Method for operating a refrigeration system of a motor vehicle and refrigeration system with backflow prevention

Abstract

A method (500) for operating a refrigeration system (10) for a motor vehicle is described, wherein the refrigeration system (10) comprises: a refrigerant compressor (12) which can be connected to or is connected to a primary line (14); at least one evaporator (18, 22) arranged in the primary strand (14); a chiller (28) which is arranged in a chiller branch (28.1, 28.3) which is flow-parallel to the evaporator (18, 22), wherein an expansion element (AE1) is assigned to the chiller (28) in the chiller branch (28.1) and wherein the chiller (28) is connected to a coolant circuit (28.2) separate from the refrigerant circuit (11); the procedure includes the following steps: Directing refrigerant from the refrigerant compressor (12) to the evaporator (18, 22), so that it is supplied with refrigerant, and up to the expansion element (AE1) of the chiller branch; and when the temperature (Tcool) of the coolant is lower than the temperature of the refrigerant (Tcol) (S503): repeatedly opening and closing (S504) the expansion element (AE1) associated with the chiller (28), such that refrigerant drawn in from the low-pressure side connection (22.2) between the evaporator (22) and the refrigerant compressor (12) downstream of the chiller (28) is purged from the chiller (28).

Description

[0001] The invention relates to a method for operating a refrigeration system for a motor vehicle, wherein the refrigeration system comprises: a refrigerant compressor that can be connected to or is connected to a primary string; at least one evaporator arranged in the primary line; a chiller which is arranged in a chiller branch which is flow-parallel to the evaporator, wherein the chiller in the chiller branch is assigned an expansion element and wherein the chiller is connected to a coolant circuit separate from the refrigerant circuit; in this process, refrigerant is directed from the refrigerant compressor to the evaporator, so that it is supplied with refrigerant, and is directed to the expansion element of the chiller branch.

[0002] From DE 10 2018 209 769 A1 a method for operating a refrigeration system without a heating coil for an electric vehicle is known.

[0003] A refrigeration system with chiller and heating coil is known from DE 10 2011 118 162 A1.

[0004] DE 10 2016 007 490 A1 discloses a refrigeration system in which a check valve is arranged in a chiller line downstream of a chiller and upstream of a connection node with a low-pressure connection extending between an evaporator and a refrigerant compressor.

[0005] Furthermore, reference is made to DE 10 2012 108 731 A1 and WO 2010 / 003484 A1, which also deal with refrigeration systems.

[0006] In refrigeration systems, especially those with a heat pump function, it is frequently the case that inactive system sections are present in the refrigeration system during both cooling operation (AC operation) and heat pump operation, which are not supplied with refrigerant in the respective activated circuit.

[0007] If the refrigeration system is connected and operated in a cooling mode (AC mode), for example, a chiller branch and / or a rear evaporator branch and / or a heating branch may not be supplied with refrigerant.

[0008] In a heat pump process, for example, a front evaporator branch and / or a rear evaporator branch and / or a chiller branch and / or a branch with an external heat exchanger (condenser or gas cooler branch) may not be supplied with refrigerant.

[0009] If inactive components of the refrigeration system are exposed to a medium flowing through or around them, for example, water as a coolant in the chiller's coolant circuit (battery cooling and / or electric motor cooling), the temperature of the medium can be lower than the evaporation temperature established in the refrigeration system. This creates a kind of cold spot in the refrigeration system, where gaseous refrigerant is drawn in or flows to it, condenses, and is removed. The condensed refrigerant is thus extracted from the active process at this cold component and is no longer available. This can potentially lead to underfilling of components in the actively connected refrigerant circuit or process, preventing optimal operation of the refrigeration system in the desired mode (AC operation, heat pump operation).Furthermore, by relocating the refrigerant, oil bound in the refrigerant can also be relocated and removed from the active process.

[0010] The object underlying the invention is seen as being to provide a method for operating a refrigeration system and a refrigeration system, whereby the above disadvantages are to be avoided.

[0011] This problem is solved by a method and by a refrigeration system with the features of the respective independent patent claims. Advantageous embodiments with expedient further developments are specified in the dependent patent claims.

[0012] According to a first aspect, a method for operating a refrigeration system for a motor vehicle is proposed, wherein the refrigeration system comprises: a refrigerant compressor that can be connected to or is connected to a primary string; at least one evaporator arranged in the primary line; a chiller arranged in a chiller branch flow-parallel to the evaporator, wherein the chiller in the chiller branch is associated with an expansion element and wherein the chiller is connected to a coolant circuit separate from the refrigerant circuit; and A secondary circuit valve is located between the refrigerant compressor and the heating coil. The procedure comprises the following steps: Conveying refrigerant from the refrigerant compressor to the evaporator, so that it is supplied with refrigerant, and up to the expansion element of the chiller branch; If the temperature of the coolant is lower than the temperature of the refrigerant: repeated opening and closing of the expansion valve associated with the chiller, such that refrigerant drawn in downstream of the chiller from the low-pressure side connection between the evaporator and the refrigerant compressor is flushed out of the chiller.

[0013] By repeatedly opening and closing the chiller, also known as pulsed opening / closing, it is possible to cyclically flush refrigerant and the oil contained within it from the chiller, even if the chiller branch is not actively being flushed with refrigerant during the relevant operating state of the refrigeration system. This ensures that, in addition to the maximum refrigerant quantity, the optimal and required amount of oil is also active in the refrigerant circuit or the refrigeration system, thus preventing refrigerant / oil from migrating into inactive areas, i.e., pipe segments or sectors not actively being flushed. Pulsed opening / closing can be performed at a frequency advantageous for the flushing process.

[0014] At least one evaporator can be a heat exchanger that conditions the cabin air. However, one or more evaporators can also serve as heat exchangers for operating a heat pump, such as an air-source heat pump, to absorb heat contained in the ambient air. Depending on the design and topology of the systems or refrigeration unit, the positions of the respective evaporators may differ between AC operation and air-source heat pump operation, but their fundamental function in each operation remains the same.

[0015] A second aspect, which can also be understood as complementary to the first aspect, proposes a method for operating a refrigeration system for a motor vehicle, wherein the refrigeration system comprises: a refrigerant compressor which is connectable to or connected with a primary line; at least one evaporator arranged in the primary line; a chiller which is arranged in a chiller branch which is flow-parallel to the evaporator, wherein the chiller in the chiller branch is assigned an expansion element and wherein the chiller is connected to a coolant circuit separate from the refrigerant circuit; The process includes the following steps: Conveying refrigerant from the refrigerant compressor to the evaporator, so that it is supplied with refrigerant, and up to the expansion element of the chiller branch; If the temperature of the coolant is lower than the temperature of the refrigerant: Close or keep closed the expansion valve associated with the chiller and heat the coolant in the chiller by means of the coolant circuit to a temperature higher than the temperature of the refrigerant, such that the refrigerant in the chiller is brought to a temperature / pressure level that prevents backflow of refrigerant from the low-pressure side connection between the evaporator and the refrigerant compressor.

[0016] Closing the expansion valve stops the active flow of refrigerant through the chiller. Consequently, any refrigerant in the chiller can be reheated and evaporated by the warmer coolant, preventing it from accumulating due to the changing temperature and pressure conditions and preventing backflow from the low-pressure connection between the evaporator and the refrigerant compressor. This step can also be combined with the repeated opening and closing of the expansion valve described above. In particular, such opening / closing or pulsed actuation of the expansion valve can be performed after the refrigerant has been temporarily warmed (by a longer period of time with the expansion valve closed).

[0017] In this process, refrigerant can be routed from the refrigerant compressor via a heat exchanger, which acts as a heat source, to the evaporator and / or the chiller branch. Such a heat exchanger can be designed as a condenser or gas cooler, which can transfer heat to the environment or the cabin supply air stream directly or indirectly.

[0018] Furthermore, a refrigeration system for a motor vehicle is proposed, comprising a refrigerant compressor that can be connected to or is connected to a primary line; at least one evaporator arranged in the primary line; a chiller which is arranged in a chiller branch which is flow-parallel to the evaporator, wherein a chiller expansion element is assigned to the chiller in the chiller branch and wherein the chiller is connected to a coolant circuit separate from the refrigerant circuit, wherein a check valve is arranged in the chiller branch downstream of the chiller and upstream of a connection node with a low-pressure connection which extends between the evaporator and the refrigerant compressor.

[0019] In the refrigeration system, according to the invention, a section of the chiller branch is designed to rise upstream of the connection node, starting from the connection node and relative to the low-pressure connection. This inclined design of the chiller branch prevents gravity-assisted oil seepage into the chiller branch.

[0020] Such a check valve prevents refrigerant from being drawn into the chiller branch and deposited there when the chiller is not actively flowing through it, or from flowing back after it has been extracted from the chiller.

[0021] In a refrigeration system, a check valve or a low-pressure expansion valve can be installed downstream of the evaporator and upstream of the connection point. A check valve prevents refrigerant from flowing back into the evaporator and accumulating there when the refrigerant circuit is not actively flowing through it, for example, when the entire refrigerant circuit is routed through the chiller. An optional expansion valve allows the system to operate at two low-pressure levels on the low-pressure side. For example, the evaporator can be operated at a specific pressure level, cooling the air flowing towards the evaporator to 2°C or more to prevent icing.

[0022] The rising section of the chiller branch can project upwards at an angle of 30° to 90° relative to an imaginary plane in which the low-pressure connection runs.

[0023] The refrigeration system may include at least one heat exchanger that serves as a heat source. Such a heat exchanger may be designed as a condenser or gas cooler, which can transfer heat to the environment or the cabin supply air stream directly or indirectly.

[0024] The refrigeration system may further comprise: a secondary circuit to which the refrigerant compressor can be connected or is connected; a heat exchanger, in particular a heating coil, which is arranged in the secondary circuit; and a secondary circuit valve arranged between the refrigerant compressor and the heat exchanger.

[0025] The refrigeration system with the structure or setup described above can also be configured to carry out the procedure described above.

[0026] In an embodiment of the refrigeration system with a secondary circuit and heat exchanger (heating coil), the two methods described above can also include the following step: opening the secondary circuit valve so that refrigerant is directed from the refrigerant compressor to the heating coil and downstream of the heating coil to the evaporator and / or to the chiller circuit.

[0027] A motor vehicle can be equipped with such a refrigeration system.

[0028] Further advantages and details of the invention will become apparent from the following description of embodiments with reference to the figures. These show: Fig. 1. A schematic and simplified circuit diagram of a refrigeration system for a motor vehicle; Fig. 2 a schematic and simplified circuit diagram of a modified refrigeration system for a motor vehicle; Fig. 3. A flowchart of an exemplary implementation of the reheating process, in particular by means of the [missing information] Fig. 1 and Fig. 2 described refrigeration system.

[0029] In Fig. Figure 1 is a schematic and simplified representation of an embodiment of a refrigeration system 10 for a motor vehicle. The refrigeration system 10 comprises a refrigerant circuit 11, which can be operated in both refrigeration mode (also referred to as AC mode) and heat pump mode. In the embodiment shown, the refrigeration system 10 comprises a refrigerant compressor 12, an external heat exchanger 18, an optional internal heat exchanger 20, an evaporator 22, and a refrigerant accumulator or receiver 24. The external heat exchanger 18 can be configured as a condenser or a gas cooler.

[0030] The evaporator 22 is shown here as an example of a front evaporator for a vehicle. The evaporator 22 also represents other possible evaporators in a vehicle, such as rear evaporators, which can be arranged parallel to each other in terms of airflow. In other words, the refrigeration system 10 includes at least one evaporator 22.

[0031] A shut-off valve A4 is arranged downstream of the compressor 12. An expansion valve AE2 is provided upstream of the evaporator 22.

[0032] Within the scope of this description, the section from the compressor 12 to the external heat exchanger 18, to the internal heat exchanger 20 and to the evaporator 22 in the entire refrigerant circuit 11 of the refrigeration system 10 is referred to as the primary circuit 14.

[0033] The refrigeration system 10 further comprises a heating coil 26 (also referred to as a heating condenser or hot gas cooler). A shut-off valve A3 is arranged upstream of the heating coil 26, and a check valve R4 is arranged downstream of the heating coil 26.

[0034] Within the scope of this description, the section of the entire refrigerant circuit of the refrigeration system 10 from the compressor 12 to the heating coil 26 and the check valve R4 is referred to as the secondary circuit 16. The secondary circuit 16 comprises a heating branch that extends from the shut-off valve A3 via the heating coil 26 to the branch Ab4.

[0035] The refrigeration system 10 includes an additional evaporator or chiller 28. Chiller 28 is arranged parallel to evaporator 22 in terms of flow direction. Chiller 28 can, for example, be used to cool an electrical component of the vehicle, or to implement a water-source heat pump function by utilizing the waste heat from at least one electrical component. An expansion valve AE1 is installed upstream of chiller 28.

[0036] On the low-pressure side, a chiller line 28.3 extends between the chiller 28 and a branch Ab2. The chiller line 28.3 opens at branch Ab2 into the low-pressure-side connection 22.2, which extends between the evaporator 22 and the refrigerant compressor 12. In the embodiment shown here with a low-pressure refrigerant receiver 24, branch Ab2 is arranged between the evaporator 22 and the low-pressure refrigerant receiver 24.

[0037] To prevent refrigerant from flowing back through the low-pressure side connection 22.2 in the chiller line 28.3, a check valve R5 is arranged in the chiller line 28.1. The check valve R5 can be located closer to branch Ab2 than to the chiller 28, relative to the length of the chiller line 28.3. In particular, the check valve R5 can be located as close as possible to branch Ab2, for example, a few centimeters, and especially approximately 2 cm to 15 cm away from branch Ab2.

[0038] A section 28.4 of the chiller line 28.3 can be configured to rise upstream of branch Ab2, starting from branch Ab2 and relative to the low-pressure connection 22.2. The rising section 28.4 of the chiller line 28.3 can project upwards at an angle of 30° to 90° relative to an imaginary plane in which the low-pressure connection 22.2 runs.

[0039] It should be noted that if section 28.4 in the chiller line 28.3 has an ascending section, the check valve R5 can also be omitted. In this respect, the ascending section 28.4 in the chiller line 28.3 also constitutes an independent aspect of the present application.

[0040] Downstream of the evaporator 22 and upstream of the connection node Ab2, a check valve R1 can be provided in connection 22.2. Alternatively, a low-pressure-side expansion device AE5 can be arranged instead of the check valve R1. The check valve R1 and the expansion valve AE5 are therefore located in the Fig. 1 are shown with dashed lines because they each represent an optional design.

[0041] The check valve R5 prevents refrigerant from flowing back into the evaporator 22 and being deposited there, as is usually the case when the refrigerant circuit 11 is completely routed through the chiller 28. An optional expansion valve AE5 allows the system to operate at two low-pressure levels on the low-pressure side. For example, the evaporator 22 can be operated at a specific pressure level, cooling the air flowing towards the evaporator 22 to 2°C or more to prevent icing during dehumidification.

[0042] In Fig. 2 is a comparison to the Fig. Figure 1 shows a modified embodiment of a refrigeration system 10 for a motor vehicle, schematically and in a simplified manner. In particular, the external heat exchanger 18 in the illustrated embodiment allows bidirectional flow. Unlike in the embodiment of the Fig. A shut-off valve A1 is arranged downstream of the heating coil 26. The shut-off valve A1 is arranged between a branch Ab4 and the branch Ab1. Furthermore, an expansion valve AE4 is arranged downstream of the heating coil 26.

[0043] The secondary circuit 16 further comprises a reheat branch 16.2, which can be fluid-connected upstream to the heating coil 26 and downstream to the external heat exchanger 18. The secondary circuit 16, or reheat branch 16.2, connects to the primary circuit 14 at a branch point Ab6.

[0044] The above to Fig. 1. The statements made regarding the chiller section 28.1 with check valve R5 and / or with rising section 28.3 also apply to the embodiment of the Fig. 2 applicable and it refers to the relevant text passages. Fig. Reference is made to section 1 to avoid repetition. The same applies, incidentally, to the check valve R1 and the expansion valve AE5 in connection 22.2.

[0045] It is generally pointed out that in the Fig. 1 and Fig. Figure 2 shows several sensors, which are usually designated pTX (X = 1...n). The pTX sensors are used to measure the pressure and / or temperature of the refrigerant. It should be noted that the number of pTX sensors (X = 1...n) and their arrangement in all figures are only examples. A refrigeration system 10 according to the Fig. 1 to Fig. 2 can also have fewer or more sensors. In the examples shown, combined pressure / temperature sensors pTX are used. However, it is equally conceivable that separate and independently designed sensors are used for measuring pressure and / or temperature, and that these may also be arranged spatially separated from each other along the refrigerant lines. Nevertheless, any sensor pTX explicitly mentioned in the description and / or explicitly shown in the figures can be considered a potentially relevant part of the refrigerant circuit and can be claimed as needed, particularly to describe the structure of the refrigeration system 10 in more detail.

[0046] Furthermore, it is pointed out that in the Fig. 1 and Fig. Two multiple branches or nodes with AbY (Y = 1... n) are shown, not all of which are explicitly described. It should be noted that the number of branches AbY (Y = 1... n) and their arrangement in all figures are only examples. A refrigeration system 10 according to the Fig. 1 to Fig. 2 may also have fewer or more branches. However, each branch AbY explicitly mentioned in the description and / or explicitly shown in the figures can be understood as a potentially relevant part of the refrigerant circuit topology and can be claimed if necessary, in particular to describe the structure of the refrigeration system 10 in more detail if required.

[0047] The refrigeration system 10 can be operated in different modes, which are briefly described below.

[0048] In AC operation of the refrigerant circuit 11, the high-pressure compressed refrigerant flows from the refrigerant compressor 12, with shut-off valve A4 open, into the outer heat exchanger 18. From there, it flows to the high-pressure section of the inner heat exchanger 20 and the fully open expansion valve AE3. Via a branch point Ab1, the refrigerant can flow to the expansion valve AE2 and into the interior evaporator 22 (evaporator section 22.1). In parallel or alternatively, the refrigerant can flow via a branch point Ab8 and the expansion valve AE1 into the chiller 28 (chiller section 28.1). From the evaporator 22 and / or the chiller 28, the refrigerant flows on the low-pressure side into the receiver 24 and through the low-pressure section of the inner heat exchanger 20 back to the compressor 12.

[0049] In AC operation, the heating branch 16.1, or secondary circuit 16, is shut off by means of the shut-off valve A3, so that hot refrigerant cannot flow through the heating coil 26. To retrieve refrigerant from the inactive heating branch 16.1, the shut-off valve A5 can be opened, allowing the refrigerant to flow towards the receiver 24 via the shut-off valve A5 and the check valve R2, while the shut-off valve A2 remains closed.

[0050] In heating mode of the refrigerant circuit 11, the shut-off valve A4 is closed and the shut-off valve A3 is opened, so that hot refrigerant can flow into the heating branch 16.1.

[0051] To perform the heating function using the chiller 28 for water-source heat pump operation, the refrigerant compressed by the refrigerant compressor 12 flows through the open shut-off valve A3 into the heating coil 26. Heat is transferred from the heating coil 26 to a supply air stream directed into the vehicle interior. The refrigerant then flows through the open shut-off valve A1 and the branch point Ab1. It expands through the expansion valve AE1 into the chiller 28 to absorb waste heat from the electrical and / or electronic components arranged in a coolant circuit 28.2. During this heating function, the expansion valves AE3 and AE4 are closed, the shut-off valve A5 is closed, and the shut-off valve A2 is open. During this process, refrigerant extracted from a bidirectional branch 14.1 during water-source heat pump operation can be released through the shut-off valve A2.The primary line 14 is extracted and fed to the collector 24 via the check valve R2.

[0052] To perform the heating function using the external heat exchanger 18 as a heat pump evaporator, the refrigerant, compressed by the refrigerant compressor 12, flows through the open shut-off valve A3 into the heating coil 26 to transfer heat to a supply air stream. It is then expanded through the open shut-off valve A1 and expansion valve AE3 into the external heat exchanger 18 to absorb heat from the ambient air. The refrigerant then flows through a heat pump return line 15 to the manifold 24 and back to the refrigerant compressor 12. Expansion valves AE1, AE2, and AE4, as well as shut-off valve A5, remain closed during this process.

[0053] An indirect delta connection can be implemented by opening the shut-off valve A1 and allowing the refrigerant compressed by the refrigerant compressor 12 to expand into the chiller 28 via the expansion valve AE1. Simultaneously, no mass flow is generated on the coolant side, i.e., in the coolant circuit 28.2. This means that, for example, the fluid used as a coolant, such as water or a water-glycol mixture, remains stationary on the coolant side of the chiller 28, and the chiller 28 is not actively circulated with coolant. In this configuration, the expansion valves AE2, AE3, and AE4 remain closed.

[0054] During reheating operation, the supply air flow introduced into the vehicle interior is first cooled and thus dehumidified by means of the evaporator 22. The heat transferred to the refrigerant through evaporation and dehumidification, as well as the heat supplied to the refrigerant via the compressor 12, can then be used to completely or at least partially reheat the supply air flow L by means of the heating coil 26.

[0055] Fig. Figure 3 shows a simplified and schematic method 500 for operating a refrigeration system 10 of the Fig. 1 and Fig. 2, wherein the method is designed such that backflow of refrigerant into the chiller 28 is prevented.

[0056] In process 500, in a first step S501, the system switches to one of the (post-)heating or heat pump modes described above, in particular air-source heat pump mode. For this purpose, according to step S502, refrigerant is routed from the refrigerant compressor 12 to the evaporator 22 and to the chiller branch 28.1 or 28.3. In AC operation, the primary branch valve A4 can be open and the secondary branch valve A3 closed. Alternatively, in this step, for example, the secondary branch valve A3 can also be open and the primary branch valve A4 closed, so that refrigerant is routed from the refrigerant compressor 12 to the heating coil 26 and downstream of the heating coil 26 to the evaporator 22 and to the chiller branch 28.1 or 28.3.

[0057] In step S503, it is checked whether the coolant temperature Tcool in the coolant circuit 28.2 is lower than the refrigerant temperature Tcold in the chiller 28. This value is determined or estimated via the measured low pressure. If the condition in S503 is met, in step S504 the expansion valve AE1 associated with the chiller 28 is repeatedly opened and closed, such that refrigerant drawn in from the low-pressure side connection 22.2 between the evaporator 22 and the refrigerant compressor 12 downstream of the chiller 28 is purged from the chiller 28. If the condition in S503 is not met, the operating procedure carried out up to that point is maintained, with the condition in S503 being checked again.

[0058] If the condition in S503 is met, step S505 can alternatively or additionally be performed. In this step, the expansion valve AE1 is closed or held closed, and the coolant in the chiller 28 is heated by means of the coolant circuit 28.1 (waste heat from an electric drive component) to a temperature Tcool that is higher than the temperature Tcold of the refrigerant. This value is determined or estimated via the low pressure measured by sensors, such that the refrigerant in the chiller 28 is brought to a temperature / pressure level that prevents refrigerant from flowing back out of the low-pressure connection 22.2 between the evaporator 22 and the refrigerant compressor 12.

[0059] This process step S505 can also be combined with the repeated opening and closing (S504) of the expansion valve AE1 described above. In particular, such opening / closing or pulsed actuation of the expansion valve AE1 can be carried out after the refrigerant has been warmed (with the expansion valve closed for a longer period). The combination of S505 and S504 is indicated by the dashed connecting arrow in Fig. 3 illustrated.

[0060] Procedure 500 can be used for both here in the Fig. 1 and Fig. The embodiments of refrigeration systems 10 shown in the two examples are carried out. In refrigeration system 10 of the Fig. For example, evaporator 22 is included in 1. In the refrigeration system 10 of the Fig. In air source heat pump operation, the external heat exchanger 18 is included as an evaporator, which, with a corresponding configuration (A1, AE3, A2 open, AE1, AE2, AE4 closed), is arranged in parallel with the chiller 28 in terms of flow characteristics, according to the heating function already described above, by means of the external heat exchanger 18 as a heat pump evaporator. Of course, the refrigeration system 10 is also connected to the Fig. 2 a connection is possible in which the evaporator 22 is included in the procedure 500 to be carried out.

[0061] Of course, this can be done in Fig. The simplified procedures shown here may also be interrupted or stopped due to other system conditions, which are not shown in detail here. In this respect, the Fig. 3 merely represents a small excerpt from a comprehensive overall operating procedure.

[0062] In summary, it should be noted that the inventive concept presented and described here is for - Prevention of refrigerant shifting - Oil storage - Refrigerant recovery and - Oil flush This method is applicable to any system, regardless of whether it is a refrigeration system with or without a heat pump function. It is particularly important to note that the method is also applicable to system sections that are inactive and set to a low-pressure level in their passive state. Therefore, the application described here as an example for the chiller, and the method provided for the chiller, can also be transferred to other components and system sections. The system topology used is an exemplary representation of an application that is particularly suitable for describing the problem and the associated solution methodology.

[0063] The decisive factor for refrigerant redistribution in all cases is that lower medium temperatures prevail in inactive system sections than in active system sections. The medium flowing through or towards the inactive heat exchanger is lower compared to the evaporation pressure and the resulting evaporation temperature in the active system section, thus promoting the inflow and condensation of refrigerant into the inactive system section. This can be limited and prevented by the described structural (valve) and process-related solutions.

[0064] In general terms, the inventive concept can thus also be described as a method for operating a refrigeration system for a motor vehicle, wherein, in a low-pressure branch comprising a heat exchanger, an expansion element associated with the heat exchanger is repeatedly opened and closed in an inactive state, such that refrigerant drawn in downstream of the heat exchanger is flushed out of the heat exchanger. Alternatively or additionally, in the method, refrigerant stored in the heat exchanger can be heated and evaporated, for example, by another medium acting on or flowing through the heat exchanger, whereby the refrigerant in the heat exchanger is brought to a temperature / pressure level that prevents refrigerant backflow. This results in a lower-density gas phase instead of a high-density liquid phase.

Claims

[1] Method (500) for operating a refrigeration system (10) for a motor vehicle, wherein the refrigeration system (10) comprises: a refrigerant compressor (12) which can be connected to or is connected to a primary line (14); at least one evaporator (18, 22) arranged in the primary strand (14); a chiller (28) which is arranged in a chiller branch (28.1, 28.3) which is flow-parallel to the evaporator (18, 22), wherein an expansion element (AE1) is assigned to the chiller (28) in the chiller branch (28.1) and wherein the chiller (28) is connected to a coolant circuit (28.2) separate from the refrigerant circuit (11); the procedure includes the following steps: Conveying refrigerant from the refrigerant compressor (12) to the evaporator (18, 22) so that it is supplied with refrigerant, and to the expansion element (AE1) of the chiller branch (28.1); if the temperature (Tcool) of the coolant is lower than the temperature of the refrigerant (Tcold) (S503): repeated opening and closing (S504) of the expansion element (AE1) associated with the chiller (28) such that refrigerant drawn in downstream of the chiller (28) from the low-pressure side connection (22.2) between evaporator (22) and refrigerant compressor (12) is flushed out of the chiller (28). [2] Method (500) for operating a refrigeration system (10) for a motor vehicle, wherein the refrigeration system (10) comprises: a refrigerant compressor (12) which can be connected to or is connected to a primary line (14); at least one evaporator (18, 22) arranged in the primary strand (14); a chiller (28) which is arranged in a chiller branch (28.1, 28.3) which is flow-parallel to the evaporator (22), wherein an expansion element (AE1) is assigned to the chiller (28) in the chiller branch (28.1) and wherein the chiller (28) is connected to a coolant circuit (28.2) separate from the refrigerant circuit (11); the procedure includes the following steps: Conveying refrigerant from the refrigerant compressor (12) to the evaporator (22) so that it is supplied with refrigerant, and to the expansion element (AE1) of the chiller branch (28.1); if the temperature (Tcool) of the coolant is lower than the temperature (Tcol) of the refrigerant (S503): Close or keep closed (S505) the expansion valve (AE1) associated with the chiller (28) and Heating the coolant in the chiller (28) by means of the coolant circuit (28.2) to a temperature (Tcool) which is greater than the temperature (Tcol) of the refrigerant, such that the refrigerant in the chiller (28) is brought to a temperature / pressure level which prevents a backflow of refrigerant from the low-pressure side connection (22.2) between evaporator (22) and refrigerant compressor (12). [3] Method (500) according to claim 1 or 2, wherein refrigerant is passed from the refrigerant compressor via a heat exchanger forming a heat source to the evaporator (18, 22) and to the chiller branch (28.1, 28.3). [4] Refrigeration system (10) for a motor vehicle (10) with a refrigerant compressor (12) which can be connected to or is connected to a primary line (14); at least one evaporator (18, 22) arranged in the primary strand (14); a chiller (28) which is arranged in a chiller branch (28.1, 28.3) which is flow-parallel to the evaporator (18, 22), wherein an expansion element (AE1) is assigned to the chiller (28) in the chiller branch (28.1) and wherein the chiller (28) is connected to a coolant circuit (28.2) separate from the refrigerant circuit (11); wherein a check valve (R5) is arranged in the chiller line (28.3) downstream of the chiller (28) and upstream of a connection node (Ab2) with a low-pressure connection (22.2) extending between the evaporator (18, 22) and the refrigerant compressor (12), characterized by that it is equipped to carry out the method (500) according to claim 1 or 2. [5] Refrigeration system according to claim 4, characterized by, that a section (28.4) of the chiller branch (28.3) is designed upstream of the connecting node (Ab2) starting from the connecting node (Ab2) and rising relative to the low-pressure connection (22.2). [6] Refrigeration system (10) according to claim 4 or 5, characterized by , that a check valve (R1, R2) or a low-pressure side expansion device (AE5) is arranged downstream of the evaporator (18, 22) and upstream of the connection node (Ab2). [7] Refrigeration system (10) according to any one of claims 4 to 6, characterized by , that the rising section (28.4) of the chiller branch (28.3) projects upwards at an angle of 30° to 90° relative to an imaginary plane in which the low-pressure connection (22.2) runs. [8] Refrigeration system according to any one of claims 4 to 7, characterized by , that it has at least one heat exchanger (18, 26) that represents a heat source. [9] Refrigeration system (10) according to claim 8, characterized by , that it further shows: a secondary line (16) to which the refrigerant compressor (12) can be connected or is connected; a heat exchanger (26), in particular a heating coil (26), which is arranged in the secondary circuit; a secondary circuit valve (A3) arranged between the refrigerant compressor (12) and the heat exchanger (26). [10] Motor vehicle with a refrigeration system (10) according to any one of claims 4 to 9.

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