Refrigerant circuit with calming device between a branch line for hot gas and a refrigerant receiver, motor vehicle and method for operating a refrigerant circuit

Abstract

The invention relates to a refrigerant circuit (10) for a motor vehicle, wherein a compressor (14) in heat pump operation supplies compressed refrigerant to a heat exchanger (16) via a heating branch (22). The heat exchanger (16) is designed to heat an airflow that can be introduced into a passenger compartment (24). A branch line (40), which can be shut off by means of a shut-off device (42) and leads from the heating branch (22), can be used in air conditioning operation to extract refrigerant from the heat exchanger (16). A refrigerant receiver (36) is arranged in a return line (32), through which refrigerant that can be expanded by means of an expansion device (28) can be supplied to a suction side (34) of the compressor (14). The refrigerant circuit (10) has a calming device (50) which is arranged upstream of an inlet (44) of the refrigerant collector (36).In heat pump operation, refrigerant originating from the branch line (40) can only be supplied to the inlet (44) of the refrigerant receiver (36) after passing through the calming device (50). The invention also relates to a motor vehicle and a method for operating the refrigerant circuit (10).

Description

The invention relates to a refrigerant circuit for a motor vehicle, having a compressor which is designed to feed refrigerant compressed in a heat pump mode of the refrigerant circuit to a heating heat exchanger of the refrigerant circuit via a heating branch of the refrigerant circuit. The heating heat exchanger is designed to heat an air flow that can be introduced into a passenger compartment of the motor vehicle. The refrigerant circuit has a branch line which leads away from the heating branch and which can be shut off by means of a shut-off device. In an air-conditioning mode of the refrigerant circuit, the branch line can be used for extracting refrigerant from the heating heat exchanger. In a return line of the refrigerant circuit, via which refrigerant which can be expanded by means of at least one expansion device of the refrigerant circuit can be fed to a suction side of the compressor, a refrigerant collector is arranged. Furthermore, the invention relates to a motor vehicle having such a refrigerant circuit and to a method for operating the refrigerant circuit.DE 10 2017 218 424 A1 describes a vehicle refrigeration system which can be used, on the one hand, in an air-conditioning mode and, on the other hand, in a heating mode, wherein a heat pump function is realized in the heating mode. In the heating mode, compressed and heated refrigerant is supplied to a heating gas cooler via a heating branch of the vehicle cooling system. In the air-conditioning mode, refrigerant can be extracted from the heating gas cooler arranged in the heating branch via an extraction branch. For this purpose, a shut-off element arranged in the suction branch is opened. The branch line opens upstream of a refrigerant collector into a return line of the vehicle cooling system. Relaxed refrigerant can be supplied via the return line to a suction side of a compressor of the vehicle cooling system.In the case of the refrigerant circuit mentioned at the beginning, it is favorable if, in the heat pump mode and thus the heating mode, the heating heat exchanger can very rapidly provide a high heating power. For this purpose, it is possible to open the shut-off device, which is arranged in the branch line leading from the heating branch, to a certain extent. As a result, refrigerant can be supplied to the suction side of the compressor, which refrigerant has an elevated temperature despite expansion effected via the shut-off device. At a given volume flow of the refrigerant which the compressor delivers in the heat pump mode, the higher density of the refrigerant on the suction side of the compressor leads to a greater mass flow of refrigerant, with which the heating heat exchanger is acted upon, on account of the heat input and a resulting rising low-pressure level. This in turn leads to a higher heating power of the heating heat exchanger at the given volume flow.When using the branch line for supplying refrigerant to the suction side of the compressor, however, turbulences of refrigerant on a low-pressure side of the refrigerant circuit may occur, in particular in the inflow to the refrigerant collector and / or within the refrigerant collector, which may result in an inhomogeneous and consequently poorly mixed refrigerant state.In addition, in the heat pump operation of the refrigerant circuit, it may occur that no complete evaporation of the refrigerant takes place in an evaporator of the refrigerant circuit, but the refrigerant still contains liquid droplets. The refrigerant coming from the branch line is then combined with such refrigerant which still contains liquid droplets. It may be that there is insufficient mixing of the hot gas originating from the branch line with the refrigerant having two phases, which is drawn from the heating heat exchanger in the heat pump operation and then expanded, wherein the refrigerant has only been insufficiently evaporated after the expansion.Both the turbulence and the non-uniformity of the refrigerant state as a result of insufficient mixing can lead to the situation that generally on the low-pressure side, in particular in the refrigerant collector, there is not sufficiently good separation of liquid droplets from the refrigerant stream. Then, when the compressor draws in refrigerant containing droplets of liquid refrigerant to an increased extent, it may impair the operability of the compressor. This is disadvantageous.It is an object of the present invention to provide a refrigerant circuit of the type mentioned at the beginning, in which an impairment of the compressor can be particularly largely avoided in heat pump operation, and to specify a motor vehicle having such a refrigerant circuit and a corresponding method for operating the refrigerant circuit.This object is achieved by a refrigerant circuit having the features of claim 1, a motor vehicle having the features of claim 9 and a method having the features of claim 10. Advantageous embodiments with expedient developments of the invention are specified in the dependent patent claims and in the following description.The refrigerant circuit for a motor vehicle according to the invention comprises a compressor, wherein the compressor is designed to supply refrigerant compressed to a heating heat exchanger of the refrigerant circuit via a heating branch of the refrigerant circuit in a heat pump operation of the refrigerant circuit. The heating heat exchanger is designed to heat an air flow that can be introduced into a passenger compartment of the motor vehicle. The refrigerant circuit has a branch line which can be shut off by means of a shut-off device and which leads away from the heating branch. The branch line can be used in an air-conditioning mode of the refrigerant circuit for extracting refrigerant from the heating heat exchanger. In a return line of the refrigerant circuit, via which refrigerant which can be expanded by means of at least one expansion device of the refrigerant circuit can be fed to a suction side of the compressor, a refrigerant collector is arranged. The refrigerant circuit has at least one settling device which is arranged upstream of an inlet of the refrigerant collector. In this case, in the heat pump operation of the refrigerant circuit, refrigerant originating from the branch line can only be supplied to the inlet of the refrigerant collector after flowing through the at least one settling device.If, in the heat pump operation of the refrigerant circuit, the compressor introduces the compressed and heated refrigerant into the heating branch and thus supplies it to the heating heat exchanger, then by partially opening the shut-off device, refrigerant in the form of (expanded) hot gas can be supplied via the branch line outgoing from the heating branch to a low-pressure side of the refrigerant circuit and thus to the suction side of the compressor. The arrangement of the settling device upstream of the inlet of the refrigerant collector ensures here that the hot gas together with the refrigerant flowing on the low-pressure side initially passes through the at least one settling device before the refrigerant or hot gas originating from the branch line reaches the inlet of the refrigerant collector and the compressor.The settling device accordingly has the effect that turbulences or turbulent flows of the refrigerant can be reduced to a particularly large extent and the partial refrigerant flows mix before the refrigerant or the total refrigerant flow reaches the inlet of the refrigerant collector and of the compressor. As a result, the refrigerant collector can very well fulfill the function of separating liquid refrigerant from gaseous refrigerant. Consequently, it can be ensured to a large extent that as few liquid droplets of the refrigerant as possible and a homogeneous refrigerant state are supplied to the suction side of the compressor. This makes it possible to avoid adverse effects on the compressor due to fluid impacts particularly largely during the heat pump operation of the refrigerant circuit.In addition, the settling device advantageously leads to mass flows of the refrigerant expanded by means of the at least one expansion device of the refrigerant circuit and of the refrigerant originating from the branch line being mixed particularly largely or very homogeneously. This also contributes to keeping a proportion of liquid droplets in the refrigerant mass flow particularly low, which reaches the suction side of the compressor in the heat pump operation.Liquid droplets can be present in the relaxed refrigerant in particular when no complete evaporation of the refrigerant takes place in the heat pump operation of the refrigerant circuit in a heat exchanger of the refrigerant circuit usable as an evaporator. In particular in this case, the settling device advantageously ensures that particularly homogeneously mixed and settled, preferably laminarly flowing refrigerant is supplied to the inlet of the refrigerant collector and the compressor, and preferably non-turbulently flowing refrigerant.In the heat pump mode, the air stream can be heated by means of the heating heat exchanger in a direct manner or in an indirect manner, that is to say via an intermediate medium.Furthermore, it is advantageous if the shut-off device is designed to be continuously adjustable. This is because a recirculation of hot gas to the suction side of the compressor can be set in very fine doses.In the air-conditioning mode of the refrigerant circuit, the expanded refrigerant can be used in particular to cool the air stream which can be introduced into the passenger compartment of the motor vehicle and / or a coolant which can flow through a coolant circuit, for example in order to cool at least one component of the motor vehicle. In the air-conditioning mode, the expanded refrigerant can accordingly flow in particular through an interior evaporator of the refrigerant circuit and / or a chiller of the refrigerant circuit.The settling device preferably provides an additional flow path for the refrigerant, along which flow paths turbulence in the refrigerant flow duct is largely reduced, and / or the hot gas originating from the branch line and the expanded refrigerant are particularly largely mixed. This applies in particular to the case of a combination of at least two partial refrigerant streams having a qualitatively different composition with respect to their refrigerant state, in particular their vapor content.For example, the reduction of the turbulence and / or the good mixing can be achieved by the fact that the settling device has a multiplicity of flow channels through which the refrigerant can flow. Additionally or alternatively, a particularly long flow path from an inlet of the pacifier to an outlet of the pacifier or homogenizer can be provided within the pacifier by deflecting devices or the like. Each of these measures is conducive to uniformizing the flow of the refrigerant before reaching the inlet of the refrigerant collector and the compressor.Furthermore, the settling device is preferably designed such that the pressure loss in the refrigerant circuit caused by the provision of the settling device is particularly low.The refrigerant circuit preferably comprises a chiller through which refrigerant can flow on the one hand and a coolant on the other hand. In this case, the settling device is arranged between a junction point of the refrigerant circuit and the inlet of the refrigerant collector, wherein a refrigerant line coming from the chiller opens into the return line at the junction point. By providing the chiller, in the air-conditioning mode of the refrigerant circuit, the chiller can be used as an evaporator in order to dissipate heat from components which can be acted upon by the coolant. This is advantageous.The branch line can open into a section of the return line upstream of the junction point, wherein refrigerant expanded via the section can be discharged from a heat exchanger of the refrigerant circuit to which ambient air can be applied in the heat pump operation. The heat exchanger can be used as an evaporator in heat pump operation. Due to the opening of the branch line upstream of the junction point into the section of the return line, it can be ensured in a particularly simple manner that, in the heat pump mode, the refrigerant introduced into the section or expanded hot gas from the branch line reaches the stilling device together with the expanded refrigerant. This is advantageous for very substantial stilling of the refrigerant flow before reaching the inlet of the refrigerant collector and of the compressor.If reference is made below to the chiller and / or the heat exchanger of the refrigerant circuit that can be supplied with ambient air, the aforementioned chiller through which refrigerant can flow on the one hand and coolant on the other hand or the aforementioned heat exchanger of the refrigerant circuit that can be supplied with ambient air is meant, even if the indefinite article "on" is placed in front of this component of the refrigerant circuit.The heat exchanger of the refrigerant circuit, which can be supplied with ambient air, can be arranged in particular in a front region of the motor vehicle when the refrigerant circuit is installed in the motor vehicle. Accordingly, the heat exchanger to which ambient air can be applied can be designed as a front end cooler of the motor vehicle or can be associated with a front end cooler of the motor vehicle. And the heating heat exchanger, by means of which the air flow that can be introduced into the passenger compartment of the motor vehicle can be directly heated, can be arranged in particular in an air conditioning box or air conditioning device, from which the heated air flow can pass into the passenger compartment of the motor vehicle.If indirect heating of the air stream takes place, an additional heat transport medium transporting a heat stream is integrated between the refrigerant circuit and the air stream receiving the heat, for example in the form of a liquid coolant which represents the heat source for the air stream to be heated.Additionally or alternatively, the branch line may open into the return line at the node or between the node and the settling device. In this case, the refrigerant discharged from the heat exchanger can be introduced into the chiller via a section of the return line. In addition, refrigerant expanded in the heat pump mode can be discharged via the section of the return line from a heat exchanger of the refrigerant circuit that can be acted upon by ambient air, wherein the heat exchanger can be used as an evaporator in the heat pump mode.By introducing the refrigerant discharged from the heat exchanger into the chiller via the section of the return line, particularly extensive evaporation of the expanded refrigerant can be achieved very effectively. This is because even if liquid refrigerant leaves the heat exchanger used as evaporator in the heat pump mode, this liquid refrigerant can be evaporated or post-evaporated in the chiller arranged downstream of the heat exchanger. In the chiller, heat can be transferred to the refrigerant by the coolant which flows through the chiller. This heat can be used in the chiller for evaporating liquid refrigerant. The corresponding post-evaporation of liquid refrigerant is conducive to particularly efficient operation of the refrigerant circuit.In this case, the heat exchanger, which is supplied with the air or ambient air as a heat source, and the downstream chiller, which is supplied with the coolant serving as a heat source, are connected to one another in series. A series connection is thus realized.The refrigerant circuit preferably comprises a chiller through which refrigerant can flow on the one hand and a coolant on the other hand. In this case, the at least one settling device comprises the chiller or the at least one settling device is provided by the chiller, and in the heat pump operation of the refrigerant circuit refrigerant originating from the branch line can only be supplied to the inlet of the refrigerant collector and of the compressor after flowing at least through the chiller. Accordingly, if the refrigerant circuit already has the chiller, the chiller can be used as the at least one settling device. As a result, no further component needs to be provided in the refrigerant circuit in order to realize, upstream of the inlet of the refrigerant collector and of the compressor, the settling or homogenization of the refrigerant flow supplied to the refrigerant collector and the compressor in the heat pump operation. The refrigerant flow or total flow of refrigerant that is established is composed here of at least two partial mass flows.And if at least one further stilling device is provided in addition to the chiller, a particularly extensive homogenization and / or mixing of the refrigerant or hot gas originating from the branch line with the expanded refrigerant can advantageously be realized before the homogenized refrigerant thus formed reaches the refrigerant collector and compressor. This is advantageous.At a junction point of the refrigerant circuit, a refrigerant line coming from the chiller and a section of the return line can be joined together, wherein refrigerant expanded via the section in the heat pump operation can be discharged from a heat exchanger of the refrigerant circuit to which ambient air can be applied, and the heat exchanger can be used as an evaporator in the heat pump operation. Here, the node is arranged upstream of the inlet of the refrigerant collector. In this way, it can be ensured very reliably that refrigerant flowing through the branch line initially flows through the chiller and then reaches the junction point at which the refrigerant is combined with the expanded refrigerant, which is discharged in the heat pump operation from the heat exchanger of the refrigerant circuit, which heat exchanger can be acted upon with ambient air. As a result, particularly largely homogenized refrigerant reaches the inlet of the refrigerant collector. This is advantageous for acting on the refrigerant collector and the compressor with a very well calmed mass flow of refrigerant.Additionally or alternatively, a section of the return line, via which refrigerant expanded in the heat pump mode can be discharged from a heat exchanger of the refrigerant circuit that can be acted upon by ambient air, can open into the branch line upstream of the chiller, wherein the heat exchanger can be used as an evaporator in the heat pump mode. In this way, it can be achieved in the heat pump operation that both the expanded refrigerant discharged from the heat exchanger to which ambient air can be supplied and the refrigerant discharged from the heating branch via the branch line flow through the chiller before this combined refrigerant mass flow reaches the inlet of the refrigerant collector. This is conducive to a particularly extensive homogenization and mixing of the expanded refrigerant with the hot gas flowing through the branch line.Preferably, a check valve is arranged in the branch line. It can thus be ensured in a particularly simple manner that when, in the air-conditioning mode of the refrigerant circuit, the branch line is used for extracting refrigerant from the heating heat exchanger, no return flow of refrigerant into the heating heat exchanger takes place. By configuring the valve arranged in the branch line as a nonreturn valve instead of an electrically controllable valve, no control mechanism having corresponding software for controlling the valve needs to be implemented. In particular, it is not necessary to detect pressure signals and / or temperature signals from active and inactive lines of the refrigerant circuit and evaluate them for controlling an electrically controllable valve. This is advantageous.Additionally or alternatively, a check valve can be arranged in a section of the return line, via which refrigerant can be discharged from a heat exchanger of the refrigerant circuit, which heat exchanger can be supplied with ambient air. The following finding is based on the following: in a heat pump operation of the refrigerant circuit, in which the chiller is used as a heat source for the refrigerant, the chiller of the refrigerant circuit is charged with relaxed refrigerant. In this heat pump operation, in which heat of the coolant is transferred to the expanded refrigerant in the chiller, refrigerant can be extracted via the section of the return line from the heat exchanger of the refrigerant circuit, which heat exchanger can be acted upon by ambient air. The provision of the check valve ensures in a simple manner that no return flow of suctioned refrigerant into the heat exchanger to which ambient air can be applied occurs. This is advantageous.In particular, if the section of the return line, via which refrigerant expanded in the heat pump mode can be discharged from the heat exchanger of the refrigerant circuit, which exchanger can be acted upon by ambient air, opens into the branch line upstream of the chiller, a common nonreturn valve can be arranged downstream of an opening of the section into the branch line in the branch line. By means of this nonreturn valve, both the branch line and the section of the return line via which refrigerant can be discharged from the heat exchanger of the refrigerant circuit, which heat exchanger can be acted upon by ambient air, are then mechanically or automatically secured against a return flow of refrigerant. This is advantageous.The motor vehicle according to the invention has the refrigerant circuit according to the invention. As a result, the refrigerant supplied to the compressor via the branch line can be advantageously used in the motor vehicle in order to provide a high heating power at the heating heat exchanger particularly quickly in the heat pump operation. This is advantageous.The motor vehicle is preferably designed as an electric vehicle or as a hybrid vehicle. In particular in such a motor vehicle, it is favorable if a high heating power can be rapidly provided at the heating heat exchanger by returning a partial mass flow of (expanded) hot gas to the suction side of the compressor even at very low ambient temperatures. During the electric driving operation of the motor vehicle, it may take a period of time for heat to be dissipated from components of the motor vehicle that are to be cooled, which heat can be introduced into the refrigerant during the heat pump operation of the refrigerant circuit.When an electrical energy store of the electric vehicle or hybrid vehicle is designed as a high-voltage battery, the electrical energy store generally has a rated voltage of more than 48 volts and in particular of up to several hundred volts.In the method according to the invention for operating a refrigerant circuit for a motor vehicle, a compressor supplies refrigerant compressed to a heating heat exchanger of the refrigerant circuit via a heating branch of the refrigerant circuit in a heat pump operation of the refrigerant circuit. The heating heat exchanger is designed to heat an air flow that can be introduced into a passenger compartment of the motor vehicle. The refrigerant circuit has a branch line which can be shut off by means of a shut-off device and which leads away from the heating branch and which can be used in an air-conditioning mode of the refrigerant circuit for removing refrigerant from the heating heat exchanger. In a return line of the refrigerant circuit, via which refrigerant expanded by means of at least one expansion device of the refrigerant circuit is supplied to a suction side of the compressor, a refrigerant collector is arranged. The refrigerant circuit has at least one settling device which is arranged upstream of an inlet of the refrigerant collector. In the heat pump operation of the refrigerant circuit, refrigerant originating from the branch line is only supplied to the inlet of the refrigerant collector after flowing through the at least one settling device. It can thus be ensured that at most a small proportion of refrigerant containing liquid droplets is supplied to the compressor from the refrigerant collector. Consequently, in the heat pump operation, adverse effects on the compressor due to liquid impacts or the like can be particularly largely avoided.In the heat pump mode, the air stream can be heated directly by means of the heating heat exchanger or indirectly, that is to say via an intermediate medium.The advantages and preferred embodiments described for the refrigerant circuit according to the invention apply analogously to the motor vehicle according to the invention and to the method according to the invention and vice versa.Accordingly, the invention also includes developments of the method according to the invention and of the motor vehicle which have features as have already been described in connection with the developments of the refrigerant circuit according to the invention. For this reason, the corresponding developments of the method according to the invention and of the motor vehicle are not described again here.The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus.The invention also includes the combinations of the features of the described embodiments. The invention therefore also comprises implementations which each have a combination of the features of a plurality of the described embodiments, provided that the embodiments have not been described as mutually exclusive.Exemplary embodiments of the invention are described below. The following shows: FIG. 1 schematically shows a refrigerant circuit for a motor vehicle, in which, in a heat pump mode, an (optional) settling device arranged upstream of an inlet of a refrigerant ensures good mixing and good homogenization of a refrigerant stream containing hot gas; FIG. 2 shows a variant of the refrigerant circuit, in which a branch line, which can be used for removing refrigerant, opens into a return line upstream of the settling device, wherein the refrigerant removed from the heat exchanger is introduced into a chiller via a section of the return line, via which relaxed refrigerant can be removed from a heat exchanger to which ambient air can be applied; FIG. 3 shows a further variant of the refrigerant circuit, in which the settling device is formed by the chiller of the refrigerant circuit, wherein expanded hot gas, after flowing through the chiller, is mixed via the branch line with expanded refrigerant, which is discharged from the heat exchanger of the refrigerant circuit, which heat exchanger can be acted upon by ambient air; FIG. 4 shows a further variant of the refrigerant circuit, in which a section of the return line, via which relaxed refrigerant can be discharged from the heat exchanger to which ambient air can be applied, opens into the branch line upstream of the chiller; and FIG. 5 schematically shows a motor vehicle which has the refrigerant circuit.The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that are to be considered independently of one another and that also develop the invention independently of one another. Therefore, the disclosure is intended to include combinations of the features of the embodiments other than those illustrated. Furthermore, the described embodiments can also be supplemented by further features of the invention that have already been described.In the figures, identical reference numerals designate functionally identical elements.FIG. 1 shows schematically and by way of example a refrigerant circuit 10 as can be used in a motor vehicle 12 shown in FIG. 5. The refrigerant circuit 10 comprises a compressor 14, and compressed and heated refrigerant can be supplied to a heating heat exchanger 16 of the refrigerant circuit 10 by means of the compressor 14 in a heat pump operation of the refrigerant circuit 10. For this purpose, a first valve 18 or first shut-off valve is opened and a second valve 20 or second shut-off valve is closed. By opening the first valve 18, the refrigerant compressed by means of the compressor 14 reaches a heating branch 22 of the refrigerant circuit 10. In the heat pump mode, an air stream can be heated directly or indirectly by means of the heating heat exchanger 16, which air stream can be introduced into a passenger compartment 24 of the motor vehicle 12 (compare FIG. 5 ).In the heat pump mode, the refrigerant continues to flow from the heating heat exchanger 16 to a third valve or third shut-off valve 26 which is open in the heat pump mode of the refrigerant circuit 10. As a result, the refrigerant coming from the heating heat exchanger 16 reaches a first expansion device 28, by means of which the refrigerant previously cooled in the heating heat exchanger 16 is expanded. From the first expansion device 28, the refrigerant continues to pass to a heat exchanger 30 of the refrigerant circuit 10, which can be used as an evaporator in the heat pump operation.The expanded refrigerant coming from the heat exchanger 30 reaches a suction side 34 of the compressor 14 via a return line 32 in the heat pump mode.In an air conditioning operation of the refrigerant circuit 10, the first valve 18 is closed and the second valve 20 is opened. As a result, the compressed refrigerant conveyed by the compressor 14 initially reaches the heat exchanger 30, which then functions as a refrigerant cooler. Depending on the refrigerant used, this refrigerant cooler can be designed as a gas cooler or as a condenser.The heat exchanger 30, which functions as a refrigerant cooler in the air-conditioning mode and as an evaporator in the heat pump mode, is arranged in the present case in the region of a vehicle front 38 of the motor vehicle 12 (compare FIG. 5 ) and can accordingly be supplied with ambient air. In the air-conditioning mode, the ambient air ensures cooling of the refrigerant compressed by means of the compressor 14 in the heat exchanger 30. In contrast, in the heat pump operation of the refrigerant circuit 10, in which the heat exchanger 30 is used as an evaporator, the refrigerant expanded by means of the first expansion device 28 can evaporate in the heat exchanger 30 while absorbing heat from the ambient air.In particular at low ambient temperatures, it is desirable in heat pump operation or heating operation if a high heating power is provided very quickly at the heating heat exchanger 16. For this purpose, compressed and heated refrigerant can be discharged or branched off via a branch line 40 branching off from the heating branch 22. In this case, a shut-off device 42 is opened a certain distance, by means of which the branch line 40 can be shut off or closed in a targeted manner. The shut-off device 42 usable in the manner of an expansion valve ensures, in the position in which it is opened to a certain extent, that refrigerant compressed via the branch line 40 expands and can reach the suction side 34 of the compressor 14. It is particularly advantageous if the shut-off device 42 can be opened continuously.If the refrigerant originating from the branch line 40 reaches an inlet 44 of the refrigerant collector 36 as a partial mass flow without a previous settling, then turbulences can occur in the refrigerant collector 36. This applies in particular if no good mixing of the partial mass flow with the main mass flow conducted via the heating heat exchanger 16 takes place. The occurrence of turbulence can in turn lead to the situation that sufficiently good separation of liquid refrigerant does not take place in the refrigerant collector 36. However, if droplets of liquid, i.e. droplets of liquid refrigerant, reach the suction side 34 of the compressor 14 to a greater extent, the compressor 14 may be impaired in function or even damaged. This is avoided in the present case.Portions of liquid refrigerant in the refrigerant stream which reaches the refrigerant collector 36 can be caused in particular in the heat pump operation of the refrigerant circuit 10 by the fact that no complete evaporation of the refrigerant takes place in the heat exchanger 30 which can be supplied with ambient air. In this case, a two-phase refrigerant flow, which contains liquid refrigerant and gaseous refrigerant, flows through a section 46 of the return line 32, via which refrigerant expanded in the heat pump mode can be discharged from the heat exchanger 30.In the present case, it is ensured that good mixing and homogenization of the refrigerant containing the liquid phase and the gaseous phase, which comes from the heat exchanger 30, and of the hot gas, which flows through the branch line 40, takes place.For this purpose, in the variant of the refrigerant circuit 10 shown in FIG. 1, a settling device 48 is arranged upstream of the inlet 44 of the refrigerant collector 36. Due to the provision of the settling device 48, a longer flow path toward the inlet 44 of the refrigerant collector 36 is present in the refrigerant circuit 10 than would be the case without the provision of the settling device 48. Accordingly, the settling device 48 provides better mixing and homogenization of the refrigerant flow. In particular, by providing deflecting devices (not shown) in the settling device 48, a particularly long flow path for the refrigerant can be provided before it reaches the inlet 44 of the refrigerant collector 36.The described settling device 48 can be designed in such a way that at least two refrigerant partial mass streams are combined at their inlet 44 and then flow jointly through the interior of the settling device 48. By lengthening the flow path for the refrigerant realized in this way, an inlet section and / or settling section or mixing section for the total refrigerant mass flow is formed. In this way, homogenization of the refrigerant flow can be effected. The settling device 48 is preferably designed in such a way that a flow path which is as long as possible is provided with low pressure losses. This is because potential losses in performance and / or losses in efficiency can be at least largely avoided as a result.In the variant of the refrigerant circuit 10 shown in FIG. 1, it is ensured that the refrigerant originating from the branch line 40 reaches the inlet 44 of the refrigerant collector 36 only after flowing through the settling device 48 and then further to the compressor 14.The refrigerant circuit 10 preferably comprises a chiller 50, through which a refrigerant can flow on the one hand and a coolant on the other hand. Accordingly, the chiller 50 is integrated on the one hand into the refrigerant circuit 10 and on the other hand into a coolant circuit 52, which is illustrated only schematically and in detail in FIG. 1. By means of the coolant flowing through the chiller 50, electrical and / or electronic components of the motor vehicle 12 can be cooled, for example an electrical energy store 80 and / or at least one electrical drive device 82 (compare FIG. 5 ) of the motor vehicle 12, provided that cooling of such components is desirable.In the variant of the refrigerant circuit 10 shown in FIG. 1, the settling device 48 is arranged between a junction 54 of the refrigerant circuit 10 and the inlet 44 of the refrigerant collector 36. At the junction 54, a refrigerant line 56 coming from the chiller 50 opens into the return line 32. Consequently, the settling unit 48 is preferably placed or / provided at a location at which the total mass flow of the refrigerant circulating in the refrigerant circuit 10 is present again at the earliest. In the variant shown in FIG. 1, this location is arranged directly upstream of the refrigerant collector 36 and downstream of the node 54.In the air conditioning operation of the refrigerant circuit 10, the chiller 50 may be used to cool the coolant flowing through the coolant circuit 52. For this purpose, the refrigerant coming from the heat exchanger 30 in the air-conditioning mode can be expanded by means of a second expansion device 58, which is arranged upstream of the chiller 50.Additionally or alternatively, in the air-conditioning mode, a third expansion device 60 of the refrigerant circuit 10 can be opened in order to expand the refrigerant coming from the heat exchanger 30. The refrigerant expanded by means of the third expansion device 60 can be fed to an interior evaporator 62 of the refrigerant circuit 10, by means of which evaporator the air stream which can be introduced into the passenger compartment 24 can be cooled and optionally dehumidified in the air-conditioning mode.The interior evaporator 62 and the heating heat exchanger 16 can be arranged in an air conditioning unit 64, which is shown only schematically in the present case.The functions and arrangement of further components of the refrigerant circuit 10 shown by way of example in FIG. 1, such as a first nonreturn valve 66 and an inner heat exchanger 74 of the refrigerant circuit 10, need not be discussed in more detail here.In the variant of the refrigerant circuit 10 shown in FIG. 1, the branch line 40 opens into the section 46 of the return line 32 upstream of the junction point 54. Furthermore, the section 46 can be shut off by means of a further shut-off valve 70. In this way, it can be ensured in the air-conditioning operation that compressed and heated refrigerant coming from the second valve 20 exclusively reaches the heat exchanger 30, which can be supplied with the ambient air.Also shown in FIG. 1 is a second check valve 72 which is arranged in the section 46 of the return line 32 between the second shut-off valve 70 and the junction point 54. If, in a water heat pump mode of the refrigerant circuit 10, the compressed refrigerant coming from the heating heat exchanger 16 is expanded by means of the second expansion device 58 when the first shut-off valve 26 is open, refrigerant can be extracted from the heat exchanger 30 via the section 46. This applies in the case that a pressure level is set or set at least briefly on the low-pressure side of the refrigerant circuit 10, which pressure level comes to lie below the pressure level resulting around the heat exchanger 30 in the inactive sector of the refrigerant circuit 10. In this case, the second nonreturn valve 72 ensures, in the case of reversing pressure levels, that the refrigerant which is drawn off does not return to the heat exchanger 30. The function can be implemented independently of interventions by a controller and functions automatically.In the air heat pump operation of the refrigerant circuit 10, in which heat of the ambient air in the heat exchanger 30 is transferred to the expanded refrigerant, the portion 46 provides for a return of the expanded refrigerant toward the suction side 34 of the compressor 14.The variant of the refrigerant circuit 10 shown in FIG. 2 corresponds in part to the variant of the refrigerant circuit 10 shown in FIG. 1, but here the branch line 40 opens into the return line 32 at the junction point 54. In addition, the section 46 of the return line 32, via which the expanded refrigerant can be discharged from the heat exchanger 30 to which the ambient air can be applied in the heat pump operation, opens between the second expansion device 58 and the chiller 50 into a line leading from the second expansion device 58 to the chiller 50. Accordingly, the refrigerant discharged or exiting from the heat exchanger 30 can be introduced into the chiller 50 via the section 46.The course of the return line 32 with the section 46 opening upstream of the chiller 50 entails the possibility of implementing a dual heat pump operation in which the air heat pump and the water heat pump are active. The air heat pump operation and the water heat pump operation can be implemented in a partial series connection.Furthermore, as shown in FIG. 1, the dual heat pump operation can be implemented in a pure parallel connection of the heat exchanger 30 to which the ambient air can be applied and of the chiller 50.If coolant does not flow through the coolant circuit 52, i.e. the coolant is in the chiller 50, the mode of operation of an air heat pump in the refrigerant circuit 10 according to FIG. 2 using the heat exchanger 30 corresponds to the corresponding operation of the refrigerant circuit 10 explained with reference to FIG. 1. Liquid refrigerant which has not yet been vaporized in the heat exchanger 30 can then evaporate or re-evaporate in the chiller 50. By means of the post-evaporation of refrigerant in the chiller 50, a heating power of the refrigerant circuit 10 in the heat pump operation can be advantageously increased.Furthermore, when both the first expansion device 28 and the second expansion device 58 are opened in the heat pump operation, a part of the refrigerant, which comes from the heating heat exchanger 16 when the first shut-off valve 26 is opened, can be directly supplied to the chiller 50. Accordingly, in the refrigerant circuit 10, the chiller 50 can be flowed through on the one hand in series with the heat exchanger 30 and on the other hand in parallel with the heat exchanger 30.If, in the heat pump mode, the first expansion device 28 is open, but the second expansion device 58 is closed, coolant flowing through the chiller 50, then a pure series connection of the heat exchanger 30 and the chiller 50 and thus of two heat pump evaporators can be produced in the refrigerant circuit 10 according to FIG. 2.In addition, the refrigerant circuit 10 can be operated in a triangular process in which the refrigerant coming from the heating heat exchanger 16 is expanded by means of a fourth expansion device 68 when the first shut-off valve 26 is closed. The refrigerant expanded by means of the fourth expansion device 68 can then pass via the chiller 50 and the settling device 48 to the refrigerant collector 36 and then to the suction side 34 of the compressor 14.When no coolant flows through the coolant circuit 52, only by compressing the coolant by means of the compressor 14 is the heating power provided, which can be output to the air flow for the passenger compartment 24 in the heating heat exchanger 16. In an additional or alternatively possible triangular process, refrigerant can be conducted over the chiller 50 by opening the second expansion device 58 when the first expansion device 28 and the fourth expansion device 68 are closed, without the refrigerant flowing through the chiller 50. Thus, no heat transfer takes place between coolant and the refrigerant flowing through the chiller 50, and consequently no evaporation of refrigerant takes place in the chiller 50.Furthermore, in the triangular process in which coolant does not flow through the chiller 50, a portion of the refrigerant flow can be conveyed by opening the first expansion device 28 toward the heat exchanger 30, and a further portion of the refrigerant flow can be conveyed by opening the second expansion device 58 toward the chiller 50.The pressure to which the refrigerant is expanded by actuating the first expansion device 28 is preferably set such that no icing takes place at the heat exchanger 30 to which the ambient air can be applied. This applies in particular to the case in which both heat absorption from the ambient air takes place in the heat exchanger 30 and heat absorption from the coolant which flows through the coolant circuit 52 takes place in the chiller 50.In the variant of the refrigerant circuit 10 shown in FIG. 3, the settling device 48 is provided by the chiller 50. The refrigerant originating from the branch line 40 is therefore only supplied to the inlet 44 of the refrigerant collector 36 after flowing through the chiller 50 in the heat pump operation of the refrigerant circuit 10.In contrast, in the variant shown in FIG. 3 (as described with reference to FIG. 1 ), the refrigerant line 56 coming from the chiller 50 and the section 46 of the return line 32 are also joined together at the junction point 54. The refrigerant originating from the branch line 40 accordingly flows in the heat pump mode first through the chiller 50 serving as a settling device before the combination with the refrigerant discharged from the heat exchanger 30 takes place. The combined refrigerant mass flow then reaches the inlet 44 of the refrigerant collector 36.Furthermore, as in the variant shown in FIG. 2, a check valve 76 is also arranged in the branch line 40 in the variant of the refrigerant circuit 10 shown in FIG. 3. When the branch line 40 is used for extracting refrigerant from the heating branch 22, this check valve 76 ensures that a return flow of refrigerant into the heating heat exchanger 16 is prevented.In the variant of the refrigerant circuit 10 shown in FIG. 4, the chiller 50 also provides the settling device 48. Furthermore, as in the variant explained with reference to FIG. 3, the branch line 40 opens upstream of the chiller 50, that is to say between the second expansion device 58 and the chiller 50, into the line leading to the chiller 50.However, in the variant of the refrigerant circuit 10 shown in FIG. 4, in contrast to the variant shown in FIG. 3, the section 46 of the return line 32, via which the expanded refrigerant is discharged from the heat exchanger 30 in the heat pump operation, opens into the branch line 40 upstream of the chiller 50. As a result, both the refrigerant which comes from the heat exchanger 30 and the refrigerant which comes from the branch line 40 flow through the chiller 50. As a result, at the inlet of the chiller 50 or directly upstream of the chiller 50, the total mass flow of the refrigerant flowing in the refrigerant circuit 10 is present.In this variant, the check valve 76 arranged in the branch line 40 can be arranged downstream of a junction 78, at which the section 46 leads into the branch line 40. Accordingly, it is possible to dispense with the nonreturn valve 72 shown in FIG. 3, which, according to FIG. 3, is arranged between the second shutoff valve 70 and the junction point 54 in the section 46 of the return line 32. This is advantageous.The variants of the refrigerant circuit 10 shown in FIGS. 1 to 4 can be combined with one another. For this purpose, in particular the branch line 40 and / or the section 46 can be branched into corresponding branches or branch lines. And shut-off devices (not shown in the present case) can be provided in order to shut off respectively unused branches or branch lines of the refrigerant circuit 10.For implementing a reliable function, the refrigerant circuit 10 has measurement sensors, such as pressure sensors and / or temperature sensors, or combinations of these sensors. In the present case, a representation of these sensors is omitted, since an explanation of the function of such sensors is not necessary for the description of the core idea presented on the basis of the figures.The motor vehicle 12 shown schematically in FIG. 5 is preferably designed as an electric vehicle or as a hybrid vehicle. Accordingly, the motor vehicle 12 preferably has the electrical energy store 80 which provides energy for the at least one electrical drive device 82 of the motor vehicle 12. Wheels 84 of the motor vehicle 12 can be driven by means of the electric drive device 82.Overall, the examples show how topology adaptation may be provided for operating branch line 40 as a hot gas bypass and an air heat pump.

Claims

Refrigerant circuit (10) for a motor vehicle (12), having a compressor (14) which is designed to feed refrigerant compressed in a heat pump mode of the refrigerant circuit (10) to a heating heat exchanger (16) of the refrigerant circuit (10) via a heating branch (22) of the refrigerant circuit (10), wherein the heating heat exchanger (16) is designed to heat an air stream which can be introduced into a passenger compartment (24) of the motor vehicle (12), wherein the refrigerant circuit (10) has a branch line (40) which can be shut off by means of a shut-off device (42) and which leads away from the heating branch (22) and which can be used in an air-conditioning mode of the refrigerant circuit (10) for extracting refrigerant from the heating heat exchanger (16), and wherein in a return line (32) of the refrigerant circuit (10), A refrigerant collector (36) via which refrigerant which can be expanded by means of at least one expansion device (28) of the refrigerant circuit (10) can be supplied to a suction side (34) of the compressor (14), characterized in that the refrigerant circuit (10) has at least one settling device (48, 50) which is arranged upstream of an inlet (44) of the refrigerant collector (36), wherein refrigerant originating from the branch line (40) in the heat pump operation of the refrigerant circuit (10) can be supplied to the inlet (44) of the refrigerant collector (36) only after flowing through the at least one settling device (48, 50).Refrigerant circuit (10) according to Claim 1, characterized in that the refrigerant circuit (10) comprises a chiller (50) through which refrigerant can flow on the one hand and a coolant on the other hand, wherein the settling device (48) is arranged between a junction point (54) of the refrigerant circuit (10), at which a refrigerant line (56) coming from the chiller (50) opens into the return line (32), and the inlet (44) of the refrigerant collector (36).Refrigerant circuit (10) according to Claim 2, characterized in that the branch line (40) opens upstream of the junction point (54) into a section (46) of the return line (32), wherein refrigerant expanded via the section (46) in the heat pump mode can be discharged from a heat exchanger (30) of the refrigerant circuit (10) which can be acted upon by ambient air, and wherein the heat exchanger (30) can be used as an evaporator in the heat pump mode.Refrigerant circuit (10) according to Claim 2 or 3, characterized in that the branch line (40) opens into the return line (32) at the junction point (54) or between the junction point (54) and the settling device (48), it being possible for the refrigerant discharged from a heat exchanger (30) of the refrigerant circuit (10), which heat exchanger can be acted upon by ambient air, to be introduced into the chiller (50) via a section (46) of the return line (32) via which refrigerant expanded in the heat pump mode can be discharged from a heat exchanger (30) of the refrigerant circuit (10), and it being possible for the heat exchanger (30) to be used as an evaporator in the heat pump mode.Refrigerant circuit (10) according to one of the preceding claims, characterized in that the refrigerant circuit (10) comprises a chiller (50) through which refrigerant can flow on the one hand and a coolant on the other hand, wherein the at least one settling device comprises the chiller (50) or is provided by the chiller (50), wherein refrigerant originating from the branch line (40) in the heat pump mode of the refrigerant circuit (10) can be fed to the inlet (44) of the refrigerant collector (36) only after flowing at least through the chiller (50).Refrigerant circuit (10) according to Claim 5, characterized in that a refrigerant line (56) coming from the chiller (50) and a section (46) of the return line (32) are joined together at a junction point (54) of the refrigerant circuit (10), wherein refrigerant expanded via the section (46) in the heat pump mode can be discharged from a heat exchanger (30) of the refrigerant circuit (10) which can be acted upon by ambient air, wherein the heat exchanger (30) can be used as an evaporator in the heat pump mode, and wherein the junction point (54) is arranged upstream of the inlet (44) of the refrigerant collector (36).Refrigerant circuit (10) according to Claim 5 or 6, characterized in that a section (46) of the return line (32), via which refrigerant expanded in the heat pump mode can be discharged from a heat exchanger (30) of the refrigerant circuit (10), which heat exchanger can be acted upon by ambient air, opens into the branch line (40) upstream of the chiller (50), wherein the heat exchanger (30) can be used as an evaporator in the heat pump mode.Refrigerant circuit (10) according to one of the preceding claims, characterized in that a nonreturn valve (72, 76) is arranged in the branch line (40) and / or in a section (46) of the return line (32), via which refrigerant can be discharged from a heat exchanger (30), which can be acted upon by ambient air, of the refrigerant circuit (10).Motor vehicle (12) having a refrigerant circuit (10) according to one of the preceding claims, wherein the motor vehicle (12) is designed as an electric vehicle or as a hybrid vehicle.Method for operating a refrigerant circuit (10) for a motor vehicle (12), in which a compressor (14), in a heat pump operation of the refrigerant circuit (10), supplies refrigerant compressed to a heating heat exchanger (16) of the refrigerant circuit (10) via a heating branch (22) of the refrigerant circuit (10), wherein the heating heat exchanger (16) is designed to heat an air stream which can be introduced into a passenger compartment (24) of the motor vehicle (12), wherein the refrigerant circuit (10) has a branch line (40) which can be shut off by means of a shut-off device (42) and which leads away from the heating branch (22) and which, in an air-conditioning operation of the refrigerant circuit (10), can be used for extracting refrigerant from the heating heat exchanger (16), and wherein, in a return line (32) of the refrigerant circuit (10), Refrigerant collector (36) via which refrigerant expanded by means of at least one expansion device (28) of the refrigerant circuit (10) is supplied to a suction side (34) of the compressor (14), characterized in that the refrigerant circuit (10) has at least one settling device (48, 50) which is arranged upstream of an inlet (44) of the refrigerant collector (36), wherein refrigerant originating from the branch line (40) in the heat pump operation of the refrigerant circuit (10) is supplied to the inlet (44) of the refrigerant collector (36) only after flowing through the at least one settling device (48, 50).

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