Refrigerant circuit and method of operating a refrigerant circuit

Abstract

A refrigerant circuit (1) includes at least a compressor (2) having an upstream suction side (3) and a downstream pressure side (4), a condenser (5), a first evaporator (6), and at least one second evaporator (7); wherein the compressor (2) is a compressor with at least two stages, the compressor having on the suction side (3) a first input line (8) leading to the compressor (2) with a first pressure level (9) and a second input line (10) leading to the compressor (2) with a second pressure level (11), wherein the second pressure level is higher than the first pressure level; wherein the first evaporator (6) and the second evaporator (7) are at least temporarily connected to the compressor (2) through different input lines (8, 10). Furthermore, a method for operating the refrigerant circuit is proposed.

Description

Technical Field

[0001] The invention relates to a refrigerant circuit and a method for operating a refrigerant circuit. The refrigerant circuit comprises in particular at least one compressor for compressing a refrigerant, a condenser for cooling and liquefying the compressed refrigerant and at least one evaporator for converting the liquefied refrigerant back into a gaseous state. The at least one evaporator is used for cooling a fluid flow or a component. The refrigerant flows through the refrigerant circuit, which starts from the compressor, via the condenser and the at least one evaporator and returns to the compressor. The refrigerant circuit is used in particular in motor vehicles. Background Art

[0002] In motor vehicles with traction drives, batteries that provide electrical energy are cooled or temperature-controlled. In particular, in such motor vehicles with traction drives, the noise of the air conditioning system for controlling the temperature of the motor vehicle interior is always perceptible at high outside temperatures. In order to reduce the fan noise of the air conditioning unit while maintaining the cooling capacity, the supply air temperature must be reduced. This can be achieved by using a further evaporator, which further reduces the temperature of the air supplied to the interior, in particular to below zero degrees.

[0003] It is known to cool the battery via a coolant circuit in which the coolant is cooled by an air conditioning unit. It is also known to lower the evaporator temperature to below zero, wherein the air is already precooled to 2 degrees Celsius in the dehumidification phase.

[0004] In both cases, the efficiency and performance of the refrigerant circuit are not optimal. In both cases, there are different temperature levels provided by the refrigerant circuit. For example, the temperature of the battery should be controlled at around 20 degrees Celsius. The air conditioner should control the air temperature at around 2 degrees Celsius. If the fan noise is to be reduced further, the air needs to be cooled to around minus 10 degrees Celsius. This results in the pressure level on the suction side of the compressor of the refrigerant circuit following the lowest temperature level, and the compressor therefore requires more energy than it would require at a higher temperature level.

[0005] A refrigerant circuit for a motor vehicle is known from DE 10 2013 204 188 A1. The refrigerant circuit comprises a compressor, a condenser, a heat exchanger and one or more evaporators. The compressor can be a two-stage compressor, and the refrigerant that has not yet liquefied is fed back to the medium-pressure region of the compressor.

[0006] DE 10 2011 118 162 A1 discloses a combined refrigeration device and heat pump, wherein an optimum refrigerant quantity should always be maintained and refrigerant migration should be avoided.

[0007] DE 10 200 9 030 041 A1 discloses a vehicle air conditioning system with a coolant circuit. In the high-pressure branch downstream of the compressor, a condenser and a plurality of evaporators are arranged in sequence. Each evaporator is loaded with coolant via an expansion device. A single overpressure valve is arranged in the high-pressure branch. The overpressure valve can be used to guide the overpressure in the high-pressure branch to the low-pressure branch. Summary of the invention

[0008] The technical problem to be solved by the present invention is to at least partially solve the problems listed with reference to the prior art. In particular, a refrigerant circuit should be proposed, which can be operated in an energy-saving manner. In addition, a method for operating a refrigerant circuit should be proposed, by which an energy-saving operation of the refrigerant circuit can be performed.

[0009] A refrigerant circuit is proposed, which comprises at least a compressor with an upstream suction side and a downstream pressure side, a condenser, a first evaporator and at least one second evaporator. The compressor is an at least two-stage compressor, which has a first input line to a first stage of the compressor with a first pressure level on the suction side and a second input line to a second stage of the compressor with a second pressure level. The second pressure level is higher than the first pressure level. The first evaporator and the second evaporator can be connected to the compressor at least temporarily via different input lines.

[0010] The compressor is used in particular to compress a gaseous refrigerant, such as carbon dioxide, to a higher pressure. In this case, the pressure existing on the suction side is increased by the compressor to the pressure existing on the pressure side of the compressor. The compressor comprises in particular at least two stages, that is to say, the pressure existing on the suction side can be different. For this purpose, different feed lines are provided, through which the refrigerant is fed into the compressor. The first feed line has a lower pressure level, that is to say, the pressure existing in the first feed line is generally lower than the pressure of the refrigerant existing in the second feed line. The refrigerant supplied to the compressor from the first feed line is compressed by the compressor in particular to the pressure on the pressure side, that is to say, there is a highest pressure difference between the pressure side and the suction side (here, the first feed line).

[0011] The second feed line has a higher pressure level, i.e. the pressure prevailing in the second feed line is generally higher than the pressure of the refrigerant prevailing in the first feed line. The refrigerant supplied from the second feed line to the compressor is compressed by the compressor to the pressure of the pressure side, i.e. the pressure difference between the pressure side and the suction side (here the second feed line) is smaller.

[0012] The refrigerant circuit is provided in particular for operation with a refrigerant and a pressure or pressure difference which is given therein.

[0013] In particular, the second pressure level is higher than the first pressure level by at least 10%, preferably by at least 20%, particularly preferably by at least 30% of the second pressure level.

[0014] The refrigerant is compressed on the pressure side, in particular to a common pressure, ie the refrigerant is conducted from the feed line, in particular via a common line, onward toward the condenser.

[0015] The compressed refrigerant is cooled, in particular, by the condenser and at least partially liquefied. The cooling is carried out, in particular, by heat transfer with the ambient air. The condenser can also be configured as a gas cooler, wherein the refrigerant is cooled without a phase change.

[0016] The at least partially liquefied refrigerant is fed to at least one evaporator, wherein the liquefied refrigerant is expanded to a lower pressure and at least partially converted into a gaseous state.

[0017] At least part of the refrigerant in a gaseous state is fed into the compressor through an inlet line.

[0018] An expansion device is arranged upstream of the evaporators, in particular individually for each evaporator, by means of which the at least partially liquefied refrigerant is expanded and at least partially converted into the gaseous state.

[0019] In particular, a shutoff device is arranged downstream and / or upstream of the evaporator, in particular for each evaporator individually, by which the volume flow of the refrigerant through the evaporator can be adjusted. The shutoff device can be realized, for example, as an expansion valve, wherein the expansion valve is associated with the evaporator and is arranged upstream of the evaporator.

[0020] In the evaporator, heat is transferred between the fluid and the refrigerant so that the fluid can be cooled by the refrigerant.

[0021] In particular, the first evaporator is used to cool the battery and the second evaporator is used to cool the air. Alternatively, both evaporators can be used to cool the air.

[0022] The battery is in particular an electric current storage device for a traction drive of a motor vehicle. The air is in particular ambient air which is supplied, for example, to the interior of a motor vehicle.

[0023] The cooled ambient air can be used, for example, to control the temperature of the passenger compartment or at least one transport compartment. In particular, goods to be tempered at a predetermined temperature can be transported in the transport compartment, such as meat at approximately 2 degrees Celsius, frozen products at approximately -15 degrees Celsius, etc. If necessary, a plurality of transport compartments that must be tempered differently can be provided.

[0024] In particular, the evaporators are used for different temperature levels. The temperature levels differ in particular by at least 5 Kelvin, preferably by at least 10 Kelvin. For example, a first evaporator provided for cooling the battery is provided for adjusting the temperature of the battery to approximately 20 degrees Celsius. A second evaporator provided for cooling the air is provided for example for adjusting the temperature of the air to 2 degrees Celsius or -15 degrees Celsius.

[0025] In particular, it is proposed that the evaporator can be connected to the compressor via at least temporarily different supply lines. Thus, the evaporator can be connected to different pressure levels on the suction side of the compressor. This allows efficient operation of the refrigerant circuit, since different cooling powers can be provided to each evaporator.

[0026] In particular, the evaporators are connected in parallel with each other. In particular, the evaporators are connected in parallel with each other between the condenser and the compressor.

[0027] In particular, in a first operating state of the refrigerant circuit, the first evaporator is connected to the compressor via the second feed line, and the second evaporator is connected to the compressor via the first feed line.

[0028] In particular, in the first operating state, there is a cooling demand for the battery and for the ambient air, for example. The lowest temperature level is then present, for example, at the second evaporator provided for cooling the ambient air, for example for tempering the air to approximately 2 degrees Celsius, wherein the battery should be tempered to approximately 20 degrees Celsius by the first evaporator, for example. The second evaporator is then connected to the compressor via the first feed line, so that the second evaporator is connected to the compressor via the first, lower pressure level.

[0029] In particular, the refrigerant circuit comprises a third evaporator for further cooling the air cooled by the second evaporator. In particular, the air is further cooled by the third evaporator, for example to a temperature level which is at least 5 Kelvin, preferably at least 10 Kelvin lower than the temperature level set by the second evaporator. In particular, the air is cooled by the third evaporator to -10 degrees Celsius, or even to -15 degrees Celsius or lower.

[0030] In particular, in the second operating state of the refrigerant circuit, only the second evaporator is connected to the compressor via the second feed line, and the third evaporator is connected to the compressor via the first feed line.

[0031] In particular, in the second operating state, the first evaporator is not charged with refrigerant.

[0032] In this case, the lowest temperature level is present at the third evaporator, so that the third evaporator is connected to the compressor via the first feed line and the first, lower pressure level.

[0033] In particular, in the third operating state of the refrigerant circuit, the first evaporator and the second evaporator are connected to the compressor via the second feed line, and the third evaporator is connected to the compressor via the first feed line.

[0034] In the third operating state, there is a cooling demand for all evaporators. In this case, the pressure level on the suction side must be used, in particular, for the different temperature levels of the evaporators. In this case, the efficiency and performance of the refrigerant circuit are reduced because the pressure level in the evaporator cannot be matched to the temperature level or temperature requirement of the evaporator.

[0035] In this case, the most efficient possible operation of the refrigerant circuit is achieved by connecting the first evaporator and the second evaporator to the second feed line, wherein the third evaporator is connected to the compressor via the first feed line.

[0036] In particular, when connecting the evaporator to the corresponding supply line or the pressure level on the suction side present there, the power requirement of the corresponding evaporator must be taken into account. In addition, the connection of the evaporator to the corresponding supply line can be carried out according to a predeterminable priority. For example, ensuring a predetermined temperature in the transport space of the motor vehicle should have the highest possible priority, so that at least one evaporator provided for this purpose is then connected to the compressor via the first supply line. In order to ensure the driving readiness of the motor vehicle, sufficient battery cooling should be ensured, so that the evaporator provided for this purpose is also operated with a high, but possibly not the highest, priority. The cooling of the air for controlling the temperature of the passenger compartment can, for example, be carried out with a low priority.

[0037] In particular, the operation of the refrigerant circuit can then be carried out taking into account the energy efficiency when the respectively required refrigeration power is available at an operating point.

[0038] In particular, the second evaporator and the third evaporator are connected in parallel to each other and are respectively connectable to the compressor in a switchable manner via each of the first feed line and the second feed line.

[0039] In particular, at least one of the evaporators can be connected to the compressor only via the feed line. In particular, only the first evaporator can be connected to the compressor only via the second feed line.

[0040] Furthermore, a method for operating a refrigerant circuit is proposed, in particular for operating a refrigerant circuit as described above. The refrigerant circuit has at least one compressor, a condenser, a first evaporator and at least one second evaporator, the compressor having an upstream suction side and a downstream pressure side. The compressor is an at least two-stage compressor, which has a first supply line to a first stage of the compressor with a first pressure level on the suction side and a second supply line to a second stage of the compressor with a second pressure level, wherein the second pressure level is higher than the first pressure level. The refrigerant circuit is operated at least in a first operating state, in which the first evaporator and the second evaporator are at least temporarily connected to the compressor via different supply lines.

[0041] In particular, it is proposed that the evaporator can be connected to the compressor via at least temporarily different supply lines. Thus, the evaporator can be connected to different pressure levels on the suction side of the compressor. This allows efficient operation of the refrigerant circuit, since different cooling powers can be provided to each evaporator.

[0042] The method is implemented in particular using a controller. The controller is designed, configured or programmed to perform the method. The controller can in particular determine the corresponding cooling requirements on at least one evaporator, in particular all evaporators, and can control the connection of the refrigerant circuit.

[0043] In particular, the refrigerant circuit is operated and / or the method is carried out in such a way that as little energy as possible is consumed in the process, ie an operation of the refrigerant circuit that is as energy-efficient as possible is possible.

[0044] Furthermore, the method may also be implemented by a computer or by using a processor of a control unit.

[0045] Therefore, a system for data processing is also proposed, the system comprising a processor, the processor being adapted / configured such that the processor performs the proposed method or a part of the steps of the proposed method.

[0046] A computer-readable storage medium may be provided, the storage medium comprising instructions which, when executed by a computer / processor, cause the computer / processor to perform the proposed method or at least a part of the proposed method.

[0047] Furthermore, a motor vehicle is proposed which comprises at least a traction drive and a battery in which electrical energy for operating the traction drive can be stored, and the described refrigerant circuit, wherein the first evaporator is suitable for cooling the battery.

[0048] In particular, the motor vehicle has a control unit which is designed, configured or programmed to carry out the method.

[0049] In particular, the embodiments concerning the refrigerant circuit can be transferred to the method and / or the motor vehicle and / or the computer-implemented method (ie a computer or a processor, a system for data processing, a computer-readable storage medium) and vice versa.

[0050] In particular, the use of the indefinite article ("a") in the claims and the description that embodies the claims is to be understood as "the" rather than a number. The terms or components introduced accordingly are therefore to be understood as being present at least once, but in particular also multiple times.

[0051] As a precaution, it should be noted that the numerals used here ("first", "second", ...) are primarily (only) used to distinguish between multiple objects, sizes or processes of the same type, i.e., in particular, do not necessarily define dependencies and / or sequences between these objects, sizes or processes. If dependencies and / or sequences are required, this is explicitly stated here or is clear to a person skilled in the art when studying the specifically described design. If a component can occur multiple times ("at least one"), the description of one of these components can also apply to all or part of a plurality of these components, but this is not mandatory. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] The present invention and the technical field are described in detail below based on the accompanying drawings. It should be noted that the present invention should not be limited to the described embodiments. In particular, unless otherwise explicitly indicated, some aspects of the facts described in the drawings can also be extracted and combined with other components and cognitions in this specification. In particular, it should be noted that the drawings and the dimensional ratios shown in particular are only schematic. In the drawings:

[0053] Figure 1 A motor vehicle having a refrigerant circuit is shown, which is operated according to a first operating state;

[0054] Figure 2 Show according to Figure 1 a refrigerant circuit that operates according to a second operating state; and

[0055] Figure 3 Show according to Figure 1 and 2 A refrigerant circuit is provided which operates according to a third operating state. DETAILED DESCRIPTION

[0056] Figure 1A motor vehicle 18 is shown having a refrigerant circuit 1, which is operated in a first operating state 14. The motor vehicle 18 comprises a traction drive 19 and a battery 12, in which electrical energy for driving the traction drive 19 can be stored. The refrigerant circuit 1 comprises a compressor 2 having an upstream suction side 3 and a downstream pressure side 4, a condenser 5, a first evaporator 6, a second evaporator 7 and a third evaporator 15. The compressor 2 is a two-stage compressor, which has a first feed line 8 on the suction side 3 to a first stage 9 of the compressor 2 with a first pressure level and a second feed line 10 to a second stage 11 of the compressor 2 with a second pressure level. The second pressure level is higher than the first pressure level.

[0057] The first evaporator 6 is used to cool the battery 12 and the second evaporator 7 is used to cool the air 13. The third evaporator 15 is provided to cool the air 13 further.

[0058] The evaporators 6, 7, 15 are used for different temperature levels. The first evaporator 6 provided for cooling the battery 12 is configured to adjust the temperature of the battery 12 to about 20 degrees Celsius. The second evaporator 7 provided for cooling the air 13 is configured to adjust the temperature of the air 13 to 2 degrees Celsius, and the third evaporator 15 is configured to adjust the temperature of the air to -15 degrees Celsius.

[0059] The air 13 is driven in an air conditioning device 23 by a blower 22 and is conducted through the evaporators 7 , 15 to an interior 24 of the motor vehicle 18 .

[0060] The evaporators 6, 7, 15 can be connected to the compressor 2 via at least temporarily different supply lines 8, 10. The evaporators 6, 7, 15 can thus be connected to different pressure levels on the suction side 3 of the compressor 2. This allows efficient operation of the refrigerant circuit 1, since each evaporator 6, 7, 15 can be provided with a different cooling capacity.

[0061] The evaporators 6 , 7 , 15 are connected in parallel with each other.

[0062] An expansion device 20 is arranged upstream of each evaporator 6 , 7 , 15 , by means of which the refrigerant at least partially liquefied in the condenser 5 is expanded and at least partially converted into the gaseous state.

[0063] At least one shut-off device 21 is arranged downstream of each evaporator 6 , 7 , 15 , by means of which the volume flow of the refrigerant through the respective evaporator 6 , 7 , 15 can be adjusted.

[0064] The motor vehicle 18 has a control unit 25. The control unit 25 is designed, configured or programmed to carry out the method. The control unit 25 can determine the corresponding cooling requirements on the evaporators 6, 7, 15 and can control the connection of the refrigerant circuit 1, that is, the connection of the corresponding evaporator 6, 7, 15 to the first supply line 8 or the second supply line 10. The shut-off device 21 and, if necessary, the expansion device 20 can be controlled by the control unit 25.

[0065] In a first operating state 14 of the refrigerant circuit 1, the first evaporator 6 is connected to the compressor 2 via the second feed line 10 and the second evaporator 7 is connected to the compressor 2 via the first feed line 8. The third evaporator 15 is not charged with refrigerant.

[0066] Figure 2 Show according to Figure 1 The refrigerant circuit 1 is operated according to the second operating state 16. Figure 1 implementation plan.

[0067] In a second operating state 16 of the refrigerant circuit 1 , only the second evaporator 7 is connected to the compressor 2 via the second feed line 10 , and the third evaporator 15 is connected to the compressor 2 via the first feed line 8 .

[0068] In the second operating state 16 , the first evaporator 6 is not charged with refrigerant.

[0069] Figure 3 Show according to Figure 1 and 2 The refrigerant circuit 1 is operated according to the third operating state 17. Figure 1 and Figure 2 implementation plan.

[0070] In a third operating state 17 of the refrigerant circuit 1 , the first evaporator 6 and the second evaporator 7 are connected to the compressor 2 via the second feed line 10 , and the third evaporator 15 is connected to the compressor 2 via the first feed line 8 .

[0071] In the third operating state 17, there is a cooling demand for all evaporators 6, 7, 15. In this case, the second pressure level on the suction side 3 must be used for the different temperature levels of the first evaporator 6 and the second evaporator 7. In this case, the efficiency and performance of the refrigerant circuit 1 are reduced, since the pressure level in the evaporators 6, 7 cannot be matched to the temperature level or temperature requirement of the evaporators 6, 7. In this case, the most efficient operation of the refrigerant circuit 1 is achieved by connecting the first evaporator 6 and the second evaporator 7 to the second feed line 10, wherein the third evaporator 15 is connected to the compressor 2 via the first feed line 8.

[0072] Reference numerals list

[0073] 1 Refrigerant circuit

[0074] 2 compressor

[0075] 3 Suction side

[0076] 4 Pressure side

[0077] 5. Condenser

[0078] 6First evaporator

[0079] 7. Second evaporator

[0080] 8First input pipeline

[0081] 9First Level

[0082] 10 Second input pipeline

[0083] 11 Second Level

[0084] 12 batteries

[0085] 13 Air

[0086] 14First operating state

[0087] 15Third evaporator

[0088] 16 Second operating state

[0089] 17Third operating state

[0090] 18 Motor Vehicles

[0091] 19 Traction drive

[0092] 20 Expansion device

[0093] 21 Cut-off device

[0094] 22 Blower

[0095] 23 Air conditioning unit

[0096] 24Interior Space

[0097] 25 Controller

Claims

1. A refrigerant circuit (1) comprising at least a compressor (2) having an upstream suction side (3) and a downstream pressure side (4), a condenser (5), a first evaporator (6) and at least one second evaporator (7); wherein: The compressor (2) is a compressor with at least two stages, and the compressor has a first input line (8) with a first pressure level to the first stage (9) of the compressor (2) and a second input line (10) with a second pressure level to the second stage (11) of the compressor (2) on the suction side (3), wherein the second pressure level is higher than the first pressure level; wherein the first evaporator (6) and the second evaporator (7) can be connected to the compressor (2) at least temporarily via different input lines (8, 10), wherein the first evaporator (6) is used to cool a battery (12) and the second evaporator (7) is used to cool air (13); the refrigerant circuit also includes a third evaporator (15), which is used to further cool the air (13) cooled by the second evaporator (7); wherein in the refrigerant circuit In a first operating state (14) of the refrigerant circuit (1), the first evaporator (6) is connected to the compressor (2) via the second input line (10), and the second evaporator (7) is connected to the compressor (2) via the first input line (8), wherein, in a second operating state (16) of the refrigerant circuit (1), only the second evaporator (7) is connected to the compressor (2) via the second input line (10), and the third evaporator (15) is connected to the compressor (2) via the first input line (8), and wherein, in a third operating state (17) of the refrigerant circuit (1), the first evaporator (6) and the second evaporator (7) are connected to the compressor (2) via the second input line (10), and the third evaporator (15) is connected to the compressor (2) via the first input line (8).

2. The refrigerant circuit (1) according to claim 1, wherein: The first evaporator (6), the second evaporator (7) and the third evaporator (15) are connected in parallel to each other.

3. The refrigerant circuit (1) according to claim 1, wherein: The second evaporator (7) and the third evaporator (15) are connected in parallel to each other and can be switchably connected to the compressor (2) via each of the first input line (8) and the second input line (10), respectively.

4. A method for operating a refrigerant circuit (1) according to any one of claims 1 to 3, wherein: The refrigerant circuit (1) operates at least in a first operating state (14), in which the first evaporator (6) and the second evaporator (7) are at least temporarily connected to the compressor (2) via different input lines (8, 10), and wherein the refrigerant circuit (1) operates at least in a second operating state (16), in which only the second evaporator (7) is connected to the compressor (2) via the second input line (10), and the third evaporator (15) is connected to the compressor (2) via the first input line (8); and wherein the refrigerant circuit (1) operates in a third operating state (17), in which the first evaporator (6) and the second evaporator (7) are connected to the compressor (2) via the second input line (10), and the third evaporator (15) is connected to the compressor (2) via the first input line (8).

5. A motor vehicle (18) comprising at least a traction drive (19) and a battery (12) in which electrical energy for driving the traction drive (19) can be stored, and a refrigerant circuit (1) according to any one of the preceding claims 1 to 3, wherein: The first evaporator (6) is embodied to be suitable for cooling the battery (12).

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