WO2010070034A2

WO2010070034A2 - Method for utilizing heat

Info

Publication number: WO2010070034A2
Application number: PCT/EP2009/067380
Authority: WO
Inventors: Christian VÖLKL; Leopold Kehrein
Original assignee: Htps Hirschmanner Kg
Priority date: 2008-12-18
Filing date: 2009-12-17
Publication date: 2010-06-24
Also published as: AT507217B1; EP2376838A2; WO2010070034A3; AT507217A4

Abstract

The invention relates to a method for utilizing heat, in which a working medium inside a rapidly rotating rotor (5) is brought into thermal contact with an inner heat transfer surface (6a) of an annular gas chamber (6) in order to dissipate heat at a low temperature and in which a working medium is brought into contact with an outer heat transfer surface (6b) of the annular gas chamber (6) in order to absorb heat at a higher temperature. An improved efficiency is achieved in that the heat transfer in the area of the inner heat transfer surface (6a) is performed through thermal radiation preferably by way of radial lamellae (9, 10) which are in thermal connection with the gas chamber (6) on one side and with the working medium on the other. The invention further relates to a device for carrying out the method.

Description

Method of using heat

The invention relates to a method for using heat, in which a working medium is brought inside a fast rotating rotor in thermal contact with an inner heat transfer surface of an annular gas space to give off heat at a low temperature and in which a working medium with an outer heat transfer surface of the annular gas space is brought to absorb heat at a higher temperature.

Methods of utilizing the heat in the above sense can be roughly classified into cycles for obtaining mechanical work from heat energy and heat energy conversion processes, for example, a heat pump in which heat is transferred from one temperature level to another temperature level. Applicants have developed such methods using high speed centrifuges having a substantially annular gas space. Such a method is disclosed, for example, in WO 2005/049973 A. Further known methods can be taken from DE 38 12 928 A or DE 38 07 783 A.

In order to use such methods economically, extremely high speeds of the centrifuge are required and it is necessary to keep the friction losses as low as possible. Moreover, high demands are placed on the heat transfer, so that the realization of such methods is difficult.

The object of the present invention is to further develop a method of the type described above, in particular as described in the first-mentioned document of the present application, in such a way that optimum efficiencies and a possibility of economic application are achieved. Another object of the present invention is to provide an apparatus for carrying out such a method which satisfies the above criterion.

According to the invention these objects are achieved in that the heat transfer in the region of the inner heat transfer surface by heat radiation, preferably via radial lamellae takes place, which are thermally connected on the one hand with the gas space and on the other hand with the working medium.

Generally, in thermal engines, heat transfer is accomplished primarily by heat conduction and convection. Heat conduction takes place, for example, in the heat transfer surfaces of heat exchangers, as convection, the heat transfer by movement of a working medium or War- meträgermediums called. In general, this is forced convection, in which the heat transfer medium is moved by pumping. For most practical applications realized so far, these heat transport mechanisms have proven to be efficient and practical. It has been found, however, that problems occur in processes of the type described above in connection with the high-speed centrifuge, which hinder a practical conversion to economic conditions.

Surprisingly, these problems can be avoided by using a heat transfer by radiation, at least in the area of the inner heat transfer surface. In this way, the losses can be substantially reduced by mechanical friction, which improves the overall efficiency accordingly. To compensate for the smaller amount of heat that can be transmitted by radiation, it is particularly advantageous if the heat transfer surfaces are formed as radial lamellae, so that the transfer surfaces are increased accordingly. An additional advantage of the transmission via radial lamellae is that the distances between the heat transfer surfaces can be kept very low.

As already stated above, the method of the type described above can be configured as a thermal power process in which mechanical work is obtained by circulating the working medium in which it is first cooled at the inner heat transfer surface, then compressed, thereafter the outer heat transfer surface is heated and then relaxed to obtain mechanical work.

Alternatively, however, it is also possible for the working medium to be circulated, where it is first cooled at the inner heat transfer surface, then preferably heated in an ambient heat exchanger, then further heated at the outer heat transfer surface, and then the heat to a consumer emits. Such a process corresponds to that of a heat pump. In the case of cooling demand, the working medium after flowing through the inner heat transfer surface can of course also be used for cooling.

A particularly simple and efficient embodiment variant of the method according to the invention is ensured if the working medium is guided essentially in the axial direction through the rotor. It is particularly advantageous if a temperature difference of at least 100 K, preferably of at least 300 K and particularly preferably of at least 500 K is built up in the rotor. In this way, high efficiencies are achieved. Furthermore, the present invention relates to a device for using heat in mechanical work, with a rotor in which a substantially annular gas space is arranged, on the inner circumference of a first heat exchanger is provided and on the outer periphery of a second heat exchanger is provided. According to the invention, it is provided that the first heat exchanger has fixed heat exchanger surfaces and rotating heat exchanger surfaces, between which heat is transferred primarily by radiation. A device according to the invention has a high efficiency thanks to the lowest possible mechanical losses. Is particularly favorable - as stated above - when the stationary heat exchanger surfaces and the rotating heat exchanger surfaces are formed as radial lamellae, which are arranged intermeshing. It is particularly advantageous if first fins are firmly connected to a rigid longitudinal axis and if second fins are connected to the inner wall of the gas space. In this way, a particularly robust and simple mechanical construction is achieved. Advantageously, the working medium flows through the rigid longitudinal axis in the longitudinal direction.

The surfaces of the lamellae are preferably formed profiled, for example in the form of small pyramidal elevations, which serves to increase the surface for radiation transmission.

In order to minimize the mechanical resistances, it is furthermore of particular advantage if the interstices between the stationary heat exchanger surfaces and the rotating heat exchanger surfaces are evacuated, the pressure in the interspaces preferably being less than 1 mbar, preferably less than 0.1 mbar. Although the evacuation reduces the convective heat transfer between the heat transfer surfaces to almost zero, this is certainly intended in the sense of the present invention, since the heat transfer is supposed to take place primarily by radiation. At the same time, however, the losses due to the viscosity of the air are correspondingly reduced, which results in the advantages described above.

Analogously to the conditions at the first heat exchanger, it is likewise of particular advantage if the second heat exchanger has stationary heat exchanger surfaces and rotating heat exchanger surfaces, between which heat is transferred primarily by radiation. Again, the reduction of friction losses in the foreground. At this point, it is provided according to a preferred embodiment of the invention that the stationary heat exchanger surfaces and the rotating heat exchanger surfaces of the second heat exchanger is provided with a surface enlarging structure, which is designed approximately with small pyramidal elevations. It is also possible that the stationary heat exchanger surfaces and the rotating heat exchanger surfaces of the second heat exchanger are formed frusto-conical surfaces which are directed towards each other. It has been found that frusto-conical surfaces are particularly suitable here to increase the heat transfer surfaces accordingly. In order to keep the mechanical loads due to the centrifugal forces low, but apart from the use of fins at this point, in order not to limit the achievable speeds. The somewhat unfavorable geometry of the frusto-conical heat exchanger surfaces in comparison to the lamellae is not significant here, because due to the larger peripheral surface on the outside of the rotor more area is available anyway and on the other hand correspondingly improves the heat transfer by radiation due to the higher temperatures present here is. But even in this area, it is advantageous if the spaces between the stationary heat exchanger surfaces and the rotating heat exchanger surfaces of the second heat exchanger are evacuated, wherein the pressure is preferably less than 1 mbar, preferably less than 0.1 mbar.

A further reduction of the friction losses can be achieved by supporting the rotor via magnetic bearings.

As a result, the present invention will be explained in more detail with reference to the embodiments illustrated in FIGS. Show it :

Fig. 1 shows schematically a first embodiment of the device according to the invention in section; and

Fig. 2 shows a detail of another embodiment.

The apparatus of Fig. 1 generally consists of a centrifuge 1 with a fixed housing 2 and a rigid axle 3 arranged in the housing 2.

On the axle 3, a fast-running rotor via the magnetic bearing 4 mounted, which typically rotates at a rotational speed of 50,000 min ^{". 1} in the rotor 5, an annular gas chamber 6 is arranged, which comprises an inner heat transfer surface 6a and an outer heat transfer surface 6b. Within the inner heat transfer surface 6a, a first heat exchanger 7 is arranged, which consists of intermeshing arranged fins 9, 10. In this case, first fins 9 are fixedly connected to the longitudinal axis 3, while second fins 10 are formed as parts of the rotor 5 and with the inner wall of the gas space The intermediate space 11 between the lamellae 9, 10 is made as small as possible taking into account the achievable tolerances and to a pressure of less than 10 ^-3 mbar, preferably less than 10 ^"4 mbar and particularly preferably less than 10 ^{" 5} mbar evacuated. The stationary heat exchanger surfaces 9a of the first fins 9 are thus thermally in contact with the rotating heat exchanger surfaces 10a of the second fins 10 by thermal radiation.

The supply of heat into the device takes place via a working medium which flows in a longitudinally extending flow channel 12 within the longitudinal axis 3 in the longitudinal direction. On the outside of the housing 2, a further heat exchanger 8 is provided for dissipating the heat, as indicated by the arrows 13. This can be done for example via a liquid heat exchanger, not shown here.

2, a particularly advantageous embodiment of the second heat exchanger 8 is shown. In this case, frustoconical surfaces 14 are formed on the rotor 5 and are in thermal contact via thermal radiation corresponding to the arrows 15 with associated truncated conical surfaces 16 of the housing 2.

In the embodiment of Fig. 1, the slats 9, 10 are shown as substantially cylindrical discs. It is alternatively also possible within the scope of the invention for the lamellae 9, 10 to be tapered at their respective ends in longitudinal section. The heat transfer surfaces 6a, 6b are shown in FIG. 1 smooth, but it is also possible here to improve the heat transfer to provide a corresponding profiling. The gas space 6 is preferably filled with a gas of higher atomic mass or molecular mass, such as argon or halogenated hydrocarbons. In particular, it is advantageously possible to use gas mixtures of gases with different atomic masses or molecular masses. In the static case, ie when the rotor is not rotating, the pressure is in the range from 1 bar to 20 bar. In a rotor having an outer diameter of 300 mm can typically speeds of 50,000 min ^{"are 1} is achieved.

The present invention makes it possible to present heat engines and heat pumps with particularly high efficiencies.

Claims

PATENT CLAIMS

A method of utilizing heat in which a working medium inside a high-speed rotor (5) is brought into thermal contact with an inner heat transfer surface (6a) of an annular gas space (6) to discharge heat at a low temperature and in which a working medium with an outer heat transfer surface (6b) of the annular gas space (6) is brought to receive heat at a higher temperature, characterized in that the heat transfer in the region of the inner heat transfer surface (6a) by thermal radiation preferably via radial blades (9, 10 ) takes place, on the one hand with the gas space (6) and on the other hand with the working medium thermally in communication.

2. The method according to claim 1, characterized in that the working medium is guided in a circuit in which it is first cooled at the inner heat transfer surface (6a), then compressed, then at the outer heat transfer surface (6b) is heated and then under Gaining mechanical work is relaxed.

3. The method according to claim 1, characterized in that the working medium is guided in a circuit in which it is first cooled on the inner heat transfer surface (6a), then preferably in an ambient heat exchanger is heated, then on the outer heat transfer surface (6b) on is heated and then gives the heat to a consumer.

4. The method according to any one of claims 1 to 3, characterized in that the working medium is guided substantially in the axial direction by the rotor (5), wherein it is preferably guided by a fixed axis (3).

5. The method according to any one of claims 1 to 4, characterized in that in the rotor (5) between the inner heat transfer surface (6a) and the outer heat transfer surface (6b) has a temperature difference of at least 100 K, preferably at least 300 K and more preferably of at least 500 K is built.

6. A device for using heat in mechanical work, with a rotor (5) in which a substantially annular gas space (6) is arranged, on the inner circumference of a first heat exchanger (7) is provided and on the outer circumference of a second Heat exchanger (8) is provided, characterized in that the first heat exchanger (7) stationary heat exchanger surfaces (9a) and rotating heat exchanger surfaces (10a), between which the heat transfer takes place primarily by radiation.

7. The device according to claim 6, characterized in that the stationary heat exchanger surfaces (9a) and the rotating heat exchanger surfaces (10a) as a radial blades (9, 10) are formed, which are arranged interdigitated.

8. The device according to claim 7, characterized in that first lamellae (9) are fixedly connected to a rigid longitudinal axis (3) and that second lamellae (10) are connected to the inner wall (6a) of the gas space (6).

9. Apparatus according to claim 8, characterized in that the rigid longitudinal axis (3) has a flow channel (12) for a working medium, which can be flowed through in the longitudinal direction.

10. Device according to one of claims 6 to 9, characterized in that the intermediate spaces (11) between the stationary heat exchanger surfaces (9a) and the rotating heat exchanger surfaces (10a) are evacuated, wherein the pressure in the intermediate spaces (11) is preferably smaller than 1 mbar, preferably less than 0.1 mbar.

11. The device according to one of claims 6 to 10, characterized in that the second heat exchanger (8) stationary heat exchanger surfaces (16) and rotating heat exchanger surfaces (14), between which the heat transfer takes place primarily by radiation.

12. The apparatus according to claim 11, characterized in that the stationary heat exchanger surfaces (16) and the rotating heat exchanger surfaces (14) of the second heat exchanger (8) as a frusto-conical surfaces (14, 16) are formed, which are directed against each other.

13. The apparatus of claim 11 or 12, characterized in that the stationary heat exchanger surfaces (16) and the rotating heat exchanger surfaces (14) of the second heat exchanger (8) with a the surface enlarging structure is provided, which is preferably designed with small pyramidal elevations.

14. Device according to one of claims 11 to 13, characterized in that the intermediate spaces between the stationary heat exchanger surfaces and the rotating heat exchanger surfaces of the second heat exchanger (8) are evacuated, wherein the pressure is preferably less than 1 mbar, preferably less than 0.1 mbar.

15. Device according to one of claims 6 to 14, characterized in that the rotor is mounted on magnetic bearings.