Dilution chiller

Description

[0001] The invention relates to a dilution refrigeration device.

[0002] The invention relates more particularly to a dilution refrigeration device for obtaining very low temperatures, in particular in the range between one milliKelvin and one hundred milliKelvin, comprising a loop working circuit containing a cycle fluid comprising a mixture of helium of isotope 3 (3He) and helium of isotope 4 (4He), the working circuit comprising, arranged in series and fluidically connected via a first set of pipes, a mixing chamber, a boiler and a transfer member, the first set of pipes being configured to transfer cycle fluid from an outlet of the mixing chamber to an inlet of the boiler and from an outlet of the boiler to an inlet of the transfer member, the working circuit comprising a second set of pipes connecting an outlet of the transfer member to an inlet of the mixing chamber,the working circuit comprising at least a first heat exchange section between at least a portion of the first set of pipes and the second set of pipes, the first heat exchange section comprising at least one heat exchanger located between the boiler and the mixing chamber.,

[0003] The invention relates in particular to a high-power cryogenic refrigeration device at low or very low temperature (i.e. potentially up to the temperature range of milliKelvin to hundreds of milliKelvin).

[0004] The use of refrigeration at temperatures below a hundred milliKelvin mainly concerns applications for the study of matter and quantum phenomena, for the production of electromagnetic radiation detectors.

[0005] The cooling power requirements provided by such a device are increasing. However, the increase in power generally requires an increase in the volume of helium required. The increase in power supplied also has consequences for the components of the device and in particular the mixing box and the heat exchangers (heat exchange section(s)). FR 3 107 586 Al discloses a dilution refrigeration device according to the preamble of claim 1.

[0006] An aim of the present invention is to overcome all or part of the drawbacks of the prior art noted above.

[0007] For example, one goal is to allow an increase in the cold power produced by such a device while controlling its size and / or the quantity of helium 3 required.

[0008] To this end, the device according to the invention as defined in claim 1, moreover in accordance with the generic definition given in the preamble above, is essentially characterized in that the first set of pipes comprises, between the mixing chamber and the boiler, a first portion with several first branches of pipes arranged in parallel subdividing the cycle flow into several parallel flows, and in that the second set of pipes comprises, between the boiler and the mixing chamber, a second portion with several second branches of pipes arranged in parallel subdividing the cycle flow into several parallel flows, and in that the first heat exchange section comprises several countercurrent heat exchangers each ensuring a heat exchange between a first branch of pipe of the first portion and a second branch of pipe of the second portion.

[0009] Furthermore, embodiments of the invention may include one or more of the following features: the working circuit comprises as many first pipe branches arranged in parallel as second pipe branches arranged in parallel, each first pipe branch is in heat exchange with a second pipe branch in at least one counter-current heat exchanger, each first pipe branch is in heat exchange with a second pipe branch in a respective group of several separate counter-current heat exchangers arranged in series in the circuit, the first portion comprises two, three or more first pipe branches arranged in parallel, the second portion comprises two, three or more second pipe branches arranged in parallel, the first heat exchange section comprises two, three or four,five or more separate counter-current heat exchangers arranged in series in the circuit, each providing heat exchange between a first branch and a second branch of pipes, the upstream ends of the first branches of pipes of the first portion are connected to the same mixing chamber, the downstream ends of the second branches of pipes of the second portion are connected to the same mixing chamber, the device comprises a thermally insulated enclosure which contains the cryogenic cold parts of the device and in particular the first heat exchange section, the enclosure has a generally cylindrical shape extending in a vertical direction, the counter-current heat exchangers being arranged in horizontal planes and distributed vertically, the heat exchangers being fluidically connected to each other via pipes,the device comprises several groups of distinct counter-current heat exchangers arranged in series in the circuit, at least a portion of the heat exchangers of each of the groups are arranged substantially horizontally, at least two groups of exchangers being arranged adjacently and extending along respective distinct vertical axes, the heat exchangers of at least one group are arranged substantially in the same horizontal plane, the exchangers being distributed in an arc of a circle and fluidically connected to each other via pipes, for example curved, at least a portion of the heat exchangers of a first group of heat exchangers are interposed at least in part between the heat exchangers of a second adjacent group of heat exchangers.

[0010] The invention may also relate to any alternative device or method comprising any combination of the above or below features. The scope of the invention is defined solely by the appended claims.

[0011] Other features and advantages will appear on reading the description below, made with reference to the figures in which: [ Fig.1 ] represents a schematic and partial view illustrating a first example of structure and operation of a refrigeration device according to the invention, [ Fig.2 ] represents a schematic and partial top view, illustrating a detail of a first possible embodiment of the arrangement of heat exchangers of such a device, [ Fig.3 ] represents a schematic and partial side view illustrating a second possible embodiment of the heat exchanger arrangement of such a device, [ Fig.4 ] represents a schematic and partial side view illustrating a third possible embodiment of the heat exchanger arrangement of such a device.

[0012] The dilution refrigeration device 1 shown in [ Fig.1 ] comprises a loop working circuit 20 containing a cycle fluid typically comprising a mixture of helium of isotope 3 (“3He” or “helium 3”) and helium of isotope 4 (“4He” or “helium 4”). This working circuit 20 comprises, arranged in series and fluidically connected via a first set of pipes 2, 12, 4, a mixing chamber 3, a boiler 5 and a member 6 for fluid transfer of the cycle fluid.

[0013] The first set of pipes 2, 12, 4 is configured to transfer cycle fluid from an outlet of the mixing chamber 3 to an inlet of the boiler 5 and from an outlet of the boiler 5 to an inlet of the transfer member 6.

[0014] The working circuit 20 comprises a second set of pipes 7, 17 connecting an outlet of the transfer member 6 to an inlet of the mixing chamber 3.

[0015] The boiler 5 (or evaporator) conventionally ensures a phase separation between helium 3 and helium 4 (the bath, which contains for example 1% by mole of helium 3 is for example at a temperature between 0.7K and 1K). The boiler 5 supplies the transfer member 6 with helium 3 via the first pipe assembly 4.

[0016] In the mixing chamber 3 the temperature may be of the order of, for example, 5mK to 300mK and in particular between 5mK and 150mK. The concentrated helium 3 returned by the transfer member 6 into the mixing chamber 3 may be located in the upper part of this chamber 3, above a dilute liquid phase (containing, for example, 6 to 7% of helium 3). One end of the first set of pipes 7 opens, for example, into this upper concentrated phase.

[0017] In mixing chamber 3, the injected helium 3 concentrated phase dilutes into the diluted phase; it is this endothermic dilution process that produces the cooling power at the temperature of mixing chamber 3.

[0018] The cold produced can be used to cool a user (symbolized by the reference 24 at [ Fig.1 ]) or at the level of thermal conductive plates of the device not shown for the sake of simplification.

[0019] The working circuit 20 comprises at least a first heat exchange section 9 between at least part of the first set of pipes 2, 12, 4 and the second set of pipes 7. The first heat exchange section 9 is located between the boiler 5 and the mixing chamber 3.

[0020] All cryogenic components (cold in operating mode) are placed, for example, in a sealed enclosure or “cold box” (and preferably vacuum insulated).

[0021] This heat exchange portion 9 conventionally uses at least one counter-current heat exchanger which makes it possible to pre-cool the concentrated Helium3 phase reinjected into the mixing box 3 by the diluted Helium3 phase which rises from this mixing chamber 3 towards the boiler 5.

[0022] The efficiency of the countercurrent heat exchangers 9 between the diluted and concentrated phases is the critical point of these dilution refrigerators. The so-called Kapitza thermal resistances which appear at very low temperatures between helium and solid materials and increase as the inverse square of the temperature make the sizing of these exchangers very difficult and critical.

[0023] The transfer member 6 comprises, for example, a cycle fluid compressor and / or a heat exchanger. For example, this compressor 6 operates at ambient temperature (for example outside a cold box 30 which contains the rest of the device). That is to say, this compressor 6 can be at non-cryogenic temperature in the operating configuration of the dilution refrigeration device 1.

[0024] The device 1 may further comprise at least one cooling member 22 in heat exchange with the working circuit 20 and configured to transfer frigories to the cycle fluid, i.e. to cool the cycle fluid. For example, the cooling member 22 comprises a heat exchange with the working circuit 20 (second set of pipes 7) to cool the fluid at the outlet of the transfer member 6 (for example to a temperature of between 1.3 and 1.4K.

[0025] The working circuit 20 may further comprise a cryogenic pumping member (not shown for the sake of simplification).

[0026] According to an advantageous feature, the first set of pipes comprises, between the mixing chamber 3 and the boiler 5, a first portion with several first branches of pipes 12 arranged in parallel subdividing the cycle flow into several parallel flows.

[0027] For example, between boiler 5 and mixing chamber 3, single lines 2, 7 have parallel branches.

[0028] Likewise, the second set of pipes comprises, between the boiler 5 and the mixing chamber 3, a second portion of several second branches of pipes 17 arranged in parallel subdividing the cycle flow into several parallel flows.

[0029] In addition, the first heat exchange section 9 comprises several discrete counter-current heat exchangers 19, 29 each providing a heat exchange between at least a first pipe branch 12 of the first portion and at least a second pipe branch 17 of the second portion.

[0030] This arrangement of the exchangers relative to the cycle fluid flows allows an increase in the available cooling power while maintaining a limited footprint. In addition, for the same cooling power, the volume of He3 required is reduced (for example, around 20 to 30 liters to produce 20µW at 20mK instead of 50 liters for known solutions for an equivalent pressure). This parallel architecture also allows the use of several identical or different heat exchangers, for example sintered type heat exchangers with identical shells or casings or with variable dimensions.

[0031] Similarly, the size (section) of the branches (pipes) connecting the exchangers can vary or be identical.

[0032] Preferably, the working circuit 20 comprises as many first branches of pipes 12 arranged in parallel as second branches of pipes 17 arranged in parallel (two and two in the example of the [ Fig.1 ] and in the example of the [ Fig.3 ]).

[0033] As illustrated, preferably each first branch of pipes 12 is in heat exchange with a second branch of pipe 17 in at least one counter-current heat exchanger 19, 29 (and preferably in several heat exchangers).

[0034] For example, each first branch of pipes 12 is in heat exchange with a second branch of pipe 17 in a respective group of several separate counter-current heat exchangers 19, 29 arranged in series in the circuit 20 (two heat exchangers in the example of the [ Fig.1 ], three in the example of the [ Fig.4 ] and five in the example of the [ Fig.3 ]).

[0035] Thus, the first heat exchange section 9 may comprise two, three, four, five or more than five separate counter-current heat exchangers 19, 29 arranged in series in the circuit 20, each providing heat exchange between a first branch and a second branch of pipes. Of course, any other number of heat exchangers in series may be envisaged and the number of exchangers may be different from one pair of branches in parallel in heat exchange to another pair of branches in parallel in heat exchange.

[0036] For example, the first portion may comprise two, three or more first branches of pipes 12 arranged in parallel. Similarly, the second portion may comprise two, three or more second branches of pipes 17 arranged in parallel.

[0037] The upstream ends of the first branches of pipes 12 of the first portion are preferably connected to the same mixing chamber 3 (but an architecture with several discrete mixing chambers 3 receiving the cycle fluid flow from one or more pipes 12 can be envisaged).

[0038] Likewise, the downstream ends of the second branches of pipes 17 of the second portion are preferably connected to the same mixing chamber 3 (or several mixing chambers 3).

[0039] As symbolized in [ Fig.1], [Fig.2 ] And [ Fig.4 ], the enclosure 30 may have a generally cylindrical shape extending in a vertical direction. The counter-current heat exchangers 19, 29 may be arranged in horizontal planes and distributed vertically (cf. [ Fig.1 ], [ Fig.3] et [Fig.4 ]). The heat exchangers 19, 29 may be fluidically connected to each other via pipes 13 or fittings. Thus, the device 1 may comprise several groups of separate counter-current heat exchangers 19, 29 arranged vertically in series in the circuit 20.

[0040] As visible at the [ Fig.3 ], all or part of the exchangers 19, 29 may have the shape of a flat plate, for example discoidal (possibly openwork in the center).

[0041] Similarly, at least a portion of the heat exchangers 19, 29 of each of the groups of heat exchangers in series may be arranged substantially horizontally. At least two groups of exchangers may be arranged adjacently and extending along distinct respective vertical axes.

[0042] Furthermore, as schematized in [ Fig.4 ], at least a portion of the heat exchangers 19, 29 of a first group of heat exchangers may be interposed at least in part between the heat exchangers 29, 19 of a second adjacent group of heat exchangers. This makes it possible to limit the volume of the device 1 in the direction transverse to the vertical direction of stacking of the exchangers.

[0043] As illustrated in the example of the [ Fig.2], the heat exchangers 19, 29 of each group can be arranged substantially in the same horizontal plane. The exchangers 19, 29 can be distributed in an arc of a circle and fluidically connected to each other via pipes 13, for example curved.

[0044] In addition, the pipes 13 of the different groups of exchangers can be interlaced or crossed. The exchangers 19, 29 can thus be arranged concentrically and / or arranged alternately from one group to the other. That is to say that the heat exchangers 19, 29 of each of the two groups of exchangers can be arranged alternately substantially on the same arc of a circle and substantially in the same plane.

[0045] Of course, the invention is not limited to the examples described above. Thus, the heat exchangers 19, 29 may be arranged in other configurations (for example in a branched configuration). In addition, at least a portion of the several heat exchangers 19, 29 designated above may be several distinct sections of the same heat exchanger (for example an exchanger housing comprising several distinct independent sections).

[0046] Likewise, the circuit of the device 1 may comprise other cooling portion(s) in exchange with a cooling member to ensure pre-cooling of the cycle fluid (for example to a temperature of the order of 4K and / or 2K).

[0047] The device 1 may optionally comprise several dilution loops sharing the same heat exchangers 19, 29 or having separate respective heat exchangers.

[0048] The invention makes it possible to increase the cold power produced by dilution.

Claims

1. Dilution refrigeration device for achieving very low temperatures, in particular in the range between one millikelvin and around one hundred millikelvin, comprising a working circuit (20) in the form of a loop containing a cycle fluid comprising a mixture of helium-3 (3He) and helium-4 (4He), the working circuit (20) comprising a mixing chamber (3), a boiler (5) and a transfer member (6), which are arranged in series and fluidically connected via a first set of pipes (2, 12, 4), the first set of pipes (2, 12, 4) being configured to transfer cycle fluid from an outlet of the mixing chamber (3) to an inlet of the boiler (5) and from an outlet of the boiler (5) to an inlet of the transfer member (6), the working circuit (20) comprising a second set of pipes (7, 17) connecting an outlet of the transfer member (6) to an inlet of the mixing chamber (3), the working circuit (20) comprising at least a first section (9) for heat exchange between at least some of the first set of pipes (2, 12) and the second set of pipes (7, 17), the first heat exchange section (9) comprising a set of one or more heat exchangers (5) and being situated between the boiler (5) and the mixing chamber (3), characterized in that the first set of pipes comprises, between the mixing chamber (3) and the boiler (5), a first portion with a plurality of first pipe branches (12) that are arranged in parallel and subdivide the cycle flow into a plurality of parallel flows, and in that the second set of pipes comprises, between the boiler (5) and the mixing chamber (3), a second portion with a plurality of second pipe branches (17) that are arranged in parallel and subdivide the cycle flow into a plurality of parallel flows, and in that the first heat exchange section (9) comprises a plurality of counter-current heat exchangers (19, 29), each ensuring heat exchange between a first pipe branch (12) of the first portion and a second pipe branch (17) of the second portion.

2. Device according to Claim 1, characterized in that the working circuit (20) has as many first pipe branches (12) arranged in parallel as second pipe branches (17) arranged in parallel.

3. Device according to Claim 1 or 2, characterized in that each first pipe branch (12) is in heat exchange with a second pipe branch (17) in at least one counter-current heat exchanger (19, 29).

4. Device according to any one of Claims 1 to 3, characterized in that each first pipe branch (12) is in heat exchange with a second pipe branch (17) in a respective group of a plurality of separate counter-current heat exchangers (19, 29) arranged in series in the circuit (20).

5. Device according to any one of Claims 1 to 4, characterized in that the first portion comprises two, three or more than three first pipe branches (12) arranged in parallel.

6. Device according to any one of Claims 1 to 5, characterized in that the second portion comprises two, three or more than three second pipe branches (17) arranged in parallel.

7. Device according to any one of Claims 1 to 6, characterized in that the first heat exchange section (9) comprises two, three, four, five or more than five separate counter-current heat exchangers (19, 29) arranged in series in the circuit (20), each ensuring heat exchange between a first pipe branch and a second pipe branch.

8. Device according to any one of Claims 1 to 7, characterized in that the upstream ends of the first pipe branches (12) of the first portion are connected to the same mixing chamber (3).

9. Device according to any one of Claims 1 to 8, characterized in that the downstream ends of the second pipe branches (17) of the second portion are connected to the same mixing chamber (3).

10. Device according to any one of Claims 1 to 9, characterized in that it comprises a thermally insulated enclosure (30) that contains the cryogenic cold parts of the device and in particular the first heat exchange section (9).

11. Device according to Claim 10, characterized in that the enclosure (30) has a cylindrical overall shape extending in a vertical direction, and in that the counter-current heat exchangers (19, 29) are arranged in horizontal planes and distributed vertically, the heat exchangers (19, 29) being fluidically connected to one another via pipework (13).

12. Device according to Claims 4 and 11 considered in combination, characterized in that it comprises a plurality of groups of separate counter-current heat exchangers (19, 29) arranged in series in the circuit (20).

13. Device according to Claim 12, characterized in that at least some of the heat exchangers (19, 29) of each of the groups are arranged substantially horizontally, at least two groups of exchangers being arranged adjacently and extending along separate respective vertical axes.

14. Device according to Claim 12, characterized in that the heat exchangers (19, 29) of at least one group are arranged substantially within the same horizontal plane, the exchangers (19, 29) being distributed in a circular arc and fluidically connected to one another via pipework (13), which is for example curved.

15. Device according to any one of Claims 12 to 14, characterized in that at least some of the heat exchangers (19, 29) of a first group of heat exchangers are at least partially interposed between the heat exchangers (29, 19) of an adjacent second group of heat exchangers.