Method for defrosting an air-source heat pump evaporator of a refrigeration system in a motor vehicle using a bypass line section, refrigeration system with control unit for carrying out the method and motor vehicle with such a refrigeration system

Abstract

A method for defrosting a heat exchanger (18) operating as an air-source heat pump evaporator of a refrigeration system (10) of a motor vehicle (200) is described, wherein the refrigeration system has a refrigerant circuit (11) in which at least one first valve assembly (V1, A3, A4) is arranged downstream of a refrigerant compressor (12), through which a refrigerant flow to the heat exchanger (18) and / or to a third heat exchanger (26) can be adjusted; and wherein a bypass line section (15) branches off on the high-pressure side between the first valve assembly (V1, A3, A4) and the first heat exchanger (18), which has at least one second valve assembly (A2); wherein the method comprises the following steps: starting from an air-source heat pump operation, the first valve assembly (V1, A3, A4) is adjusted so that the refrigerant flow is directed at least partially to the first heat exchanger (18);and the second valve assembly (A2) arranged in the bypass line section (15) is partially opened, so that a partial refrigerant flow from the refrigerant flow directed to the first heat exchanger (18) is directed directly to the low-pressure side of the refrigerant circuit (11). Furthermore, a refrigeration system (10) with a control unit for carrying out the process and a motor vehicle (200) with such a refrigeration system (10) are described.

Description

[0001] The invention relates to a method for defrosting a heat exchanger operating as an air-source heat pump evaporator in a refrigeration system of a motor vehicle, as well as to a refrigeration system of a motor vehicle with a control device for carrying out the method. Furthermore, the invention also relates to a motor vehicle with an internal combustion engine and / or an electric drive equipped with such a refrigeration system.

[0002] Methods for defrosting a heat exchanger operating as an air-source heat pump evaporator in a motor vehicle are known from the prior art. Reference is made to DE 10 2020 107 652 A1 and DE 10 2019 203 293 A1 as examples. Further reference is made to DE 11 2019 007 174 T5, US 2013 / 0 098 092 A1, US 2012 / 0 272 669 A1, DE 10 2004 031 384 A1 and DE 10 2015 008 325 A1 for the technological background.

[0003] It is known from methods for defrosting an air-source heat pump evaporator that refrigerant (hot gas) compressed by the refrigerant compressor is fed to the air-source heat pump evaporator to heat and defrost it. Furthermore, it is also known to additionally restrict or, if possible, eliminate the airflow of fresh air or ambient air to the corresponding heat exchanger.

[0004] It has been shown that with such solutions, it is difficult to achieve a complete seal of the air inlets, so that during vehicle operation a sufficient amount of (very) cold ambient air can still reach the first heat exchanger, making it difficult or impossible to reach a suitable high-pressure level in the heat exchanger to defrost frozen condensate on its air-facing outer surfaces. In particular, it is difficult to achieve sufficient heating across the entire volume of the heat exchanger to lead to complete defrosting.

[0005] The object underlying the invention is seen as being to provide a method and a refrigeration system in which the above disadvantages are avoided and, in particular, improved or complete defrosting of the heat exchanger in question is made possible.

[0006] This problem is solved by a method for a refrigeration system and a motor vehicle with the features of the respective independent patent claim. Advantageous embodiments with expedient further developments are specified in the dependent patent claims.

[0007] A method is proposed for defrosting a heat exchanger operating as an air-source heat pump evaporator in a refrigeration system of a motor vehicle, wherein the refrigeration system has a refrigerant circuit with: a refrigerant compressor; at least one first heat exchanger, which functions as an air-source heat pump evaporator or as a gas cooler, respectively.a condenser can be used; at least a second heat exchanger, in particular an evaporator and / or a chiller; a third heat exchanger, in particular a heating coil; wherein at least one first valve assembly is arranged downstream of the refrigerant compressor, through which a refrigerant flow to the first heat exchanger and / or to the third heat exchanger can be adjusted; wherein on the high-pressure side, a bypass line section branches off between the first valve assembly and the first heat exchanger or between the refrigerant compressor and the first valve assembly, which ends on the low-pressure side upstream or downstream of the second heat exchanger and which has at least one second valve assembly; . The method comprises the following steps: starting from an air-source heat pump operation in which a refrigerant flow circulates from the refrigerant compressor to the heating coil and then to the first heat exchanger, which acts as an air-source heat pump evaporator, and to the low-pressure side of the refrigerant circuit, in particular the second heat exchanger, the first valve device is adjusted so that the refrigerant flow is directed at least partially to the first heat exchanger; and the second valve device arranged in the bypass line section is partially opened so that a partial refrigerant flow from the refrigerant flow directed to the first heat exchanger is directed directly to the low-pressure side of the refrigerant circuit.

[0008] By including the bypass section, a shift in pressure level can be achieved. This increases the low pressure upstream of the refrigerant compressor, thus enabling an increase in the high pressure level after compression. Furthermore, the bypass section increases the suction gas density and consequently the refrigerant mass flow rate.

[0009] The second valve assembly can be opened, at least partially, in particular in stages.

[0010] In this method, the second valve assembly can remain partially open or be moved in an open state as required until a refrigerant temperature measured in, at, or downstream of, or on the outlet side of, the first heat exchanger is greater than 0°C, in particular between 2° and 5°C.

[0011] In this process, the second valve assembly can remain partially open until the refrigerant pressure measured in or on the first heat exchanger is greater than 35 bar, in particular at least 37 to 45 bar.

[0012] Adjusting the second valve also allows for fine-tuning of the compressor and its resulting volume flow. In the steps described above involving temperature and / or refrigerant pressure measurement, the term "partially open second valve" also encompasses any intermediate settings of the second valve when it is opened incrementally.

[0013] In particular, a further stepwise opening of the second valve device can also be repeated if the desired refrigerant temperature and / or a desired refrigerant pressure has not (yet) been reached.

[0014] In this method, before the second valve assembly is partially opened, a third valve assembly of a refrigerant connection section, located downstream of the first valve assembly and upstream of the third heat exchanger, can be opened. This third valve assembly connects a heating branch to the low-pressure side of the refrigerant circuit, allowing refrigerant to be extracted from the third heat exchanger. This ensures that a sufficient quantity of refrigerant is available in the actively flowing part of the refrigerant circuit when it is no longer being supplied to the third heat exchanger (heating coil), particularly if the first valve assembly is appropriately adjusted.

[0015] In this procedure, the third valve assembly can be closed before the second valve assembly is partially opened.

[0016] In this method, the first valve assembly can be adjusted to split the refrigerant mass flow delivered by the refrigerant compressor into two refrigerant partial flows. A larger refrigerant partial flow is directed to the first heat exchanger and the second valve assembly, while a smaller refrigerant partial flow is directed to the third heat exchanger. For example, it is conceivable that a refrigerant partial flow of 60% to 99% is directed to the first heat exchanger and the second valve assembly or the bypass line section, while a refrigerant partial flow of 40% to 1% is directed to the third heat exchanger. This also makes it possible to achieve at least moderate heating of the vehicle's interior air by the third heat exchanger (heating coil) during defrosting of the first heat exchanger, which is then unavailable as an air-source heat pump evaporator.

[0017] Furthermore, a refrigeration system for a motor vehicle is proposed, wherein the refrigeration system has a refrigerant circuit with: a refrigerant compressor; at least one first heat exchanger, which can be used as an air-source heat pump evaporator or as a gas cooler or condenser; at least one second heat exchanger, in particular an evaporator and / or a chiller; a third heat exchanger, in particular a heating coil; wherein at least one first valve assembly is arranged downstream of the refrigerant compressor, through which a refrigerant flow to the first heat exchanger and / or to the third heat exchanger can be adjusted; wherein a bypass line section branches off on the high-pressure side between the first valve assembly and the first heat exchanger or between the refrigerant compressor and the first valve assembly, which ends upstream or downstream of the second heat exchanger on the low-pressure side and which has at least one second valve assembly; and with a control unit configured to carry out the method described above.

[0018] In the refrigeration system, a refrigerant connection section can branch off downstream from the first valve assembly and upstream from the third heat exchanger, connecting a heating branch to the low-pressure side of the refrigerant circuit and in which a third valve assembly is arranged.

[0019] In the refrigeration system, the refrigerant connection section can terminate downstream of the second heat exchanger if the bypass line section terminates upstream of the second heat exchanger.

[0020] In the refrigeration system, the refrigerant connection section can lead upstream of the second heat exchanger, and the bypass line section can lead into the refrigerant connection section.

[0021] The refrigeration system can have two first heat exchangers, between which a low-temperature cooler (coolant cooler) of a coolant circuit is arranged with respect to an airflow direction, wherein in an air duct in which the first heat exchangers and the low-temperature cooler are arranged, an airflow direction can be reversed as required in order to supply air heated by the low-temperature cooler to one or the other first heat exchanger.

[0022] The first two heat exchangers can be supplied with refrigerant in series or in parallel.

[0023] It is possible for the first two heat exchangers to be selectively supplied with refrigerant, particularly by providing supplementary interconnection devices. Especially for air-source heat pump operation, it can prove advantageous to use only one of the first two heat exchangers and to actively supply refrigerant to the second or last heat exchanger located in the air duct, relative to the natural airflow direction.

[0024] In the air duct, air supply flaps may be provided, which may be (partially) open or closed, in relation to a typical flow direction of fresh air upstream of the first heat exchangers and the low-temperature cooler.

[0025] The air duct may contain at least one air exhaust flap, which is arranged between the air supply flaps and a foremost first heat exchanger in such a way that, when the air supply flaps are closed, air conveyed against the usual flow direction of fresh air (reverse airflow) can escape through the then open air exhaust flap.

[0026] If only the first heat exchanger, the second or last one in the airflow and operating as an evaporator, is filled with refrigerant during air-source heat pump operation, then reversing the airflow via a modified fan is not strictly necessary. The refrigerant cooler, located upstream on the air side, can transfer its heat flow directly to the first heat exchanger, which is actively filled with refrigerant.

[0027] Furthermore, a motor vehicle with an internal combustion engine and / or an electric drive and with a refrigeration system as described above is proposed.

[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 simplified and schematic representation of an example of a refrigeration system with heat pump function; Fig. 2 a simplified and schematic representation of an example of a refrigeration system with heat pump function; Fig. 3 a simplified and schematic representation of an example of a refrigeration system with heat pump function; Fig. 4 a simplified and schematic representation of an air duct with heat exchangers and air dampers; Fig. 5 a simplified scheme of a procedure for defrosting a first heat exchanger of the refrigeration system.

[0029] In Fig. Figure 1 is a schematic and simplified embodiment of a refrigeration system 10 for a motor vehicle 200, shown here in simplified form as a rectangle. The refrigeration system 10 comprises a refrigerant circuit 11, which in the embodiment shown has the following components: a refrigerant compressor 12, a first heat exchanger 18, in particular a gas cooler or condenser, at least one second heat exchanger, in particular an evaporator 22 and / or chiller 28, and an accumulator or refrigerant receiver 24.

[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 an 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 includes a third heat exchanger, a heating coil 26 (also referred to as a heating condenser or hot gas cooler). A shut-off valve A3 is located upstream of the heating coil 26. A shut-off valve A1 is located downstream of the heating coil 26. Furthermore, an expansion valve AE4 is located downstream of the heating coil 26. The third heat exchanger 26 can alternatively operate as an indirect heat exchanger. In this case, its heat flow is transferred to an intermediate heat transfer medium, which in turn transfers the heat contained within it to an airflow passing through the air conditioning unit 32.

[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, to the expansion valve AE4, and to a branch Ab2 is referred to as the secondary circuit 16. The secondary circuit 16 comprises a heating branch 16.1, which extends from the shut-off valve A3 via the heating coil 26 to the shut-off valve A1. The secondary circuit 16 also includes a reheat branch 16.2, which is fluid-connected upstream to the heating coil 26 and downstream to the external heat exchanger 18. The secondary circuit 16, or rather the reheat branch 16.2, connects to the primary circuit 14 at branch Ab2.

[0035] The refrigeration system 10 comprises the third heat exchanger, in particular a further evaporator or chiller 28. The chiller 28 is arranged parallel to the evaporator 22 in terms of flow direction. The chiller 28 can, for example, be used to cool an electrical component of the vehicle, but also 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 the chiller 28.

[0036] The refrigeration system 10 or the refrigerant circuit 11 also includes the internal heat exchanger 20 as a further component.

[0037] The two shut-off valves A3, A4, which are arranged downstream of the refrigerant compressor 12, are collectively understood within the scope of this application as the first valve unit V1. It should be noted that the first valve unit V1 need not necessarily consist of two separate shut-off valves A3, A4, but may also be designed as a multi-way valve that performs at least the functions of the two shut-off valves A3, A4, in particular the release of refrigerant into the primary line 14 and / or the secondary line 16.

[0038] The refrigeration system 10 further comprises a bypass line section 15 branching off on the high-pressure side between the first valve assembly V1, in particular the shut-off valve A4, and the first heat exchanger 18, which terminates on the low-pressure side downstream of the second heat exchanger, in particular the evaporator 22 and the chiller 28, and which has at least one second valve assembly A2. With regard to the Fig. 1. Bypass line section 15 extends between branch Ab6 and branch Ab2.

[0039] In the refrigeration system 10, a refrigerant connection section 13 (branch Ab5) branches off downstream from the first valve assembly V1, in particular the shut-off valve A3, and upstream from the third heat exchanger 26 (heating coil). This section connects the heating branch 16.1 to the low-pressure side of the refrigerant circuit 11 and contains a third valve assembly A5. In this example, the refrigerant connection section 13 extends from branch Ab5 to branch Ab7, so that it opens into the bypass line section 15.

[0040] In the Fig. Figure 1 also shows various valve devices Ax and AEx (where x is a number), branches Aby (where y is a number), and sensors pTz (where z is a number) for measuring the pressure and / or temperature of the refrigerant, which are not discussed in detail here. However, such components of the refrigeration system 10 and the refrigerant circuit 11, in combination with the information from the Fig. 1 in their position or function within the refrigeration system 10 as identifiable and disclosed, in particular due to the respective numbers (x, y, z) which are assigned to a respective prefix.

[0041] The refrigeration system also has a control unit 50, which is designed to set the refrigeration system to desired operating modes or to control or regulate the operation of the refrigeration system, but also to stop the operation of the refrigeration system or to switch off the refrigeration system.

[0042] This application focuses in particular on an operating mode of the refrigeration system 10 in which the first heat exchanger 18 operates as an air-source heat pump evaporator. In such an operating mode, the refrigeration system 10 is configured and connected as follows: Refrigerant flows from the refrigerant compressor 12 through the open shut-off valve A3 into the secondary circuit 16 or the heating circuit 16.1. The refrigerant then flows to the third heat exchanger or heating coil 26.

[0043] Downstream of the heating coil 26, the shut-off valve A1 is open and the expansion valve AE4 is closed. The refrigerant expands through the at least partially open expansion valve AE3 into the first heat exchanger 18, which serves as the air-source heat pump evaporator. From the first heat exchanger 18, with the shut-off valve A2 open, the refrigerant flows to the branch Ab2 on the low-pressure side of the refrigerant circuit 11, so that, particularly after passing through the refrigerant receiver 24 and the internal heat exchanger 20, it is drawn in and compressed again by the refrigerant compressor 12.

[0044] In such an operating condition, it is also conceivable that downstream from the heating coil 26 or from the shut-off valve A1, at least a partial refrigerant flow is directed to the chiller 28 with the expansion valve AE1 at least partially open.

[0045] In such an air-source heat pump operation, heat is extracted from the ambient air or fresh air supplied to the first heat exchanger 18 to evaporate the refrigerant. Depending on the temperature and humidity of the ambient air, this condenses on the first heat exchanger 18, so that icing can form on it depending on the evaporation pressure level and the resulting evaporation temperature.

[0046] Referring to the Fig. 2 and Fig. 3 Two examples of the refrigeration system 10 are briefly described, which are modified with regard to the bypass line section 15 and the refrigerant connection section 13.

[0047] According to the example of Fig. 2. The refrigeration system 10 has a bypass line section 15 branching off on the high-pressure side between the first valve assembly V1, in particular the shut-off valve A4, and the first heat exchanger 18. This bypass line section terminates on the low-pressure side upstream of the second heat exchanger, in particular the chiller 28. As in the example of Fig. 1. The bypass line section 15 has the second valve device A2.

[0048] Regarding the Fig. 2. Bypass section 15 extends between branch Ab6 and branch Ab7a.

[0049] In the example of the Fig. 2 further branches off downstream from the first valve assembly V1, in particular the shut-off valve A3, and upstream from the third heat exchanger 26 (heating coil) the refrigerant connection section 13 (branch Ab5), which connects the heating branch 16.1 to the low-pressure side of the refrigerant circuit 11 and in which a third valve assembly A5 is arranged. In this example, the refrigerant connection section 13 extends from branch Ab5 to branch Ab2, so that it opens downstream of the second heat exchanger, in particular evaporator 22 and chiller 28.

[0050] In the example of the Fig. 3 branches off downstream from the first valve assembly V1, in particular the shut-off valve A3, and upstream from the third heat exchanger 26 (heating coil) the refrigerant connection section 13 (branch Ab5), which connects the heating branch 16.1 to the low-pressure side of the refrigerant circuit 11 and in which a third valve assembly A5 is arranged. In this example, the refrigerant connection section 13 extends from branch Ab5 to branch Ab7a. The refrigerant connection section 13 thus ends upstream of the second heat exchanger, in particular chiller 28.

[0051] In the example of the Fig. 3. The refrigeration system 10 has a bypass line section 15 branching off on the high-pressure side between the first valve assembly V1, in particular the shut-off valve A4, and the first heat exchanger 18. This bypass line section terminates at a branch Ab7b, so that it opens into the refrigerant connection section 13. As in the example of the Fig. 1 and Fig. 2. The bypass line section 15 has the second valve assembly A2. With regard to the Fig. 2. Bypass section 15 extends between branch Ab6 and branch Ab7b.

[0052] Fig. Figure 4 shows an exemplary arrangement of two first heat exchangers 18 and a coolant cooler, also referred to as a low-temperature cooler NK, in an air duct 40. The two first heat exchangers 18 are in the Fig. 4 are arranged in series as examples. In other words, with regard to a flow direction of fresh air FL (dashed contour arrows), one can speak of a front first heat exchanger 18 and a rear first heat exchanger 18.

[0053] The air duct 40 is associated with at least one blower device 46, which is designed to convey fresh air FL (dotted contour arrows) or to convey air in the opposite direction UK.

[0054] The integration of the first two heat exchangers into the refrigerant circuit 11 is illustrated by the branches Ab6 and Ab8, which are also found in the Fig. Have them identify 1 to 3.

[0055] The low-temperature cooler NK is part of a coolant circuit 28.2, which also consists of the Fig. 1 to 3 are visible. The coolant circuit 28.2 can be connected to the chiller 28 and thus connected as needed ( Fig. 1 to 3) and serves in particular to cool at least one electrical component of the motor vehicle 200, such as a battery storage unit (high-voltage battery) and / or an electric drive or the like. The low-temperature cooler NK can, for example, be arranged between the two first heat exchangers 18.

[0056] In the air duct 40, with respect to a typical flow direction of fresh air FL (dotted contour arrow) upstream of the first heat exchangers 18 and the low-temperature cooler NK, air supply flaps 42 or alternative closing devices can be provided, which can be (partially) open or closed. Fig. Figure 4 illustrates the (partially) open state with the dotted air flaps 42.

[0057] In the air duct 40 at least one air discharge flap 44 can be provided, which is arranged between the air supply flaps 42 and a foremost first heat exchanger 18 in such a way that, when the air supply flaps 42 are closed, air conveyed against the usual flow direction of fresh air FL (reverse airflow UK, solid contour arrows) can escape through the then open air discharge flap 44.

[0058] The supply of fresh air FL or of air with reversed flow direction UK can be carried out in particular by at least one fan device 46 which is arranged in the air duct 40.

[0059] It is pointed out that the in Fig. Figure 4, an example of a structure with two first heat exchangers 18, can also be configured differently. For example, the two first heat exchangers 18 can be connected in parallel to each other in the refrigerant circuit 11. In this case, depending on the selected system configuration or connection, only one of the two heat exchangers 18 may be filled with refrigerant. Furthermore, it is also possible that only one first heat exchanger 18 is present, which, with respect to the flow direction of fresh air FL, is located before or after the low-temperature cooler NK.

[0060] The following refers to the Fig. 5. A method 500 for defrosting the first heat exchanger 18 is described when it operates as an air-source heat pump evaporator. For better understanding, reference is made to the above-described methods. Fig. Reference is made to sections 1 to 4 and the components of the refrigeration system 10 described therein.

[0061] Based on a circuit configuration in an air-source heat pump operation, as described above with reference to the Fig. As described in section 1, in which an entire refrigerant flow circulates from the refrigerant compressor 12 to the heating coil 26 and then to the first heat exchanger 18 operating as an air heat pump evaporator and the second heat exchanger 28, in particular chiller, the first valve device V1 is set according to step S501 so that the refrigerant flow is directed at least partially to the first heat exchanger 18.

[0062] With regard to the exemplary design of the refrigeration system 10, as described in the Fig. As shown in 1 to 3, in step S501 the shut-off valve A3 is at least partially or completely closed and the shut-off valve A4 is at least partially or completely opened.

[0063] According to step S502, the second valve device A2 arranged in the bypass line section 15 is partially opened, so that a partial refrigerant flow from the refrigerant flow directed to the first heat exchanger 18 is directed directly to the low-pressure side of the refrigerant circuit 11.

[0064] In this context, it is also possible that the flow through valve units A2 and A5 is prioritized based on the position of valve unit V1. If the cross-section, and thus the mass flow, is predominantly directed towards valve A3, a partial bypass flow to the low-pressure side can preferably be routed via valve A5. Conversely, if valve A4 is primarily subjected to mass flow, the partial mass flow to be discharged to the low-pressure side can be routed via valve unit A2.

[0065] However, if there is an unsketched refrigerant branch directly downstream of compressor 12 to the low-pressure side, a possible mass flow distribution-dependent prioritization becomes unnecessary, since this central branch is always used for converting the refrigerant supply to the low-pressure side.

[0066] By including the bypass line section 15, a shift in the pressure level can be achieved. This increases the low pressure upstream of the refrigerant compressor 12, thus enabling an increase in the high pressure level after compression. Furthermore, the inclusion of the bypass line section 15 increases the suction gas density and therefore the refrigerant mass flow rate.

[0067] The at least partial opening of the second valve assembly A2 can be carried out in a stepwise manner in step S502. For example, step S502 can also be performed multiple times to allow for a stepwise opening.

[0068] Compressor 12, in conjunction with the cross-sectional opening of A2, can increase the volume flow rate, for example, by increasing its speed. If the target low pressure is reached or exceeded, the operation of valve A2 can be stopped, or conversely, the valve can be moved back towards the "closed" position. Accordingly, compressor 12 can reduce its volume flow rate if necessary.

[0069] According to step S503, the second valve assembly A2 can be readjusted until the refrigerant temperature measured in or on the first heat exchanger is greater than 0°C, in particular between 2° and 5°C. The refrigerant temperature can be measured, for example, using a sensor assembly pT5 ( Fig. 1 to 3) are recorded.

[0070] According to an optional step S504, the second valve assembly can remain partially open until a refrigerant pressure measured in or on the first heat exchanger 18 is greater than 35 bar, in particular between 37 and 45 bar. The refrigerant pressure can be measured, for example, by means of a sensor device pT5 ( Fig. 1 to 3) are recorded.

[0071] In particular, by fully opening valve A4 and by closing valve A3, the maximum mass flow of refrigerant and thus the maximum heat flow in the refrigerant can be directed towards the first heat exchanger(s) 18.

[0072] In the steps S503 and S504 described above, involving temperature measurement and / or refrigerant pressure measurement, the term "the second valve device A2 remains partially open" also includes any intermediate settings of the second valve device A2, especially if it is opened step by step.

[0073] In procedure 500, before step S502, i.e., before the partial opening of the second valve assembly A2, the third valve assembly A5 of the refrigerant connection section 13, located downstream of the first valve assembly V1 (shut-off valve A3) and upstream of the third heat exchanger 26 (heating coil), can be opened (S505). This connects the heating branch 16.1 to the low-pressure side of the refrigerant circuit 11, allowing refrigerant to be extracted from the third heat exchanger 26 (heating coil). For refrigerant extraction, valve A3 must be fully closed. Extraction can only occur if valve A2 is closed to prevent any potential backflow of refrigerant into the secondary branch 16.

[0074] In procedure 500, according to step S506, the third valve device A5 is closed before the second valve device A2 is partially opened (S502).

[0075] In the process 500, in the first step S501, the first valve assembly V1, in particular the two shut-off valves A3, A4, can be set so that the refrigerant mass flow delivered by the refrigerant compressor12 is divided into two refrigerant partial flows, whereby a larger refrigerant partial flow is directed to the first heat exchanger 18 and to the second valve assembly A2, and a smaller refrigerant partial flow is directed to the third heat exchanger 26 (heating register).

[0076] For example, it is conceivable that a refrigerant flow of 60% to 99% is directed to the first heat exchanger 18 and the second valve assembly A2 or the bypass line section 15, while a refrigerant flow of 40% to 1% is directed to the third heat exchanger 26. This also makes it possible to achieve at least moderate heating of the interior air of the vehicle 200 by the third heat exchanger 26 (heating coil) during defrosting of the first heat exchanger 18, which is then not available as an air-source heat pump evaporator.

[0077] If one or both of the conditions mentioned in steps S503 and S504 are met, respectively, procedure 500 for defrosting the first heat exchanger 18 can be terminated according to step S507. After termination of procedure 500, the refrigeration system can, for example, be reset to operating mode with the (then defrosted) first heat exchanger 18 as an air-source heat pump evaporator, as described above with reference to the Fig. 1 has already been described.

[0078] It should also be noted that defrosting of the first heat exchanger 18 can also be achieved or supported by incorporating a reverse airflow UK in the air duct 40. In particular, it is conceivable that a reversal of the airflow could be combined with the above-mentioned method 500.

[0079] For the sake of completeness, it should also be noted that the control unit 50 of the refrigeration system 10 ( Fig.1 to 3) is configured to carry out the process steps described above. The control unit 50 can also be configured to control the blower device 46 and / or the air supply flaps 42 or the air discharge flap 44.

Claims

[1] Method (500) for defrosting a heat exchanger (18) operating as an air-source heat pump evaporator of a refrigeration system (12) of a motor vehicle (200), wherein the refrigeration system has a refrigerant circuit (11) comprising: a refrigerant compressor (12); at least one first heat exchanger (18) which can be used as an air heat pump evaporator or as a gas cooler or condenser; at least a second heat exchanger (22, 28), in particular an evaporator and / or a chiller; a third heat exchanger (26), in particular a heating coil; wherein at least one first valve assembly (V1, A3, A4) is arranged downstream of the refrigerant compressor (12), through which a refrigerant flow to the first heat exchanger (18) and / or to the third heat exchanger (26) can be adjusted; wherein a bypass line section (15) branches off on the high-pressure side between the first valve assembly (V1, A3, A4) and the first heat exchanger (18) or between the refrigerant compressor (12) and the first valve assembly (V1, A3, A4), which ends upstream or downstream of the second heat exchanger (22, 28) on the low-pressure side and which has at least one second valve assembly (A2); wherein the method (500) comprises the following steps starting from an air-source heat pump operation in which a refrigerant flow circulates from the refrigerant compressor (12) to the heating coil (26) and then to the first heat exchanger (18) operating as an air-source heat pump evaporator and to the low-pressure side of the refrigerant circuit (11), in particular the second heat exchanger (22, 28), the first valve assembly (V1, A3, A4) is set (S501) such that the refrigerant flow is directed at least partially to the first heat exchanger (18); and the second valve assembly (A2) arranged in the bypass line section (15) is partially opened (S502), so that a partial refrigerant flow from the refrigerant flow directed to the first heat exchanger (18) is directed directly to the low-pressure side of the refrigerant circuit (11). [2] Method (500) according to claim 1, wherein the second valve device (A2) remains partially open until a refrigerant temperature measured in or on the first heat exchanger (18) is greater than 0°C, in particular 2° to 5°C (S503). [3] Method (500) according to claim 1 or 2, wherein the second valve device (A2) remains partially open until a refrigerant pressure measured in or on the first heat exchanger (18) is greater than 35 bar, in particular 37 to 45 bar (S504). [4] Method (500) according to one of the preceding claims, wherein prior to the partial opening (S502) of the second valve assembly (A2), a third valve assembly (A5) of a refrigerant connection section (13) arranged downstream of the first valve assembly (V1, A3, A4) and upstream of the third heat exchanger (26) is opened (S505), which connects a heating branch (16.1) to the low-pressure side of the refrigerant circuit (11), so that refrigerant is extracted from the third heat exchanger (26). [5] Method (500) according to claim 4, wherein the third valve device (A5) is closed (S506) before the second valve device (A2) is partially opened (S502). [6] Method (500) according to one of the preceding claims, wherein the first valve assembly (V1, A3, A4) is adjusted such that the refrigerant mass flow delivered by the refrigerant compressor (12) is divided into two refrigerant partial flows, wherein a larger refrigerant partial flow is directed to the first heat exchanger (18) and to the second valve assembly (A2), and a smaller refrigerant partial flow is directed to the third heat exchanger (26). [7] Refrigeration system (10) of a motor vehicle (200), wherein the refrigeration system (10) comprises a refrigerant circuit (11) with: a refrigerant compressor (12); at least one first heat exchanger (18) which can be used as an air heat pump evaporator or as a gas cooler or condenser; at least a second heat exchanger (22, 28), in particular an evaporator and / or a chiller; a third heat exchanger (26), in particular a heating coil; wherein at least one first valve assembly (V1, A3, A4) is arranged downstream of the refrigerant compressor (12), through which a refrigerant flow to the first heat exchanger (18) and / or to the third heat exchanger (26) can be adjusted; wherein a bypass line section (15) branches off on the high-pressure side between the first valve assembly (V1, A3, A4) and the first heat exchanger (18) or between the refrigerant compressor (12) and the first valve assembly (V1, A3, A4), which terminates on the low-pressure side upstream or downstream of the second heat exchanger (22, 28) and which has at least one second valve assembly (A2); and a control unit (50) configured to perform the method (500) according to any one of claims 1 to 6. [8] Refrigeration system (10) according to claim 7, wherein a refrigerant connection section (13) branches off downstream from the first valve assembly (V1, A3, A4) and upstream from the third heat exchanger (26), connecting a heating branch (16.1) to the low-pressure side of the refrigerant circuit (11) and in which a third valve assembly (A5) is arranged, and / or wherein, in particular, the refrigerant connection section (13) opens downstream from the second heat exchanger (22, 28) when the bypass line section (15) opens upstream from the second heat exchanger (22, 28), or wherein, in particular, the refrigerant connection section (13) opens upstream from the second heat exchanger (22, 28) and the bypass line section (15) opens into the refrigerant connection section (13). [9] Refrigeration system (10) according to claim 7 or 8, wherein it has two first heat exchangers (18) between which, with respect to an airflow direction (FL, UK), a low-temperature cooler (NK) of a coolant circuit (28.2) is arranged, wherein in an air duct (40) in which the first heat exchangers (18) and the low-temperature cooler (NK) are arranged, an airflow direction (FL, UK) can be reversed as required in order to supply air heated by the low-temperature cooler (NK) to one or the other first heat exchanger (18). [10] Motor vehicle (200) with an internal combustion engine and / or an electric drive and with a refrigeration system (10) according to one of claims 7 to 9.

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