DEVICE AND METHOD FOR CONVERTING THERMAL ENERGY

Abstract

A device and a method for converting low temperature thermal energy into high temperature thermal energy using mechanical energy with a rotor for a working medium passing through a closed cycle. The rotor has a compressor unit with compression channels and an expansion unit with expansion channels, and has heat exchangers for exchanging heat between the working medium and a heat exchange medium. The device has an impeller which can be rotated relative to the rotor. The impeller is arranged between supply channels 9 which conduct the flow of the working medium in the heat pump and at least one rotor discharge channel which discharges the flow of the working medium in the heat pump. The supply channels have outlet sections which extend up to a point directly upstream of an inlet opening of the impeller such that flows of the working medium are conducted out of the supply channels.

Claims

1. A device for converting thermal energy with a low temperature into thermal energy with a higher temperature and vice versa using mechanical energy, having a rotor rotatably arranged around a rotational axis for a working medium passing through a closed cycle process, wherein the rotor has a compressor unit with multiple compression channels, in which flows of the working medium may be guided substantially radially to the outside with respect to the rotational axis for a pressure increase, and an expansion unit with multiple expansion channels, in which flows of the working medium may be guided substantially radially to the inside with respect to the rotational axis for a pressure decrease, wherein the rotor further has heat exchangers for exchanging heat between the working medium and a heat exchange medium, and having an impeller which can be rotated relatively to the rotor, provided in a heat pump operating state for maintaining the flows of the working medium around the rotational axis of the rotor and/or in a generator operating state for using a flow energy of the working medium, wherein the impeller is arranged between supply channels, which supply the flow of the working medium in the heat pump operating state, and at least one discharge channel of the rotor, which discharges the flow of the working medium in the heat pump operating state, wherein the supply channels have outlet sections which run substantially parallel to the rotational axis and extend up to a point directly upstream of an inlet opening of the impeller such that individual flows of the working medium from the supply channels are guided into the impeller substantially parallel to the rotational axis.

2. The device according to claim 1, wherein the supply channels have supply sections extending substantially in a radial direction, which are arranged between the outlet sections and inner heat exchangers with respect to the rotational axis.

3. The device according to claim 1, wherein the at least one discharge channel is connected to the compression channels, which are connected to outer heat exchangers with respect to the rotational axis.

4. The device according to claim 2, wherein in the radial direction the impeller is arranged closer to the rotational axis than the inner heat exchanger, with the impeller being preferably arranged concentrically around the rotational axis of the rotor.

5. The device according to claim 2, wherein the supply channels have arcuately curved walls at the outlet sections, which cause a deflection of the working medium by substantially 90 from the supply sections into the outlet sections.

6. The device according to claim 2, wherein the outlet sections of the supply channels are formed between separating elements, which extend substantially in the radial and axial direction with respect to the rotational axis.

7. The device according to claim 2, wherein the impeller includes a plurality of blades.

8. The device according to claim 7, wherein the impeller has a radial section free from blades on the side facing the rotational axis.

9. The device according to claim 8, wherein the impeller has an arcuately curved deflection wall on the radial section for deflecting the working medium by substantially 90 in the radial direction.

10. The device according to claim 2, wherein the at least one discharge channel has an inlet section arranged inclined to the radial direction, which is connected to a discharge section extending substantially in the radial direction.

11. The device according to claim 1, wherein the impeller has an impeller shaft that is rotatable parallel to the rotational axis of the rotor and that is connected to a motor or a generator.

12. The device according to claim 11, wherein the motor is arranged for rotation of the impeller in the same direction of rotation as the rotor having the expansion and compression channels for the working medium.

13. The device according to claim 1, wherein at least one inner heat exchanger with respect to the rotational axis and at least one outer heat exchanger with respect to the rotational axis are provided.

14. The device according to claim 13, wherein the number of the inner heat exchangers is a multiple of the outer heat exchangers or vice versa.

15. The device according to claim 13, wherein the at least one inner heat exchanger and the at least one outer heat exchanger extend substantially parallel to the rotational axis while the compression and/or expansion channels extend between the inner heat exchanger and the outer heat exchanger.

16. The device according to claim 1, wherein the impeller has multiple impeller stages through which the working medium may flow sequentially.

17. A method for converting thermal energy with a low temperature into thermal energy with a higher temperature and vice versa using mechanical energy, wherein a working medium passes through a closed cycle process within a rotor rotating around a rotational axis, wherein multiple flows of the working medium are guided substantially radially to the outside with respect to the rotational axis for a pressure increase, wherein the flows of the working medium are guided substantially radially to the inside with respect to the rotational axis for a pressure decrease, wherein heat is exchanged between the working medium and a heat exchange medium, with the working medium being guided around the rotational axis of the rotor in a heat pump operating state for maintaining the flows of the working medium and/or through an impeller in a generator operating state for using the flow energy of the working medium, wherein in the heat pump operating state individual flows of the working medium are guided up to a point directly upstream of the impeller and introduced into the impeller substantially parallel to the rotational axis.

18. The method according to claim 17, wherein the impeller is rotated in the same direction of rotation as the rotor and at a higher absolute speed than the rotor having the expansion channels and compression channels.

19. The device according to claim 7, wherein the plurality of blades are arcuately curved blades.

20. The device according to claim 13, wherein both multiple inner heat exchangers and outer heat exchangers are provided.

Description

[0036] The invention will be explained in more detail below by means of exemplary embodiments illustrated in the drawings, however without being limited to them. Individually, in the drawings:

[0037] FIG. 1 schematically shows a diagrammatic view of a device according to the invention for converting thermal energy, in which a working medium in a rotor passes through a closed cycle process, wherein the cycle process is closed by means of a rotating impeller;

[0038] FIG. 2 shows a longitudinal section through the device of FIG. 1, wherein only the parts relevant for the function of the impeller are shown for the sake of clarity;

[0039] FIG. 2a shows a temperature/entropy diagram of the cycle process performed in the device according to the invention;

[0040] FIG. 3 shows a longitudinal section of the device according to FIGS. 1, 2 in the region of the impeller;

[0041] FIG. 4 shows a transverse section of the device according to line IV-IV in FIG. 2 in the region of the impeller, wherein both the outlet sections of the supply channels and the inlet sections of the discharge channels are to be seen;

[0042] FIG. 5 shows a schematic diagrammatic view of parts of the rotor in the region of the supply channels, which have outlet sections extending in the axial direction upstream of the inlet point into the impeller;

[0043] FIG. 6 schematically shows a diagrammatic view of the impeller of the device illustrated in FIGS. 1 to 5; and

[0044] FIG. 7 shows a longitudinal section of the device according to FIG. 3 in the region of the impeller, which has multiple impeller stages for a sequentially flow-through in this embodiment.

[0045] FIG. 1 shows a device 20 for converting thermal energy using mechanical energy and vice versa, which is used as a heat pump in the embodiment shown. The device 20 includes a rotor 21 which is rotatable around a rotational axis 22 by means of a motor (not illustrated). The rotor 21 includes a compressor unit 23 and an expansion unit 24, which have flow channels for a working medium. When flowing through the rotor 21, the working medium, for example a noble gas, passes through a closed cycle process, which includes the working steps of a) compression of the working medium, b) heat exchange between the working medium and a heat exchange medium in an outer heat exchanger 1, c) expansion of the working medium, and d) heat exchange between the working medium and a heat exchange medium in an inner heat exchanger 1. For this purpose, the compressor unit 23 has compression channels 25 extending substantially in the radial direction, in which the working medium flows to the outside in the radial direction with respect to the rotational axis 22. Due to centrifugal acceleration, the working medium is compressed in the compression channels 25. Correspondingly, the working medium is guided substantially radially to the inside in expansion channels 26 of the expansion unit 24 in order to decrease the pressure.

[0046] The compressor unit 23 and the expansion unit 24 are connected to one another by flow channels extending axially, i. e. in the direction of the rotational axis 22, in which heat exchange between the working medium and a heat exchange medium, for example water, takes place. For this purpose, outer heat exchangers 1 and inner heat exchangers 1 with respect to the rotational axis are provided, extending substantially parallel to the rotational axis 22. When the device 20 is operated as a heat pump, the working medium in the outer heat exchangers 1, which has been compressed in the compression channels 25, transfers heat to a heat exchange medium with a first, comparably high temperature while the working medium which has been expanded in the expansion channels 26 receives heat from the heat exchange medium with a second, comparably low temperature.

[0047] According to this, the centrifugal acceleration acting on the working medium is used to generate various pressure levels and/or temperature levels. High temperature heat is extracted from the compressed working medium, and heat having a comparably low temperature is supplied to the expanded working medium. When operating the device 20 as a motor, the working medium flows through the flow channels in an opposite direction. Correspondingly, the heat exchange is changed, with heat being supplied to the working medium at the outer heat exchanger 1 and heat being extracted from the working medium at the inner heat exchanger 1.

[0048] As can further be seen from FIG. 1, multiple inner heat exchangers 1, twelve in the embodiment shown, and multiple outer heat exchangers 1, twelve in the embodiment shown, are provided, arranged in regular angular distances with respect to the rotational axis. The inner heat exchangers 1 and the outer heat exchangers 1 each extend substantially parallel to the rotational axis 22, with the compression 23 and the expansion channels 25 extending between the inner heat exchangers 1 and the outer heat exchangers 1.

[0049] In FIG. 2, parts of the device 20 are shown in a longitudinal section, wherein only one of the inner heat exchangers 1 and one of the outer heat exchangers 1 are depicted. Moreover, an impeller 30 for maintaining the flow of the working medium around the rotational axis 22 in the embodiment shown can be seen in FIG. 2. On one side, the impeller 30 is connected to supply channels 31 for receiving the working medium from the inner heat exchangers 1. Furthermore, the impeller 30 is connected to discharge channels 32 for guiding the working medium into the compression channels 25 of the compressor unit 23. The compression channels 25 are connected to the outer heat exchangers 1.

[0050] As can further be seen from FIG. 2, in the radial direction the impeller 30 is arranged closer to the rotational axis 22 than the inner heat exchanger 1. In the embodiment shown, the rotational axis of the impeller 30 is arranged flush on top of the rotational axis 22 of the rotor 21 in order to reduce the loads due to centrifugal acceleration acting on the suspension of the shaft of the impeller 30.

[0051] FIG. 2a shows a diagram of temperature (T) and entropy (S), in which the individual states of the working medium are designated by Z1 to Z7. Correspondingly, the positions within the device 20 where the working medium substantially reaches the states Z1 to Z7 are marked in FIG. 2. According to this, the following process steps are passed through during operation as a heat pump (during operation as a thermal engine the cycle process would be performed in reverse order):

[0052] 1 to 2: substantially isentropic compression due to the main rotation from the radius Z1 of the heat exchanger 1 near the axis to the radius Z2 of the heat exchanger 1 far from the axis;

[0053] 2 to 3: substantially isobaric heat transfer from the working medium to the heat exchange medium in the outer heat exchanger 1 at a comparably high temperature and consistent radius of the flow;

[0054] 3 to 4: substantially isentropic expansion due to the main rotation from the radius of the outer heat exchanger 1 to the radius of the inner heat exchanger 1;

[0055] 4 to 5: substantially isobaric heat transfer at a comparably low temperature and consistent radius in the inner heat exchanger 1;

[0056] 5 to 6: substantially isentropic expansion due to the main rotation from the radius of the inner heat exchanger to the inlet radius of the impeller;

[0057] 6 to 7: compression within the impeller, wherein the losses cause an increase in entropy; and

[0058] 7 to 1: substantially isentropic compression due to the main rotation from the outlet of the impeller to the radius according to state Z1.

[0059] As can be seen from FIG. 3, the supply channels 31 have outlet sections 34 running substantially parallel to the rotational axis 22 and extending up to a point directly upstream of an inlet opening 33 of the impeller 30 such that the flows of the working medium can be guided into the impeller 30 separated from one another in the supply channels 31 and substantially parallel to the rotational axis 22.

[0060] As can further be seen from FIG. 3, the supply channels 31 have supply sections 35 extending substantially in the radial direction, which are arranged between the outlet sections 34 terminating in the impeller 30 and the inner heat exchangers 1. The discharge channels 32 are connected to the compression channels 25, which guide the working medium to the outer heat exchangers 1.

[0061] As can be seen from FIG. 3, in particular, the supply channels 31 have arcuately curved walls 36 at the outlet sections 34, which cause a deflection of the working medium by substantially 90 from the radial supply sections 35 into the axial outlet sections 34.

[0062] As can be seen from FIG. 4, in particular, the outlet sections 34 of the supply channels 31 are delimited by separating elements 37 extending substantially in the radial and axial direction with respect to the rotational axis 22, which are formed by substantially even separating walls in the embodiment shown. The separating elements 37 have a radial extension and are arranged in a star pattern. In the embodiment shown, the outlet sections 34 are thus arranged regularly and in consistent radial distances around the rotational axis 22 of the rotor 21.

[0063] As can further be seen from FIG. 4, the impeller 30 has a plurality of arcuately curved blades 38 for accelerating the working medium in the direction of rotation 39 of the impeller 30 while it flows through the impeller 30. On the side facing the rotational axis 22, the impeller 30 has a radial section 40 free from blades 38, in which the flows of the working medium from the supply channels 31 are combined and homogenised. On the radial section 40 an arcuately curved deflection wall 41 is provided (cf. FIG. 3) for deflecting the working medium by substantially 90 from the axial flow when entering the impeller 30 to a radial flow in front of the blades 38.

[0064] As can be seen from FIG. 4, the discharge channels 32 include inlet sections 42 extending inclined to the radial direction with respect to an enclosure of the impeller 30, i. e. with respect to the outer surface of the impeller 30 having a circular cross-section, which inlet sections are connected to discharge sections 43 extending substantially in the radial direction.

[0065] As can be seen schematically from FIGS. 4, 6, the impeller 30 includes an impeller shaft 44 which is connected to a motor (not shown). The motor is configured to rotate the impeller 30 in the direction of rotation 45 of the rotor 21. In the embodiment shown, the rotational axis of the impeller 44 and the rotational axis 22 of the rotor 21 coincide. During operation as a thermal engine, a generator is connected to the impeller 30, which acts as a turbine in this case. When an adequate mass flow passes through the turbine, it converts a resulting differential pressure into shaft power.

[0066] As can be seen from FIG. 5, the device 20 has dynamical sealing gaps 46 intended to minimise back flows due to increased pressure at the outlet of the impeller 30 with respect to the inlet. Matching ribs 47 of the impeller 30 engage the sealing gaps 46 in order to provide multiple gaps that are as small as possible.

[0067] FIG. 7 shows an alternative embodiment in which the single impeller 30 has multipletwo in the embodiment shownimpeller stages 30, 30 for sequential flow-through. The impeller stages 30, 30 are connected to one another via a deflection 30 for deflecting the working medium, after the first impeller stage 30, from a flow radially to the outside first to a flow radially to the inside and then to a flow in the direction of the rotational axis 22 to a point directly upstream of the second impeller stage 30. Each impeller stage 30, 30 is designed according to the single-stage design of FIGS. 1 to 6. In the embodiment shown, the impeller stages 30, 30 are arranged on the same impeller shaft 44, which is connected to a motor or a generator. Alternatively, the impeller stages 30, 30 may be arranged on separate impeller shafts, with each impeller stage 30, 30 being connected to a motor and/or a generator.