EP3191712B1 - Compressor device, cooling device equipped therewith, and method for operating the compressor device and the cooling device - Google Patents

Description

The invention relates to a compressor device, a cooling device equipped therewith and a method for operating the compressor device.

For cooling magnetic resonance tomographs, cryopumps, etc., pulse tube coolers or Gifford-McMahon coolers are used. Gas and especially helium compressors are used in combination with rotary or rotary valves. The rate at which compressed helium is introduced and re-circulated to the cooling device is in the range of 1 Hz. A problem with conventional screw or piston compressors is that oil from the compressor may enter and contaminate the working gas and thus the cooling device ,

There are also known acoustic compressors or high-frequency compressors in which one or more pistons are caused by a magnetic field in linear resonant vibrations. These resonant frequencies are in the range of a few 10 Hz and are therefore not suitable for use with pulse tube coolers and Gifford-McMahon coolers to produce very low temperatures in the lower than 10 K range.

From the CH 457147 B For example, a membrane compressor or pump is known, which has a working space that is divided into a gas volume and a liquid volume by an elastic, gas and liquid-tight membrane. By means of a liquid pump liquid is periodically pressed into the liquid volume of the working space, whereby the elastic membrane expands in the direction of gas volume and this compresses - compressor function - or pushing out of the gas volume - pump function. A disadvantage is the fact that the gas-, liquid-tight and pressure-resistant sealing of the elastic membrane in the working space is relatively expensive. Especially in the field of sealing, the membrane is heavily loaded, so that either very expensive materials must be used or a shorter life has to be accepted.

CH 457 147 A also shows a membrane compressor and mentions the lack of tightness of the membrane to helium. DE 20 2007 018538 U1 shows a multi-stage diaphragm suction pump whose pumping chambers work in parallel or serially.

From the DE10344698B4 For example, a heat pump and a refrigerator with a compressor device are known. The compressor device comprises a compressor chamber in which a balloon is arranged. The balloon is periodically pressurized with liquid so that the gas surrounding the balloon is periodically compressed and relaxed again. The disadvantage here is that the balloon envelope can scrape or rub in certain operating conditions on the hard and possibly edged inner surface of the compressor chamber. As a result, due to the pressure conditions hole or cracking in the balloon envelope occur. In addition, the permeability - permeability - of the balloon envelope for helium as a working gas is too large, so you quickly lose substantial amounts of helium. Thus, the service life of such systems with balloon is unsatisfactory.

From the DE-A-91837 is known a diaphragm pump for liquids, which can also serve as a "gas compression pump". For this purpose it is stated that a liquid must be introduced between the membrane and pump valves, ie a liquid is provided in the gas space. It is thus a compression device with a liquid stamp. A physical separation between compressed gas and hydraulic fluid therefore does not take place. DE 10 2008 060598 A1 shows an apparatus for compressing a gas, comprising two cylinder filled with a hydraulic fluid or a working gas. The hydraulic fluid is preferably pumped back and forth between these cylinders with a hydraulic pump. Again, the physical separation between gas and liquid is not sufficient.

US 1 580 479 A describes a diaphragm pump with two chambers (or bellows) without working fluid, which are mutually compressed or relaxed via a yoke separating the chambers.

From the WO2014 / 016415A2 is a compressor device with a metal bellows known as a compressor element, which is impermeable to hydrogen except for all possible working gases. The working gas may be due to the Metal bellows are also kept oil-free. However, the efficiency due to the interaction with the working fluid balance tank is unsatisfactory.

Starting from the WO2014 / 016415A2 It is therefore an object of the invention to provide a compressor device with a metal bellows as the compressor element, which is more efficient. It is another object of the invention to provide a cooling device and a method for operating the compressor device.

The solution of these objects is achieved by the features of the claims.

Because of that from the WO2014 / 016415A2 known working fluid balance tank is extended to a second compressor stage, the common pumping device is used twice. In each flow direction of the working fluid is a compression of the working gas; in the one flow direction in the first compressor stage and in the opposite direction of flow in the second compressor stage. This increases the efficiency of the compressor device. Characterized in that the high and low pressure gas line are designed so that they act as a gas storage due to their volume, the operating frequency of a compressor operated with the device cooler can be decoupled from the pumping frequency of the pumping device.

By check valves at the high pressure and low pressure working gas connections, the gas flow is controlled in compression and expansion in a simple manner.

By the high pressure working gas connections in the two compressor stages after switched heat exchangers, the compressed working gas is cooled after each compression stroke.

Multi-stage metal bellows compressor

In the conveying compressor according to the invention of claims 1 and 5, first working gas in the first compressor stage is compressed or precompressed and stored temporarily in a buffer memory. The second compressor stage is operated virtually idle and serves as a working fluid expansion tank. If in the buffer memory, a working gas at a mean pressure p _{mid is} reached, which corresponds to the second gas volume in the second compressor stage, in the next compressor stroke in the second compressor stage, the pre-compressed working gas from the buffer memory to the final pressure p _{end is} compressed. The compressed to the final pressure p _end working gas is then discharged to the outside or stored in a high-pressure gas storage.

In the compressor of claims 2 and 5, first working gas in the first compressor stage is compressed or precompressed and simultaneously transferred to the second gas volume of the second compressor stage. In the second compressor stage, the pre-compressed working gas to the mean pressure p _mid is then compressed to the final pressure p _end . The compressed to the final pressure p _end working gas is then discharged to the outside or stored in a high-pressure gas storage.

As a working fluid preferably hydraulic oil according to DIN 51524 is used, which is additionally dehydrated or anhydrous. The hydraulic oil is in a closed system of pumping device, working fluid equalizing device and fluid volume in the compressor chamber, so that during operation no water from the environment can be absorbed by the hydraulic oil. Alternatively, water can also be used as the working fluid. Water as a working fluid is also advantageous because in the event of defects, water that has penetrated into a downstream cryocooler can be removed more easily than hydraulic oil that has entered a downstream cooler. Also, water is suitable as a working medium in explosion-protected applications, since water is non-flammable and non-explosive. In addition, water is non-toxic and therefore environmentally friendly.

For cryogenic applications, depending on the temperature range, helium, neon or nitrogen is preferably used as working gas.

Multi-stage metal bellows compressor

The remaining subclaims relate to further advantageous embodiments of the invention. Further details, features and advantages of the invention will become apparent from the following description of various embodiments.

• Fig. 1 eine schematische Darstellung eines nicht beanspruchten Verdichters mit zwei Verdichterstufen als nicht-fördernde Kompressorvorrichtung,
• Fig. 2a bis 2e schematische Darstellungen dieses Verdichters,
• Fig. 3 eine schematische Darstellung der Erfindung mit zwei Verdichterstufen als fördernde Kompressorvorrichtung,
• Fig. 4a bis 4d schematische Darstellungen der zum Betrieb dieses Verdichters, und
• Fig. 5 eine Anwendung der Erfindung als Antrieb eines Joule-Thomson-Kühlers.

It shows:

• Fig. 1 a schematic representation of an unclaimed compressor with two compressor stages as a non-promotional compressor device,
• Fig. 2a to 2e schematic representations of this compressor,
• Fig. 3 a schematic representation of the invention with two compressor stages as a promotional compressor device,
• Fig. 4a to 4d schematic representations of the operation of this compressor, and
• Fig. 5 an application of the invention as a drive a Joule-Thomson cooler.

Fig. 1 shows an unclaimed compressor device with a first and a second compressor stage 2-1, 2-2, in the form of a non-promoting compressor device. Each of the two compressor devices 2-1, 2-2 has a gas-tight closed compressor chamber 4-1, 4-2. In each of the two compressor rooms 4-1, 4-2, a metal bellows 6-1, 6-2 is arranged. The metal bellows 6-1, 6-2 subdivide the compressor chambers 4-1, 4-2 into a first and a second gas volume 8-1, 8-2 for a working gas 10 and into a first and second fluid volume 12-1, 12, respectively -2 for a working liquid 14. The gas volumes 8-1, 8-2 are inside the metal bellows 6-1, 6-2, and the liquid volumes are outside the bellows 6-1, 6-2. From the liquid volumes 12-1, 12-2 performs a respective working fluid port 16-1, 16-2 out. The gas volumes 8-1, 8-2 are each provided with a high pressure working gas port 18-1, 18-2 and a low pressure working gas port 20-1, 20-2 connected. The low pressure working gas ports 20-1, 20-2 are provided with check valves 22 which are permeable toward the compressor stages 2-1, 2-2. The high pressure working gas ports 18-1, 18-2 are also provided with check valves 22 having opposite directions of passage as compared to the check valves 22 on the low pressure working gate ports 20-1, 20-2. The high pressure working gas ports 18-1, 18-2 are connected via the check valves 22 to a common high pressure gas line 24, and the low pressure working gas ports 20-1, 20-2 are connected to a low pressure gas line 26 via the check valves 22. The check valves 22 in the high-pressure working gas ports 18-1, 18-2 are in the direction of common high-pressure gas line 24 and the check valves 22 on the low-pressure working gas ports 20-1, 20-2 are in the direction of compressor stages 2-1, 2-2 permeable. The common high pressure gas line 24 and the common low pressure gas line 26 terminate in a motorized rotary valve 28 which alternately the high pressure gas line 24 and the low pressure gas line 26 with a cooling device 30, for. In the form of a Gifford-McMahon cooler or a pulse tube refrigerator. The high and low pressure gas line 24, 26 act due to their volume as a gas storage or it is explicitly a low-pressure gas storage 27 and a high-pressure gas storage 25 in the low-pressure or high-pressure gas line 26, 24 are provided. The check valves 22 at the two high pressure working gas ports 18-1, 18-2 are each followed by heat exchangers 32-1, 32-2 for cooling the compressed working gas. The two compressor stages 2-1, 2-1 are constructed analogously, ie, the gas volumes 8-1, 8-2 and the liquid volumes 12-1, 12-2 are equal.

The two working fluid ports 16-1, 16-2 are connected to a common electromotive pumping device 34, which alternately pumps working fluid 14 into the first and second fluid volumes 12-1, 12-2 of the first and second compressor stages 2-1, 2-2. Ie. either working fluid 14 is pumped from the second fluid volume 12-2 into the first fluid volume 12-1 or vice versa.

The FIGS. 2a to 2e illustrate the various phases of operation of the compressor device Fig. 1 , In the in Fig. 2a phase shown by the common Pumping 34 working fluid 14 from the second fluid volume 12-2 of the second compressor stage 2-2 in the first fluid volume 12-1 in the first compressor stage 2-1 pumped. The first metal bellows 6-1 is compressed and the working gas 10 therein is pressed into the high pressure gas reservoir 25 via the first high pressure working gas port 18-1, the first heat exchanger 32-1 and the common high pressure gas line 24. The second metal bellows 6-2 expands through working gas 10, which flows back out of the low-pressure working gas reservoir 27 via the low-pressure gas line 26 and the second low-pressure working gas connection 20-2. The rotary valve 28 connects the cooling device 30 via the low pressure gas line 26 with the low pressure gas storage 27th

In the in Fig. 2b As shown in the second phase, the compression in the first compressor stage 2-1 is complete and the rotary valve 28 connects the high-pressure gas storage 25 with the cooling device 30, so that compressed and cooled in the first heat exchanger 32-1 working gas 10 enters the cooling device 30.

In the in Fig. 2c shown third phase, the working fluid flow is reversed and the pumping device 34 now pumps working fluid 14 from the first fluid volume 12-1 of the first compressor stage 2-1 in the second fluid volume 12-2 in the second compressor stage 2-2. Thereby, the second metal bellows 6-2 is compressed and the working gas 10 therein is compressed and pressed into the high pressure gas reservoir 25 via the second high pressure working gas port 18-1, the second heat exchanger 32-2 and the common high pressure gas line 24. The first metal bellows 6-1 expands through working gas 10 flowing back from the low-pressure gas reservoir 27 via the low-pressure gas line 26 and the first low-pressure working gas port 20-1.

In the in Fig. 2d shown fourth phase, the compression in the second compressor stage 2-2 is complete and the rotary valve 28 connects again via the common high-pressure gas line 24, the high-pressure gas storage 25 with the cooling device 30, so that compressed and cooled in the second heat exchanger 32-2 working gas 10 in the cooling device 30 arrives.

In the Fig. 2e phase shown is again the first phase and the compression takes place in the first compressor stage 2-1. Fig. 2a and 2e differ only in that in Fig. 2e the first metal bellows 6-1 still relaxed and the second metal bellows 6-2 is still compressed. In Fig. 2a is the compression in the first compressor stage 2-1 completed and the first metal bellows 6-1 is compressed, while the second metal bellows 6-2 is relaxed.

By providing the high-pressure accumulator 25 and the low-pressure accumulator 27, the rotational frequency of the rotary valve 28 is decoupled from the frequency of the compression in the two compressor stages. Alternatively, the rotational frequency of the rotary valve 28 may be synchronized with the frequency of the compressor strokes. In this case, the high-pressure and low-pressure gas storage 25, 27 could be dispensed with.

Fig. 3 shows the invention with two compressor stages 2-1, 2-2 in the form of a working gas 10 promotional compressor device. For components corresponding in the two embodiments, the same reference numerals are used. The structure of the two compressor stages 2-1, 2-2 and the connection of the two compressor stages 2-1, 2-2 with the common pumping device (34) corresponds to the structure in Fig. 1 and 2 , Likewise, that of the two heat exchangers 32-1, 32-2 corresponds to the arrangement according to the first embodiment. In the embodiment according to Fig. 3 the working gas 10 is first compressed in the first compressor stage 2-1 from an initial pressure po to a first average pressure p _mid1 and then subsequently in the second compressor stage 2-2 from a second average pressure p _mid2 to the final pressure p _end . The following applies: p _mid1 > p _mid2 .

In particular, the differences in the two compressors will be described below. A buffer store 42 is connected via a first gas line 40-1 and a first shut-off valve 44-1 to the second low-pressure working gas port 20-2 of the second compressor stage 2-2. Via a first heat exchanger 32-1 and a second gas line 40-2, the first high pressure Arbeitsgansanschluss 20-1 is connected to the buffer memory 42. A low-pressure gas storage 27 is connected via a third gas line 40-3 to a first low-pressure working gas connection 20-1 with a check valve 22 in the first compressor stage 2-1. The second high pressure working gas connection 18-2 of the second compressor stage 2-2 is connected via a check valve 22, a second heat exchanger 32- 2 and a fourth gas line 40-4 with a high-pressure gas storage 25. Via the first low-pressure working gas connection 20-1, the first compressor stage 2-1 is supplied with working gas 10 to be compressed from the low-pressure gas reservoir 27.

The following is based on the FIGS. 4a to 4d the operation of the compressor device after Fig. 3 described.

In an in Fig. 4a shown first phase is pumped by the common pumping device 34 working fluid 14 from the first fluid volume 12-1 of the first compressor stage 2-1 in the second fluid volume 12-2 in the second compressor stage 2-1. The first metal bellows 6-1 expands and uncompressed working gas 10 flows via the third gas line 40-3 and the first low-pressure working gas connection 20-1 with check valve 22 into the first gas volume 8-1. The first check valve 44-1 in the first gas line is closed. The second compressor stage 2-2 serves only as a working fluid expansion tank. In the second gas volume 8-2 prevails in the relaxed state, the second average pressure p _mid2 and in the compressed state in about the final pressure p _end .

In the second in Fig. 4b operating phase shown rotates view the flow direction of the working fluid 14 and working gas 10 in the first compressor stage 2-1 is compressed and the first high-pressure working gas port 20-2 with check valve 22, the first heat exchanger 32-1 and the second gas line 40-2 in pressed the buffer memory 42. The check valve 22 at the first high-pressure working gas port 18-2 prevents the backflow of the working gas 10 compressed to the mean pressure p _mid . The first shut-off valve 44-1 is further closed and the second compressor stage 2-2 functions merely as a working fluid equalizing reservoir.

The operating phases after Fig. 4a and 4b are repeatedly carried out until the amount of compressed to the first average pressure p _mid1 working gas 10 in the buffer memory 42 is sufficient, when connected to the second gas volume 8-2 via the first gas line 40-1 and the open check valve 44-1 to generate the second average pressure p _mid2 in the second gas volume 8-2.

If this amount of gas is reached in the buffer memory 42, the first shut-off valve 40-1 is opened during the next compression stroke in the first compressor stage 2-1, so that the working gas 10 pre-compressed to the first average pressure p _mid1 from the buffer _reservoir 42 via the open first shut-off valve 44th -1 and the first gas line 40-1 can flow into the second gas volume 8-2 of the second compressor stage 2-2, wherein the second average pressure p _mid2 sets - see Fig. 4c ,

In the next in Fig. 4d shown operating phase, the working fluid 14 is pumped through the common pumping device 34 in the second compressor stage 2-2. The working gas 10 pre-compressed to the second average pressure p _mid2 in the second gas volume 8-2 is at the final pressure p _end . further compressed and pressed via the second heat exchanger 32-2 and the fourth gas line 40-4 in the high-pressure gas storage 25.

Thus, a compression cycle from the output pressure po to the final pressure p _{end is} completed and the cycle starts again.

In an alternative embodiment of the embodiment according to Fig. 3 the first high-pressure working gas connection 18-1 is connected via a gas line 40-1, 40-2 to the low-pressure working gas connection 20-2 of the second compressor stage 2-2. The buffer memory 42 and the first shut-off valve 44-1 are unnecessary. Here, the working gas 10 is pre-compressed in the first compressor stage 2-1 to a mean pressure p _mid and in the countermovement of the common electromotive Pumpeninreichtung 34, the working gas 10 in the second compressor stage 2-2 then compressed to the final pressure p _end . The compressed to the final pressure p _end working gas is then discharged to the outside or stored in a high-pressure gas storage 25.

Fig. 5 shows an application as a drive of a Joule-Thomson refrigerator 50 with closed working gas circuit.

Hydraulic oils according to DIN 51524 are suitable as working fluids. These H, HL, HLP and HVLP oils are oils which are well tolerated with common sealants such as NBR (acrylonitrile-butadiene rubber) etc. NBR, however, is not sufficiently helium-tight. HF oils are often incompatible with common sealing materials ( http://de.wikipedia.org/wiki/List of plastics ).

Alternatively, water can also be used as the working fluid. Water as a working fluid is also advantageous because in the event of defects, water that has penetrated into a downstream cryocooler can be removed more easily than hydraulic oil that has entered a downstream cooler. Also, water is suitable as a working medium in explosion-protected applications, since water is non-flammable and non-explosive. In addition, water is non-toxic and therefore environmentally friendly.

LIST OF REFERENCE NUMBERS

p ₀

output pressure

p _mid1

mean pressure 1

p _mid2

mean pressure 2

p _end

final pressure

2-1

first compressor stage

2-2

second compressor stage

4-1

first compressor room

4-2

second compressor room

6-1

first metal bellows

6-2

second metal bellows

8-1

first gas volume

8-2

second gas volume

10

working gas

12-1

first fluid volume

12-2

second liquid volume

14

working fluid

16-1

first working fluid connection

16-2

second working fluid connection

18-1

first high-pressure working gas connection

18-2

second high pressure working gas connection

20-1

first low-pressure working gas connection

20-2

second low-pressure working gas connection

22

check valves

24

High-pressure gas line

25

High-pressure gas storage

26

Low-pressure gas line

27

Low pressure gas

28

electromotive rotary valve

30

cooling device

32-1

first heat exchanger

32-2

second heat exchanger

34

common electromotive pumping device

40-1

first gas line

40-2

second gas line

40-3

third gas line

40-4

fourth gas line

42

buffer memory

44-1

first shut-off valve

50

Joule-Thomson cooling machine

Claims (9)

1. Compressor device, comprising:

   a first compressor stage (2-1), including:

   a first compressor chamber (4-1) having a defined volume in which a first metal bellows (6-1) sub-divides the first compressor chamber (4-1) into a first gas volume (8-1) with a working gas (10) and a first liquid volume (12-1) with a working liquid (14),

   a first high-pressure and a first low-pressure working gas connection (18-1, 20-1) that lead to the first gas volume (8-1), and

   a first working liquid connection (16-1) leading to the first liquid volume (12-1); and

   a pump device (34) periodically pumping the working liquid (14) via the first working liquid connection (16-1) into the liquid volume (12-1), thereby compressing the working gas (10) in the gas volume (8-1) periodically,

   characterized in

   that a second compressor stage (2-2) is provided including a second compressor chamber (4-2) that is sub-divided by a second metal bellows (8-2) into a second gas volume (8-2) with working gas (10) and a second liquid volume (12-2) with working liquid (14),

   that the second compressor stage (2-2) includes a second high-pressure working gas connection and a second low-pressure working gas connection (18-2, 20-2) leading into the second gas volume (8-2),

   that the second compressor stage (2-2) includes a second working liquid connection (16-2) leading into the second liquid volume (12-2),

   that the pump device (34) is a common pump device,

   that the common pump device (34) is connected with the second compressor stage (2-2) via the second working liquid connection (16-2),

   that the second low-pressure working gas connection (20-2) of the second compressor stage (2-2) is connected with a buffer storage (42) via a first gas line (40-1) and a first lock valve (44-1), and

   that the first high-pressure working gas connection (18-1) of the first compressor stage (2-1) is connected with the buffer storage (42) via a second gas line (40-2).
2. Compressor device, comprising:

   a first compressor stage (2-1), including:

   a first compressor chamber (4-1) having a defined volume in which a first metal bellows (6-1) sub-divides the first compressor chamber (4-1) into a first gas volume (8-1) with a working gas (10) and a first liquid volume (12-1) with a working liquid (14),

   a first high-pressure and a first low-pressure working gas connection (18-1, 20-1) that lead to the first gas volume (8-1), and

   a first working liquid connection (16-1) leading to the first liquid volume (12-1); and

   a pump device (34) periodically pumping the working liquid (14) via the first working liquid connection (16-1) into the liquid volume (12-1), thereby compressing the working gas (10) in the gas volume (8-1) periodically,

   characterized in

   that a second compressor stage (2-2) is provided including a second compressor chamber (4-2) that is sub-divided by a second metal bellows (8-2) into a second gas volume (8-2) with working gas (10) and a second liquid volume (12-2) with working liquid (14),

   that the second compressor stage (2-2) includes a second high-pressure working gas connection and a second low-pressure working gas connection (18-2, 20-2) leading into the second gas volume (8-2),

   that the second compressor stage (2-2) includes a second working liquid connection (16-2) leading into the second liquid volume (12-2),

   that the pump device (34) is a common pump device,

   that the common pump device (34) is connected with the second compressor stage (2-2) via the second working liquid connection (16-2), and

   that the second low-pressure working gas connection (20-2) of the second compressor stage (2-2) is connected to the first high-pressure working gas connection (18-1) of the first compressor stage (2-1) via a gas line (40-1; 40-2).
3. Compressor device according to claim 1 or 2, characterized in that the high-pressure working gas connections (18-1, 18-2) and the low-pressure working gas connections (20-1, 20-2) of the two compressor stages (2-1, 2-2) each are provided with check valves (22),
   that the check valves (22) on the low-pressure working gas connections (20-1, 20-2) each are permeable in a direction of the compressor stages (2-1, 2-2), and that the check valves (22) on the high-pressure working gas connections (18-1, 18-2), as opposed to the check valves on the low-pressure working gas connections (20-1, 20-2) are permeable in an opposite direction.
4. Compressor device according to one of the preceding claims 1 to 3, characterized in that a heat exchanger (32-1, 32-2) is connected downstream of each of the high-pressure working gas connections (18-1, 18-2) of the two compressor stages (2-1, 2-2) in order to cool the compressed working gas (10).
5. Compressor device according to one of the claims 1 to 4, characterized in that the first low-pressure working gas line (20-1) is connected with a low-pressure gas storage (27) via a third gas line (40-3), and
   that the second high-pressure working gas connection (18-2) of the second compressor stage (2-2) is connected with a high-pressure gas storage (25) via a fourth gas line (40-4).
6. Cooling device including a compressor device according to claim 5 and a Joule-Thomson cooler (50) that is connected with the low-pressure gas storage (27) and the high-pressure gas storage (25).
7. Method for operating a compressor device according to one of claims 1, 3, 4, or 5 and a cooling device according to claim 6, with the method steps of:

   - repeatedly compressing working gas (10) in the first compressor stage (2-1) from an outlet pressure (po) to a first middle pressure (p_mid1), the second compressor stage (2-2) serving as a compensation container for working liquid;

   - temporarily storing the working gas (10) that was pre-compressed to a first middle pressure (p_mid1) in a buffer storage (42);

   - repeating the previous method steps until, when the buffer storage (42) is connected with the second gas volume (8-2) in the second compressor stage (2-2), a second middle pressure (p_mid2) is achieved with p_mid1 > p_mid2;

   - transferring the working gas (10) that was pre-compressed to a first middle pressure (p_mid1) from the buffer storage (42) into the gas volume (8-2) of the second compressor stage (2-1); and

   - compressing the working gas (10) that was pre-compressed to the second middle pressure (p_mid2) in the second compressor stage (2-2) to an end pressure (pend).
8. The method for operating a compressor device according to one of claims 2 to 5 and a cooling device according to claim 6, with the method steps of:

   - compressing working gas (10) in a first compressor stage (2-1) from an outlet pressure (po) to a middle pressure (p_mid) and transferring the working gas (10) pre-compressed to the middle pressure (p_mid) into the second gas volume (8-2) of the second compressor stage (2-2); and

   - compressing the working gas (10) pre-compressed to the middle pressure (p_mid) in the second compressor stage (2-2) to an end pressure (pend).
9. The method according to claim 7 or 8, characterized in that the compressed working gas (10) from the two compressor stages (2-1, 2-2) is cooled after each compressor stroke.

Images