration. It will become evident that a phase separator according
20 to the present invention may be constructed in many different forms.
In the main, the phase separator comprises a first and second disk, SI and S2, whose mating surfaces are polished. Because of the roughness of the two surfaces, a
25 gap 8 exists between the two disks. Disk SI is supported by a wall T which also separates the interior B of the container from the external environment. The disk S2 is mounted on top of disk SI and may be rotated relative thereto. This is indicated by the arrow around the axis
30 of rotation of the two disks. The latter is indicated by a dash dot line. Each of the disks has a through passage, for example a bore. The bore in disk SI is denoted by Dl, while that in disk S2 is denoted by D2. Both bores are eccentrically arranged at a distance E from the axis
35 of rotation. Rotation of the disks relative to each other will thus cause one of the through passages to move along a circular path relative to each other, thereby changing the distance between the two bores. As shown in FIG. 3, as a special case bores Dl and D2 may be
40 moved to a position where they overlap fully. It should also be noted that bores Dl and D2 may be located at different distances from the axis of rotation so that they may overlap only partially or may perhaps not overlap at all.
45 In FIG. 2 it is assumed that the roughness of the polished surfaces are such that a gap in the order of magnitude of approximately 10 u.m exists or, alternatively, that for a lesser roughness a sealing ring A at the circumference of the disk causes a gap SI of, for exam
50 pie, between 10-15 fim to be formed. The helium will then pass from the inside B of the container in the direction of the arrow through through passage Dl, gap 81, and bore D2 in the direction of the arrow. It is, of course, possible that each disk has a plurality of through
55 passages rather than just one. A wide variety of designs is possible. Another possibility for varying the design includes the selection of the material for the disks. For example, a non-porous material may be used, or one of the two disks may be made of a porous material. When
60 a porous material is used, a steady minimum flow of helium will result, thereby assuring at least a minimum cooling effect. The rotation of the disks relative to each other then controls whatever additional amounts of mass flow may be required.
65 Disk S2 may be rotated relative to disk SI by a motor, which, preferably, is a step motor. A particularly fine regulation may be achieved by use of a step motor with a wobble plate. This allows very fine positioning with
