WO2013092849A1

WO2013092849A1 - Heat pump

Info

Publication number: WO2013092849A1
Application number: PCT/EP2012/076365
Authority: WO
Inventors: Urban Kronstrom; Simon Klink; Dennis Pfeil
Original assignee: Robert Bosch Gmbh
Priority date: 2011-12-21
Filing date: 2012-12-20
Publication date: 2013-06-27
Also published as: EP2795209A1; DE102011121859A1; CN104114962A; EP2795209B1; DE102011121859B4

Abstract

The invention relates to a heat pump (2), which can be changed over between cooling mode and heating mode, having a first heat exchanger (4), a second heat exchanger (6), two compressor stages (8, 10) for compressing a medium and a medium pressure bottle (12), inserted between the compressor stages (6, 8) and the second compressor stage (10) for phase separation of the fluid medium. Downstream of the second compressor stage (8), a changeover valve (16) is arranged, by means of which a flow connection between the second compressor stage (8) and the second heat exchanger (6) can be established in cooling mode, and a flow connection between the second compressor stage (8) and the first heat exchanger (4) can be established in heating mode.

Description

DESCRIPTION Heat pump

The invention relates to a heat pump which can be switched between cooling mode and heating mode, which has a first heat exchanger and a second heat exchanger, between which energy can be transmitted in one or the other direction and a compressor assembly.

Heat pumps of the type mentioned are known in the art. Such heat pumps serve to transport heat energy from a first reservoir to a second reservoir by using labor. Heat pumps are usually operated with fluids that evaporate at low pressure with heat and condense again after compression to a higher pressure with heat release. The pressures are selected so that the temperatures of the phase change have sufficient for the heat transfer distance to the temperatures of the heat sources or sinks.

Heat pumps work in their simplest embodiment with a fluid circuit with an evaporator in which the fluid or medium vaporizes energy, a downstream, driven compressor in which the medium is compacted with the introduction of mechanical work, a subsequent condenser, in which the fluid below Loss of energy is liquefied and last of the condenser downstream throttle in which relaxes the fluid. The throttle is the output side again connected to the evaporator, whereby the circuit is closed.

In addition, reversible heat pumps are known in which the two heat exchangers provided are interconnected once as a condenser or evaporator or vice versa, as an evaporator and condenser.

The efficiencies and performance figures of conventional reversible heat pumps are technically limited. It would be desirable to improve the efficiencies or performance figures of heat pumps. The object of the invention is to provide a reversible heat pump with a large temperature increase, which has a higher efficiency or a higher coefficient of performance than conventional known reversible heat pumps.

The object is achieved by a heat pump according to claim 1. Further embodiments of the invention are the subject of the dependent claims.

A heat pump according to the invention, which can be switched between cooling mode and heating mode, has a first heat exchanger for receiving energy in cooling mode and for emitting energy in heating mode, which is thermally coupled to the object to be cooled or heated. A second heat exchanger is provided for delivering energy in the cooling mode and for receiving energy in the heating mode, which serves as a heat sink or as a heat source.

For compressing a fluid or a medium, a first compressor stage and a second compressor stage connected downstream of the first compressor stage are provided which further compresses the medium pre-compressed in the first compressor stage. This allows a higher degree of compaction and the two-stage compression a larger temperature stroke is realized, which in turn can be achieved higher condensation temperatures.

The pressure level at the outlet of the first compressor stage corresponds to the pressure level at the inlet of the second compressor stage.

Between the first compressor stage and the second compressor stage, a medium-pressure cylinder is interposed, in which a phase separation of liquid medium and separation of the liquid medium takes place. The hot gas rising in the medium-pressure cylinder and precompressed by the first compressor stage is then further compressed and superheated in the second compressor stage, which is connected upstream of the medium-pressure cylinder.

According to the invention it is further provided that the second compressor stage downstream of a switching valve is connected, by means of which in the cooling operation, a flow connection between the second compressor stage and the second heat exchanger and in the heating operation between the second compressor stage and the first heat exchanger can be produced. In this way it can be achieved that the heat exchangers, depending on the desired mode of operation, alternately operated either as an evaporator or as a capacitor.

According to a first possible further embodiment, an internal heat exchanger may be provided, the first stream of the medium-pressure bottle is removed and the first compressor stage is connected upstream, and the second stream is removed before the compressor and a liquid outlet of the medium-pressure bottle is connected downstream, so that in the medium-pressure bottle separated and discharged via the liquid outlet of the medium-pressure cylinder liquid medium emits energy to the gas flowing into the first compressor stage. In this way, an additional overheating of the medium to be compressed can be achieved.

According to another possible embodiment of the invention, it can be provided that the changeover valve has four connections, wherein a first connection to the first compressor stage, a second connection to the first heat exchanger, a third connection to the first compressor stage or, if provided, to the heat exchanger and a fourth port is flow connected to the second heat exchanger.

In the context of this embodiment, an interconnection can be provided such that in the cooling mode the second compressor stage with the first heat exchanger and the first heat exchanger with the first compressor stage or, if provided, are flow connected to the heat exchanger, whereas in the heating mode, the second compressor stage with the first heat exchanger and the second heat exchanger with the first compressor stage or with the heat exchanger fluidly connected. In this way, a spatially concentrated switchover between heating mode and cooling mode can be achieved in a simple manner.

According to a further possible embodiment of the invention, a switching device may be provided which supplies the medium from the first heat exchanger or from the second heat exchanger and by means of one of the heat exchanger downstream expansion valve to a medium pressure relaxed medium of a connection between the first compressor stage and medium-pressure bottle, so that the from the first compressor stage pre-compressed medium and the medium from the respective high-pressure stage, which is relaxed to medium pressure, mixed and fed to the medium-pressure bottle, where then takes place a phase separation of the medium.

According to a further possible embodiment of the invention can be provided that the switching device has four terminals, wherein a first connection means of the first expansion valve with the first heat exchanger, a second connection by means of a second expansion valve with the second heat exchanger, a third connection to the heat exchanger and a fourth connection is fluidly connected to the connection between the first compressor stage and the medium-pressure cylinder.

By means of the switching device, the second heat exchanger by means of the second expansion valve with the connection between the first compressor stage and medium-pressure cylinder and the internal heat exchanger with the first heat exchanger by means of the first expansion valve is fluidly connected in the cooling mode. Here, in the heating mode, the first heat exchanger by means of the first expansion valve with the connection between the first compressor stage and medium-pressure cylinder and the internal heat exchanger to the second heat exchanger by means of the second expansion valve fluidly connected. In this way, it is possible to switch between cooling and heating operation at a single location, which reduces space requirements and component costs.

According to another possible embodiment of the invention can be provided that the first compressor stage and the second compressor stage are arranged in a common compressor. The two compressor stages can then be arranged, for example, on a common shaft, with the medium pre-compressed by the first compressor stage being led out of the compressor into the medium-pressure bottle, from where it is fed to the second compressor stage. In this way, a compact design can be realized and reduce the required number of components.

According to another possible embodiment of the invention can be provided that the first compressor stage and the second compressor stage are realized by a single-stage compressor with intermediate injection. According to another possible embodiment of the invention can be provided that the first heat exchanger is a plate heat exchanger and / or the second heat exchanger is a fin exchanger.

According to a further possible embodiment of the invention can be provided that the switching device and / or the switching valve are designed as four-way valves, in which in each switching positions two ports are in fluid communication with each other in pairs. Such changeover valves can be designed such that they manage with only a few moving components, which makes corresponding changeover valves very reliable.

According to another possible embodiment of the invention can be provided that the switching device is designed as an arrangement of four check valves, in which each port is connected with two ports each by means of a check valve connected therebetween such that depending on the pressure conditions at the terminals depending one Check valve is locked and one is open, so that each two ports are fluidly connected to each other. The switching device can then be designed, for example, as a line ring with four correspondingly aligned non-return valves with intermediate connections.

In yet another embodiment of the invention, the gas outlet of the medium-pressure cylinder, the outlet of the first compressor stage and the entrance of the second compressor stage can also be connected to a star point, so that no medium-pressure bottle is required.

In the context of the invention, it may be sufficient depending on the embodiment to provide an actively switchable component, so that the number of driven components is reduced in the context of this embodiment of the invention, which positively affects reliability, complexity of the device and the cost.

Flow connections can be made within the scope of the invention by means of lines, for example pipelines.

The invention will be explained with reference to an embodiment. Here are shown schematically: FIG. 1A: heat pump according to the invention in heating mode,

Figure 1 b: the heat pump according to the invention in the cooling mode and

Figure 2: a detailed view of a possible embodiment

Switching device in the context of the invention.

FIGS. 1 a and 1 b show a heat pump 2 according to the invention in heating mode (FIG. 1 a) or in cooling mode (FIG. 1 b). In the illustrated circuit diagrams different phase states or pressure levels of the medium or coolant are shown by different types of connection. Essentially, three different states occur in the heat pump according to the invention: First, the coolant or medium is partly conveyed in the liquid state, which is represented by a solid line. Furthermore, the medium is partly transported as cold gas, which is represented by dashed connections. In addition, the medium can still be carried as a hot gas, which is shown as a dotted connection. Flow directions are indicated by arrows.

The heat pump 2 according to the invention has a first heat exchanger 4, which may be designed as a plate heat exchanger. The first heat exchanger 4 communicates with the object to be heated or cooled. A second heat exchanger 6, which may be designed as a plate heat exchanger, produces a thermal coupling to a heat source or heat sink.

The conveyed in the circuit medium is precompressed by means of a first compressor stage 8 and recompressed by means of a second compressor stage 10. Between the first compressor stage 8 and the second compressor stage 10, a medium-pressure bottle 12 is arranged, which carries out a phase separation at the introduced via the input 12.1 medium. Medium in the liquid phase is discharged via the outlet 12.2, medium in the gaseous phase rises in the medium-pressure bottle and is sucked off by the second compressor stage 10 via the outlet 12.3 of the medium-pressure bottle 12. The liquid medium derived from the medium-pressure cylinder 12 is passed through a heat exchanger 14 through a first stream 14.1, where it gives off its heat to the medium present in the second stream 14.2, which is sucked in by the first compressor stage 8.

Downstream of the second compressor stage 10, a switching valve 16 is provided, which is configured here as a four-way valve. The changeover valve 16 is connected in flow communication with a first connection 16.1 to the second compressor stage 10, with a second connection 16.2 with the first heat exchanger 4, with a third connection 16.3 with the heat exchanger 14 and with a fourth connection 16.4 with the second heat exchanger 6.

On the other hand, the first heat exchanger 4 and the second heat exchanger 6 are indirectly flow-connected to a switching device 18. Between the first heat exchanger 4 and the switching device 18, a first expansion valve 20 is provided. Between the second heat exchanger 6 and the switching device 18, a second expansion valve 22 is provided. The flow connection with the first expansion valve 20 is via a first port 18.1. produced. The flow connection between the second expansion valve 22 and the switching device 18 is made via a second port 18.2. A third port 18.3 is in fluid communication with the first stream 14.1 of the heat exchanger 14. A fourth port 18.4 of the switching device 18 is connected to a port 24 of a connection 26 between an outlet 8.2 of the first compressor stage 8 and the inlet 12.1 of the medium pressure bottle 12.

In the heating operation illustrated in FIG. 1a, the changeover valve 16 is connected such that it produces a flow connection between the second compressor stage 10 and the first heat exchanger 4 and at the same time a flow connection between the second heat exchanger 6 and the first compressor stage 8 by means of the heat exchanger 14. As a result, the heat exchanger 4 Hot gas supplied, which was heated by the second compressor stage 10, where the hot gas releases its heat under condensation and leaves the first heat exchanger 4 in the liquid phase. By the expansion valve 20, the liquid medium is brought to medium pressure and evaporated. The switching device 18 is connected so that it connects the terminals 18.1 and 18.4, so that the relaxed to medium pressure gas the Terminal 24 between the first compressor stage 8 and medium pressure bottle 12 is supplied.

On the low pressure side, the output of the heat exchanger 14 is in flow communication with the second heat exchanger 6, which via the switching valve 16 and the interconnected ports 16.4 and 16.3 with the heat exchanger 14 and then the first compressor stage 8. The heat exchanger 14 and the second heat exchanger. 6 upstream second expansion valve 22 are interconnected via the interconnected ports 18.3 and 18.2 of the switching device 18.

In heating mode, therefore, the connections 16.1 and 16.2 of the changeover valve 16 as well as 18.1 and 18.4 of the changeover device 18 are interconnected on the high pressure side. Low pressure side, the terminals 16.3, 16.4 of the switching valve 16 and 18.2 and 18.3 of the switching device 18 are interconnected.

In the cooling operation illustrated in FIG. 1b, the connections 16.1 and 16.4 of the reversing valve 16 are flow-connected to one another on the high-pressure side and the connections 16.2 and 16.3 are on the low-pressure side. The output of the second compressor stage 10 is thus coupled via the switching valve 16 to the second heat exchanger 6.

The first heat exchanger 4 is fluidly connected by means of the switching valve 16 with the heat exchanger 14 and the input 8.1 of the subsequent first compressor stage 8. The switching device 18 connects the high-pressure side ports 18.2 and 18.4 and thus the second heat exchanger 6 by means of the expansion valve 22 to the port 24 of the connection 26 between the first compressor stage 8 and medium-pressure bottle 12th

The heat pump 2 according to the invention thus makes it possible to use a plurality of compressor stages with intermediately connected medium-pressure cylinder 12, since in both switching states the medium-pressure cylinder 12 is always flowed through in the same direction. Furthermore, in this way the use of a heat exchanger 14 for overheating the refrigerant gas drawn in by the first compressor stage 8 is connected. In this way, the refrigerant gas in the compressor stages 8, 10 additionally overheat. FIG. 2 shows a possible embodiment of the switching device 18 according to the invention.

In the switching device 18 four check valves 18.5 to 18.8 are provided, each having a reverse direction and a respective forward direction. The connections 18.1 to 18.4 are connected to a line ring 18.9. connected, wherein between each two ports 18.1 to 18.4 each a check valve 18.5 to 18.8 is arranged, which are each arranged such that a flow of each port 18.1 to 18.4 can take place only in one direction and a flow to the respective port 18.1 to 1 8.4 also only from one direction, namely the other, can be done. Depending on the pressure conditions, two connections can be connected in this way.

LIST OF REFERENCE NUMBERS

2 heat pump

4 first heat exchanger

6 second heat exchanger

8 first compressor stage

8.1 Input of the first compressor stage

8.2 Output of the first compressor stage

10 second compressor stage

12 medium pressure bottle

12.1 Input of medium pressure bottle

12.2 Fluid outlet of the medium pressure bottle

12.3 Gas outlet of medium pressure bottle

14 internal heat exchanger

14.1 first stream of the heat exchanger

14.2 second stream of the heat exchanger

16 changeover valve

16.1 - ^■ 16.4 Connections of the changeover valve

18 switching device

18.1 - 18.4 ^■ connections of the switching device

18.5-18.8 check valves

18.9 Line ring

20 first expansion valve

22 second expansion valve

24 connection line

26 connection

Claims

1 . Heat pump, which can be switched between cooling mode and heating mode, with:

A first heat exchanger (4) for receiving energy in the cooling mode and for delivering energy in the heating mode;

A second heat exchanger (6) for emitting energy in the cooling mode and for receiving energy in the heating mode;

A first compressor stage (8) for compressing a medium;

• one of the first compressor stage (8) downstream of the second compressor stage (10);

Wherein the pressure level at the outlet of the first compressor stage (6) corresponds to the pressure level at the inlet of the second compressor stage (10),

Wherein the second compressor stage (8) downstream of a switching valve (16) is connected, by means of which in the cooling operation, a flow connection between the second compressor stage (8) and the second heat exchanger (6) and in the heating mode between the second compressor stage (8) and the first Heat exchanger (4) can be produced.

2. Heat pump according to claim 1,

characterized in that a medium-pressure bottle (12) for phase separation of the liquid medium between the first compressor stage (6) and the second compressor stage (10) is connected.

3. Heat pump according to one of the preceding claims, characterized in that an internal heat exchanger (14) is provided, the first stream (14.1) of the first compressor stage (8) is connected upstream and its second stream (14.2) a liquid outlet (12.2) of the medium-pressure bottle (12) is downstream, so that in the medium-pressure bottle (12) separated and discharged via the liquid outlet (12.2) liquid medium emits energy to the in the first compressor stage (8) flowing gaseous medium.

4. Heat pump according to one of the preceding claims, characterized in that a switching valve (16) with four terminals (16.1, 16.2, 16.3, 16.4) is provided, wherein the first terminal (16.1) with the second compressor stage (10), the second Connection (16.2) with the first heat exchanger (4), the third port (16.3) with the first compressor stage (8) or with the heat exchanger (14) and the fourth port (16.4) with the second heat exchanger (6) is fluidly connected, wherein

In cooling mode, the second compressor stage (10) with the second heat exchanger (6) and the first heat exchanger (4) with the first compressor stage (8) or with the internal heat exchanger (14) and in

• Heating operation, the second compressor stage (10) with the first heat exchanger (4) and the second heat exchanger (6) with the first compressor stage (8) or with the internal heat exchanger (14) are flow-connected.

5. Heat pump according to one of the preceding claims, characterized in that a switching device (18) is provided, the first heat exchanger (4) or the second heat exchanger (6) by means of an intermediate expansion valve (20, 22) of a compound (24). between first compressor stage (8) and medium pressure bottle (12) feeds.

6. Heat pump according to one of the preceding claims, characterized in that the switching device (18) has four ports (18.1, 18.2, 18.3, 18.4), wherein the first port (18.1) by means of the first expansion valve (20) with the first heat exchanger ( 4), the second connection (18.2) by means of the second expansion valve (22) with the second heat exchanger (6), the third connection (18.3) with the internal heat exchanger (14) and the fourth connection (18.4) with the connection (24) between the first compressor stage (8) and medium-pressure cylinder (12) is fluidly connected, wherein

In the cooling mode, the second heat exchanger (6) by means of the second expansion valve (22) with the connection (24) between the first compressor stage (8) and medium-pressure cylinder (12) and the heat exchanger (12) by means of the first expansion valve (20) with the first heat exchanger (4) and im In the heating mode, the first heat exchanger (4) by means of the first expansion valve (20) with the connection (24) between the first compressor stage (8) and medium-pressure cylinder (12) and the internal heat exchanger (14) by means of the second expansion valve (22) with the second Heat exchangers (6) are fluidly connected.

Heat pump according to one of the preceding claims, characterized in that the first compressor stage (8) and the second compressor stage (10) are arranged in a common compressor.

Heat pump according to one of claims 1 to 6, characterized in that the first compressor stage (8) and the second compressor stage (10) are realized by a single-stage compressor with intermediate injection.

Heat pump according to one of the preceding claims, characterized in that first heat exchanger (4) is a plate heat exchanger and / or second heat exchanger (6) is a fin heat exchanger.

10. Heat pump according to one of the preceding claims, characterized in that the switching device (18) and / or the switching valve (16) are designed as four-way valve, in which in the respective switching positions in each case two connections (16.1, 16.2, 16.3 , 16.4, 18.1, 18.2, 18.3, 18.4) are connected in pairs with each other.

1 1. Heat pump according to one of the preceding claims, characterized in that the switching device (18) as an array of four check valves (18.5, 18.6, 18.7, 18.8) is formed, in which each port (18.1, 18.2, 18.3, 18.4), each with two terminals (18.1, 18.2, 18.3, 18.4) is connected in each case by means of an interposed check valve (18.5, 18.6, 18.7, 18.8) such that depending on the pressure conditions at the ports (18.1, 18.2, 18.3, 18.4) one check valve (18.5, 18.6, 18.7, 18.8) is locked and one is open, so that each two ports (18.5, 18.6, 18.7, 18.8) are fluidly connected to each other.

12. Heat pump according to one of the preceding claims, characterized in that the gas outlet of the medium-pressure bottle (12), the outlet (8.2) of the first compressor stage (8) and the entrance of the second compressor stage (10) are connected to a star point.