Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning

Abstract

Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning, comprising a section for a total refrigerant flow, a section for a suction jet refrigerant partial flow, and a section for a motive jet refrigerant partial flow, wherein in the section for the suction jet refrigerant partial flow an air conditioning evaporator (8) with associated expansion element (9) for providing cooling in an air conditioning system (32), a compressor (1), a gas cooler (2), an expansion element (5), and a suction jet heat exchanger (6), and in the section for the motive jet refrigerant partial flow a motive jet heat exchanger (33), wherein an ejector (7) is provided in which the suction jet refrigerant partial flow and the motive jet refrigerant partial flow of the refrigerant circuit are combined.wherein an ambient heat exchanger (10) and, in parallel, an air conditioning gas cooler (12) for providing heat in the air conditioning system (32) and, subsequently, a subcooler (11) are arranged in the total refrigerant flow, after which the total refrigerant flow is divided into the suction jet refrigerant partial flow and the motive jet refrigerant partial flow.

Description

The invention relates to a hybrid compressor-ejector cooling system for vehicles. A preferred application of the invention lies in the use of supercritical refrigerant circuits with R744 as the refrigerant for vehicle air conditioning. Such systems are particularly suitable for battery-electric vehicles. Ejector-compressor combinations for refrigerant circuits are known in the prior art. A vapor compression cycle with an ejector is known from US 205 2005 / 0 268 644 A1. The problem to be solved is to provide a vapor compression cycle that includes multiple evaporators and overcomes the disadvantages of the known prior art. The solution involves a vapor compression cycle consisting of: - a compressor that draws in and compresses refrigerant; - a condenser that radiates heat from the compressed, high-pressure refrigerant delivered by the compressor; - an ejector comprising: - a nozzle section that depressurizes and expands the refrigerant on a downstream side of the condenser; - a refrigerant intake inlet from which refrigerant is drawn in by the action of a flow of the high-speed refrigerant exiting the nozzle section; - a mixing section through which the high-speed refrigerant delivered by the nozzle section and the refrigerant drawn in from the intake inlet are mixed; and - a pressurization section that converts the kinetic energy of a flow of the mixed refrigerant being mixed through the mixing section into pressure energy.- a first evaporator connected to a downstream side of the ejector and - a second evaporator connected to the suction inlet of the ejector, wherein the first evaporator and the second evaporator are integrally constructed to cool an airflow directed to a common subject cooling space.; JP 2006-29 714 A concerns an ejector circuit with an internal heat exchanger. The problem to be solved is to prevent the refrigerant at the inlet of an ejector from entering an excessively cooled state due to a factor such as fluctuations in the cooling load within the ejector circuit, thereby reducing the system's performance. To solve this problem, a cooler and an internal heat exchanger are arranged between the compressor outlet and the ejector inlet, with the cooler being located in the most downstream position. For example, DE 103 33 535 A1 describes an ejector circuit with a compressor in which the air conditioning heat load is greater than or equal to a predetermined value. The degree of a throttle opening in a nozzle arrangement of an ejector is controlled in such a way that the efficiency corresponds to a target value. Another ejector-based cooling system and cooling method is described in DE 10 2019 111 309 A1. EP 2 754 979 A1 also discloses a cooling system with an ejector, in which two compressors are combined with an ejector in the cooling system. The special features of vehicle air conditioning in combination with ejector refrigeration systems are taken into account, for example in DE 103 17 875 A1, where a vehicle air conditioning system with ejector cooling cycle is disclosed. US patent 2009 / 0049852 A1 discloses an ejector air conditioning system and a cooling system for vehicles. The systems known in the state of the art have in common that they predominantly operate with refrigerants whose use in the future is undesirable or even prohibited by law due to their climate-damaging properties. Refrigerant circuits using natural refrigerants such as carbon dioxide, also known as R744, offer a solution to this problem. However, R744 cooling systems exhibit lower cooling capacity at high ambient temperatures. The heat dissipation temperature far exceeds the critical point of the liquid's thermodynamic properties, and the subsequent expansion ends in a region of the two-phase system with a high vapor content. Furthermore, a high pressure ratio increases the compressor's power consumption. These two parameters negatively impact the efficiency of the cooling system and the COP (Coefficient of Performance). The object of the invention is to provide a refrigerant circuit and a method for operating such a refrigerant circuit for vehicle air conditioning, which can be used for vehicle air conditioning in supercritical process conditions. The problem is solved by a supercritical refrigerant circuit with compressor-ejector combination for automotive air conditioning and a method for operating such a system according to the independent patent claims. Further developments of the invention are specified in the dependent patent claims. The problem is solved in particular by a supercritical refrigerant circuit with a compressor-ejector combination, the refrigerant circuit consisting of a total of three sections: one section for the total refrigerant flow, one section for a suction jet refrigerant partial flow, and one section for a motive jet refrigerant partial flow. The section for the suction jet refrigerant partial flow has, in the direction of refrigerant flow, an air conditioning evaporator with an upstream associated expansion device for providing cooling in an air conditioning system, followed by a compressor, a gas cooler, an expansion device and a heat exchanger that acts as an evaporator. In the section for the jet refrigerant flow, a heat exchanger is arranged to warm this flow. The two flows are combined in the ejector. An ejector, also known as a jet pump, combines a jet flow and a suction flow, with the jet flow drawing in the suction flow. Downstream of the ejector, an ambient heat exchanger and, in parallel, an air conditioning gas cooler for providing heat to the air conditioning system are arranged, followed by a subcooler within the total refrigerant flow. The total refrigerant flow is then split into the jet refrigerant flow and the jet refrigerant flow. According to a particularly advantageous embodiment of the invention when using the refrigerant circuit in battery electric vehicles, a battery cooler with an associated upstream expansion element is arranged in the suction jet refrigerant partial flow of the refrigerant circuit upstream of the compressor. To improve efficiency, a battery cooling circuit is designed as a cold carrier circuit with a battery coolant pump for cooling the battery and is integrated into the system. Advantageously, a motive jet heating circuit is designed as a heat transfer circuit with a motive jet heating circuit pump, a motive jet heat exchanger and the gas cooler, whereby heat is absorbed from the compressed refrigerant in the gas cooler and transferred to the motive jet refrigerant partial flow in the motive jet heat exchanger. Furthermore, a subcooler cooling circuit is advantageously designed as a refrigerant circuit with a subcooler circuit pump, the subcooler and the suction jet heat exchanger, whereby heat is transported from the subcooler to the suction jet heat exchanger and thus the total refrigerant flow in the subcooler is subcooled. According to an advantageous embodiment of the invention, two internal heat exchangers are connected in series with their heat-discharging side downstream of the gas cooler and arranged upstream of the suction jet heat exchanger in the suction gas refrigerant partial flow. The heat-receiving side of the first internal heat exchanger is located downstream of the suction jet heat exchanger, and the heat-receiving side of the second internal heat exchanger is located upstream of the compressor. Preferably, a motive jet heating circuit is designed as a heat transfer circuit with a motive jet heating circuit pump, a motive jet heat exchanger and the gas cooler, as well as a subcooler cooling circuit as a refrigerant circuit with a subcooler cooling circuit pump, the subcooler and the suction jet heat exchanger. Advantageously, a gas auxiliary cooler is arranged between the gas cooler and the expansion element, as well as a bypass to the suction jet heat exchanger and its associated expansion element. A bypass is understood to be a bypass line through which the refrigerant can be routed parallel to the suction jet heat exchanger and its associated, upstream expansion element. The heat-emitting side of the suction jet heat exchanger is advantageously arranged downstream of the ambient heat exchanger in the overall refrigerant flow. The heat-absorbing side of the gas cooler, on the other hand, is arranged in the motive jet refrigerant subflow of the refrigerant circuit. Carbon dioxide is preferably used as a refrigerant in the refrigerant cycle. The object of the invention is further achieved by a method for operating a supercritical refrigerant circuit for cooling a vehicle, as shown in the two-phase diagram according to Fig. 1b, in that the suction jet refrigerant partial flow of the refrigerant circuit evaporates in the air conditioning evaporator from point a to point b for cooling in the air conditioning system, absorbing heat, is then compressed in the compressor from point b to point c, cooled in the gas cooler from point c to point d, expanded in the expansion element from point d to point e, heated in the suction jet heat exchanger from point e to point f, combined in the ejector from point f to point g with the motive jet refrigerant partial flow of the refrigerant circuit from point k to point g, and the total refrigerant flow is cooled in the ambient heat exchanger from point g to point h.The refrigerant is cooled in the subcooler from point h to point i and then split at point i into the motive jet refrigerant flow and the suction jet refrigerant flow, after which the suction jet refrigerant flow is expanded in the expansion element from point i to point a and the motive jet refrigerant flow is pumped by means of the motive jet pump from point i to point j and heated in the motive jet heat exchanger from point j to point k. Advantageously, the suction jet refrigerant flow of the refrigerant circuit is split into a partial flow through the air conditioning evaporator for cooling in the air conditioning system and a partial flow through the battery cooler for cooling the battery. The air conditioning evaporator and the battery cooler are equipped with dedicated expansion devices, which are installed upstream and can be operated alternatively or simultaneously. Alternatively and advantageously, the object of the invention is solved by a method for operating a supercritical refrigerant circuit for heating a vehicle, illustrated in Fig. 2b, in that the suction jet refrigerant partial flow of the refrigerant circuit evaporates in the ambient heat exchanger from point a to point b while absorbing heat, is then compressed in the compressor from point b to point c, cooled in the gas cooler from point c to point d, expanded in the expansion element from point d to point e, heated in the suction jet heat exchanger from point e to point f, and combined in the ejector from point f to point g with the motive jet refrigerant partial flow of the refrigerant circuit from point k to point g.Subsequently, the total refrigerant flow is cooled in the air conditioning gas cooler for heating in the air conditioning system from point g to point h, cooled in the subcooler from point h to point i, and then split at point i into the motive jet refrigerant flow and the suction jet refrigerant flow, after which the suction jet refrigerant flow is expanded in the expansion element from point i to point a, and the motive jet refrigerant flow is conveyed by means of the motive jet pump from point i to point j and heated in the motive jet heat exchanger from point j to point k. The object of the invention is further achieved by a method for operating a supercritical refrigerant circuit with increased cooling capacity through internal heat transfer, as shown in Fig. 3a. The suction jet refrigerant partial flow of the refrigerant circuit is evaporated in the air conditioning evaporator from point a to point b for cooling in the air conditioning system, absorbing heat. It is then superheated in the internal heat exchanger from point b to point o, compressed in the compressor from point o to point c, cooled in the gas cooler from point c to point d, cooled in the internal heat exchanger from point d to point I, cooled in the internal heat exchanger from point I to point m, expanded in the expansion element from point m to point e, heated in the suction jet heat exchanger from point e to point f, heated in the internal heat exchanger from point f to point n, and combined in the ejector from point n to point g with the motive jet refrigerant partial flow of the refrigerant circuit from point k to point g.The total refrigerant flow in the ambient heat exchanger is subsequently cooled from point g to point h, cooled in the subcooler from point h to point i, and then divided at point i into the motive jet refrigerant flow and the suction jet refrigerant flow, after which the suction jet refrigerant flow is expanded in the expansion element from point i to point a, and the motive jet refrigerant flow is conveyed by means of the motive jet pump from point i to point j and heated in the motive jet heat exchanger from point j to point k. Advantageously, the suction jet refrigerant partial flow of the refrigerant circuit is further cooled to ambient temperature in the gas auxiliary cooler after cooling in the gas cooler. To increase the ejector's discharge pressure, the suction jet refrigerant partial flow of the refrigerant circuit is directed directly into the ejector via the bypass after the gas auxiliary cooler. The concept of the invention essentially consists in the fact that the use of an ejector in the refrigerant circuit enables the reuse of the heat derived from the gas cooler and the increase of the cooling capacity of the cooling system in refrigeration system mode -AC mode-. The system according to the invention can utilize internal heat recovery to lower the heat dissipation temperature and pressure of the gas cooler, which shifts the refrigerant expansion to a higher liquid fraction. The overall compression ratio is lower compared to the standard system, which helps the compressor reduce consumption and increases the efficiency of the refrigeration system. The use of an ejector heat recovery loop in the system's high-pressure mode enables expansion at a higher liquid fraction and a reduction in the pressure increase at the compressor. Both factors have a positive effect on the energy efficiency of the refrigerant circuit in heat pump mode (HP mode). In summary, the invention can be described as follows: The R744 hybrid compressor-ejector refrigerant system for motor vehicles uses the heat released by the gas cooler after the compressor as a heat source to operate the cooling circuit with ejector drive. The refrigerant R744 serves as the working medium. The ejector circuit is integrated into the compressor system, and therefore the overall system is also referred to as a hybrid system. A particular advantage of the disclosed system is that it solves the problem of insufficient heat source capacity due to low ambient temperatures when switching between air conditioning (AC) and heat pump (HP) modes. Furthermore, the invention overcomes the disadvantage that, in prior art systems, expansion tends to occur more in the vapor phase of the two-phase region, thus reducing the evaporator's heat absorption capacity. This reduces compressor work and allows heat output to reach the required temperature level for effectively heating a vehicle cabin. Further details, features, and advantages of embodiments of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. These show: Fig. 1a: Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning in refrigeration system operation; Fig. 1b: log pH diagram in refrigeration system operation; Fig. 2a: Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning in heat pump operation; Fig. 2b: log pH diagram in heat pump operation; Fig. 3a: Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning with internal heat transfer; Fig. 3b: log pH diagram with internal heat transfer; Fig. 4a: Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning with gas auxiliary cooler and bypass. Fig. 4b: log pH diagram in refrigeration system operation with bypass; Fig.5a : Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning in integrated design and Fig. 5b : log pH diagram in refrigeration system operation without bypass and in integrated design. Figure 1a shows a supercritical refrigerant circuit with a compressor-ejector combination for vehicle air conditioning in a refrigeration system configuration, and Figure 1b shows a corresponding log pH diagram during refrigeration system operation. The following description refers to the arrangement and interconnection of the system and its components, and the method implemented in the respective circuit, based on the state points from the corresponding log pH diagram. The refrigerant circuit consists of a compressor 1, which compresses the refrigerant R744 from the evaporation pressure point (b) to the high pressure point (c). At this point, the working fluid enters the gas cooler 2, where the heat is dissipated and transferred to the motive jet heating circuit 29. The heat transfer fluid of the motive jet heating circuit 29 is heated at point (d) in the gas cooler 2, close to ambient temperature, by the high-pressure compressed refrigerant, or the refrigerant is cooled accordingly. The pressurized, cold refrigerant enters the electronic expansion device 5, designed as an expansion valve, and expands isenthalpically to a lower pressure and below ambient temperature up to point (e). The refrigerant then enters the suction jet heat exchanger 6 and absorbs heat, which is transferred via the subcooler cooling circuit 30 from the subcooler 11 by means of a coolant and subcooler cooling circuit pump 15. From this point (e), the refrigerant is heated to the temperature of point (f). The superheated refrigerant is drawn into the ejector 7 through the suction port. The refrigerant entering the suction port is mixed with the high-velocity flow, the motive jet refrigerant partial flow, in the ejector 7, and the total refrigerant flow is expelled at higher pressure and temperature through the diffuser of the ejector 7 at point (g). The ejector 7 directs the entire mass flow of refrigerant through the 3-way valve 16 to the ambient heat exchanger 10. The ambient heat exchanger 10 operates in gas cooler mode and cools the refrigerant to the ambient temperature (h). The heat is then dissipated to the environment. After the ambient heat exchanger 10, the working fluid is directed through a 3-way valve 17 into the subcooler 11. The additional heat is transferred from the subcooler 11 to the heat transfer fluid of the subcooler cooling circuit 30 and directed to the suction jet heat exchanger 6, which acts as an evaporator. The refrigerant is cooled below the ambient temperature and reaches the minimum temperature at point (i). The total mass flow of refrigerant at point (i) is divided into two partial flows, a driving jet refrigerant partial flow and a suction jet refrigerant partial flow. The suction jet refrigerant partial flow flows towards the air conditioning unit 32 and through the expansion device 9, which is designed as an electronic expansion valve, where the refrigerant adjusts to the evaporation pressure and the corresponding temperature from point (a). After the expansion device 9, the refrigerant is directed through the 3-way valve 19 to the air conditioning evaporator 8. The refrigerant cools and absorbs the heat from the vehicle cabin air circulating through the air conditioning evaporator 8. The refrigerant becomes superheated vapor at point (b). The motive jet refrigerant partial flow flows to point (i), the refrigerant split, to the ejector 7 and is pumped and compressed by the motive jet pump 13 from point (i) to the pressure of point (j). The motive jet heating circuit pump 13 pumps and compresses the motive jet refrigerant partial flow. In particular, when the ambient temperature exceeds the critical temperature of the working fluid R744 (31.7°C), the motive jet heating circuit pump 13 operates as a compressor. The fluid below the critical point can change its phase into a liquid (condensate), but above the critical point it is in the supercritical region, where it has a high density close to that of a liquid, but does not change its phase and behaves like a supercritical fluid (gas). At the state of point (j) the refrigerant enters the motive jet heat exchanger 33, where it is heated to the maximum temperature at point (k) by the heat absorbed by the motive jet heating circuit 29 of the gas cooler 2 before the motive jet refrigerant partial flow enters the ejector 7. The hot motive jet refrigerant partial flow is a high-velocity flow under high kinematic and low static pressure with a corresponding fluid enthalpy, whereas the suction jet refrigerant partial flow is located at the level of point (f) before merging with the motive jet refrigerant partial flow. This allows additional refrigerant mass to be drawn through the intake opening of ejector 7 and the suction jet refrigerant partial flow to be drawn in. The strong motive jet refrigerant partial flow, which is heated by the heat of the gas cooler 2, generates an additional force to drive the entire system. The system shown in Fig. 1a is capable of cooling the vehicle cabin air via the air conditioning evaporator 8 and the battery 23 via the battery cooler 22. First, the total refrigerant flow is split at point (i), and the suction jet refrigerant partial flow is directed to the coolers and again split into two partial flows. These partial flows are directed via the expansion devices 9 and 25, designed as expansion valves, to the air conditioning evaporator 8 and the battery cooler 22. The process of evaporation in the battery cooler 22 from point (a') to point (b) is analogous to the evaporation from point (a) to (b) shown in Fig. 1b. The transport of cold from the battery cooler 22 to the battery 23 is carried out via the battery cooling circuit 31 as a refrigerant circuit by means of a battery coolant pump 24. The battery cooling circuit 31 removes heat from the batteries 23 to maintain them within the required or optimal operating temperature range. The refrigerant evaporates in the battery cooler 22 and mixes with the refrigerant partial flow from the air conditioning evaporator 8. This mixture is then directed as a suction jet refrigerant partial flow via the 3-way valve 18 to the compressor 1. The total refrigerant flow is split after the subcooler 11 at point (i) into the motive jet refrigerant partial flow and the suction jet refrigerant partial flow and is combined again in the ejector 7 to form the total refrigerant flow. Fig. 2a shows a supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning in heat pump mode, and Fig. 2b shows a log pH diagram in heat pump operation, where the components of the refrigerant circuit are identical to those in Fig. 1a. The following description refers to the arrangement and interconnection of the system and its components according to Fig. 1a and the method implemented in the respective circuit based on the state points from the respective associated log pH diagram, here according to Fig. 2b. The refrigerant circuit is capable of operating in heat pump mode when the ambient temperature is too low and heating of the vehicle cabin is required. In this case, the total refrigerant flow after the ejector 7 passes through the 3-way valve 16 with valves 20 and 21 closed to dissipate heat via the air conditioning gas cooler 12 in the air conditioning unit 32 and the 3-way valve 17 from point (g) to point (h). This transfers heat from the air conditioning unit 32 to the air for heating the vehicle cabin. After passing through the subcooler 11, the total refrigerant flow is split at point (i), and the suction gas refrigerant partial flow passes through the 3-way valve 19, the ambient heat exchanger 10, and the 3-way valve 18 to the compressor 1 from point (a) to point (b) in the log pH diagram according to Fig. 2b. This allows heat to be absorbed from the surrounding air. Fig. 3a shows a supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning with internal heat transfer, and Fig. 3b shows the associated log pH diagram for internal heat transfer for the process. The modification of the refrigerant circuit according to Figs. 1a and 2a to the system according to Fig. 3a allows for an improvement through the use of internal heat exchangers, also referred to as IHXs, a first internal heat exchanger 3 and a second internal heat exchanger 4. This enables an increase in cooling capacity, represented by the increase in the enthalpy difference between points (a) and (b'), which increases the efficiency of the system. Furthermore, the maximum pressure at the compressor outlet at point (c) can be reduced, thereby decreasing the power consumption of compressor 1. The refrigerant is compressed starting at point (b') and proceeding in compressor 1 towards point (c) in the log pH diagram according to Fig. 3b. After cooling in gas cooler 2 towards point (d), the suction jet refrigerant flow passes through the first internal heat exchanger 3 to point (d') and then through the second internal heat exchanger 4 to point (d"). The suction jet refrigerant flow releases heat in internal heat exchangers 3 and 4. In expansion unit 5, the refrigerant expands towards point (e) and finally evaporates in suction jet heat exchanger 6 towards point (f). The refrigerant then absorbs heat in the first internal heat exchanger 3 towards point (f') and is subsequently combined with the motive jet refrigerant flow in ejector 7. This state is shown at point (g).The total refrigerant flow passes through the 3-way valve 16 through the ambient heat exchanger 10 and through the 3-way valve 17 with state at point (h) further through the subcooler 11 to point (i), where the total refrigerant flow then branches into the suction jet refrigerant partial flow to the air conditioning unit 32 and the battery cooler 22 on one side and to the other side as the motive jet refrigerant partial flow to the motive jet heat exchanger 33 and to the ejector 7. The state points are marked with point (j) after compression in the motive jet pump 13 and with point (k) after heating in the motive jet heat exchanger 33 in the log pH diagram according to Fig. 3b. The suction jet refrigerant partial flow is expanded in the expansion element 9 towards point (a) and flows via the 3-way valve 19 to the air conditioning evaporator 8 and via the 3-way valve 18 to the second internal heat exchanger 4 and to the compressor 1 with the state points (a), (b) and (b'), where the cycle is closed. A battery cooling circuit 31 with the battery cooler 22, the battery coolant pump 24 for cooling the battery 23 is also provided in this circuit and a partial flow of the suction gas refrigerant partial flow is expanded in the expansion element 25 towards point (a') and flows via the battery cooler 22 and 3-way valve 18 to point (b). Analogous to the systems according to Fig. 1a and Fig. 2a, a motive jet heating circuit 29 and a subcooler cooling circuit 30 are provided, each with motive jet heating circuit pump 14 as well as motive jet pump 13 and also subcooler cooling circuit pump 15. Fig. 4a shows a supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning with gas auxiliary cooler 26 and bypass 28, and Fig. 4b shows the associated log pH diagram in bypass operation of the process in refrigeration system circuit. A modification of the supercritical refrigerant cycle according to Fig. 1a, as shown in the cycle according to Fig. 4a, consists in the fact that an auxiliary gas cooler 26 is additionally arranged in the suction jet refrigerant partial flow after the gas cooler 2 at point (d), the resulting state point (d') being shown in Fig. 4b. After the ejector 7, the total refrigerant flow has a state according to point (g) and is cooled in the ambient heat exchanger 10 to point (h). No additional subcooling occurs in the process shown; state points (h) and (i) are identical, and state points (a) and (a') also coincide. Furthermore, a 3-way valve 27 with a branching bypass 28 is arranged between the gas auxiliary cooler 26 and the expansion element 5. The bypass 28 runs parallel to the expansion element 5 and the suction jet heat exchanger 6, which can be bypassed via the bypass 28 parallel to the aforementioned components to the suction jet connection of the ejector 7. The auxiliary gas cooler 26, which is arranged downstream of the gas cooler 2, enables the dissipation of residual heat to cool the suction jet refrigerant partial flow to ambient temperature. The auxiliary gas cooler 26 shown in Figs. 4a and 5a can advantageously be used in any proposed configuration of the refrigerant circuit according to Figs. 1a, 2a and 3a. This configuration increases the discharge pressure of the ejector 7 and allows the compressor 1 to be relieved, resulting in a reduction in energy consumption. Finally, Figure 5a shows an integrated design of a supercritical refrigerant circuit with a compressor-ejector combination for vehicle air conditioning. The corresponding log pH diagram in Figure 5b shows the process during refrigeration system operation without a bypass circuit in an integrated system design. The modification of the circuit compared to the configuration shown in Fig. 4a consists in the fact that no motive jet heating circuit 29 is designed as an additional heat transfer circuit, but rather that the motive jet refrigerant partial flow is passed directly through the gas cooler 2 and heated by it. Similarly, the subcooler cooling circuit 30 according to Fig. 4a is not implemented indirectly, but rather the total refrigerant flow is passed directly through the suction jet heat exchanger 6 and cooled by it. The ambient heat exchanger 10 is connected to the suction jet heat exchanger 6 via the 3-way valve 17, and the refrigerant is routed from point (g) downstream of the ejector 7 to point (h) downstream of the ambient heat exchanger 10 to point (i) for the division of the total refrigerant flow into the motive jet refrigerant partial flow and the suction jet refrigerant partial flow. Thus, the functions of the subcooler 11 and the suction jet heat exchanger 6 in this circuit according to Fig.5a are integrated into each other and the motive jet heat exchanger 33 can be completely eliminated by directly guiding the motive jet refrigerant partial flow through the gas cooler 2. The proposed design scheme according to Fig. 5a integrates the gas cooler 2 and the jet heat exchanger 33 into a single component. The jet heating circuit pump 14 is therefore eliminated entirely. Furthermore, the subcooler 11 is advantageously integrated into the suction jet heat exchanger 6 as a single component in Figures 1a to 4a. With this design, the coolant circuit operated by the subcooler cooling circuit pump 15 is eliminated. Reference symbol list 1 Compressor 2 Gas cooler 3 First internal heat exchanger 4 Second internal heat exchanger 5 Expansion element 6 Suction jet heat exchanger 7 Ejector 8 Air conditioning evaporator (refrigeration mode) 9 Expansion element 10 Ambient heat exchanger 11 Subcooler 12 Air conditioning gas cooler (heat pump mode) 13 Drive jet pump 14 Drive jet heating circuit pump 15 Subcooler cooling circuit pump 16 3-way valve 17 3-way valve 18 3-way valve 19 3-way valve 20 Valve 21 Valve 22 Battery cooler 23 Battery 24 Battery coolant pump 25 Expansion element 26 Gas auxiliary cooler 27 3-way valve 28 Bypass 29 Drive jet heating circuit 30 Subcooler cooling circuit 31 Battery cooling circuit 32 Air conditioning 33 Jet heat exchanger

Claims

Supercritical refrigerant circuit with compressor-ejector combination for vehicle air conditioning, comprising a section for a total refrigerant flow, a section for a suction jet refrigerant partial flow, and a section for a motive jet refrigerant partial flow, wherein in the section for the suction jet refrigerant partial flow an air conditioning evaporator (8) with associated expansion element (9) for providing cooling in an air conditioning system (32), a compressor (1), a gas cooler (2), an expansion element (5), and a suction jet heat exchanger (6), and in the section for the motive jet refrigerant partial flow a motive jet heat exchanger (33), wherein an ejector (7) is provided in which the suction jet refrigerant partial flow and the motive jet refrigerant partial flow of the refrigerant circuit are combined.wherein an ambient heat exchanger (10) and, in parallel, an air conditioning gas cooler (12) for providing heat in the air conditioning system (32) and, subsequently, a subcooler (11) are arranged in the total refrigerant flow, after which the total refrigerant flow is divided into the suction jet refrigerant partial flow and the motive jet refrigerant partial flow. Refrigerant circuit according to claim 1, characterized in that a battery cooler (22) with associated expansion element (25) is arranged in the suction jet refrigerant partial flow of the refrigerant circuit upstream of the compressor (1). Refrigerant circuit according to claim 2, characterized in that a battery cooling circuit (31) is designed as a refrigerant circuit with a battery coolant pump (24) for cooling the battery (23). Refrigerant circuit according to one of claims 1 to 3, characterized in that a motive jet heating circuit (29) is designed as a heat transfer circuit with a motive jet heating circuit pump (14), a motive jet heat exchanger (33) and the gas cooler (2). Refrigerant circuit according to one of claims 1 to 4, characterized in that a subcooler cooling circuit (30) is designed as a refrigerant circuit with a subcooler cooling circuit pump (15), the subcooler (11) and the suction jet heat exchanger (6). Refrigerant circuit according to claim 1, characterized in that a first internal heat exchanger (3) and a second internal heat exchanger (4) are each connected in series with their heat-releasing side downstream of the gas cooler (2) and upstream of the suction jet heat exchanger (6) in the suction gas refrigerant partial flow, wherein the heat-receiving side of the first internal heat exchanger (3) is downstream of the suction jet heat exchanger (6) and the heat-receiving side of the second internal heat exchanger (4) is upstream of the compressor (1). Refrigerant circuit according to claim 6, characterized in that a motive jet heating circuit (29) is designed as a heat transfer circuit with a motive jet heating circuit pump (14), a motive jet heat exchanger (33) and the gas cooler (2), and a subcooler cooling circuit (30) is designed as a refrigerant circuit with a subcooler cooling circuit pump (15), the subcooler (11) and the suction jet heat exchanger (6). Refrigerant circuit according to one of claims 1 to 5, characterized in that a gas auxiliary cooler (26) is arranged between the gas cooler (2) and the expansion element (5) as well as a bypass (28) to the suction jet heat exchanger (6) and the associated expansion element (5). Refrigerant circuit according to claim 1, 2, 3 or 8, characterized in that the heat-emitting side of the suction jet heat exchanger (6) is arranged downstream of the ambient heat exchanger (10) in the total refrigerant flow and the heat-absorbing side of the gas cooler (2) is arranged in the motive jet refrigerant partial flow of the refrigerant circuit. Refrigerant circuit according to one of claims 1 to 9, characterized in that carbon dioxide is used as a refrigerant in the refrigerant circuit. Method for operating a supercritical refrigerant circuit for cooling a vehicle according to one of the preceding claims, characterized in that the suction jet refrigerant partial flow of the refrigerant circuit in the air conditioning evaporator (8) for cooling in the air conditioning system (32) evaporates from point a to point b with heat absorption, is then compressed in the compressor (1), cooled in the gas cooler (2), expanded in the expansion element (5), heated in the suction jet heat exchanger (6), combined in the ejector (7) with the motive jet refrigerant partial flow of the refrigerant circuit, the total refrigerant flow is cooled in the ambient heat exchanger (10), cooled in the subcooler (11) and is then divided into the motive jet refrigerant partial flow and the suction jet refrigerant partial flow.whereupon the suction jet refrigerant partial flow is expanded in the expansion element (9) and the motive jet refrigerant partial flow is conveyed and compressed by means of the motive jet pump (13) and heated in the motive jet heat exchanger (33). Method for operating a supercritical refrigerant circuit for cooling a vehicle according to claim 11, characterized in that the suction jet refrigerant partial flow of the refrigerant circuit is divided into a partial flow through the air conditioning evaporator (8) for cooling in the air conditioning system (32) and a partial flow through the battery cooler (22) for cooling the battery (23). Method for operating a supercritical refrigerant circuit for heating a vehicle according to one of claims 1 to 10, characterized in that the suction jet refrigerant partial flow of the refrigerant circuit evaporates in the ambient heat exchanger (10) while absorbing heat, is then compressed in the compressor (1), cooled in the gas cooler (2), expanded in the expansion element (5), heated in the suction jet heat exchanger (6), combined in the ejector (7) with the motive jet refrigerant partial flow of the refrigerant circuit, the total refrigerant flow is cooled in the air conditioning gas cooler (12) for heating in the air conditioning system (32), cooled in the subcooler (11) and then divided into the motive jet refrigerant partial flow and the suction jet refrigerant partial flow, after which the suction jet refrigerant partial flow is expanded in the expansion element (9) and the motive jet refrigerant partial flow is conveyed and compressed by means of the motive jet pump (13) and heated in the motive jet heat exchanger (33).Method for operating a supercritical refrigerant circuit with increased cooling capacity by internal heat transfer according to one of claims 6 to 10, characterized in that the suction jet refrigerant partial flow of the refrigerant circuit evaporates in the air conditioning evaporator (8) for cooling in the air conditioning system (32) by absorbing heat, is subsequently superheated in the inner heat exchanger (4), compressed in the compressor (1), cooled in the gas cooler (2), cooled in the inner heat exchanger (3), cooled in the inner heat exchanger (4), expanded in the expansion element (5), heated in the suction jet heat exchanger (6), heated in the inner heat exchanger (3), combined in the ejector (7) with the motive jet refrigerant partial flow of the refrigerant circuit, the total refrigerant flow is cooled in the ambient heat exchanger (10), cooled in the subcooler (11) and subsequently divided into the motive jet refrigerant partial flow and the suction jet refrigerant partial flow.whereupon the suction jet refrigerant partial flow is expanded in the expansion element (9) and the motive jet refrigerant partial flow is conveyed and compressed by means of the motive jet pump (13) and heated in the motive jet heat exchanger (33). Method for operating a supercritical refrigerant circuit according to claim 14, characterized in that the suction jet refrigerant partial flow of the refrigerant circuit is cooled to ambient temperature in the gas auxiliary cooler (26) after cooling in the gas cooler (2). Method for operating a supercritical refrigerant circuit according to claim 14, characterized in that, in order to increase the discharge pressure of the ejector (7), the suction jet refrigerant partial flow of the refrigerant circuit after the gas auxiliary cooler (26) is directed via the bypass (28) directly into the ejector (7).

Images