DILUTION REFRIGERATION DEVICE

Abstract

The invention relates to a dilution refrigeration device for obtaining very low temperatures, in particular in the range comprised between one millikelvin and one hundred millikelvins, comprising a looped working circuit containing a cycle fluid comprising a mixture of helium isotope 3 and helium isotope 4, the working circuit comprising a first set of pipes that includes, between a mixing chamber and a boiler, a first portion having a plurality of first pipe branches arranged in parallel, subdividing a cycle flow into a plurality of parallel flows, and in that a second set of pipes comprises, between the boiler and the mixing chamber, a second portion of a plurality of second pipe branches arranged in parallel, subdividing the cycle flow into a plurality of parallel flows, and in that the first heat exchange section comprises a plurality of counterflow heat exchangers each providing heat exchange between a first pipe branch of the first portion and a second pipe branch of the second portion.

Description

The invention relates to a dilution refrigeration device.

The invention relates more particularly to a 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 in the form of a loop containing a cycle fluid comprising a mixture of helium-3 (3He) and helium-4 (4He), the working circuit comprising a mixing chamber, a boiler and a transfer member, which are arranged in series and fluidically connected via a first set of pipes, 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 section for heat exchange between at least some of the first set of pipes and the second set of pipes, the first heat exchange section comprising at least one heat exchanger situated between the boiler and the mixing chamber.

The invention relates in particular to a low-temperature or very-low-temperature (meaning potentially down to the temperature range from one millikelvin to around one hundred millikelvin) high-power cryogenic refrigeration device.

Refrigeration at temperatures lower than around one hundred millikelvin is used for the most part in applications for studying matter and quantum phenomena, for the production of electromagnetic radiation detectors.

The cooling power needs supplied 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 an impact on the components of the device and in particular the mixing chamber and the heat exchangers (one or more heat exchange sections).

One aim of the present invention is to overcome all or some of the disadvantages of the prior art that are set out above. For example, one aim is to enable an increase in the cooling power produced by such a device while at the same time managing its bulk and/or the amount of helium-3 required.

To this end, the device according to the invention, which is otherwise in accordance with the generic definition thereof 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 a plurality of first pipe branches 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 and the mixing chamber, a second portion with a plurality of second pipe branches that are arranged in parallel and subdivide the cycle flow into a plurality of parallel flows, and in that the first heat exchange section comprises a plurality of counter-current heat exchangers, each ensuring heat exchange between a first pipe branch of the first portion and a second pipe branch of the second portion.

Furthermore, embodiments of the invention may have one or more of the following features:

• • the working circuit has 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 a plurality of separate counter-current heat exchangers arranged in series in the circuit,
  • the first portion comprises two, three or more than three first pipe branches arranged in parallel,
  • the second portion comprises two, three or more than three second pipe branches arranged in parallel,
  • the first heat exchange section comprises two, three, four, five or more than five separate counter-current heat exchangers arranged in series in the circuit, each ensuring heat exchange between a first pipe branch and a second pipe branch,
  • the upstream ends of the first pipe branches of the first portion are connected to the same mixing chamber,
  • the downstream ends of the second pipe branches of the second portion are connected to the same mixing chamber,
  • the device comprises a thermally insulated enclosure that contains the cryogenic cold parts of the device and in particular the first heat exchange section,
  • the enclosure has a cylindrical overall 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 one another via pipework,
  • the device comprises a plurality of groups of separate counter-current heat exchangers arranged in series in the circuit,
  • at least some 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 separate respective vertical axes,
  • the heat exchangers of at least one group are arranged substantially within the same horizontal plane, the exchangers being distributed in a circular arc and fluidically connected to one another via pipework, which is for example curved,
  • at least some of the heat exchangers of a first group of heat exchangers are at least partially interposed between the heat exchangers of an adjacent second group of heat exchangers.

The invention may also relate to any alternative device or method comprising any combination of the features above or below within the scope of the claims.

Other particular features and advantages will become apparent from reading the following description, which is provided with reference to the figures, in which:

FIG. 1 shows a schematic and partial view illustrating a first example of the structure and operation of a refrigeration device according to the invention,

FIG. 2 shows 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 shows a schematic and partial side view illustrating a second possible embodiment of the arrangement of heat exchangers of such a device,

FIG. 4 shows a schematic and partial side view illustrating a third possible embodiment of the arrangement of heat exchangers of such a device.

The dilution refrigeration device 1 shown in [FIG. 1] comprises a working circuit 20 in the form of a loop containing a cycle fluid typically comprising a mixture of helium-3 (“3He”) and helium-4 (“4He”). This working circuit 20 comprises a mixing chamber 3, a boiler 5 and a transfer member 6 for fluidically transferring the cycle fluid, 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 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.

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.

The boiler 5 (or evaporator) conventionally carries out phase separation between helium-3 and helium-4 (the bath, which contains for example 1 mol % of helium-3, is, for example, at a temperature of between 0.7 K and 1 K). The boiler 5 supplies the transfer member 6 with helium-3 via the first set of pipes 4.

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

In the mixing chamber 3, the injected concentrated phase of helium-3 is diluted in the diluted phase, and it is this endothermic dilution process that produces the cooling power at the temperature of the mixing chamber 3.

The cold produced may be used to cool a user (symbolized by the reference 24 in [FIG. 1]) or at thermally conductive plates of the device, which are not shown for the sake of simplicity. The working circuit 20 comprises at least a first section 9 for heat exchange between at least some of the first set of pipes 2, 12, 4 and the second set of pipes 7. The first heat exchange section 9 is situated between the boiler 5 and the mixing chamber 3.

The set of cryogenic components (which are cold during operation) are placed for example in a sealed (and preferably vacuum-insulated) enclosure 30 or “cold box”.

This heat exchange portion 9 conventionally uses at least one counter-current heat exchanger, which makes it possible to pre-cool t he concentrated helium-3 phase reinjected into the mixing chamber 3 by way of the diluted helium-3 phase, which rises from this mixing chamber 3 toward the boiler 5.

The efficiency of the counter-current heat exchangers 9 between the diluted phase and concentrated phase is the critical point of these dilution refrigerators. The thermal resistances known as Kapitza resistances that arise at very low temperatures between helium and the solid materials and increase as the inverse square of the temperature make the dimensioning of these exchangers very difficult and critical.

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 that contains the rest of the device). This means that this compressor 6 can be at a non-cryogenic temperature in the operating configuration of the dilution refrigeration device 1. The device 1 may also comprise at least one cooling member 22 that is in heat exchange with the working circuit 20 and configured to transfer cold energy to the cycle fluid, that is to say to cool the cycle fluid. For example, the cooling member 22 comprises heat exchange with the working circuit 20 (second set of pipes 7) in order to cool the fluid at the outlet of the transfer member 6 (for example at a temperature between 1.3 and 1.4 K).

The working circuit 20 may also comprise a cryogenic pumping member (which is not shown for the sake of simplicity).

According to one advantageous particular feature, 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.

For example, between the boiler 5 and the mixing chamber 3, the single pipes 2, 7 have parallel branches.

Similarly, 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 177 that are arranged in parallel and subdivide the cycle flow into a plurality of parallel flows.

In addition, the first heat exchange section 9 comprises a plurality of discrete counter-current heat exchangers 19, 29, each ensuring heat exchange between at least one first pipe branch 12 of the first portion and at least one second pipe branch 17 of the second portion.

This arrangement of the exchangers relative to the flows of cycle fluid enables an increase in the cooling power available while maintaining a limited bulk. In addition, for the same cooling power, the volume of He-3 required is reduced (for example around 20 to 30 liters in order to produce 20 μW at 20 mK instead of 50 liters for the known solutions for an equivalent pressure). This parallel architecture also makes it possible to use a plurality of identical or different heat exchangers, for example heat exchangers of sintered type, with identical or variably dimensioned shells or casing.

Similarly, the size (cross section) of the branches (pipelines) connecting the exchangers may vary or be identical.

Preferably, the working circuit 20 has as many first pipe branches 12 arranged in parallel as second pipe branches 17 arranged in parallel (two of each in the example in [FIG. 1] and in the example in [FIG. 3]).

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

For example, 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 (two heat exchangers in the example in [FIG. 1], three in the example in [FIG. 4] and five in the example in [FIG. 3]).

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 ensuring heat exchange between a first pipe branch and a second pipe branch. Of course, any other number of heat exchangers in series may be envisioned and the number of exchangers may be different from one pair of parallel branches in heat exchange to another pair of parallel branches in heat exchange.

For example, the first portion may comprise two, three or more three first pipe branches 12 arranged in parallel. Similarly, the second portion may comprise two, three or more than three second pipe branches 17 arranged in parallel.

The upstream ends of the first pipe branches 12 of the first portion are preferably connected to the same mixing chamber 3 (but an architecture with a plurality of discrete mixing chambers 3 receiving the flow of cycle fluid from one or more pipes 12 may be envisioned).

Similarly, the downstream ends of the second pipe branches 17 of the second portion are preferably connected to the same mixing chamber 3 (or a plurality of mixing chambers 3).

As symbolized in [FIG. 1], [FIG. 2] and [FIG. 4], the enclosure 30 may have a cylindrical overall 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] and [FIG. 4]). The heat exchangers 19, 29 may be fluidically connected to one another via pipework 13 or connectors. Thus, the device 1 may comprise a plurality of groups of separate counter-current heat exchangers 19, 29 arranged vertically in series in the circuit 20.

As can be seen in [FIG. 3], all or some of the exchangers 19, 29 may have the shape of a planar plate, which is for example disk-shaped (optionally with a hole in the center).

Similarly, at least some 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 separate respective vertical axes.

In addition, as shown schematically in [FIG. 4], at least some of the heat exchangers 19, 29 of a first group of heat exchangers may be at least partially interposed between the heat exchangers 29, 19 of an adjacent second group of heat exchangers. This makes it possible to limit the volume of the device 1 in the direction transverse to the vertical direction in which the exchangers are stacked.

As illustrated in the example in [FIG. 2], the heat exchangers 19, 29 of each group may be arranged substantially within the same horizontal plane. The exchangers 19, 29 may be distributed in a circular arc and fluidically connected to one another via pipework 13, which is for example curved.

In addition, the pipework 13 of the different groups of exchangers may be interlaced or crossed. The exchangers 19, 29 may thus be arranged concentrically and/or arranged so as to alternate from one group to another. This means that the heat exchangers 19, 29 of each of the two groups of exchangers may be arranged so as to alternate substantially over the same circular arc and substantially within the same plane.

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 some of the plurality of heat exchangers 19, 29 specified above may be a plurality of separate sections of the same heat exchanger (for example an exchanger housing comprising a plurality of separate independent sections).

Similarly, the circuit of the device 1 may have one or more other cooling portions in exchange with a cooling member for pre-cooling the cycle fluid (for example to a temperature of around 4 K and/or 2 K).

The device 1 may optionally have a plurality of dilution loops that share the same heat exchangers 19, 29 or have separate respective heat exchangers.

The invention makes it possible to increase the cooling power produced by dilution.

Claims

1. A 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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. The device as claimed in 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 as claimed in 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.