CRYOGENIC REFRIGERATION INSTALLATION AND METHOD

Abstract

The invention provides a cryogenic refrigeration installation comprising an enclosure with thermally conductive trays (thermal stages) and plates. A cooling system uses a refrigerator with a helium-based cycle fluid. The cycle circuit incorporates a first storage vessel for liquefied cycle fluid. After initial tray/plate cooling, a first bypass line with an expansion member diverts some cycle fluid to this vessel. Subsequently, the main cycle fluid is cooled by heat exchange with the liquefied fluid in said first vessel before further tray/plate cooling. A key feature is a second bypass line within the enclosure, which further expands a portion of this pre-cooled cycle fluid. This expansion generates an even colder flow (e.g., 1 K to 2 K) to cool an additional tray or plate, facilitating efficient multi-temperature cryogenic cooling.

Claims

1. A cryogenic refrigeration installation comprising: an enclosure delimiting a sealed volume closed by a cover, the enclosure accommodating at least two thermally conductive trays distributed in a distribution direction in the enclosure and forming thermal stages, at least one of the two thermally conductive trays being connected to a heat shield forming a thermal insulation volume; a cooling system configured to cool to a cryogenic temperature by cooling at least some of the thermally conductive trays and/or one or more plate(s) connected to the thermally conductive trays and forming a support for a set of cable(s) or samples to be cooled, wherein the cooling system comprises a refrigerator that is configured to perform a refrigeration cycle on a cycle fluid, said refrigerator comprising a cycle circuit containing a cycle fluid comprising helium, the cycle circuit being configured to subject the cycle fluid to a thermodynamic cycle bringing the cycle fluid at at least a cold end of the cycle circuit to a determined cold temperature, the cycle circuit placing a flow of cycle fluid at the cold end in heat exchange with at least some of the thermally conductive trays and/or plates, wherein the cycle circuit further comprises a compression mechanism configured to compress the cycle fluid, a cooling member configured to cool the cycle fluid, an expansion mechanism configured to expand the cycle fluid and a heating member configured to heat the expanded cycle fluid, wherein the cycle circuit further comprises: a first storage vessel configured to store a reserve of liquefied cycle fluid; downstream of the heat exchange with at least some thermally conductive trays and/or plates; a bypass line configured to divert at least some of the flow of cycle fluid to the first storage vessel, the bypass line comprising a bypass expansion member configured to expand the flow of cycle gas before feeding the first storage vessel; upstream of the heat exchange with at least some thermally conductive trays and/or plates, a portion in heat exchange with the liquefied cycle fluid contained in the first storage vessel; downstream of the passage inside the first storage vessel, at least one first line located in the enclosure exchanging heat with at least some thermally conductive trays and/or plates; and a second bypass line for the first line, the second bypass line being located in the enclosure and provided with a second bypass expansion member configured to expand the cycle fluid in order to produce a colder flow of bypass cycle fluid at a temperature of between 1 and 2 K, said bypass cycle fluid being placed in heat exchange with at least one additional thermally conductive tray or plate of the installation.

2. The installation according to claim 1, wherein the cycle circuit comprises, downstream of the heat exchange with the additional tray or plate, a line for returning the bypass cycle fluid to the mechanism for compressing the cycle fluid.

3. The installation according to claim 1, wherein the return line directs the bypass cycle fluid to the inlet of a dedicated compressor of the mechanism for compressing the cycle fluid, which is arranged in series upstream of the mechanism for compressing the rest of the cycle fluid.

4. The installation according to claim 2, wherein the cycle circuit comprises a portion for heat exchange between the return line and a cycle circuit line that feeds some trays and/or plates.

5. The installation according to claim 2, wherein the cycle circuit comprises, downstream of the heat exchange with the additional tray or plate, a line for transferring the bypass cycle fluid to the first storage vessel.

6. The installation according to claim 5, wherein the cycle circuit comprises a portion for heat exchange between the line for transferring the bypass cycle fluid and a cycle circuit line that feeds some trays and/or plates.

7. The installation according to claim 1, wherein the cycle circuit comprises, downstream of the heat exchange with at least some trays and/or plates, a return line that is configured to return, to the compression mechanism, the fraction of the flow of cycle fluid that has not been diverted to the first storage vessel.

8. The installation according to claim 1, wherein the cycle circuit comprises a return line connecting an outlet of the first storage vessel to the compression mechanism.

9. The installation according to claim 8, wherein the return line comprises a cryogenic compressor or pump.

10. The installation according to claim 1, wherein the cycle circuit of the refrigerator comprises a plurality of distinct lines that place different flows of cycle fluid in heat exchange with distinct trays and/or plates.

11. The installation according to claim 1, wherein the cycle circuit comprises at least one line that places the cycle fluid in heat exchange in series with a plurality of distinct trays and/or plates of the same enclosure and/or of a plurality of distinct enclosures.

12. The installation according to claim 1, wherein the cycle circuit is configured to subject the cycle fluid to a thermodynamic cycle bringing the cycle fluid to a plurality of distinct cold temperatures at a plurality of cold ends of the cycle circuit, respectively, the cycle circuit of the refrigerator comprising a plurality of distinct lines that place different flows of cycle fluid at different temperatures in heat exchange in parallel with respective distinct trays and/or plates.

13. A refrigeration method comprising the steps of: providing the installation as claimed in claim 1; producing a cooling power determined by the refrigerator, using some of this cooling power produced to cool a set of thermally conductive tray(s) and/or plate(s) through heat exchange with a flow of cycle fluid; recovering this flow of cycle fluid after heat exchange; expanding a fraction of said flow of cycle fluid recovered to the first storage vessel in order to form a reserve of cold; and cooling the flow of cycle fluid using the cycle fluid from the first storage vessel.

14. The method according to claim 13, further comprising a step of cooling the cycle fluid through heat exchange with the liquefied cycle fluid contained in the first storage vessel, a step of cooling at least some trays and/or plates to a first temperature using a first fraction of this cooled cycle fluid, the method comprising a step of expanding, in the enclosure, a second fraction of this cooled cycle fluid, this second fraction of cycle fluid being used to cool at least one tray and/or plates to a second temperature that is lower than the first temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, claims, and accompanying drawings. It is to be noted, however, that the drawings illustrate only several embodiments of the invention and are therefore not to be considered limiting of the invention's scope as it can admit to other equally effective embodiments.

[0027] Other particular features and advantages will become apparent upon reading the following description, which is provided with reference to the figures.

[0028] The invention will be better understood upon reading the following description, which is given solely by way of example and with reference to the appended drawings, in which:

[0029] FIG. 1 is a schematic and partial view illustrating an example of the structure and operation of an installation in accordance with a first embodiment of the invention,

[0030] FIG. 2 is a schematic and partial view illustrating an example of the structure and operation of an installation in accordance with a second embodiment of the invention,

[0031] FIG. 3 is a schematic and partial view illustrating an example of the structure and operation of an installation in accordance with a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] Throughout the figures, the same reference signs relate to the same elements.

[0033] In this detailed description, the following embodiments are examples. Although the description refers to one or more embodiments, this does not mean that the features apply only to a single embodiment. Individual features of different embodiments may also be combined and/or interchanged to provide other embodiments.

[0034] The cryogenic refrigeration installation 1 illustrated in [FIG. 1] comprises an enclosure 2 delimiting a sealed volume closed by a cover 3. In this example, the enclosure 2 accommodates a plurality of thermally conductive trays 4, 5, 6, 7 distributed in a distribution direction in the enclosure 2 (which is in this case vertical) and forming thermal stages. Preferably, all or some of the trays 4, 5, 6, 7 are connected to a respective heat shield 14, 15, 16 forming a thermal insulation volume. For example, in the distribution direction, each heat shield encloses (accommodates) the heat shield and the following tray (in a nesting manner).

[0035] The installation 1 comprises a system for cooling to a cryogenic temperature configured to cool at least some of the trays 4, 5, 6, 7 and/or one or more support plate(s) 24, 25, 26, 27 that may be connected (30) to the trays 4, 5, 6. These support plates 24, 25, 26, 27 may be mounted removably or detachably on the trays 4, 5, 6, 7 in question to form a support for a set of cable(s) or samples to be cooled (not shown for the sake of simplicity).

[0036] The system for cooling to a cryogenic temperature comprises a refrigerator 70 that performs a refrigeration cycle on a cycle fluid.

[0037] The refrigerator 70 comprises a cycle circuit 8 containing a cycle fluid comprising helium. The cycle fluid could be composed of one or more other gases: hydrogen, nitrogen, neon, one or more hydrocarbons or a mixture thereof. The cycle circuit 8 is configured to subject the cycle fluid to a thermodynamic cycle bringing the cycle fluid at at least a cold end of the cycle circuit 8 to a determined cold temperature.

[0038] The cycle circuit 8 has a mechanism 9 for compressing the cycle fluid (one or more compressors in series and/or in parallel), at least one member 11, 12, 13, 14 for cooling the cycle fluid (for example one or more heat exchangers), a mechanism 10, 150 for expanding the cycle fluid (one or more valve(s) and/or turbine(s) in series and/or in parallel) and at least one member 14, 13, 12, 11 for heating the expanded cycle fluid (one or more heat exchangers). As illustrated, the cycle fluid may be cooled and heated by one or more heat exchangers exchanging heat between two flows of cycle fluid at different temperatures (for example in countercurrent operation).

[0039] Some of the cycle circuit 8 and in particular the relatively hot portions may be located outside the enclosure 2.

[0040] The cycle circuit 8 has lines that place at least one flow of cycle fluid at the cold end in heat exchange with at least some of the trays 4, 5, 6, 7 and/or plates 24, 25, 26, 27. For example, lines transfer the cold cycle fluid into heat exchangers 34, 35, 36 in contact with the trays and/or plates. Alternatively or cumulatively, the lines conveying the cycle circuit 8 may have portions in direct contact with (and/or in the thickness of) the trays 4, 5, 6, 7 and/or plates 24, 25, 26, 27 and/or heat shield.

[0041] For example, the cycle circuit 8 of the refrigerator 70 comprises one or more distinct lines 208 that place different flows of cycle fluid in heat exchange with distinct trays 4, 5, 6, 7 and/or plates 24, 25, 26, 27 of the same enclosure 2 or of a plurality of distinct enclosures.

[0042] For example, the cycle circuit 8 may be configured to subject the cycle fluid to a thermodynamic cycle bringing the cycle fluid to a plurality of distinct cold temperatures at a plurality of cold ends of the cycle circuit, respectively, and the cycle circuit 8 of the refrigerator 70 comprising a plurality of distinct lines 208 that place different flows of cycle fluid at different temperatures in heat exchange in parallel with respective distinct trays 4, 5, 6, 7 and/or plates 24, 25, 26, 27.

[0043] This makes it possible to produce and send pressurized (for example at a pressure of greater than 3.5 bar) supercritical cycle fluid to one or more stages of one or more enclosures 2, for example in parallel.

[0044] The supercritical fluid may be produced in the cycle circuit 8 by an arrangement of exchangers, in order to optimally recover the available cooling power.

[0045] Thus, the cycle circuit 8 can supply cycle fluid at intermediate temperatures, for example between 4 K and 100 K, in order to cool intermediate stages in one or more enclosures 2.

[0046] This enables independent operations for different enclosures 2 with the same common refrigeration system 70.

[0047] This solution makes it possible to provide a cooling power that can be adapted in a straightforward manner.

[0048] To this end, the different lines feeding the different stages or enclosures 2 may be provided with flow rate regulating valves. These valves can be regulated according to the temperature of the element to be cooled (expected cooling power). The flow rates of cycle fluid can be regulated in order to increase or decrease the cooling power requirement in the enclosure 2.

[0049] The cycle circuit 8 comprises a first vessel 17 for storing a reserve of liquefied cycle fluid.

[0050] The cycle circuit 8 comprises, downstream of the heat exchange with at least some trays 4, 5, 6 and/or plates 24, 25, 26, a bypass line 18 for diverting at least some of the flow of cycle fluid to the first storage vessel 17.

[0051] In other words, the at least one line that brings the cycle fluid that has undergone heat exchange with the elements to be cooled in the enclosure 2 back to the heating members (exchangers 14, 13, 12, 11) and the compression members (compressor 9, 8) has a bypass 18 diverting to the first storage vessel 17. This bypass line 18 preferably has a member 19 for expanding the flow of cycle gas (valve(s) or equivalent) configured to expand the cycle gas before feeding the first storage vessel 17.

[0052] The installation 1 may be rated or the operating conditions may be such that the cooling in the enclosure 2 uses only some of the power available in the cold flow of cycle fluid. This cycle fluid returns relatively cold and the cooling power that has not been used to cool the components in the enclosure 2 can be reused.

[0053] This is achieved by expanding some of this cycle fluid towards the first storage vessel 17.

[0054] This arrangement makes it possible to optimize the cooling power produced by minimizing the flow rate of working fluid at low pressure (gas originating from the first storage vessel 17).

[0055] In addition, this makes it possible to maximize the flow rate of cold cycle fluid circulated in the one or more enclosures 2 (maximizes the available power).

[0056] The flow of cycle fluid not used for this bypass can be returned to the cycle compressor of the refrigerator by releasing cold energy to the cycle fluid downstream of the compression. To this end, the cycle circuit 8 comprises, downstream of the heat exchange with at least some trays 4, 5, 6 and/or plates 24, 25, 26, at least one return line 28 that is configured to return, to the compression mechanism 9, the fraction of the flow of cycle fluid that has not been diverted to the first storage vessel 17.

[0057] This expanded fluid produces liquid at a very low temperature (typically between 1 K and 4 K) that is placed in heat exchange with the cycle fluid before it exchanges heat with the components in the enclosure 2.

[0058] In other words, the cycle circuit 8 comprises, upstream of the heat exchange with at least some trays 4, 5, 6, 7 and/or plates 24, 25, 26, 27, a portion in heat exchange with the liquefied cycle fluid contained in the first storage vessel 17. The cold reserve formed by the first storage vessel 17 supplies cold to the cycle fluid before it is used to cool the one or more elements in the enclosure 2.

[0059] In the example in [FIG. 1], the heat exchange between the liquefied cycle fluid contained in the vessel 17 and the cycle fluid of the cycle circuit 8 comprises a passage of the cycle circuit 8 in the liquefied cycle fluid inside the first storage vessel 17. In other words, some of the cycle circuit 8 is immersed in the liquid bath of the first storage vessel 17, for example by describing a coil or several passages or bends therein.

[0060] As a variant or in combination, the liquefied cycle fluid contained in the vessel 17 could exchange heat with the cycle fluid of the cycle circuit 8 via a passage of the cycle circuit 8 in a heat exchanger 15 cooled by a liquefied cycle fluid circulation loop 47 fed by the first storage vessel 17, for example a thermosiphon. This is a more indirect heat exchange than in the preceding embodiment.

[0061] The cycle circuit 8 comprises, downstream of the passage inside the first storage vessel 17 and upstream of the heat exchange with at least some trays 4, 5, 6, 7 and/or plates 24, 25, 26, 27, at least one line 208, which may be provided with a first expansion member 808, for example an expansion valve.

[0062] The optional expansion valve 808 may preferably be provided if the cycle fluid is two-phase (liquid and gas), in fact in this case expansion reduces the temperature of the fluid.

[0063] This optional expansion 808 of the flow of cycle fluid cooled in the storage vessel 17 makes it possible to produce a flow of cycle gas at a determined temperature, for example between 2 and 4 K (helium at 3 K, for example). This working fluid can be distributed in order to cool the one or more trays or plates or any element to be cooled.

[0064] As illustrated, the cycle circuit 8 comprises, in the enclosure 2, a bypass line 308 provided with an expansion member 408 configured to expand the cycle fluid in order to produce an even colder flow of bypass cycle fluid, for example at a temperature of between 1 and 2 K. This colder bypass cycle fluid can be placed in heat exchange with at least one additional tray or plate 27 of the installation 1 that requires a colder cooling temperature.

[0065] In other words, the bypass line 308 adds a loop portion in order to produce a lower temperature.

[0066] This configuration without expansion (without expansion valve 808) or with simple expansion (expansion valve 808) offers the advantages of supercritical cooling: it can be easily distributed over a large surface area by the circulation of a pipeline, for example (simple expansion circuit). However, the cold temperature obtained is generally limited by the flow rates to be circulated, which may be relatively high. This stage can effectively absorb inputs of heat from the upper stages and any active components, for example amplification electronics.

[0067] With the bypass (and the expansion 408 in the enclosure 2), it is possible to produce and insulate a liquid at a lower temperature than the initial cycle fluid and to have a thermal power at a stable temperature (for example at a lower flow rate than in the part of the cycle circuit not subjected to this expansion 408 in the enclosure 2).

[0068] As illustrated in [FIG. 1], the cycle circuit may comprise, downstream of the heat exchange with the additional tray or plate 27 (or the like, for example with storage in another vessel), a line 608 for returning the bypass cycle fluid to the mechanism 9 for compressing the cycle fluid. The line 608 for returning the bypass cycle fluid can return the cycle fluid to the inlet of a dedicated compressor 90 of the mechanism 9 for compressing the cycle fluid, for example an ambient-temperature or cryogenic-temperature compressor, which is arranged in series upstream of the mechanism for compressing the rest of the cycle fluid.

[0069] According to the embodiment of FIG. 2, the cycle circuit comprises, downstream of the heat exchange with the additional tray or plate 27 (and/or other storage element or element to be cooled), a line 508 for transferring the bypass cycle fluid to the first storage vessel 17. In other words, the helium is returned to the first vessel 17 (for example at a temperature of 2 K), using only a compression or pumping group.

[0070] This configuration minimizes the number of compression stages of the cycle circuit.

[0071] In the embodiment in [FIG. 2], this flow of colder cycle gas (which has been used to cool to a lower temperature) is returned to the dedicated pumping (compression) system, which advantageously makes it possible to select the upstream operating pressure (for example in a vessel). This makes it possible to control the temperature of the cycle fluid that has undergone the two expansions, if necessary.

[0072] The installation thus makes it possible to distribute power to a 3 K stage over a relatively large surface area (cycle fluid circuit with simple expansion) and to have an additional colder reserve, for example at a temperature of between 1 K and 2 K in the cycle fluid circuit part undergoing expansion 408 in the enclosure 2.

[0073] The cycle circuit 8 preferably also comprises a return line 38 connecting an outlet (for example an upper outlet) of the first storage vessel 17 to the compression mechanism 9. This allows the boil-off gas to be returned to the compression within the first storage vessel 17.

[0074] The return line 38 could comprise a cryogenic compressor or pump.

[0075] Similarly, the cycle circuit 8 may have a second vessel for storing a reserve of liquefied cycle fluid. This second storage vessel could, for example, be connected in parallel with the first storage vessel 17 to the bypass line 18. The flow of fluid returning from the enclosure 2 via the return line 28 can thus be sent to the first storage vessel 17 (via a valve) or to the second vessel (via another valve). A line and valve may be provided for transferring liquid from the second storage vessel to the first vessel. This can be used to regulate the liquid level in the second vessel. The gas formed in the second storage vessel can be sent to the compressor 9. Preferably, the cycle circuit 8 does not comprise a thermosiphon at the second storage vessel but of course a thermosiphon could be provided at the second storage vessel. An exchanger may be placed on the cycle circuit 8 before the second storage vessel in order to take advantage of the low temperature of the return fluid. This makes it possible to improve the energy efficiency of the system.

[0076] All or some of the components of the refrigerator and/or of the enclosure 2 may be housed in a thermally insulated cold box, for example under vacuum. The operation can be at least partially automated, thereby limiting the handling of cryogenic fluid by the user.

[0077] The structure of the installation 1 enables cooling power along a capillary in the enclosure, unlike more localized cooling of known solutions with a bath of cryogenic liquid.

[0078] The above structure is more efficient and flexible than solutions that exclusively use gas-filled pulse tubes to cool stages of the enclosures 2.

[0079] This type of installation requires less maintenance than the solutions in the prior art.

[0080] In addition, this solution offers higher cooling power (and lower available cold temperature), which can be used to reduce the pre-cooling/cooling time of the installation at start-up. In particular, such an installation can provide a very cold flow of cycle fluid, for example at a temperature of the order of 1 K.

[0081] The installation can use one or more cryogenic compressors in the cycle circuit 8 for better heat energy recovery in the cycle exchangers.

[0082] The cycle fluid in the one or more enclosures can be drained rapidly, thereby significantly reducing the heating time of the installation during shutdown (compared to a conventional wet solution). The embodiment in [FIG. 3] differs from that in [FIG. 1] in that it has a heat exchanger 708 that exchanges heat between the cycle fluid circulating in the return line 608 and the cycle fluid circulating in the first storage vessel 17. In other words, the very cold cycle fluid (for example around 2 K), which has undergone heat exchange with the additional tray or plate 27, releases cold energy to the cooled cycle fluid (for example around 3 K) that travels towards the enclosure 2 (in particular before the expansion 408 in the enclosure 2).

[0083] Of course, this example is non-limiting. Thus, this heat exchange could be located at other places in the cycle circuit, for example further downstream, just before the bifurcation of the bypass line 308. Similarly, this heat exchanger 708 could be located downstream of the bifurcation of the bypass line 308, on a line portion of the cycle circuit that conveys the first fraction of cycle fluid.

[0084] Similarly, this heat exchanger 708 could be located downstream of the bifurcation of the bypass line, on the bypass line 308 itself.

[0085] Similarly, the return line 608 could exchange heat with a line 208 that feeds some trays 4, 5, 6, 7 and/or plates 24, 25, 26, 27 via a coaxial arrangement of said lines and/or via thermal connectors such as braids.

[0086] While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims. The present invention may suitably comprise, consist or consist essentially of the elements disclosed and may be practiced in the absence of an element not disclosed. Furthermore, if there is language referring to order, such as first and second, it should be understood in an exemplary sense and not in a limiting sense. For example, it can be recognized by those skilled in the art that certain steps can be combined into a single step.

[0087] The singular forms a, an and the include plural referents, unless the context clearly dictates otherwise.

[0088] Comprising in a claim is an open transitional term which means the subsequently identified claim elements are a nonexclusive listing (i.e., anything else may be additionally included and remain within the scope of comprising). Comprising as used herein may be replaced by the more limited transitional terms consisting essentially of and consisting of unless otherwise indicated herein.

[0089] Providing in a claim is defined to mean furnishing, supplying, making available, or preparing something. The step may be performed by any actor in the absence of express language in the claim to the contrary.

[0090] Optional or optionally means that the subsequently described event or circumstances may or may not occur. The description includes instances where the event or circumstance occurs and instances where it does not occur.

[0091] Ranges may be expressed herein as from about one particular value, and/or to about another particular value. When such a range is expressed, it is to be understood that another embodiment is from the one particular value and/or to the other particular value, along with all combinations within said range.

[0092] All references identified herein are each hereby incorporated by reference into this application in their entireties, as well as for the specific information for which each is cited.