Device and method for compressing a working medium

Abstract

The invention relates to a device and a method for compressing a working medium, comprising: compressing a drive medium in a compressor; moving a drive piston within a first cylinder by means of the compressed drive medium; moving a high-pressure piston, which compresses the working medium, within a second cylinder by means of the drive piston; and transferring heat from the compressed working medium to the compressed drive medium before the compressed drive medium enters the first cylinder of the drive piston.

Claims

1. A device for compressing a working medium comprising: a compressor for compressing a gaseous drive medium; a pressure translator with a drive piston which can be actuated by means of the gaseous drive medium within a first cylinder and with a high-pressure piston which compresses the working medium within a second cylinder, wherein the high-pressure piston has a smaller piston area than the drive piston; and a heat exchanger between the compressor and the first cylinder of the pressure translator for transferring heat from the compressed working medium to the compressed gaseous drive medium.

2. The device according to claim 1, further comprising: a closed circuit for the gaseous drive medium with a first line from the compressor to the first cylinder and with a second line from the first cylinder to the compressor.

3. The device according to claim 2, wherein the compressor is designed to be fully hermetic, semi-hermetic or open.

4. The device according to claim 3, wherein the compressor and the closed circuit for the gaseous drive medium are adapted to guide the drive medium at pressure higher than ambient pressure in the circuit.

5. The device according to claim 4, further comprising a cooler for cooling the gaseous drive medium in the second line between the first cylinder of the pressure translator and the compressor.

6. The device according to claim 5, further comprising: a temperature measuring element in the second line, and a control unit which on the one hand is connected to the temperature measuring element and on the other hand is connected to the cooler in order to control the cooler depending on the temperature of the gaseous drive medium in the second line.

7. The device according to claim 5, further comprising: a first buffer storage device between the compressor and the heat exchanger and/or a second buffer storage device between the cooler and the compressor.

8. A method for compressing a working medium comprising: compressing a gaseous drive medium in a compressor; moving a drive piston by means of the compressed gaseous drive medium within a first cylinder; and moving a high-pressure piston which compresses the working medium by means of the drive piston within a second cylinder, wherein heat is transferred from the compressed working medium to the compressed drive medium before entry of the compressed gaseous drive medium into the first cylinder of the drive piston, and the high-pressure piston has a smaller piston area than the drive piston.

9. The method according to claim 8, wherein the working medium is gaseous.

10. The method according to claim 9, wherein the working medium is molecular hydrogen.

11. The method according to claim 8, further comprising: guiding the gaseous drive medium in a closed circuit from the compressor via the first cylinder back to the compressor.

12. The method according to claim 11, wherein the gaseous drive medium in the compressor is compressed from an input pressure to an output pressure, wherein the input pressure is higher than an ambient pressure.

13. The method according to claim 12, wherein the input pressure is between 0.5 bar and 50 bar.

14. The method according to claim 13, further comprising: cooling the gaseous drive medium emerging from the first cylinder by means of a cooler.

15. The method according to claim 13, wherein the input pressure is between 2 bar and 30 bar.

16. The method according to claim 14, wherein the gaseous drive medium is selected from air, nitrogen, CO.sub.2, argon or krypton or a mixture thereof.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will be explained further hereinafter with reference to an exemplary embodiment shown in the drawing.

(2) FIG. 1 shows a device according to the invention for compressing a working medium by means of a high-pressure piston, wherein heat transfer is accomplished from the compressed working medium to the compressed drive medium for the drive piston.

DETAILED DESCRIPTION

(3) FIG. 1 shows schematically a device 1 for compressing a gaseous working medium preferably molecular hydrogen. The device 1 comprises a compressor 2 for compressing a gaseous drive medium, preferably air. Various types of compressors 2 are known in the prior art. For example, the compressor 2 can be designed as a piston or rotary-screw compressor. The compressor can have precisely one stage or at least two stages. The compressor 2 increases the pressure of the drive medium from an input pressure at an input 2a of the compressor 2 to an output pressure at an output 2b of the compressor 2.

(4) As is further apparent from the drawing, the compressed drive medium is used to drive a pressure translator 3. The pressure translator 3, also designated as pressure converter, comprises a drive piston 4 which is moved to and from within a first cylinder 5 between a first end position and a second end position. For the drive of the drive piston 4 the drive medium is guided into the first cylinder 5. The drive piston 4 seals a first volume 6 of the first cylinder 5 with respect to a second volume 7 of the first cylinder 5. The pressure translator 3 additionally comprises a high-pressure piston 8 by means of which the working medium is compressed from an initial pressure to a final pressure. The high-pressure piston 8 is movable to and fro within a second cylinder 9 between a first end position and a second end position. For this purpose, the high-pressure piston 8 is connected to the drive piston 4 in such a manner that the movement of the drive piston 4 is transmitted to the high-pressure piston 8. In order to achieve a pressure translation from the low-pressure to the high-pressure side, the high-pressure piston 8 has a smaller piston area than the drive or low-pressure piston 4. In the embodiment shown, the drive piston 4 is configured to be double-acting with a further high-pressure piston 10 within a high-pressure cylinder 11 on the side of the drive piston 4 facing away from the high-pressure piston 8. The working medium is supplied with an initial pressure via a first supply line 12 to the second cylinder 9 and via a second supply line 13 to the high-pressure cylinder 11. After the compression, the working medium at the final pressure is led off from the second cylinder 9 via a first discharge line 14 and from the high-pressure cylinder 11 via a second discharge line 15. Valves 12a, 13a, 14a, 15a are provided in the supply and discharge lines. In the embodiment shown the first discharge line 14 and the second discharge line 15 are combined in a common discharge line 16. In a single-acting design of the drive piston 4 (not shown) only a first discharge line 14 is provided.

(5) As is further apparent from FIG. 1, the working medium is guided in a closed circuit 17. The closed circuit 17 comprises a first line 18 from the output 2a of the compressor 2 to the first cylinder 5 and a second line 19 (return) from the first cylinder 5 back to the input 2b of the compressor 2. In addition, a control device, in particular a control slider 20 is provided for changing the flow direction of the drive medium in the first cylinder 5. As a result, depending on the position of the control device, the drive piston 4 can be placed under pressure from one side or from the other side so that the switching of the control device brings about the to and fro movement of the drive piston 2. In the embodiment shown, the compressor 2 is designed to be fully hermetic or semi-hermetic. Advantageously gas leaks can thus be reduced.

(6) As is apparent from FIG. 1, the drive medium is guided, when viewed in the flow direction 21 of the drive medium, between the compressor 2 and the first cylinder 5 of the pressure translator 3 via a heat exchanger 22 in which heat exchange is carried out with the compressed working medium. For this purpose, the heat exchanger 22 is connected to the first discharge line 14 and/or to the second discharge line 15, in the case of the double-acting compressor shown to the common discharge line 16. Thus, the heat content of the working medium after compression in the second cylinder 9 can be increased to increase the temperature of the drive medium before entry into the first cylinder 5 for the drive piston 4. It follows from the ideal gas equation (p*V=n*R*T) that the product p*V is increased when the temperature of the compressed drive medium is increased. The work that can be furnished and therefore power at the pressure converter is thereby increased. Thus, for the same work compared to a conventional system less (electrical) drive energy is required for the compressor 2.

(7) In the embodiment shown, a cooler 23 is additionally arranged in the second line 19 in order to achieve a cooling of the drive medium on the way from the first cylinder 5 of the pressure translator 3 back to the compressor 2. The cooler 23 can be configured as a further heat exchanger with a fan 23a. In the embodiment shown a temperature measuring element 26 is additionally provided in the second line 19 which transmits the temperature of the working medium to a control unit 27 which actuates the fan 23a depending on the temperature of the drive medium in the second line 19.

(8) Furthermore, a first buffer storage device 24 is provided between the compressor 2 and the heat exchanger 22 and a second buffer storage device 25 is provided between the cooler 23 and the compressor 2.

(9) For better clarity, only the components required to understand the embodiment shown are depicted in the drawing. Naturally, the compressor device 1 can have various additional components and modifications compared to the embodiment shown.