Refrigerant circuit of a combined refrigeration and heat pump system with integrated steam injection circuit

Abstract

Refrigerant circuit of a combined refrigeration system and heat pump with integrated steam injection circuit, wherein a 3-way valve (2) is arranged as a distribution point in the refrigerant circuit after a compressor (1), and an outdoor condenser / gas cooler (3), a main internal heat exchanger (5) and a check valve (6) as well as a connection point (19) are arranged in a refrigeration system line, and an indoor condenser / gas cooler (4) and a check valve (6) are arranged in a heat pump line,after which the heat pump line is joined to the refrigeration system line at the connection point (19) and the condensed or cooled refrigerant is subsequently led via an expansion device vapor injection (7) via the cold side of a secondary internal heat exchanger (8) to a medium-pressure chiller (9) and subsequently via a direct steam injection connection (18) into the compressor (1) and / or the condensed or cooled refrigerant is led via the warm side of the secondary internal heat exchanger (8) to an evaporator (12) and / or to a low-pressure chiller (13) before the refrigerant vapor is led via a liquid separator suction side (14) and the main internal heat exchanger (5) on the cold side to the suction side of the compressor (1).

Description

The invention relates to a refrigerant circuit of a combined refrigeration system and heat pump with an integrated steam injection circuit, which can be used in particular for use in vehicle air conditioning and in turn preferably in electric motor-driven motor vehicles. Furthermore, the invention relates to methods for operating the aforementioned refrigerant circuit in different operating modes.A preferred field of application for steam injection, which is also referred to as suction gas or steam injection or direct steam injection, is in refrigerant circuits in which scroll compressors, which are also referred to as scroll compressors, are used for compressing the refrigerant vapor.The potential advantages of suction gas or steam injection in scroll compressors in air conditioners for refrigeration applications are generally known in the art. In this case, the compaction process is mainly divided into two stages. In the case of suction gas injection, on the one hand, the compression work is reduced and, on the other hand, the additional supercooling of the liquid refrigerant by means of the internal heat exchanger lowers the enthalpy of inlet into the evaporator and thus the vapor quality. This leads to an increase in the cooling performance as well as to an increase in the performance coefficient of the system. Thermodynamically, the suction gas injection technology offers significant advantages in applications where the compression stroke or temperature rise at the compressor outlet is high, for example for low temperature cooling devices or heat pump applications. The additional cooling of the compression gas provided by the interstage injection allows the compressor to operate in a larger operating range than a conventional single stage compressor would be operable.In the prior art, electrically driven compressors are known which are equipped with a gas injection function in order to increase the refrigerant mass flow of the circulating refrigerant. For example, U.S. Pat. No. 6,293,123 B1 discloses a heat pump system for a motor vehicle having a gas injection function.The injection of suction gas in refrigerant compressors is also known from U.S. Pat. No. 5,848,537 A, US 2007 / 0039347 A1, US 2008 / 0184733 A1 and from US 2010 / 00199694 A1.Also known from DE 10 2012 208 992 A1 is a heating / cooling circuit for vehicles, in particular for hybrid vehicles or pure electric vehicles with medium-pressure injection, and DE 197 02 097 A1 discloses a cooling system of the gas injection type.The systems according to the prior art have the disadvantage that they are designed to be predominantly complicated in terms of apparatus and are equipped with a large number of components and have a susceptibility to faults associated therewith, which is ultimately associated with high costs.The object of the invention is to considerably improve the advantages of suction gas injection technology and the performance and efficiency of a heat pump system in both cooling and heating modes.Furthermore, the object of the invention is to provide a refrigerant circuit which is simple in terms of apparatus and can therefore be implemented cost-effectively.The object is achieved by a refrigerant circuit and method for operating a circuit having the features of the independent patent claims. Further developments are specified in the dependent patent claims.The object of the invention is achieved in particular by a refrigerant circuit of a combined refrigeration system and heat pump with an integrated vapor injection circuit, wherein a 3-way valve is arranged in the refrigerant circuit downstream of a compressor, which valve acts as a distribution point in the refrigerant circuit. The 3-way valve is designed to switch a refrigeration system train which has an external condenser / gas cooler, a main-internal heat exchanger and a non-return flap and a connection point arranged one after the other. The 3-way valve can alternatively switch a heat pump train to the refrigeration system train, in which an interior condenser / gas cooler and a non-return flap are arranged, after which the heat pump train is merged again at a connection point with the refrigeration system train. The 3-way valve can supply both the refrigeration system line or the heat pump line or, in intermediate positions, both lines simultaneously with the refrigerant, so that the refrigeration system and the heat pump modes are carried out in combination.After the combination of the two strands described above, the condensed or cooled refrigerant is subsequently guided via an expansion element steam injection via the cold side of a secondary-internal heat exchanger to a medium-pressure chiller, and the refrigerant steam is subsequently guided via a steam injection feed into the compressor. Simultaneously or alternatively, the condensed or cooled refrigerant is guided via the warm side of the secondary-internal heat exchanger to an evaporator and / or to a low-pressure chiller before the refrigerant vapor is guided via the liquid separator and via the cold side of the main-internal heat exchanger to the suction side of the compressor.In terms of the concept, the external condenser / gas cooler is also referred to as external heat exchanger and the internal heat exchanger is also referred to as internal condenser / gas cooler. This refrigerant circuit realizes the principle of suction gas injection.The basic principle of suction gas injection in a steam injection refrigeration circuit consists in summary in that a certain amount of condensed liquid refrigerant is branched off downstream from the condenser and is expanded below as an injection stream through an expansion valve into an internal countercurrent heat exchanger, which is also referred to as a secondary-internal heat exchanger. The sub-internal heat exchanger functions as a sub-cooler for the main liquid refrigerant flow, which is also referred to as the main flow. The main stream is expanded to low pressure by a further expansion valve and correspondingly evaporated in the evaporator and / or chiller.Saturated or superheated steam is injected into the compression chamber through the intermediate pressure port of the compressor, which leads to a reduction in the compressor outlet temperature. The additional supercooling before entering the evaporator increases the cooling capacity of the evaporator by lowering the temperature of the liquid refrigerant after the condenser in the interior heat exchanger, whereby the enthalpy of inlet into the evaporator likewise falls. The additional injection current increases the heating power by the same amount, which is advantageous in heating operation.The principle of functioning of the refrigerant circuit can be described in summary as follows. The outlet of the compressor is connected to a 3-way refrigerant valve, by means of which the refrigerant flow can be divided between the external heat exchanger and the internal heat exchanger. In the cooling operation, the refrigerant is guided to the outdoor heat exchanger to release the heat of desuperheating of the refrigerant to the atmosphere, and in the heating operation, the refrigerant is guided to the indoor heat exchanger to use the heat of desuperheating for the cabin heating. The outlet of the external heat exchanger is connected to the high-pressure side of the main-internal heat exchanger, as a result of which heat can be transferred from the high-pressure side to the low-pressure side of the system during cooling operation. In heating operation, no heat is transferred in the main-internal heat exchanger. After the heat release process, the two refrigerant flow paths are merged before flowing into the suction gas injection region of the compressor.In the suction gas injection, the refrigerant is divided into a main flow and an injection flow. The injection stream is discharged downstream from the merging point and expanded by the expander steam injection into a countercurrent minor-internal heat exchanger which serves as a aftercooler for the main refrigerant stream flowing in parallel through the expander evaporator and expander battery cooling circuit expansion valves into the evaporator and low pressure chiller.The injection stream continues to flow through the medium pressure chiller, in which the refrigerant is vaporized or superheated by absorption of heat before it is injected into the compressor through the suction gas injection port, also referred to as the direct vapor injection port. The main stream flows through the accumulator and liquid separator and through the low-pressure side of the main-internal heat exchanger, wherein the latter can be further vaporized or further superheated before flowing into the compressor. Depending on the requirements of an electric vehicle, the system may be connected to two different cooling circuits operating at different coolant temperature levels. This is done by providing cooling power at two different pressure stages within the medium pressure chiller and the low pressure chiller.As a result, for example, in the cooling mode, the low temperature level of the cooling water can be used for cooling the battery and the medium temperature level can be used for cooling the electronics. In turn, during heating operation, the waste heat from battery and E-drive components may be absorbed at different temperatures and pressures, which allows for both high flexibility and efficient operation of the heat pump system.Particularly preferably, the compressor is designed as a scroll compressor with a direct steam injection connection at medium pressure.Particularly preferably, the refrigerant circuit is operated with carbon dioxide R744 or the refrigerant R1234yf or R134a as refrigerant.Particularly preferably, the interior condenser / gas cooler is arranged as a heating heat exchanger for heating and the evaporator for cooling air in an air conditioning system of a motor vehicle, via which the motor vehicle can be supplied with conditioned air in various operating modes.The refrigerant circuit is advantageously used in an electric motor-driven vehicle, wherein the medium-pressure chiller is particularly preferably arranged as a cooler in an electric drive train cooling circuit. The electronics of the drive and the drive themselves can be cooled via the medium-pressure chiller and can thus be kept at an optimum operating temperature level under the respective operating circumstances.Particularly preferably, the low-pressure chiller is arranged as a cooler in a battery cooling circuit. The refrigerant circuit is used in a motor vehicle driven by battery electricity and is correspondingly adapted so that the batteries of the vehicles are kept at the optimum operating temperature level by cooling. In particular, when the battery is subjected to high loads during charging or discharging processes which lead to thermal loading, optimum thermal management can increase the efficiency of the processes and correspondingly extend the service life of the battery.The object of the invention is achieved in particular by a method for operating a refrigerant circuit which is carried out for cooling the vehicle cabin as described below.The refrigerant circuit is guided from the compressor via the 3-way valve to the external condenser / gas cooler and the main-internal heat exchanger. The refrigerant flow passes through the main-internal heat exchanger on the warm side and subsequently a partial flow is guided to the expansion element steam injection and expanded to medium pressure. This partial flow is evaporated on the cold side of the auxiliary-internal heat exchanger and the refrigerant vapor is injected into the compressor at medium pressure. The other partial stream is cooled on the warm side of the secondary-internal heat exchanger, expanded to low pressure in the expansion element and evaporated in the evaporator for cooling the interior air in the air conditioning system of the vehicle, after which this partial stream is guided via the liquid separator and the main-internal heat exchanger and sucked in by the compressor at low pressure on the suction side.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit, which is carried out for battery cooling of a battery-electric vehicle as described below. The refrigerant circuit is guided from the compressor via the 3-way valve to the external condenser / gas cooler and the main-internal heat exchanger. Subsequently, a partial stream is guided to the expansion element steam injection and expanded to medium pressure and evaporated on the cold side of the secondary-internal heat exchanger. The refrigerant vapor is injected into the compressor at medium pressure. The other partial flow of the refrigerant is guided on the warm side of the auxiliary-inner heat exchanger and correspondingly cooled and subsequently expanded to low pressure in the expansion element. The partial stream is then evaporated in the low-pressure chiller for cooling the battery cooling circuit, after which the partial stream is passed via the liquid separator and the main-internal heat exchanger and sucked in by the compressor on the suction side.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit which is carried out for vehicle cabin cooling and for battery cooling of a battery-electric vehicle as described below.The refrigerant circuit is guided from the compressor via the 3-way valve to the external condenser / gas cooler and the main-internal heat exchanger. Subsequently, a partial stream is guided to the expansion element steam injection and expanded to medium pressure and then evaporated on the cold side of the secondary-internal heat exchanger. The refrigerant vapor is injected into the compressor at medium pressure, the other partial flow being cooled on the warm side of the auxiliary-internal heat exchanger and again divided into an air conditioning partial flow and a battery cooling partial flow, the battery cooling partial flow being expanded to low pressure in the expansion element and evaporated in the low-pressure chiller for cooling the battery cooling circuit. The air conditioning partial stream is expanded to low pressure in the expansion element and evaporated in the evaporator for cooling the interior air in the air conditioning system, after which the air conditioning partial stream and the battery cooling partial stream are merged again. The refrigerant vapor is now guided over the liquid separator and the main-internal heat exchanger and sucked in by the compressor on the suction side.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit which is carried out in the reheat mode at mild ambient temperatures for vehicle cabin cooling, as described below.The refrigerant circuit is guided from the compressor to the 3-way valve and subsequently a first partial flow is guided via the outer condenser / gas cooler and the main-inner heat exchanger and a second partial flow is guided via the inner condenser / gas cooler. Subsequently, the two partial streams are combined and expanded to low pressure in the expansion element and evaporated in the evaporator for cooling the interior air in the air conditioning system, after which the refrigerant stream is guided via the liquid separator and the main-internal heat exchanger and sucked in by the compressor.In the case of motor vehicle air conditioning, the term "reheat" is understood to mean that the air to be supplied to the vehicle cabin is first cooled and dehumidified and is subsequently reheated to the desired temperature. Two constellations of the reheat are further distinguished. Firstly, a state of the thermal management system in which, in particular at moderate ambient temperatures, the required cooling power of the system is higher than the heating power of the air to be discharged into the vehicle cabin required for the reheating. This is referred to as a reheat in the cold plant operation.Furthermore, the constellation occurs in which the required heating power for reheating the air is higher than the cooling power required for dehumidifying the air. This is also referred to as a "reheat" in heat pump operation.The reheating of the air is referred to as a reheat.The operating mode of the rehetat at mild ambient temperatures is used at mild ambient temperatures between 18° C. and 30° C.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit which is carried out in the rehet mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating, as described below.The refrigerant circuit is guided from the compressor to the 3-way valve and via the interior condenser / gas cooler, wherein subsequently a partial flow is guided for the expansion element steam injection and expanded to medium pressure. This partial flow is then evaporated on the cold side of the auxiliary-internal heat exchanger and subsequently in the medium-pressure chiller for cooling the e-drive train cooling circuit, and the refrigerant vapor is injected into the compressor at medium pressure. The other partial flow is correspondingly cooled on the warm side of the secondary-internal heat exchanger, expanded to low pressure in the expansion element and evaporated in the evaporator for cooling the interior air in the air conditioning system of the vehicle, after which the refrigerant flow is guided via the liquid separator and the main-internal heat exchanger that is functionally free in this operating mode and sucked in by the compressor.The Reheat operating mode at low ambient temperatures is used at ambient temperatures between 0° C. and 18° C.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit which is carried out in the reheating mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating and additional battery cooling, as described below.The refrigerant circuit is guided from the compressor to the 3-way valve and via the interior condenser / gas cooler, wherein subsequently a partial flow is guided for the expansion element steam injection and expanded to medium pressure. This partial flow is then evaporated on the cold side of the auxiliary-internal heat exchanger and subsequently in the medium-pressure chiller for cooling the e-drive train cooling circuit, and the refrigerant vapor is injected into the compressor at medium pressure. The other partial flow is cooled on the warm side of the secondary-internal heat exchanger and divided into an air conditioning partial flow and a battery cooling partial flow. The partial battery cooling flow is expanded to low pressure in the expansion element battery cooling circuit and evaporated in the low-pressure chiller for cooling the battery cooling circuit. The air conditioning substream is expanded to low pressure in the expansion element evaporator and evaporated in the evaporator for dehumidifying the interior air in the air conditioning system, after which the air conditioning substream and the battery cooling substream are combined and conducted via the liquid separator and the functionally free main-internal heat exchanger and drawn in by the compressor.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit which is carried out in the reheating mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating and additional battery cooling, as described below.The refrigerant circuit is routed from the compressor to the 3-way valve and via the interior condenser / gas cooler, wherein the refrigerant flow is divided into an air conditioning partial flow and a battery cooling partial flow. The partial battery cooling flow is expanded to low pressure in the expansion element battery cooling circuit and evaporated in the low-pressure chiller for cooling the battery cooling circuit. The air conditioning substream is expanded to low pressure in the expansion element evaporator and evaporated in the evaporator for dehumidifying the interior air in the air conditioning system, after which the air conditioning substream and the battery cooling substream are combined and conducted via the liquid separator and the functionally free main-internal heat exchanger and drawn in by the compressor.At temperatures below 0° C. ambient temperature, no reheat is carried out, since otherwise the interior evaporator would ice up. In addition, the following ambient temperature ranges are assigned to the respective operating modes.At ambient temperatures of more than 30° C., the plant is operated in a pure cold plant mode.At ambient temperatures between 18° C. and 30° C., a reheat takes place in the cold plant operation.At ambient temperatures between 0° C. to 18° C., a reheat takes place in heat pump operation and at ambient temperatures below 0° C., a pure heat pump operation of the plant takes place.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit which is carried out for vehicle cabin heating and also for e-drive train cooling and battery cooling, as described below.The refrigerant circuit is guided from the compressor to the 3-way valve and via the interior condenser / gas cooler, wherein subsequently a partial flow is guided for the expansion element steam injection and expanded to medium pressure. The partial flow is evaporated on the cold side of the auxiliary-internal heat exchanger and subsequently in the medium-pressure chiller for cooling the e-drive train cooling circuit, and the refrigerant vapor is injected into the compressor at medium pressure. The other partial stream is cooled on the warm side of the secondary-internal heat exchanger, expanded to low pressure in the expansion element battery cooling circuit and evaporated in the low-pressure chiller for cooling the battery cooling circuit, after which the partial stream is guided via the liquid separator and the functionally free main-internal heat exchanger and sucked in by the compressor.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit, which is carried out for heating the vehicle cabin and for cooling the e-drive train, as described below. The refrigerant circuit is routed from the compressor to the 3-way valve and over the interior condenser / gas cooler, after which the refrigerant stream is routed and expanded to the expander vapor injection. The refrigerant flow is then guided via the inoperative secondary-internal heat exchanger and evaporated in the medium-pressure chiller for cooling the e-drive train cooling circuit and the refrigerant vapor is subsequently injected into the compressor.The object of the invention is furthermore achieved by a method for operating a refrigerant circuit which is carried out for vehicle cabin heating and battery cooling as described below.The refrigerant circuit is first guided from the compressor to the 3-way valve and via the internal condenser / gas cooler and the non-functional auxiliary-internal heat exchanger, wherein the refrigerant flow in the expansion element battery cooling circuit is expanded to low pressure and evaporated in the low-pressure chiller for cooling the battery cooling circuit. The refrigerant flow is then guided via the liquid separator and the functionally free main-internal heat exchanger and finally sucked in by the compressor.The system is designed primarily for operation with refrigerant R744, but may also be operated with other refrigerants such as R1234yf and R134a. Moreover, the system architecture allows selection between different modes, such as cooling, heating and dehumidifying, with the minimal use of expansion and directional valves. A further advantage is that this system can be used with a conventional air conditioning unit and can thus be used in many vehicle models.The advantages of the system are very varied.In the case of heating, waste heat from the e-drive train cooling circuit and from the battery cooling circuit can be absorbed simultaneously via the medium-pressure chiller and the low-pressure chiller, which leads to a high heating power.Furthermore, in the case of heating, the heat absorption or the amount of heat from the e-drive train cooling circuit and the battery cooling circuit can be adjusted independently of one another. In this case, the heat absorption takes place at different temperature levels, so that component-critical limit temperatures are not undershot. This leads to a high flexibility of the system.Waste heat can be absorbed via the medium-pressure chiller at a higher temperature level than in the case of the low-pressure chiller. In this case, the vaporized refrigerant is injected into the compressor at a higher pressure level than the suction pressure level. This means that the compressor only has to compress a part of the mass flow from the suction pressure level to the high pressure level. In this way, the electric power consumption of the compressor is reduced, resulting in the high efficiency of the process.Further details, features and advantages of embodiments of the invention are evident from the following description of exemplary embodiments with reference to the associated drawings. The following are shown: FIG. 1 : refrigerant circuit diagram of the components, FIG. 2 : refrigerant circuit diagram for vehicle cabin cooling, FIG. 3 : refrigerant circuit diagram for battery cooling, FIG. 4 : Refrigerant circuit diagram for vehicle cabin cooling and for battery cooling, FIG. 5 : Refrigerant circuit diagram in the reheat mode at mild ambient temperatures for vehicle cabin cooling, FIG. 6 : Refrigerant circuit diagram in the reheat mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating, FIG. 7 : Refrigerant circuit diagram in the reheat mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating as well as e-drive train cooling and battery cooling, FIG. 8 : Refrigerant circuit diagram in the reheat mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating and additional battery cooling, FIG. 9 : Refrigerant circuit diagram for vehicle cabin heating and E-drive train cooling and battery cooling, FIG. 10 : Refrigerant circuit diagram for vehicle cabin heating and E-drive train cooling, and FIG. 11 : Refrigerant circuit diagram for vehicle cabin heating and battery cooling.FIG. 1 shows the circuit diagram of a combined refrigeration system and heat pump with an integrated steam injection circuit. The refrigerant circuit can be switched in the two basic operating modes of the refrigeration system circuit and the heat pump circuit by the different use of various individual strings. Use as a refrigeration system is understood below to mean that the cooling of vehicle cabin air and of components of the e-drive train or of the battery is being followed as a predominant application. In the heat pump mode, in turn, the heating of the air for the vehicle cabin or also the heating of the components of the drive train or of the batteries to their optimum operating temperature is the primary factor in using the refrigerant circuit. The so-called reheat operation represents a combination of cooling and heating of the interior air. The interior air is initially dehumidified by cooling in the air conditioning system 15 of the vehicle and then heated to the desired value. The interior air 21 is understood to be the air flow which is discharged from the air conditioning system to the vehicle cabin. In the broader sense, the e-drive train cooling circuit supplies the components of the electric drive train and the electronics with cooling power.The refrigerant circuit is driven by the compressor 1. In particular, a scroll compressor is used as the refrigerant compressor 1, which offers the possibility of medium-pressure steam injection. Starting at the compressor 1, the compressed, heated, vapor refrigerant flows through the 3-way valve 2, which has three fluid connections, one inlet and two outlets. Via the 3-way valve 2, a fluid flow to the first outlet or to the second outlet or to both outlets can be switched simultaneously. In the latter case, the fluid stream is divided from the inlet into two partial streams. A first outlet of the 3-way valve 2 is connected to the outdoor condenser / gas cooler 3, where the hot refrigerant gas from the compressor 1 is condensed or cooled by the ambient air 20 flowing through the outdoor condenser / gas cooler 3. The condensed or cooled refrigerant flows on the warm side through a main-internal heat exchanger 5 and subsequently reaches a connection point 19 via a non-return flap 6, At the connection point 19, the branch is brought together via the external condenser / gas cooler 3 with the branch outgoing from the second outlet of the 3-way valve 2 via the internal condenser / gas cooler 4, which is brought together via the external condenser / gas cooler 3 after a non-return flap 6 with the previously described branch.The interior condenser / gas cooler 4 is arranged as a heating heat exchanger within an air conditioning system 15 for the temperature control of the air for the vehicle cabin.The refrigerant circuit is divided into two strings after the connection point 19. A first branch runs via the expansion element steam injection 7. After expansion of the refrigerant to medium pressure level, the expanded, cold refrigerant flows through the secondary-internal heat exchanger 8 on the cold side toward the medium pressure chiller 9, which functions as a cooler of the e-drive train cooling circuit 16. Subsequently, the refrigerant vapor at medium pressure reaches the direct vapor injection port 18 of the compressor 1. at this point, the branch of the medium-pressure vapor injection is closed in the cycle after being returned to the compressor 1.The second partial strand after the connection point 19, which is not guided via the expansion element steam injection 7, is guided on the warm side of the secondary-internal heat exchanger 8 toward the heat exchangers for further cooling tasks at low pressure. The refrigerant flow may be directed to the low pressure chiller 13 either in parallel or alternatively, via the expander evaporator 10 and evaporator 12 of the air conditioner 15 or via the expander battery cooling circuit 11. The branch from the evaporator 12 of the air conditioning system 15 is conducted via a non-return flap 6 and combined with the branch from the low-pressure chiller 13 and conducted together via the liquid separator suction side 14 and the cold side of the main-internal heat exchanger 5 toward the suction side of the compressor 1, whereby the circuit is closed.This refrigerant circuit described above with its basic components is now operated in different modes in the following FIGS. 2 to 11, which are described in detail below. Here, lines through which fluid flows are shown with double lines and lines through which fluid does not flow in the respective mode are shown with single lines.FIG. 2 shows the operating mode of the vehicle cabin cooling by means of the refrigerant circuit.In this mode, the refrigerant flows through the outdoor condenser / gas cooler and thereby gives heat of desuperheating or condensation to the environment. In the main-internal heat exchanger, heat is transferred from the high-pressure side to the low-pressure side. The injection stream is diverted downstream from the merging point and expanded via the expander steam injection into the minor-internal heat exchanger, which acts as an additional aftercooler for the main stream. The main flow is expanded in the expansion element evaporator into the evaporator in order to cool the air flowing through the evaporator into the vehicle cabin.Additionally, the medium pressure chiller may be used to provide refrigeration power at a medium temperature level, for example for electronics or inverter cooling.In the embodiment shown, the gaseous refrigerant is compressed in the compressor 1 and conducted via the 3-way valve 2 to the external condenser 3, cooled therein by means of the ambient air 20 and subsequently conducted via the warm side of the main-internal heat exchanger 5 to the expansion element steam injection 7.A partial stream is guided via the expansion element steam injection 7 and subsequently via the cold side of the secondary-internal heat exchanger 8 and finally injected at medium pressure into the compressor 1 as direct steam at the direct steam injection connection 18.The second partial stream is conducted at high pressure over the warm side of the secondary-internal heat exchanger 8 and then expanded to low pressure in the expansion element evaporator 10 and evaporated in the evaporator 12 of the air conditioning system 15 for cooling the interior air 21 in the air conditioning system 15. The refrigerant vapor flows via the non-return flap 6 to the accumulator, the liquid separator suction side 14, The refrigerant vapor is conducted via the cold side of the main-internal heat exchanger 5 to the compressor 1, where the refrigerant circuit closes.FIG. 3 shows the battery cooling by means of the refrigerant circuit. In this mode, the refrigerant flows through the external heat exchanger and thereby releases heat of desuperheating or condensation to the environment. In the main-internal heat exchanger, heat is transferred from the high-pressure side to the low-pressure side.The injection stream is discharged downstream from the merging point and expanded via the expander vapor injection into the minor-interior heat exchanger, which acts as an additional sub-cooler for the main refrigerant stream. The main stream is expanded in the expansion element evaporator into the evaporator in order to provide refrigeration power at low cooling water temperatures, for example for battery cooling.Beginning again with the compression of the refrigerant in the compressor 1, this refrigerant is expanded to medium pressure in a partial flow, as described above with reference to FIG. 2, and is injected as direct steam into the compressor 1. After cooling on the warm side of the secondary-internal heat exchanger 8, the other partial stream is now conducted via the expansion element battery cooling circuit 11 to the low-pressure chiller 13 of the battery cooling circuit 17.Subsequently, as described in the circuit of FIG. 2, the refrigerant is then fed back to the compressor 1.In the two cooling modes described above, the medium-pressure chiller 9 is not operated actively and the e-drive train cooling circuit 16 is not supplied with cold, or is not cooled.FIG. 4 shows the vehicle cabin cooling and battery cooling by means of the refrigerant circuit.In this mode, the refrigerant flows through the external heat exchanger and thereby releases heat of desuperheating or condensation to the environment. In the main-internal heat exchanger, heat is transferred from the high-pressure side to the low-pressure side.The injection stream is discharged downstream from the merging point and expanded via the expander vapor injection into the minor-interior heat exchanger, which acts as an additional sub-cooler for the main refrigerant stream. The main flow flows in a correspondingly divided manner through both the expander evaporator and the expander battery cooling circuit and is expanded to the suction pressure level in order to provide refrigeration power for both vehicle cabin and battery cooling.Beginning again at the compressor 1, the refrigerant circuit, as described with reference to FIGS. 2 and 3, is connected to the compressor 1 for medium-pressure steam injection of a first partial flow, the injection flow. The low-pressure expansion of the second partial stream, the main stream, takes place after the passage of the warm side of the secondary-internal heat exchanger 8, Now, the two heat exchangers are each supplied in parallel with refrigerant of the main stream via the associated expansion valves for realizing the cooling function, firstly via the expansion element evaporator 10 to the evaporator 12 of the air conditioning system 15 and in parallel with this branch with the expansion element battery cooling circuit 11 to the low-pressure chiller 13 for cooling the battery cooling circuit 17. The circuit of Fig. 4 thus represents a combination of the circuits of Figs. 2 and 3.FIG. 5 shows the reheat mode at mild ambient temperatures for vehicle cabin cooling by means of the refrigerant circuit.In this mode, the refrigerant mass flow downstream of the compressor is divided between the external and internal heat exchangers. In this way, a portion of the heat of desuperheating is used to warm up the air flowing into the vehicle cabin. In the main-internal heat exchanger, heat is transferred from the high-pressure side to the low-pressure side.The refrigerant flow is merged again after heat emission and expanded by the expansion element evaporator into the evaporator in order to cool or de-wet the air flowing into the vehicle cabin.The expansion element steam injection is completely closed, so that the refrigerant can only flow over the high-pressure side of the secondary-internal heat exchanger.In the reheat mode, both the interior condenser / gas cooler 4 and the evaporator 12 of the air conditioning system 15 of the motor vehicle are operated. At mild ambient temperatures, this means that the indoor condenser / gas cooler 4 operates in the heating mode while simultaneously operating the evaporator 12 in the cooling mode to reduce the humidity of the indoor air 21. Since in this mode not all the heat of condensation of the refrigerant vapor downstream of the compressor 1 is used for heating the vehicle cabin, a first partial flow of the refrigerant vapor after compression is conducted via the outer condenser / gas cooler 3 and a second partial flow is conducted via the inner condenser / gas cooler 4. The two refrigerant substreams are subsequently combined before expansion in the expansion element evaporator 10 and subsequent evaporation in the evaporator 12. The refrigerant vapor from the evaporator 12 is fed to the compressor 1 via the liquid separator suction side 14 and the cold part of the main-internal heat exchanger 5.In this operating mode of the refrigerant circuit, no direct steam injection takes place at medium pressure. Consequently, the e-powertrain cooling circuit 16 is also not supplied with refrigerant. The battery cooling circuit 17 is also not supplied with refrigerant in this mode.FIG. 6 shows the reheat mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating by means of the refrigerant circuit.In this mode, the refrigerant flows through the interior heat exchanger and thereby outputs heat of desuperheating or condensation to the air flowing into the vehicle cabin. In the main-internal heat exchanger, no heat is transferred from the high-pressure side to the low-pressure side. The refrigerant flows back to the compressor only through the low-pressure side of the main-internal heat exchanger.The injection stream is discharged downstream from the merging point and expanded via the expander vapor injection into the minor-interior heat exchanger, which acts as an additional sub-cooler for the main refrigerant stream. The medium-pressure chiller is used to provide waste heat from the electric drive train as heat of vaporization for the refrigerant, and the waste heat is thus used for heating the vehicle cabin.The main stream is expanded in the expansion element evaporator into the evaporator in order to cool or de-wet the air flowing through the evaporator into the cabin.The low ambient temperature reheat mode requires providing all condensation heat from the refrigerant to the interior condenser / gas cooler 4 that heats the interior air 21 as a heating heat exchanger of the vehicle cabin air conditioner 15. At the same time, in the reheat mode, the evaporator 12 of the air conditioning system 15 is active for dehumidifying the interior air 21. The refrigerant vapor from the compressor 1 is conducted in the 3-way valve 2 completely via the interior condenser / gas cooler 4. The refrigerant mass flow is then divided into two partial flows and the injection flow is expanded in the expansion element steam injection 7, then guided via the secondary-internal heat exchanger 8 and the medium-pressure chiller 9 to the direct steam injection connection 18 of the compressor 1. The other refrigerant substream, the main stream, is conducted via the warm side of the secondary-internal heat exchanger 8 to the expansion element evaporator 10, expanded there and passes into the evaporator 12 and via a non-return flap 6 to the liquid separator suction side 14 back to the suction side of the compressor 1; the circuit is closed.In this circuit, the external condenser / gas cooler 3 and the main-internal heat exchanger 5 and also the battery cooling circuit 17 are inactive.FIG. 7 shows the reheat mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating by means of the refrigerant circuit.The operating mode of the refrigerant circuit corresponds to the operating mode described above in the reheat mode according to FIG. 6, with the additional special feature that the low-pressure chiller 13 is also operated parallel to the evaporator 12 for cooling the battery cooling circuit 17. Accordingly, the main stream for the low pressure is divided into a partial stream for expansion in the expansion element evaporator 10 and a further partial stream for expansion in the expansion element battery cooling circuit 11.FIG. 8 shows the reheat mode at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating by means of the refrigerant circuit.In this reheat mode, only the low-pressure chiller is used to use waste heat from components connected to the low-temperature circuit, such as the battery, as heat of vaporization for the refrigerant.The refrigerant is compressed in the compressor 1 and passes completely via the 3-way valve 2 into the interior condenser / gas cooler 4 for heating the interior air 21 in the air conditioning system 15. The refrigerant is subsequently divided into two partial streams, a partial stream for the evaporator 12 and a partial stream for the low-pressure chiller 13 with its respectively associated expansion element evaporator 10 and expansion element battery cooling circuit 11.The main-internal heat exchanger 5 and the secondary-internal heat exchanger 8 and also the e-drive train cooling circuit 16 are not operated, but are inoperative within the circuit and the relevant heat exchangers are thus flowed through without heat transfer tasks.FIG. 9 shows the mode at cold ambient temperatures for vehicle cabin heating and also for e-drive train cooling and battery cooling by means of the refrigerant circuit.At low ambient temperatures between 0° C. and 18° C., the air flowing into the cabin is first dehumidified via the evaporator and then heated to a desired target temperature. At cold ambient temperatures below 0° C., the air flowing into the cabin is heated only via the interior condenser / gas cooler. In the case of cold ambient temperatures, the refrigerant flow through the evaporator is also prevented, since otherwise the interior evaporator would ice.In this mode, the refrigerant flows through the interior heat exchanger and thereby outputs heat of desuperheating or condensation to the air flowing into the vehicle cabin. In the main-internal heat exchanger, no heat is transferred from the high-pressure side to the low-pressure side. The refrigerant flows back to the compressor only through the low-pressure side of the main-internal heat exchanger.The injection stream is discharged downstream from the merging point and expanded via the expander vapor injection into the minor-interior heat exchanger, which acts as an additional sub-cooler for the main refrigerant stream. The medium-pressure chiller is used to provide waste heat from the electric drive train as heat of vaporization for the refrigerant, and the waste heat is thus used for heating the vehicle cabin.The main flow is expanded in the expander battery cooling circuit 11 into the low-pressure chiller 13 to use waste heat from components connected to the low-temperature circuit, such as the battery, as heat of vaporization for the refrigerant.The refrigerant vapor from the compressor 1 is conducted completely to the interior condenser / gas cooler 4 in the 3-way valve 2 and gives off its heat there to the interior air 21 for heating the vehicle cabin in the air conditioning system 15. The refrigerant is subsequently conducted in a partial train via the expansion element steam injection 7 and the secondary-internal heat exchanger 8 to the medium-pressure chiller 9. In the medium-pressure chiller 9, heat is absorbed from the e-drive train cooling circuit 16 by evaporation from the injection stream. Subsequently, the injection stream is injected into the compressor 1 at medium pressure. The main flow downstream of the interior condenser / gas cooler 4 is conducted on the warm side of the secondary-interior heat exchanger 8 to the expansion element battery cooling circuit 11 and evaporated at low pressure in the low-pressure chiller 13. Heat from the battery cooling circuit 17 is absorbed by the refrigerant, which is subsequently conducted via the liquid separator suction side 14 and the functionally free main-internal heat exchanger 5 to the compressor 1. Thus, in this circuit variant, the refrigerant circuit receives heat from the e-powertrain cooling circuit 16 and the battery cooling circuit 17 for heating the vehicle cabin. The waste heat generated by the components concerned is thus made usable for heating within the air conditioning system 15 of the motor vehicle. The evaporator 12 of the air conditioning system 15 is inoperative in this circuit, since at very cold temperatures the absolute humidity of the air is relatively low and therefore no additional dehumidifying of the interior air has to take place.FIG. 10 shows the mode at cold ambient temperatures for vehicle cabin heating and for e-drive train cooling by means of the refrigerant circuit.In this mode, the refrigerant flows through the interior heat exchanger and thereby outputs heat of desuperheating or condensation to the air flowing into the vehicle cabin. In the secondary-internal heat exchanger, no heat is transferred from the high-pressure side to the low-pressure side. The medium-pressure chiller is used to provide waste heat from the electric drive train as heat of vaporization for the refrigerant. In this case, all the refrigerant flows into the compressor only through the direct-steam injection connection.The refrigerant is compressed in the compressor 1 and is guided completely via the 3-way valve 2 to the interior condenser / gas cooler 4, where the condensation heat is emitted to the interior air 21 for heating. The refrigerant is subsequently guided via the expansion element steam injection 7 and the functionally free secondary-internal heat exchanger 8 to the medium-pressure chiller 9, evaporated there and introduced into the compressor 1 at the direct-steam injection connection 18. The thermal energy for evaporating the refrigerant is completely taken from the e-powertrain cooling circuit 16.FIG. 11 shows the mode at cold ambient temperatures for vehicle cabin heating and for e-drive train cooling by means of the refrigerant circuit.In this mode, the refrigerant flows through the interior heat exchanger and thereby outputs heat of desuperheating or condensation to the air flowing into the cabin. In the main-internal heat exchanger and in the secondary-internal heat exchanger, no heat is transferred from the high-pressure side to the low-pressure side. The refrigerant flows back to the compressor only through the low-pressure side of the main-internal heat exchanger. The entire refrigerant mass flow is expanded in the expansion element battery cooling circuit into the low-pressure chiller in order to use waste heat from components which are connected to the low-temperature circuit, such as the battery, as vaporization heat for the refrigerant.The refrigerant vapor is compressed in the compressor 1 and is completely guided via the interior condenser / gas cooler 4 for heating the vehicle cabin of the vehicle in the air conditioning system 15. Subsequently, the refrigerant flow in the expansion element battery cooling circuit 11 is expanded and evaporated in the low-pressure chiller 13. The energy for this purpose is taken from the battery cooling circuit 17 and the refrigerant vapor reaches the compressor 1 via the liquid separator suction side 14 and the functionally free main-internal heat exchanger 5, the circuit being closed.List of reference characters1 Compressor 2 3-way valve 3 External condenser / gas cooler 4 Internal condenser / gas cooler 5 Main-internal heat exchanger 6 Non-return flap 7 Expansion element steam injection 8 Secondary-internal heat exchanger 9 Medium-pressure chiller 10 Expansion element evaporator 11 Expansion element battery cooling circuit 12 Evaporator 13 Low-pressure chiller 14 Liquid separator suction side 15 Air conditioning system 16 E-drive train cooling circuit 17 Battery cooling circuit 18 Direct steam injection connection 19 Connection point 20 Ambient air 21 Interior air

Claims

Refrigerant circuit of a combined refrigeration system and heat pump with an integrated steam injection circuit, wherein a 3-way valve (2) is arranged as a distribution point in the refrigerant circuit downstream of a compressor (1) and an external condenser / gas cooler (3), a main-internal heat exchanger (5) and a non-return valve (6) and a connection point (19) are arranged in a refrigeration system line and an internal condenser / gas cooler (4) and a non-return valve (6) are arranged in a heat pump line, according to which the heat pump train is brought together with the refrigeration system train at the connection point (19) and the condensed or cooled refrigerant is subsequently guided via an expansion element steam injection (7) via the cold side of a secondary internal heat exchanger (8) to a medium-pressure chiller (9) and subsequently via a direct steam injection connection (18) into the compressor (1) and / or the condensed or cooled refrigerant is guided via the warm side of the secondary internal heat exchanger (8) to an evaporator (12) and / or to a low-pressure chiller (13), before the refrigerant steam is guided via a liquid separator suction side (14) and the main internal heat exchanger (5) on the cold side to the suction side of the compressor (1).Refrigerant circuit according to Claim 1, characterized in that the compressor (1) is designed as a scroll compressor with a direct-steam injection connection (18) at medium pressure.Refrigerant circuit according to claim 1 or 2, characterized in that the refrigerant circuit is operated with R744, R1234yf or R134a as refrigerant.Refrigerant circuit according to one of Claims 1 to 3, characterized in that the interior condenser / gas cooler (4) is arranged as a heating heat exchanger for heating and the evaporator (12) for cooling air is arranged in an air conditioning system (15) of a motor vehicle.Refrigerant circuit according to one of Claims 1 to 4, characterized in that the medium-pressure chiller (9) is arranged as a cooler in an E-drive train cooling circuit (16).Refrigerant circuit according to one of Claims 1 to 5, characterized in that the low-pressure chiller (13) is arranged as a cooler in a battery cooling circuit (17).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, for the purpose of cooling the vehicle cabin, the refrigerant circuit is guided from the compressor (1) via the 3-way valve (2) to the outer condenser / gas cooler (3) and the main-inner heat exchanger (5) and subsequently a partial stream is guided for the expansion element steam injection (7) and is expanded to medium pressure and is evaporated on the cold side of the secondary-inner heat exchanger (8) and the refrigerant vapor is injected into the compressor (1) at medium pressure, the other partial stream being cooled on the warm side of the secondary-inner heat exchanger (8), expanded to low pressure in the expansion element evaporator (10) and evaporated in the evaporator (12) for cooling the interior air (21) in the air conditioning system (15), after which the partial stream is guided via the liquid separator suction side (14) and the main-internal heat exchanger (5) and sucked in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, for battery cooling, the refrigerant circuit is guided from the compressor (1) via the 3-way valve (2) to the outer condenser / gas cooler (3) and the main-inner heat exchanger (5) and subsequently a partial stream is guided for the expansion element steam injection (7) and expanded to medium pressure and evaporated on the cold side of the secondary-inner heat exchanger (8) and the refrigerant vapor is injected into the compressor (1) at medium pressure, wherein the other partial stream is cooled on the warm side of the secondary-inner heat exchanger (8), expanded to low pressure in the expansion element battery cooling circuit (11) and evaporated in the low-pressure chiller (13) for cooling the battery cooling circuit (17), after which the partial stream is guided via the liquid separator suction side (14) and the main-internal heat exchanger (5) and sucked in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, for vehicle cabin cooling and for battery cooling, the refrigerant circuit is guided from the compressor (1) via the 3-way valve (2) to the external condenser / gas cooler (3) and the main-internal heat exchanger (5) and subsequently a partial stream is guided for the expansion element steam injection (7) and expanded to medium pressure and evaporated on the cold side of the secondary-internal heat exchanger (8) and the refrigerant vapor is injected into the compressor (1) at medium pressure, the other partial stream being cooled on the warm side of the secondary-internal heat exchanger (8) and divided into an air-conditioning partial stream and a battery cooling partial stream, wherein the battery cooling substream is expanded to low pressure in the expansion element battery cooling circuit (11) and evaporated in the low-pressure chiller (13) to cool the battery cooling circuit (17), and the air conditioning substream is expanded to low pressure in the expansion element evaporator (10) and evaporated in the evaporator (12) to cool the interior air (21) in the air conditioner (15), after which the air conditioning substream and the battery cooling substream are combined and conducted via the liquid separator suction side (14) and the main-interior heat exchanger (5) and drawn in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, in the reheat mode at mild ambient temperatures for vehicle cabin cooling, the refrigerant circuit is guided from the compressor (1) to the 3-way valve (2) and a first partial stream is subsequently guided via the outer condenser / gas cooler (3) and the main-inner heat exchanger (5) and a second partial stream is guided via the inner condenser / gas cooler (4) and the two partial streams are subsequently combined and expanded to low pressure in the expansion element evaporator (10) and evaporated in the evaporator (12) for cooling the interior air (21) in the air conditioning system (15), after which the refrigerant stream is guided via the liquid separator suction side (14) and the main-inner heat exchanger (5) and sucked in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, in the reheat mode, at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating, the refrigerant circuit is guided from the compressor (1) to the 3-way valve (2) and via the interior condenser / gas cooler (4), wherein subsequently one partial stream is guided to the expansion element steam injection (7) and expanded to medium pressure and evaporated on the cold side of the secondary-interior heat exchanger (8) and subsequently in the medium-pressure chiller (9) for cooling the e-drive train cooling circuit (16), and the refrigerant vapor is injected into the compressor (1) at medium pressure, wherein the other partial stream is cooled on the warm side of the secondary-interior heat exchanger (8), The pressure in the expansion element evaporator (10) is expanded to low pressure and evaporated in the evaporator (12) for cooling the interior air (21) in the air conditioning system (15), after which the refrigerant flow is guided via the liquid separator suction side (14) and the functionally free main-interior heat exchanger (5) and sucked in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, in the reheat mode, at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating and additional battery cooling, the refrigerant circuit is guided from the compressor (1) to the 3-way valve (2) and via the interior condenser / gas cooler (4), wherein a partial stream for the expansion element steam injection (7) is subsequently guided and expanded to medium pressure and is evaporated on the cold side of the secondary-interior heat exchanger (8) and subsequently in the medium-pressure chiller (9) for cooling the e-drive train cooling circuit (16) and the refrigerant vapor is injected into the compressor (1) at medium pressure, wherein the other partial stream on the warm side of the secondary-internal heat exchanger (8) is cooled and divided into an air conditioning partial stream and a battery cooling partial stream, wherein the battery cooling partial stream is expanded to low pressure in the expansion element battery cooling circuit (11) and evaporated in the low-pressure chiller (13) to cool the battery cooling circuit (17), and the air conditioning partial stream is expanded to low pressure in the expansion element evaporator (10) and evaporated in the evaporator (12) to dehumidify the interior air (21) in the air conditioning system (15), after which the air conditioning partial stream and the battery cooling partial stream are combined and guided via the liquid separator suction side (14) and the functionally free main-internal heat exchanger (5) and drawn in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, in the reheat mode, at low ambient temperatures for air dehumidification and simultaneous vehicle cabin heating and additional battery cooling, the refrigerant circuit is guided from the compressor (1) to the 3-way valve (2) and via the interior condenser / gas cooler (4), wherein the refrigerant stream is divided into an air-conditioning substream and a battery cooling substream, wherein the battery cooling substream is expanded to low pressure in the expansion element battery cooling circuit (11) and evaporated in the low-pressure chiller (13) for cooling the battery cooling circuit (17), and the air-conditioning substream is expanded to low pressure in the expansion element evaporator (10) and evaporated in the evaporator (12) for dehumidifying the interior air (21) in the air-conditioning system (15), according to which the air conditioning partial stream and the battery cooling partial stream are combined and conducted via the liquid separator suction side (14) and the functionally free main-internal heat exchanger (5) and drawn in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, for the purpose of vehicle cabin heating and electric power train cooling and battery cooling, the refrigerant circuit is guided from the compressor (1) to the 3-way valve (2) and via the internal condenser / gas cooler (4), a partial flow being subsequently guided to the expansion element steam injection (7) and expanded to medium pressure and being evaporated on the cold side of the secondary internal heat exchanger (8) and subsequently in the medium-pressure chiller (9) for cooling the electric power train cooling circuit (16), and the refrigerant vapor being injected into the compressor (1) at medium pressure, the other partial flow being cooled on the warm side of the secondary internal heat exchanger (8), in the expansion element battery cooling circuit (11), the pressure is expanded to low pressure and evaporated in the low-pressure chiller (13) for cooling the battery cooling circuit (17), after which the partial flow is guided via the liquid separator suction side (14) and the functionally free main-internal heat exchanger (5) and sucked in by the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, for the purpose of vehicle cabin heating and electric power train cooling, the refrigerant circuit is guided from the compressor (1) to the 3-way valve (2) and via the internal condenser / gas cooler (4), after which the refrigerant stream is guided and expanded for the expansion element steam injection (7) and is guided via the inoperative secondary-internal heat exchanger (8) and evaporated in the medium-pressure chiller (9) for cooling the electric power train cooling circuit (16), and the refrigerant steam is injected into the compressor (1).Method for operating a refrigerant circuit according to one of Claims 1 to 6, characterized in that, for the purpose of vehicle cabin heating and battery cooling, the refrigerant circuit is guided from the compressor (1) to the 3-way valve (2) and via the interior condenser / gas cooler (4) and the functionally free secondary-interior heat exchanger (8), wherein the refrigerant stream in the expansion element battery cooling circuit (11) is expanded to low pressure and is evaporated in the low-pressure chiller (13) for cooling the battery cooling circuit (17) and is guided via the liquid separator suction side (14) and the functionally free main-interior heat exchanger (5) and is drawn in by the compressor (1).

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