Gas cycle refrigerator

Abstract

The invention relates to a cycle gas refrigerator comprising, in a cycle circuit (2) containing a cycle gas comprising, for example, helium and / or hydrogen, a cycle gas compression system (3), a regenerator system (4), a compressed cycle gas expansion system (5), the regenerator system (4) comprising at least two regenerators arranged in parallel, a first set (6) of valve(s) configured to connect the outlet of the compression system (3) with the parallel regenerators (4) alternately, a second set (7) of valve(s) configured to connect the outlet of a first regenerator (4) supplied with compressed cycle gas with the inlet of the expansion system (5) and the outlet of the expansion system (5) with a second regenerator (4),the first set (6) of valve(s) comprising a three-way valve having one inlet connected to the compression system outlet (3) and two outlets connected respectively to the two regenerators (4) arranged in parallel, and in that the second set (7) of valve(s) comprises an air-type distributor bridge. Abbreviated figure: Fig. 1,

Description

Title of the invention: Cycle gas refrigerator

[0001] The invention relates to a cycle gas refrigerator, for example helium.

[0002] The invention relates more particularly to a cycle gas refrigerator comprising, arranged in series in a cycle circuit containing a cycle gas comprising for example helium and / or hydrogen, a system for compressing the cycle gas, a system of regenerators, a system for expanding the compressed cycle gas, the system of regenerators comprising at least two regenerators arranged in parallel, the cycle circuit comprising a first set of valve(s) configured to connect the outlet of the compression system with alternately in turn the regenerators in parallel, the cycle circuit comprising a second set of valve(s) configured to connect the outlet of a first regenerator supplied with compressed cycle gas with the inlet of the expansion system and the outlet of the expansion system with a second regenerator before being returned to the inlet of the compression system,to allow the compressed cycle gas to be cooled by flowing into one regenerator and then expanded and injected into the other regenerator to pass through and cool it.

[0003] These cryogenic production equipments use a room temperature compression unit and a cryogenic temperature expansion unit connected by a heat exchanger which alternates between cooling and heating, which remains a limiting factor of the system. The delivery time, the size of the cold box (vacuum enclosure ensuring the thermal insulation of the cryogenic components), the thermal performance and the cost of the refrigeration / liquefaction unit are strongly impacted by the heat exchangers.

[0004] Standard cryogenic heat exchangers are of the recuperative type and of aluminum finned plate technology. These heat exchangers are manufactured industrially by various suppliers using an identical manufacturing process: vacuum brazing through the integration of a thin aluminum alloy strip between each layer which has a melting temperature slightly lower than the grade used for the waves or separation sheets between the different channels. The sizing of these exchangers is complex and expensive. Upstream studies are lengthy to optimize the configuration and stacking of the sheets. Manufacturing is difficult because brazing is a delicate operation, sometimes subject to scrap. This technique limits the manufacturing of large exchange blocks within a reasonable time.The thermal performance of this technology is strongly impacted by the all-aluminum construction. This material is an excellent thermal conductor. The . Longitudinal conduction losses require in some cases a significant increase in the length of the exchange blocks to reduce this effect (particularly in cases of application with a large temperature difference between the hot end and the cold end of the heat exchangers and with low cycle flow rate). This results in a large mechanical footprint, integration within the complex cold box and regularly limiting the manufacturing range and additional material costs.

[0005] Other stainless steel exchanger technologies can be used occasionally but are rarely used, as they are very expensive and not very developed for low pressure applications (for example, stainless steel brazed plate exchangers) or are not very efficient (exchangers with stamped stainless steel plates brazed with copper, nickel or other materials, stainless steel fused exchangers, etc.).

[0006] To solve these problems of aluminum finned plate exchangers (size, thermal performance, design, manufacturing, time and costs) it is known to supplement them with regenerative exchanger technology. These regenerative or "regenerator" exchangers generally consist of a matrix of high porosity, high specific heat and high surface density to optimize the exchange while maintaining a significant hydraulic passage. In practice, these exchangers can take the form of an assembly of balls or a stack of grids in a closed cylinder.

[0007] The heat exchange is done in two stages: during the outward journey, the hot fluid cools down in contact with the matrix, during the return journey, the cold fluid heats up in contact with the same matrix. The process is therefore alternative in principle.

[0008] Document GB1455293A describes an example of such a helium refrigerator.

[0009] The difficulty is to use these regenerative exchangers of an alternative nature in a continuous process such as used in cryogenic compression / expansion machines.

[0010] The installation described in this document uses a distribution circuit which generates significant pressure differentials and which are subject to failures.

[0011] The operations of the rotary valve (between compression and regenerators) and the flaps (between regenerators and expansion) are disjointed and can generate malfunctions. An accumulator system is also provided.

[0012] This can increase the risks of failure, pressure losses, costs and bulk and make such technology unviable as soon as one seeks to significantly increase the dimensions of the referenced small systems (typically cylinders of the order of a few tens of millimeters in diameter). An aim of the present invention is to overcome all or part of the disadvantages of the prior art noted above.

[0013] To this end, the refrigerator according to the invention, moreover conforming to the generic definition given in the preamble above, is essentially characterized in that that the first set of valve(s) comprises a three-way valve having an inlet connected to the compression system outlet and two outlets connected respectively to the two regenerators arranged in parallel and in that the second set of valve(s) comprises an aeraulic type distributor bridge.

[0014] Furthermore, embodiments of the invention may include one or more of the following features: - the cycle circuit comprises a third set of valve(s) configured to connect the inlet of the compression system with alternately in turn the regenerators in parallel having recovered the flow of cycle gas coming from the expansion system, - the third set of valve(s) comprises a three-way pilot-operated valve having two inlets connected respectively to the two regenerators arranged in parallel and one outlet connected to the inlet of the compression system, - the first set of valve(s) and the third set of valve(s) are pilot-operated valves controlled in a synchronized manner, - first set of valve(s) and the third set of valve(s) are pilot-operated valves controlled in a synchronized manner, - the first set of valve(s), the third set of valve(s) and the second set of valve(s) are housed in the same air distribution member configured to synchronize the operation of the first, second and third sets of valve(s), - the second set of valve(s) comprises a housing provided with four inlet / outlet ports and configured to provide fluid connections between two pairs of ports depending on the pressure differential between the ports, - the second set of valve(s) comprises a rotary or translative distributor member configured, depending on its position, to provide fluid connections between two pairs of orifices.

[0015] The invention may also relate to any alternative device or method comprising any combination of the above or below features within the scope of the claims.

[0016] Other features and advantages will appear on reading the description below, given with reference to the figures in which: Brief description of the figures

[0017] The invention will be better understood on reading the following description, given solely by way of example and with reference to the appended drawings in which:

[0018] [Fig-1] is a schematic and partial view of an example of structure and func operation of a refrigerator according to the invention in a first configuration,

[0019] [Fig.2] is a schematic and partial view of the same example of refrigerator according to the invention in a second configuration,

[0020] [Fig.3] represents schematic and partial views, in section, of a first example of structure of the second set of valve(s) of the refrigerator according to three different configurations respectively,

[0021] [Fig.4] is a schematic and partial view, in section, of a second example of the structure of the second set of valve(s) of the refrigerator,

[0022] [Fig.5] illustrates two schematic and partial views of another example of structure and operation of a refrigerator according to the invention, in respectively, two different configurations. Detailed description

[0023] In all the figures, the same references refer to the same elements.

[0024] In this detailed description, the following embodiments are examples. Well that the description refers to one or more embodiments, this does not mean that the features apply only to a single embodiment. Single features of different embodiments may also be combined and / or interchanged to provide other embodiments.

[0025] The helium refrigerator 1 illustrated in [Fig.l] and [Fig.2] comprises, arranged in series in a cycle circuit 2 containing helium, a helium compression system 3, a regenerator system 4, and a compressed helium expansion system 5.

[0026] The compression system 3 comprises one or more compressors and preferably a cooling system 11 at the outlet of the compressor 3 to cool the compressed flow (for example a heat exchanger cooled by a heat transfer fluid).

[0027] The expansion system 5 comprises one or more turbines and / or expansion valve(s).

[0028] In this example, the regenerator system 4 comprises two regenerators arranged in parallel in the cycle circuit 2.

[0029] The cycle circuit 2 comprises a first set 6 of valve(s) configured to connect the output of the compression system 3 (high pressure circuit) with alternately in turn the regenerators 4 in parallel.

[0030] The cycle circuit 2 comprises a second set 7 of hydraulic / air distribution valve(s) or member(s) configured to connect the outlet of a first regenerator 4 supplied with compressed helium with the inlet of the expansion system 5 and the outlet of the expansion system 5 with a second regenerator 4 before being returned to the inlet of the compression system 3 (low pressure circuit). This arrangement is configured to allow the compressed helium to be cooled by its flow into one regenerator 4 and then expanded and injected into the other regenerator 4 to cool the latter. This arrangement allows the flows in the two regenerators 4 to be reversed.

[0031] As illustrated, at least one counter-current heat exchanger 12 may be provided between the second set 7 of valve(s) and the expansion system, to ensure a heat exchange between two relatively hot and cold helium flows (respectively before and after expansion).

[0032] This heat exchanger 12 of recovery technology is typically an exchanger requiring a small volume because the fluids present are the densest in the process (lowest temperature of the different circuits), facilitating implementation and integration within a cold box).

[0033] After expansion 5 and before returning to compression, the very cold helium can be used to cool an application, for example, via a heat exchanger 13.

[0034] The first set 6 of valve(s) comprises a three-way valve having an inlet connected to the compression system outlet 3 and two outlets connected respectively to the two regenerators 4 arranged in parallel (a first end of each regenerator). Preferably this three-way valve 6 is of the pilot-controlled valve type.

[0035] The second set 7 of valve(s) comprises or consists of an aeraulic type distributor bridge.

[0036] All of the mobile equipment of the valves 6, 7 can be controlled by the same actuator to ensure appropriate sequencing and facilitate integration.

[0037] Such a distributor bridge is a passive system. An actuator controls a moving element (shaft machined in a housing, drawer system of the air distributor type, or other...) to supply gas to one circuit then another alternately and recover the low pressure flow expanded in the expansion turbine 5 then reheated in the heat exchanger 12. This actuator can be located at ambient temperature outside said cold box to facilitate its maintenance if necessary. A single actuator can include the function of the three-way valve systems and hydraulic or air distribution bridge as shown in the figures.

[0038] This distributor bridge isolates the high pressure and low pressure circuits alternately by means of a set of seals or any other sealing system sufficiently suitable and robust to limit the times between maintenance and substantially limit the leakage rates between the high pressure supplies and low pressure exhausts. For example, the second set 7 of valve(s) comprises a housing provided with four inlet / outlet ports and configured to provide fluid connections between two pairs of ports depending on the pressure differential. between the holes.

[0039] Thus, unlike the aforementioned prior art, the non-return valve system is replaced by an aeraulic type distributor which does not require a critical level of sealing.

[0040] For example, the second set 7 of valve(s) comprises a rotary distributor member 9 (see [Fig.3]) or translational distributor member (see [Fig.4]) configured, depending on its position, to ensure a fluid connection between two pairs of orifices.

[0041] The cycle circuit 2 comprises a third set 8 of valve(s) configured to connect the inlet of the compression system 3 with alternately in turn the regenerators 4 (the first ends of the regenerators). This makes it possible to return the flow coming from the expansion system 5 to the compression.

[0042] The third set 8 of valve(s) comprises or consists for example of a three-way pilot-operated valve having two inlets connected respectively to the two regenerators 4 (first ends) and an outlet connected to the inlet of the compression system 3.

[0043] Preferably, the first set 6 of valve(s) and the third set 8 of valve(s) are pilot-controlled valves controlled in a synchronized manner.

[0044] The first 6 set of valve(s), the third 8 set of valve(s) and the second 7 set of valve(s) can be housed in the same air distribution member configured to synchronize the operation of the first 6, second 7 and third 8 set of valve(s).

[0045] That is to say that the synchronization of all the air distribution systems can be achieved via a single component.

[0046] Of course, the invention is not limited to the above example.

[0047] Thus it could be envisaged to do without any recovery heat exchanger on the main exchange battery. That is to say that, at the outlet of the second set 7 of valve(s), the helium is directly at the suction temperature of the expansion device 5.

[0048] It is possible to provide a buffer tank at the inlet of the expansion turbine 5 (for example between the second set of valve(s) 7 and the inlet of the turbine 5) to smooth out fluctuations (in amplitude for example) in pressure and ensure a relatively constant flow rate at the suction of the expansion turbine 5.

[0049] The refrigerator 1 can operate according to a linear process for compression 3 and also according to a subsequent linear process for expansion 5. On the other hand, the aforementioned valve assemblies provide alternative switching as illustrated above and in the figures.

[0050] During a first phase, the hot fluid at high pressure is directed towards a first regenerator 4 (see [Fig.l], open valve paths in white, closed path in black). The fluid is cooled in the matrix of the regenerator 4 by passing through it.

[0051] Thanks to the pressure differential, the path of the second set 7 of valve(s) allowing the passage of the compressed flow towards the expansion 5 is open. After expansion and after its heat exchange 13 with the application, the cold flow rises via the other corresponding open path. The cold fluid heats up while progressing along the matrix of the other regenerator 4. Thus, while one regenerator 4 is heated by the descending flow, the other is cooled by the ascending flow. After a time defined for example by the maximum thermal pinch allocated, and possibly the heat storage capacity of the regenerators, the cycle is reversed.

[0052] This thermal pinch can be measured at the outlet of the regenerators to achieve a setpoint value close to conventional values ​​in low-temperature cryogenic applications. Typically, a pinch of the recuperative heat exchanger must be maintained at a value given by the following formula: Pinch temperature / 100. In addition, a temperature sensor can be integrated into the regenerator(s) 4 to control thermal balancing by lengthening or shortening the duration of one cycle relative to the other.

[0053] During a second phase the flow directions are changed (see [Fig.2]). The flows within compression 3 and expansion 5 do not change, however. This makes it possible to use widely referenced technologies such as volumetric or centrifugal compression, for example.

[0054] The refrigerator 1 may have an inexpensive structure (regenerators 4 based on steel tubes with stacking of grids or porous materials / foams or balls of various materials).

[0055] The choice of material (steel, plastic, ceramic) and its porosity can be chosen according to the expected heat exchanges and the allocated pressure losses. The regenerators 4 preferably have a modular and simple structure facilitating dimensioning (diameter / length of the balls or characteristic dimensions of the grids). It is possible to eliminate longitudinal conduction elements in the regenerators 4 (point contacts between grids and / or balls limiting longitudinal solid conduction). The regenerators have, for example, a diameter of the order of 100 to 500 mm and a length of 500 mm or more.

[0056] The installation can for example operate with the following pressure values: low pressure after expansion between 1 and 3 bara (for example 1.1 bara). The high pressure (at the compression outlet) can be between 7 and 20 bara (for example 15 bara).

[0057] The temperature at the hot end (compression) is for example at or near room temperature (for example 300K).

[0058] The temperature at the cold end (expansion) is for example at a temperature of approximately 4 to 50K or close (e.g. 4.5K for liquid helium applications or 20K for liquid hydrogen applications).

[0059] The mass flow rate of cycle fluid (helium) may be for example between 5 and 150 g / s (for example 50 g / s).

[0060] [Fig.5] shows the structure and operation in another way (compression 3 and expansion 5 in continuous mode and regenerators 4 in alternating mode). The valve assembly(s) may be simple distributors allowing the direction of passage of the fluid in the organs to be alternated.

[0061] The cycle gas may consist of helium or hydrogen or a mixture thereof or any other mixture, for example including helium and / or hydrogen.

Claims

Claims

1. A cycle gas cryogenic refrigerator comprising, arranged in series in a cycle circuit (2) containing a cycle gas comprising helium and / or hydrogen, a cycle gas compression system (3), a regenerator system (4), an expansion system (5) for the compressed cycle gas, the regenerator system (4) comprising at least two regenerators arranged in parallel, the cycle circuit (2) comprising a first set (6) of valve(s) configured to connect the outlet of the compression system (3) with alternately in turn the regenerators (4) in parallel, the cycle circuit (2) comprising a second set (7) of valve(s) configured to connect the outlet of a first regenerator (4) supplied with compressed cycle gas with the inlet of the expansion system (5) and the outlet of the expansion system (5) with a second regenerator (4) before being returned to the inlet of the system (3) compression,to allow the compressed cycle gas to be cooled by its flow in one regenerator (4) and then be expanded and injected into the other regenerator (4) to pass through it and cool it, characterized in that the first set (6) of valve(s) comprises a three-way valve having an inlet connected to the compression system outlet (3) and two outlets connected respectively to the two regenerators (4) arranged in parallel and in that the second set (7) of valve(s) comprises an aeraulic type distributor bridge.,

2. Refrigerator according to claim 1, characterized in that the cycle circuit (2) comprises a third set (8) of valve(s) configured to connect the inlet of the compression system (3) with alternately in turn the regenerators (4) in parallel having recovered the flow of cycle gas coming from the expansion system (5).

3. Refrigerator according to claim 2, characterized in that the third set (8) of valve(s) comprises a three-way pilot-operated valve having two inlets connected respectively to the two regenerators (4) arranged in parallel and an outlet connected to the inlet of the compression system (3).

4. Refrigerator according to any one of claims 1 to 3, characterized in that the first set (6) of valve(s) and the third set (8) of valve(s) are pilot-controlled valves controlled in a synchronized manner.

5. Refrigerator according to any one of claims 1 to 4, characterized in that the first (6) set of valve(s), the third (8) set of valve(s) and the second (7) set of valve(s) are housed in the same air distribution member configured to synchronize the operation of the first (6), second (7) and third (8) set of valve(s).

6. Refrigerator according to any one of claims 1 to 5, characterized in that the second set (7) of valve(s) comprises a housing provided with four inlet / outlet orifices and configured to provide fluid connections between two pairs of orifices depending on the pressure differential between the orifices.

7. Refrigerator according to claim 6, characterized in that the second set (7) of valve(s) comprises a rotary or translative distributor member (9) configured, depending on its position, to provide fluid connections between two pairs of orifices.

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