EP3551947B1 - Regenerator for a cryo-cooler with helium as a working gas, a method for producing such a regenerator, and a cryo-cooler comprising such a regenerator - Google Patents

Description

The invention relates to a regenerator for cryocoolers with helium as the working gas according to claim 1, a method for producing such a regenerator according to claims 13 and 14 and a cryocooler provided with such a regenerator according to claim 15.

Intermittently operated cryo-coolers, e.g. B. Stirling, Gifford-McMahon and pulse tube coolers are operated regeneratively. i.e. the thermal capacity of a material is used to store the cold or to pre-cool warm gas as it enters the expansion chamber. A problem here is that at temperatures in the 2K to 20K range, the heat capacity of almost all materials decreases sharply. It is therefore very difficult to find materials that have a sufficiently high heat capacity in the range between 2K and 20K. 12 shows the typical structure of a two-stage pulse tube cooler with a first cold stage of 20 to approx. 30K and a second cold stage of 22 to approx. 2K. The first cold stage 220 includes a first pulse tube 224 and a first regenerator 226. The second cold stage 222 includes a second pulse tube 228 and a second regenerator 230 in accordance with the present invention. With the first cold stage 220 approx. 30K and with the second cold stage 222 approx. 4K are achieved. The first pulse tube 224, the first regenerator 226 and the second pulse tube 228 terminate in a connecting means 232 which separates the environment from the area to be cooled. Working gas is supplied and discharged in a pulsating manner by a pump (not shown) via working gas lines 234 . The working gas lines 234 open into the first regenerator 226 and via valves 236 there is a connection to the first pulse tube 224 and the second pulse tube 228 as well as to ballast volume 238. The second regenerator 230 in the second cold stage 222 consists of a first regenerator section 240 and a low-temperature - Regenerator section 242. The first regenerator section 240 consists of superimposed metal screens 244 - see figure 13 . The cryogenic regenerator section 242 contains rare earth connections, e.g. B. ErNi, HoCu ₂ and the like. The structure of the second regenerator 230 is shown schematically in 11 shown. Rare earth compounds are relatively expensive. Furthermore, these materials are used in the form of beads 46 (100 to several 100 micrometers in diameter). A problem here is the fixation of the balls in the oscillating flow of the working gas, since any kind of movement leads to abrasion and thus dust, which drastically reduces the service life of the cryocooler. In addition, ball beds according to 13 a significant dead volume that does not contribute to heat exchange or cooling capacity.

Helium is often used as a working gas in cryogenic coolers. In the temperature range from 2K to 20K, helium has a comparatively high heat capacity, which is equal to the heat capacity of rare earth compounds in this temperature range. It has therefore been proposed to use helium as the regenerator material. From the U.S. 2012/0304668 A1 , the, DE 10319510 A1 , the DE 102005007627 A1 , CN 104197591A , DE 19924184 A1 and the US4359872A closed hollow bodies made of glass or metal and filled with helium are known as regenerator structures. This basic idea has not yet resulted in a finished product. In addition, helium-filled beads again cause attrition, reducing the service life of the cryocooler. The basic problem of these known closed hollow bodies with helium consists in the complex filling of the hollow bodies with helium under overpressure. Due to the overpressure, the wall thickness of the hollow body has to be increased, which leads to a deterioration in the heat transfer resistance.

In the article " Heat Capacity Characterization of a 4K Regenerator with Non-Rare Earth Material" in Cryocoolers 19, International Cryocooler Conference, Inc., Boulder, CO, 2016 a structure using adsorbent material capable of absorbing helium is proposed as a regenerator for cryocoolers. The structure of the regenerator is complicated and expensive, and there is a risk that parts of the adsorber material will be entrained by the working gas flow. The service life of a cryocooler with such a regenerator would be drastically reduced by the adsorber particles carried along.

It is therefore the object of the present invention to specify a regenerator which is inexpensive in comparison to regenerators with rare earth compounds and which uses helium as the heat storage material and nevertheless has a simple structure.

This problem is solved by the features of claim 1.

In the simplest case, the regenerator consists of a hollow cell with heat-conducting cell walls. The outside of the cell walls at least partially delimits a flow channel for the working gas helium. The cavity is filled with helium as a heat storage material and is connected to the outside of the cell via a pressure equalization opening. The working gas, helium, flows around the can-shaped cell, as a result of which heat transfer takes place via the cell walls between the working gas helium outside the cavity and the helium inside the cavity. The size of the cell(s) in relation to the size of the flow channel of the working gas is selected in such a way that the desired pressure differences are set between the high-pressure side and the low-pressure side of the regenerator with the smallest possible dead volume. The cell walls of the cell are very thin, so that the desired heat exchange can take place. The ratio of the volume of the cavity or cavities to the opening area or outflow resistance of the pressure equalization opening is chosen so that the pressure in the cavity or cavities in the working frequency range of cooler operation (approx. 1 to 60 Hz) hardly changes, or at least only slightly. This mode of operation can be compared to a capacitor at high frequencies - it is virtually unaware of the change in voltage if the capacity is high enough and the voltage change is small. In a typical application, the pressure in the cell would always fluctuate around the medium pressure of the cooling system, typically around 16 bar. The stable pressure is important because otherwise the volume of the cavity or cavities would be a large contributor to the "dead volume" if its pressure was between e.g. B. 8 and 24 bar would fluctuate without it contributing to the cooling. The opening area or the outflow resistance of the pressure compensation opening is selected in such a way that before the regenerator is put into operation and during the start-up phase, helium penetrates into the cavity or cavities due to the prevailing pressure conditions. The high outflow resistance of the pressure equalization opening results in the "condenser effect" explained above during the Pressure fluctuations in the area of the regenerator with the working frequency of a cooler. During the start-up phase, the temperature of the working gas helium and also of the helium in the regenerator cavities decreases. As a result, the volume of helium is reduced and helium continues to flow into the regenerator cavities via the pressure equalization opening. i.e. During the start-up phase, helium must be refilled until the working temperatures and pressures have settled. Without a pressure equalization opening, the cavities in the cell would have to be filled with helium in advance, which would require significantly thicker cell walls due to the pressures in the range of 16 bar in the working area of the cryocooler. If the hollow bodies are filled with helium at ambient temperature, significantly higher pressures must be chosen for the filling due to the lower density of helium at ambient temperature. This leads to thicker cell walls with significantly higher thermal resistance. Due to the thicker cell walls, a heat transfer resistance of the cell walls would be so high that in the working frequency range of cryogenic coolers there would hardly be any heat exchange between the working gas helium and the helium inside the cavity or cavities. This may also be the reason that there is no cryo-cooler on the market that uses a regenerator with helium in closed cavities. According to the invention, the pressure equalization opening has the form of a capillary.

The cell is penetrated by flow channels that are delimited by cell walls. This results in an enlarged heat exchange surface and thus improved heat transfer between the helium in the cavities and the working gas outside. The flow channels are preferably designed as slots. The slits end short of the edge of the cell, preventing the cell from falling apart. The flow channels are formed as a plurality of slots that are straight and parallel to each other and terminate short of the edge of the cell so that the cell cannot fall apart. A circumferential channel is formed at the edge of the cell into which the multiple interconnected cavities open.

The slit-shaped flow channels for working gas preferably run in a straight line and parallel to one another, on the one hand to minimize the flow resistance and on the other hand to uniformly close the tubular cavities between the shape. Due to the straightness and the parallelism, an equal distance is obtained in a simple manner between two flow channels.

Due to the round outer shape of the regenerator, they can easily be inserted into the usually round cross-sections of cryocoolers. A single cell, optionally with a plurality of tubular structures, can have the shape of a disc. Alternatively, multiple cells can be assembled into a disk shape. - Claim2.

The arrangement in a row according to claim 3 increases the heat storage capacity of the regenerator.

Thermal insulation between cells arranged one behind the other in the direction of flow of the working gas - claim 4 - prevents heat from being exchanged between the cavities in the direction of flow of the working gas. Such a heat exchange in the flow direction of the working gas would mean a short circuit of the regenerator; a heat exchange in the flow direction of the working gas does not contribute to the function of the regenerator. The thickness of the thermally insulating layer is preferably between 0.1 mm and 0.5 mm.

The alignment elements according to claim 5 to 7 simplify the alignment of the flow channels of cells lying one on top of the other. The alignment elements are z. B. Alignment pins having a conical or pyramidal tip.

The shape of a capillary means that the cross-sectional area of the opening is very small compared to the surface area of the hollow body.

The pressure equalization opening can also be provided by leaks that occur during the manufacture of the cells - claim 8.

The size and thus the permeability of the pressure equalization opening are chosen so that during a working cycle of the regenerator, the pressure change in the cell is a maximum of 20% and preferably a maximum of 10%. This is an optimization process. The larger the capillary, the greater the unwanted mass transfer, the greater the pressure fluctuations in the cell cavity and the faster the helium penetrates into the cavities when the regenerator is started up. The smaller the capillary, the less compression work has to be done, but the longer it takes for the helium to penetrate the cavities when the regenerator is started up.

In order to improve the heat exchange between the working gas helium and the heat-storing helium located in the hollow body, the surfaces of the hollow bodies are provided with turbulence structures - claim 9

The cross-sectional shapes of the tubular cavities according to claim 10 enable the manufacture of the regenerator by means of 3D printing (claim 14). The cuboid or rectangular shape of the cross sections of the cavities is optimal for heat exchange. Cells with tubular cavities with at least one sloping cell wall or with a triangular cross-section can be easily created using 3D printing. Using 3D printing, structures with vertical or sloping cell walls (slopes of 45° or more) can easily be produced. This is most easily ensured when the triangular cross section of the cavities has a right angle. A diamond-shaped cross-section, a pentagonal cross-section or a house-shaped cross-section is also suitable - claim 10.

For the optimal heat exchange between the helium in the tubular cavities and the working gas helium outside of the cavities, flow channels are arranged between the tubular cavities - claim 11.

The advantageous embodiment according to claim 12, in which the disk-shaped regenerator consists of one or more disk-shaped cells and each cell comprises two half-cells, means that both half-cells can be produced by means of 3D printing. At the same time, the proportion of the volume of the cavities—and thus of the helium in the cavities—in the total volume of the regenerator increases compared to regenerators that only have one-piece cells. This increases the Heat storage capacity of the regenerator or the regenerator can be made more compact with the same heat capacity.

In 3D printing processes, cuboid cavities or elliptical cavities can be produced from two components as a whole or in two steps - claim 13 or 14. According to claim 14, a first component with "open cavities" or with pot-shaped depressions is first produced. In a second step, these depressions are then covered by second components. The first and second components are permanently joined together, e.g. B. by gluing or welding.

The regenerators according to the present invention are particularly suitable for Stirling, Gifford-McMahon or pulse tube coolers in particular - claim 15.

The hollow bodies are made of metal and/or and can be made very thin compared to the prior art due to the pressure equalization opening, which reduces the heat transfer resistance between the helium inside the cavities and the helium working gas outside the cavities. The cell walls of the cavities preferably have a constant thickness, at least along the flow channels, and are in the range between 0.1 mm and 0.5 mm. Due to the constant wall thickness of the cell walls, a uniform heat transfer is achieved between the working gas helium in the flow channels and the helium in the cavities.

The entire regenerator preferably has a thickness of 5 mm to 100 mm in the flow direction of the working gas.

The remaining claims relate to further advantageous configurations of the invention.

Preferred embodiments of the invention are described below with reference to the drawing.

• Fig. 1 eine Schnittdarstellung einer ersten Ausführungsform des Regenerators in einem Strömungskanal für Arbeitsgas,
• Fig. 2 eine Schnittdarstellung der ersten Ausführungsform entlang II - II in Fig. 1,
• Fig. 3a und 3b eine schematische Darstellung einer zweiten Ausführungsform,
• Fig. 4 eine schematische Darstellung einer dritten Ausführungsform,
• Fig. 5 eine schematische Darstellung einer vierten Ausführungsform,
• Fig. 6 eine schematische Darstellung einer fünften Ausführungsform,
• Fig. 7 eine sechste Ausführungsform, die nicht durch die beanspruchte Erfindung abgedeckt ist, in Form einer dreidimensionalen Matrixanordnung mit zwei Lagen von Zellen mit einem kreisringförmigen Außendurchmesser,
• Fig. 8, die nicht durch die beanspruchte Erfindung abgedeckt ist, eine Detaildarstellung der Matrixanordnung mit drei Lagen von Zellen senkrecht zur Strömungsrichtung des Arbeitsgases betrachtet,
• Fig. 9 und 10 schematische Darstellungen zur Herstellung des Regenerators aus einer Schalenstruktur und einer Abdeckung gemäß einer siebten Ausführungsform,
• Fig. 11 eine achte Ausführungsform der Erfindung, die aus zwei mittels 3D-Druck hergestellten Strukturen besteht,
• Fig. 12a, 12b und 12c Beispiele für Querschnitte der Hohlräume mit dem wärmespeichernden Helium, die sich ohne weiteres mittels 3D-Druck herstellen lassen,
• Fig. 13 den typischen Aufbau eines Kryo-Kühlers in Form einer Pulsrohrkühlers mit zwei Kaltstufen, wobei die zweite Kaltstufe einen Tieftemperatur-Regenerator aufweist, und
• Fig. 14 den schematischen Aufbau eines Tieftemperatur-Regenerators nach dem Stand der Technik mit seltenen Erden in Form von Kügelchen.

It shows:

• 1 a sectional view of a first embodiment of the regenerator in a flow channel for working gas,
• 2 a sectional view of the first embodiment along II - II in 1 ,
• Figures 3a and 3b a schematic representation of a second embodiment,
• 4 a schematic representation of a third embodiment,
• figure 5 a schematic representation of a fourth embodiment,
• 6 a schematic representation of a fifth embodiment,
• 7 a sixth embodiment, which is not covered by the claimed invention, in the form of a three-dimensional matrix arrangement with two layers of cells with a circular outer diameter,
• 8 , which is not covered by the claimed invention, a detailed view of the matrix arrangement with three layers of cells perpendicular to the direction of flow of the working gas,
• Figures 9 and 10 schematic representations for the production of the regenerator from a shell structure and a cover according to a seventh embodiment,
• 11 an eighth embodiment of the invention consisting of two structures produced by means of 3D printing,
• Figures 12a, 12b and 12c Examples of cross-sections of the cavities with the heat-storing helium, which can be easily produced using 3D printing,
• 13 the typical structure of a cryocooler in the form of a pulse tube cooler with two cold stages, the second cold stage having a low-temperature regenerator, and
• 14 the schematic structure of a low-temperature regenerator according to the prior art with rare earths in the form of small beads.

the Figures 1 and 2 show a first embodiment of the regenerator 1 according to the invention in its simplest form. The regenerator 1 consists of a cell 2 with cell walls 4 which enclose a cavity 6 . The cell walls 4 have an outside 4a and an inside 4i. A pressure equalization opening in the form of a capillary 8 passes through the cell walls 4 . The regenerator 1 has a circular cross-section and is arranged in a tubular flow channel 10 for the working gas helium. The interior of the cavity 6 is filled with helium as a regenerator medium or a heat-accumulating medium. The regenerator 1 or the cell 2 is dimensioned in such a way that an annular gap 12 remains between the tubular flow channel 10 for the working gas and the outside 4a of the cell wall 4 . The working gas helium can thus flow around the regenerator 1 and exchange heat with the helium in the cavity 6 via the heat-conducting cell walls 4 .

Figures 3a and 3b show a second embodiment of the invention with a disc-shaped cell 2. The cell 2 differs from the cell 2 by Figure 1 and 2 in that the cell 2 according to the second embodiment is penetrated by a plurality of slots 20 running in a straight line in one plane as flow channels for the working gas. The slit-shaped flow channels 20 run parallel to one another, but end in front of the edge of the cell 2, so that the cell 2 cannot fall apart. In the cuboid areas enclosed by cell walls 4 between the slit-shaped flow channels 20 there are tubular cavities 6 with a rectangular cross section. All the cavities 6 open into a peripheral channel 24 provided at the edge of the disc-shaped cell 2, so that the cavities 6 and the peripheral channel 24 form a single cavity.

When the disc-shaped cell 2 is produced by means of 3D printing, one or two larger openings 22 initially remain through which the loose 3D printing material can be blown out before the 3D printing. These openings are then closed so that only one or more pressure equalization openings 8 remain in the form of capillaries. It is also possible to arrange several cells 2 one behind the other in the flow direction of the working gas, resulting in a regenerator with a higher output.

4 1 shows a third embodiment of the invention, in which a plurality of cells 2-1, 2-2, 2-3 are stacked one on top of the other. The three disk-shaped cells 2-i with a circular cross-section have an identical structure. The cells 2-i are similar to the cell 2 of the second embodiment and differ from the cell by Figure 1 and 2 in that the cells 2-i are penetrated by a plurality of slots 20 running in a straight line in one plane as flow channels for the working gas. The slit-shaped flow channels 20 run parallel to one another, but end in front of the edge of the cells 2-i, so that the cell 2 cannot fall apart. In the cuboid areas enclosed by cell walls 4 between the slit-shaped flow channels 20 there are tubular cavities 6-i, which have a cross-section in the form of an equilateral triangle with a right angle. The apex of the right-angled triangle points upwards, so that the two sides of the equilateral triangle extend upwards at a 45° angle. Cavities 6-i with a triangular cross-section can be easily produced using 3D printing. When the disc-shaped cells 2 are produced by means of 3D printing, one or two larger openings 22 initially remain through which the loose 3D printing material can still be blown out for the 3D printing. These openings are then closed so that only one or more pressure equalization openings 8 remain in the form of capillaries.

The cavities 6-i are connected to one another at the edge of the disc-shaped cells 2-i. A pressure equalization opening 8 connects the cavities 6-i with the area outside the cells 2-i. The cells 2-i have a plurality of alignment pins 30 on their upper side and corresponding alignment depressions 32 are arranged on the opposite side. Through these alignment elements 30, 32 is achieved that the slit-shaped flow channels 20 of the cells 6-i lying one above the other are aligned with one another, so that continuous flow channels result through the regenerator. A thermally insulating layer 34 is arranged between the individual cells 6 - i, through which the alignment pin 30 passes, so that the alignment pins can engage in the alignment openings 32 located above.

figure 5 shows schematically a fourth embodiment of the regenerator in the form of a disk-shaped cell 2, which differs from the cells 2-i according to 4 differs in that instead of a tubular cavity with a triangular cross section, two tubular cavities 6a and 6b are provided. The cross section of the tubular cavities 6a and 6b is also in the shape of a right-angled equilateral triangle. The right angle begins on the inside of the partition wall 4, which delimits the slit-shaped flow channels. This results in a partition 4 with a constant wall thickness between the flow channels 20 and the cavities 6-i. This leads to an improved heat transfer between the working gas in the flow channel 20 and the helium in the cavities 6a and 6b. The pressure equalization opening 8 connects the cavities 6a, 6b with the area outside the cell 2.

6 shows a fifth embodiment of the invention, which differs from the embodiment according to FIG figure 4 differs only in that the tubular cavities 6a, 6b are arranged with triangular cross section with the base of the right triangle towards the flow channels 20. Since the base is the length of the side of the equilateral triangle, this improves heat transfer.

figures 7 and 8th Fig. 12 schematically show the structure of a sixth embodiment not covered by the claimed invention. 7 FIG. 1 shows a regenerator 101 with a large number of cells 102 which are arranged in the form of a 3-dimensional matrix 103 with two layers of cells 102. FIG. The cells 102 are cubic and basically identical in construction. However, since the regenerator 101 fills a pipe cross section, the cells 102 inevitably have a different shape in the edge area. The individual cells 102 each comprise a cube-shaped cavity 106 with a heat-conducting shell 104 and a pressure equalization opening 108 in the form of a capillary. How out 8 can be seen, the individual cells are 102 arranged offset one behind the other in the direction of flow 112 of the working gas. The cells 102 lying next to one another are connected to one another by means of thermally conductive connecting elements 114 . The cells 102 lying one behind the other in the direction of flow 112 are connected to one another with thermally insulating or poorly conducting connecting elements 116 and form a flow channel 120. This results in the mechanically strong matrix arrangement 103 of cells 102. In Figure 7 only two tiers of cells 102 are shown, while in 8 three layers of cells 102 are shown. The gas volume of the individual cavities 106 is approximately 1 mm ² , the wall thickness of the shell 104 is approximately 0.2 mm. The distance between the individual cells 102 is approximately 0.2 mm. The total space requirement of a cell 102 is approximately 8 mm ³ .

The regenerator 101 according to the invention is preferably used as a low-temperature regenerator section 242 in the coldest cold stage of a cryocooler.

Figures 9 and 10 show seventh embodiment of the invention, in which the cell 2 with slit-shaped flow channels 20 according to the embodiments according to Figures 3 to 6 . The difference from the embodiments according to the Figures 4 to 6 consists in the form of the tubular cavities 6'. The cavities 6' are as in the second embodiment Figures 3a and 3b rectangular in cross section. In contrast to the second embodiment, production takes place in two steps with at least two components. First, a first component 40 with “open cavities” or with cup-shaped depressions 42 is produced, e.g. B. by means of 3D printing. In a second step, loose 3D printing material is removed from the cup-shaped indentations. Then, in a third step, the depressions 42 are covered by second components 44 . The first and second components 40, 44 are permanently joined together, e.g. B. by gluing or welding.

11 shows an eighth embodiment of the invention in the form of a disc-shaped cell 2, which is composed of a first and a second half-cell 50, 52, so that a cell 2 results analogously to the embodiments according to FIG figure 5 and 6 between the slit-shaped flow channels 20 has cuboid structures in cross-section. Both half-cells 50, 52 each have a plurality of first and second cavities 54 and 56 having a cross section of an isosceles triangle. The two half-cells 50, 52 can be produced using 3D printing. The two half-cells each have a flat side 58 and an uneven side 60 . The two uneven sides 60 have a complementary shape and when the two half-cells 50, 52 are assembled, the complementary uneven sides 60 of the two half-cells lie on top of each other. Compared to the embodiments according to Figures 4 to 6 increases in the regenerators with cells 2, each having two half-cells 50, 52, the proportion of the cavity volume in the total volume of the regenerator. This makes the regenerator more efficient.

Analogous to the second embodiment Figures 3a and 3b also show the embodiments Figures 4 to 6 and 9 to 11 a circumferential channel 24 on.

The pressure equalization opening 8 is in the Figures 2 to 6 and 9 to 11 not marked but available. Since the cavities 6-i; 6′, 6a, 6b are connected to one another, the pressure equalization opening 8 can be provided at any point in the cells 2.

the Figures 12a, 12b and 12c show possible further cross-sectional shapes of the cavities 6 in the disk-shaped regenerators according to FIG Figures 3 to 6 and 11 that can be easily produced using 3D printing.

Reference list:

1

regenerator

2

cell

4

cell wall

4i

Inside of the cell wall 4

4a

Outside of the cell wall 4

6, 6-i, 6a, 6b

cavity

8th

pressure equalization opening

10

Flow channel for working gas

12

Annular gap between 2 and 10

20

slit-shaped flow channels for working gas

22

exhaust openings

24

peripheral connecting channel

30

alignment pin

32

alignment dimples

34

thermally insulating layer

40

first component with cup-shaped indentations

42

pot-shaped indentations

44

covers

50

first half cell

52

second half cell

54

first cavities

56

second cavities

58

flat side of 50, 52

60

uneven side of 50, 52

101

regenerator

102

cells

103

matrix arrangement

104

shell or cell walls

106

cavity

108

pressure equalization opening

112

Flow direction of the working gas

114

thermally conductive fasteners

116

thermally insulating fasteners

120

flow channel

220

first cold stage

222

second cold stage

224

first pulse tube

226

first regenerator

228

second pulse tube

230

second regenerator

232

lanyard

234

working gas lines

236

valves

238

ballast volume

240

first regenerator section of 230

242

Cryogenic regenerator section of 230

244

Metal screens in 230

246

Rare earth compound globules

Claims (15)

1. Regenerator for cryo-coolers with helium as a working gas, comprising

   at least one cell (2) with cell walls (4) including an exterior (4a) and an inner side (4i);

   wherein the cell walls (4) are at least partly heat conductive,

   the at least one cell (2) has a plurality of cavities (6; 6-i; 6a, 6b) connected with each other, which are surrounded by cell walls (4),

   the exterior (4a) of the cell walls (4) at least partly delimits a flow channel for the helium working gas;

   the at least one cell (2) has a pressure-equalizing opening (8), and

   the at least one cell (2) includes flow channels (20) for the working gas, which are delimited by cell walls (4; 104), and

   the cavities (6; 6-I; 6a, 6b) are filled with helium gas as a heat storage material,

   characterized in that

   the pressure-equalizing opening (8) is formed as a capillary, and

   the flow channels (20) are formed as a plurality of slots extending rectilinearly and parallel to each other and end before the rim of the cell (2) so that the cell (2) cannot fall apart,

   a circumferential channel (24) is formed at the rim of the cell (2) into which the plurality of cavities (6; 6-i; 6a, 6b) connected with each other open.
2. Regenerator according to one of the preceding claims, characterized in that the at least one cell (2) is formed as a disk with a round cross-section.
3. Regenerator according to one of the preceding claims, characterized in that a plurality of cells (2) is arranged one behind the other in a flow direction of the working gas.
4. Regenerator according to claim 3, characterized in that cells (2) arranged one behind the other in a flow direction of the working gas are separated from each other by a thermally insulating layer (34) including flow channels (20) for the working gas.
5. Regenerator according to claim 4, characterized in that the cells (2) and the thermally insulating layer (34) each have alignment elements (30, 32), so that the flow channels (20) of the cells (2) and the thermally insulating layer or layers (34) are in alignment with each other.
6. Regenerator according to claim 5, characterized in that the alignment elements include a plurality of alignment pins (30) on one side of the cells (2) and complementarily formed aligning recesses (32) on the other side of the cells.
7. Regenerator according to claim 6, characterized in that the thermally insulating layer (34) includes alignment openings that are permeated by the alignment pins (30), so that the flow channels (20) for the working gas in the cells (2) and in the thermally insulating layer (34) are in alignment with each other.
8. Regenerator according to one of the preceding claims, characterized in that the pressure-equalizing opening (8) results on account of leaks occurring during production of the regenerator.
9. Regenerator according to one of the preceding claims, characterized in that the exterior of the cell walls (4) has turbulence structures in the flow channels (20) for the working gas.
10. Regenerator according to one of the preceding claims, characterized in that the cavities (6-i; 6', 6a, 6b) have the shape of a tube and a cross-section in form of a triangle, a cross-section in form of a rectangle, or a cross-section with at least one slanting cell wall.
11. Regenerator according to claim 10, characterized in that in a plurality of tube-shaped cavities (6-i, 6', 6a, 6b), flow channels (20) for the working gas are arranged per cell (2) between the tube-shaped cavities (6-i, 6', 6a, 6b).
12. Regenerator according to one of the preceding claims, characterized in that

    the cells (2) are composed of two half cells (51, 50), each including a plurality of cavities with a cross-section in form of a triangle,

    that the tube-shaped cavities (6-i; 6'; 6a, 6b) are arranged between the flow channels (20) for the working gas,

    that each of the half cells has a flat side and an uneven side,

    that the uneven sides of the two half cells are formed complementarily to each other, and

    that the two complementary uneven sides of the two half cells contact each other.
13. Method for producing a regenerator according to one of the preceding claims, characterized in that the cell (2) is produced by 3D printing.
14. Method for producing a regenerator according to one of claims 1 to 12, characterized in that the cell (2) is produced from at least two components (40, 44), which, after manufacture of the two components (40, 44), are connected to each other, and that at least one component (40) has a recess (42) forming at least part of the cavity/cavities (6').
15. Cryo-cooler in form of a Stirling cooler, a Gifford-McMahon cooler or a pulse tube cooler including at least one regenerator (1), characterized in that the at least one regenerator (1) is a regenerator according to one of the preceding claims 1 to 12.

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