PRESSURE CONTROL FOR CLOSED BRAYTON CYCLES

Abstract

An apparatus includes a closed gas system having: a working circuit in which a compressor for a working fluid, a first heat exchanger for heating the working fluid, an expander and a second heat exchanger for cooling the working fluid are arranged; a first pressurised gas tank and a first gas pipe which branches off from the working circuit between the compressor and the first heat exchanger and opens into the first pressurised gas tank; and a second gas pipe which branches off from the first pressurised gas tank and opens into the working circuit between the expander and the second heat exchanger. A method controls pressure in a closed gas system using the apparatus.

Claims

1. An apparatus, comprising: a closed gas system with a working circuit, in which a compressor for a working fluid, a first heat exchanger for heating the working fluid, an expander and a second heat exchanger for cooling the working fluid are arranged, a first pressurized gas tank and a first gas line, which branches off from the working circuit between the compressor and the first heat exchanger and opens into the first pressurized gas tank, and a second gas line, which branches off from the first pressurized gas tank and opens into the working circuit between the expander and the second heat exchanger.

2. The apparatus as claimed in claim 1, further comprising: a third gas line which branches off from the first pressurized gas tank or from the second gas line and opens into the working circuit between the compressor and the first heat exchanger.

3. The apparatus as claimed in claim 2, further comprising: a third heat exchanger which is arranged in the first gas line.

4. The apparatus as claimed in claim 3, further comprising: a first valve which is arranged in the first gas line downstream of the third heat exchanger in a direction of flow of the working fluid.

5. The apparatus as claimed in claim 3, further comprising: a first valve which is arranged in the first gas line upstream of the third heat exchanger in a direction of flow of the working fluid.

6. The apparatus as claimed in claim 3, further comprising: a fourth heat exchanger which is arranged in the second gas line and a fifth heat exchanger which is arranged in the third gas line.

7. The apparatus as claimed in claim 6, further comprising: at least one thermal store which is connected by switchable connecting lines to the third heat exchanger, the fourth heat exchanger or the fifth heat exchanger.

8. The apparatus as claimed in claim 1, wherein working fluid is replenished between the expander and the second heat exchanger.

9. The apparatus as claimed in claim 1, further comprising: at least one second pressurized gas tank which is connected in parallel with the first pressurized gas tank and the first and second pressurized gas tanks are operable at different pressure levels.

10. The apparatus as claimed in claim 9, wherein the compressor comprises at least two compressor stages and a fifth gas line branches off from the working circuit between two compressor stages and opens into at least one of the first and second pressurized gas tanks.

11. A method for pressure control in a closed gas system, wherein a working fluid is compressed, heated, expanded and cooled repeatedly one after the other in a working circuit, the method comprising: removing and storing a partial stream of the working fluid from the working circuit, or incorporating a stored amount of working fluid again into the working circuit, wherein the stored amount of the working fluid is incorporated into the working circuit between expanding and cooling of the working fluid in the working circuit.

12. The method as claimed in claim 11, wherein the working fluid is removed from the closed gas system once it has been at least partially compressed and before it is heated by heat exchange.

13. The method as claimed in claim 11, wherein the removed working fluid is cooled before it is stored.

14. The method as claimed in claim 13, wherein, in case of a positive Joule-Thomson coefficient, the working fluid is first cooled by a heat exchange and then expanded by a valve into a pressurized gas tank and, wherein in case of a negative Joule-Thomson coefficient, the working fluid is first expanded by the valve and then cooled by the heat exchange and then stored.

15. The method as claimed in claim 11, wherein the working fluid is heated before it is incorporated again into the working circuit.

16. The method as claimed in claim 13, wherein a thermal store is charged during the cooling of the working fluid and discharged during the heating of the working fluid.

17. The method as claimed in claim 11, wherein working fluid removed from the working circuit at different pressures is fed to different pressurized gas tanks.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is explained in more detail by way of example on the basis of the drawings, in which schematically and not to scale:

[0031] FIG. 1 shows the basic concept for a closed gas system with pressure control according to the invention and

[0032] FIG. 2 shows a closed gas system with various developments of the basic concept of FIG. 1.

DETAILED DESCRIPTION OF INVENTION

[0033] FIG. 1 shows schematically and by way of example an apparatus 1 comprising a closed gas system 2 with a working circuit 3, in which a compressor 4 for a working fluid, a first heat exchanger 5 for heating the working fluid, an expander 6 (gas expansion turbine) and a second heat exchanger 7 for cooling the working fluid are arranged.

[0034] In the exemplary embodiment of FIG. 1, a first gas line 9 branches off from the working circuit 3 between the compressor 4 and the first heat exchanger 5 and opens into the first pressurized gas tank 8. Furthermore, a second gas line 10 branches off from the first pressurized gas tank 8 and opens into the working circuit 3 between the expander 6 and the second heat exchanger 7.

[0035] Since leakages are inevitable, the working fluid can be replenished between the expander 6 and the second heat exchanger 7. The replenishment with the replenishing point 21, the replenishing line 22 and the replenishing pump 23 is used to compensate for the normal loss of gas in the system.

[0036] FIG. 2 shows some extensions of the basic concept shown in FIG. 1, which can be used either on their own or in combination. For example, a third gas line 11 branches off from the first pressurized gas tank 8 or from the second gas line 10 and opens into the working circuit 3 between the compressor 4 and the first heat exchanger 5.

[0037] Furthermore, the exemplary embodiment of FIG. 2 shows three further heat exchangers. A third heat exchanger 12, arranged in the first gas line 9, cools the gaseous working fluid, whereas a fourth heat exchanger 14 in the second gas line 10 and a fifth heat exchanger 15 in the third gas line 11 serve for heating the working fluid.

[0038] With respect to the storing of the working fluid in the first pressurized gas tank 8, FIG. 2 shows a first valve 13 in the first gas line 9, which is arranged downstream of the third heat exchanger 12 in the direction of flow of the working fluid. This is the relative arrangement of the two components for the case where the working fluid cools down during the expansion. If the working fluid heats up during the expansion, the arrangement of the valve 13 and the third heat exchanger 12 is changed over. This is indicated in FIG. 2 by a dashed double-headed arrow.

[0039] In addition to the first pressurized gas tank 8 already known from FIG. 1, the exemplary embodiment of FIG. 2 has a second pressurized gas tank 19, which is connected in parallel with the first pressurized gas tank 8. A corresponding second valve 20 is also shown in FIG. 2. Typically, the pressurized gas tanks 8, 19 can be operated at different pressure levels.

[0040] Although the presence of two compressor stages 17 at the compressor 4 is not absolutely necessary for the storing of the working fluid at different pressures (it can be imagined that, after a first removal of fluid from the store into the first pressurized gas tank 8, the system pressure has fallen and consequently a second removal of fluid from the store into the second pressurized gas tank 19 takes place at a lower pressure), it does make optimizations easier. This is supplemented by a fifth gas line 18, which branches off from the circuit 3 between two compressor stages 17 and opens into at least one of the pressurized gas tanks 8, 19.

[0041] An advisable addition to the concept presented is the installation of a thermal store 16, which is connected by way of switchable connecting lines A, B, C to the third heat exchanger 12, fourth heat exchanger 14 or fifth heat exchanger 15.