DE102020127300A1 - Method for operating a refrigeration system in heat pump mode with exhaust air heat utilization, refrigeration system and motor vehicle with such a refrigeration system - Google Patents

Abstract

A method (500) for operating a refrigeration system (10) with a heat pump function for a motor vehicle is described, the refrigeration system (10) comprising: a refrigerant compressor (12) which can be or is connected to a primary line (14) and a secondary line (16). is; a directly or indirectly acting external heat exchanger (18) which is arranged in the primary line (14); an evaporator (22) which is arranged in the primary line (14); at least one further heat exchanger, representing a heat source, which is arranged in the secondary line (16); a primary branch valve (A4) arranged between the refrigerant compressor (12) and the external heat exchanger (18); a secondary branch valve (A3) arranged between the refrigerant compressor (12) and the further heat exchanger representing a heat source; a first expansion valve (AE2) arranged upstream of the evaporator and a second expansion valve (AE5) arranged downstream of the evaporator; wherein the evaporator (22) is part of an air conditioning unit (32) for conditioning interior air for a motor vehicle. The method includes the following steps: Setting the first expansion valve (AE2) and the second expansion valve (AE5) so that the evaporator (22) is operated at an evaporator temperature of more than 0° C. at a low pressure level or an intermediate pressure level, and supplying from the interior originating circulating air (UL) to the evaporator (22), so that the evaporator (22) with pure circulating air (UL) or a mixture of circulating air (UL) and fresh air (FL) is applied.

Description

The invention relates to a method for operating a refrigeration system with a heat pump function for a motor vehicle, a refrigeration system and a motor vehicle with such a refrigeration system.

A refrigeration system with a heat pump function usually includes a refrigerant compressor which can be connected or is connected to a primary line and a secondary line; a directly or indirectly acting external heat exchanger, which is arranged in the primary line; an evaporator arranged in the primary line; at least one further heat exchanger acting as a heat source, in particular a heating register, which is arranged in the secondary line; a loop valve disposed between the refrigerant compressor and the outdoor heat exchanger; a secondary branch valve arranged between the refrigerant compressor and the at least one further heat exchanger, in particular a heating register.

A refrigeration system with a heat pump function for a motor vehicle is, for example DE 10 2015 112 123 A1 famous. With this refrigeration system, heat from the exhaust air or circulating air is used and used on the evaporator. A similar concept is shown in DE 10 2009 048 674 A1 . Furthermore, on the DE 10 2014 110 360 A1 pointed out.

In the process considered here, the focus is on the heat pump operation of the refrigeration system, i.e. an operating state in which the interior air is heated and/or dehumidified.

The object on which the invention is based is seen as specifying a method in which the energy consumption is optimized and, in particular, the consumption of electrical energy is also improved.

This object is achieved by a method, a refrigeration system and a motor vehicle with the features of the respective independent patent claims. Advantageous configurations with expedient developments are specified in the dependent patent claims.

A method is therefore proposed for operating a refrigeration system with a heat pump function for a motor vehicle, the refrigeration system comprising: a refrigerant compressor which can be connected or is connected to a primary line and a secondary line;
a directly or indirectly acting external heat exchanger, which is arranged in the primary line;
an evaporator arranged in the primary line;
at least one further heat exchanger representing a heat source, in particular a heating register, which is arranged in the secondary line; a loop valve disposed between the refrigerant compressor and the outdoor heat exchanger;
a secondary line valve I arranged between the refrigerant compressor and the additional heat exchanger, in particular a heating coil, which represents a heat source;
a first expansion valve arranged upstream of the evaporator and a second expansion valve arranged downstream of the evaporator; wherein the evaporator is part of an air conditioning device for conditioning interior air for a motor vehicle.

• Einstellen eines Wärmepumpenbetriebs, bei dem das Kältemittel vom Kältemittelverdichter in den Sekundärstrang geleitet wird;
• Einstellen des ersten Expansionsventils und des zweiten Expansionsventils so dass der Verdampfer bei einer Verdampfertemperatur von mehr als 0°C auf einem Niederdruckniveau oder einem Zwischendruckniveau betrieben wird, und
• Zuführen von aus dem Innenraum stammender Umluft zu dem Verdampfer, so dass der Verdampfer mit reiner Umluft oder einem Gemisch aus Umluft und Frischluft beaufschlagt wird.

The procedure includes the following steps:

• Setting a heat pump operation, in which the refrigerant is routed from the refrigerant compressor into the secondary line;
• adjusting the first expansion valve and the second expansion valve so that the evaporator operates at a low pressure level or an intermediate pressure level at an evaporator temperature greater than 0°C, and
• Supplying circulating air originating from the interior to the evaporator, so that the evaporator is subjected to pure circulating air or a mixture of circulating air and fresh air.

Such a method can be used to set a desired pressure level, in particular an intermediate pressure level, by simply setting the expansion valves assigned to the evaporator. This has the advantage that sufficient evaporation of refrigerant is achieved, with the air dehumidified by the evaporator, or the mixture of fresh air and circulating air, being cooled to a lesser extent, so that the subsequent heating by means of the heating register can take place more quickly and optimally . Furthermore, this measure is characterized in that the moisture bound in the air flow can condense out and thus dry air flows into the cabin, which in turn can reduce or eliminate the risk of window fogging.

In the method, the evaporator can be used for cooling and/or dehumidifying the circulating air and/or fresh air when the interior temperature in the motor vehicle is greater than 0°C. This ensures that the circulating air that is not supplied to the evaporator is too cold, so that icing of the evaporator can be prevented. In other words, heating up a very severely cooled motor vehicle initially by means of other heat-emitting components of the refrigeration system or air conditioner, for example with electric auxiliary heaters.

In the method, the evaporator can be used for cooling and/or dehumidifying the circulating air and/or fresh air if the intake temperature level upstream of the evaporator is greater than 0°C, in particular at least 5°C. Thus, in addition or as an alternative to monitoring the interior temperature level, in particular for mixed operation of circulating air and fresh air, it can be taken into account that the intake temperature level upstream of the evaporator is regularly, in particular also significantly, above 0°C. The intake temperature level can be monitored, for example, by means of a temperature sensor arranged in the intake area in front of the evaporator. In this way, in particular, the switch-on time or the active integration of the evaporator into the heat pump or reheat operation can be controlled. Alternatively, such a temperature or the intake temperature level can also be simulated or derived mathematically using a mathematical model and thus calculated or estimated, for example depending on the circulating air or fresh air quantities, flap positions and the respective intake temperature levels. When the system is operating below an intake temperature of 0°C, the evaporator is inactive, refrigerant does not flow through it and the expansion device positioned upstream of the evaporator remains closed.

In the method, a chiller that is fluidically arranged parallel to the evaporator can be operated simultaneously. The chiller usually extracts waste heat from electrical high-voltage components and transfers this waste heat to the refrigerant circuit.

In the method, the evaporator and the chiller can be operated at different pressure levels; in particular, the chiller can be operated at a low pressure level and the evaporator at a higher intermediate pressure level. This makes it possible for the high-voltage components of the motor vehicle to be cooled due to the low pressure in the chiller, whereas the intermediate pressure level at the evaporator enables improved heating of air, in particular of circulating air or the mixture of circulating air and fresh air for conditioning, which is optimized in particular with regard to energy consumption is made possible by indoor air supply.

In the method, the supply of pure circulating air or of a mixture of circulating air and fresh air can be carried out alternately. As a result, the air quality can be kept high, especially with low levels of carbon dioxide.

Switching from supplying pure fresh air to the recirculated air or increasing the proportion of fresh air in the set mixture of recirculated air and fresh air (also called partial recirculated air operation) or vice versa can be dependent on the air quality or carbon dioxide content measured in the interior and/or specified periods of time or /and performed by a recorded number of occupants.

• einen Kältemittelverdichter, der mit einem Primärstrang und einem Sekundärstrang verbindbar oder verbunden ist;
• einen direkt oder indirekt wirkenden äußeren Wärmeübertrager der im Primärstrang angeordnet ist;
• einen Verdampfer, der im Primärstrang angeordnet ist; wenigstens einen weiteren, eine Wärmequelle darstellenden Wärmeübertrager, insbesondere ein Heizregister, der im Sekundärstrang angeordnet ist; ein zwischen dem Kältemittelverdichter und dem äußeren Wärmeübertrager angeordnetes Primärstrangventil;
• ein zwischen dem Kältemittelverdichter und dem weiteren, eine Wärmequelle darstellenden Wärmeübertrager, insbesondere Heizregister, angeordnetes Sekundärstrangventil;
• ein stromaufwärts von dem Verdampfer angeordnetes erstes Expansionsventil und ein stromabwärts von dem Verdampfer angeordnetes zweites Expansionsventil; wobei der Verdampfer Teil eines Klimageräts für die Konditionierung von Innenraumluft für ein Kraftfahrzeug ist.

A refrigeration system with a heat pump function for a motor vehicle is also proposed, the refrigeration system comprising:

• a refrigerant compressor which is connectable or connected to a primary line and a secondary line;
• a directly or indirectly acting external heat exchanger which is arranged in the primary line;
• an evaporator arranged in the primary line; at least one further heat exchanger representing a heat source, in particular a heating register, which is arranged in the secondary line; a loop valve disposed between the refrigerant compressor and the outdoor heat exchanger;
• a secondary branch valve arranged between the refrigerant compressor and the additional heat exchanger, in particular a heating register, which represents a heat source;
• a first expansion valve arranged upstream of the evaporator and a second expansion valve arranged downstream of the evaporator; wherein the evaporator is part of an air conditioning device for conditioning interior air for a motor vehicle.

It is provided that the refrigeration system, in particular the air conditioning unit, has a circulating air supply, which is set up to direct circulating air originating from the interior to the evaporator, so that the evaporator is subjected to pure circulating air or a mixture of circulating air and fresh air.

In the refrigeration system, a sensor device, in particular a pressure/temperature sensor, can be arranged in the evaporator branch between the two expansion elements, but preferably downstream of the evaporator.

Next, in the case of the refrigeration system, in terms of flow, at least parallel to the evaporator another heat exchanger can be arranged, in particular a chiller.

For heat pump operation, there is also the option of using the heat exchanger, which works as a direct or indirect heat source in the refrigeration system process, as a direct or indirect heat sink and thus realizing an air heat pump process.

The refrigeration system can include a control device that is set up to carry out the method described above.

A motor vehicle, in particular an at least partially electrically operated motor vehicle, can have a refrigeration system as described above, with at least one intake opening for interior air being present in an interior of the motor vehicle, which is fluidically connected to the circulating air supply of the air conditioning unit. In an electric vehicle, the efficient operation of the refrigeration system can lead to electricity savings, so that a greater range of the electric vehicle can be achieved as a result.

At least one carbon dioxide interior sensor and/or at least one occupant detection device can be arranged in the interior of the motor vehicle. This makes it possible to record parameters that can be taken into account for the assessment of the air quality in the interior, in particular to determine whether pure recirculated air or a mixture of recirculated air and fresh air should or can be present at the evaporator or whether in partial recirculation mode the proportion of fresh air should be increased in a targeted manner.

The method presented here and the refrigeration system thus enable heat recovery from the interior air (circulating air) of the motor vehicle.

In this case, the refrigeration system can have an essentially unchanged structure, without additional heat exchangers having to be provided in exhaust air ducts for the interior air, for example.

It is pointed out that it can also be considered that the cabin's internal air ducts for air supply and air return to the air conditioning unit are designed in such a way that the method described here and the function of the refrigeration system can be supported, even if the air ducts themselves are of secondary importance in the context of this application.

The method and the refrigeration system can be used or operated accordingly, in particular when heating up a motor vehicle quickly, so that energy-efficient and more dynamic heating is possible in the heat pump mode. However, the method and the refrigeration system can also be used in so-called extended AC operation (cooling operation) when the interior (cabin) of the motor vehicle is already warm, but the surroundings are cold. In such a case, a so-called post-heating operation (reheat) can be carried out when the ambient temperature is below zero.

It is also pointed out that the circulating air supplied to the evaporator can be 100%, particularly at the start of the journey, or the mixture of circulating air and fresh air advantageously has a ratio of approximately 70% to 95% circulating air to 30% to 5% fresh air. This ensures that there is sufficient oxygen in the interior. Furthermore, the flow through the interior or the cabin can be improved because each interior of a motor vehicle also has at least one exhaust air duct in a rear vehicle area, where interior air can escape from the motor vehicle into the environment. As already explained above, the switching times can be determined using various criteria, such as a carbon dioxide interior sensor, in fixed time intervals with or without a dependency on the number of occupants. Alternatively, a minimum proportion of fresh air is defined from the beginning or with a delay, the amount of which can in turn be varied.

• 1 ein schematisches und vereinfachtes Schaltbild einer Kälteanlage für ein Kraftfahrzeug;
• 2 ein Flussdiagram einer beispielhaften Umsetzung des Verfahrens insbesondere mittels der in 1 beschriebenen Kälteanlage.

Further advantages and details of the invention result from the following description of embodiments with reference to the figures. It shows:

• 1 a schematic and simplified circuit diagram of a refrigeration system for a motor vehicle;
• 2 a flowchart of an exemplary implementation of the method, in particular using the 1 described refrigeration system.

In 1 an embodiment of a refrigeration system 10 for a motor vehicle is shown schematically and in simplified form. The refrigeration system 10 includes a refrigerant circuit 11, which can be operated both in a refrigeration system operation (also called AC operation for short) and in a heat pump mode. In the embodiment shown, the refrigeration system 10 comprises a refrigerant compressor 12, an outer heat exchanger 18, an inner heat exchanger 20, an evaporator 22 and an accumulator or refrigerant collector ler 24. The external heat exchanger 18 can be designed as a condenser or gas cooler. In particular, the outer heat exchanger 18 in the illustrated embodiment is bidirectional flow bar.

The evaporator 22 is shown here by way of example as a front evaporator for a vehicle. The evaporator 22 is also representative of other evaporators possible in a vehicle, such as rear evaporators, which can be arranged parallel to one another in terms of flow. In other words, the refrigeration system 10 includes at least one evaporator 22.

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

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

The refrigeration system 10 further includes a heating register 26 (also referred to as a heating condenser or heating gas cooler). A shut-off valve A3 is arranged upstream of the heating register 26 . A shut-off valve A1 is arranged downstream of the heating register 26 . Furthermore, an expansion valve AE4 is arranged downstream of the heating register 26 .

Within the scope of this description, the section from the compressor 12 to the heating register 26, to the expansion valve AE4 and to a branch Ab2 is referred to as the secondary branch 16 in the entire refrigerant circuit of the refrigeration system 10 . The secondary branch 16 includes a heating branch 16.1, which extends from the shut-off valve A3 via the heating register 26 to the shut-off valve A1. The secondary line 16 also includes an after-heating branch or reheat branch 16.2, which can be fluidly connected to the heating register 26 upstream and to the external heat exchanger 5 downstream. The secondary line 16 or the reheat branch 16.2 opens into the primary line 14 at a branching point Ab2.

The refrigeration system 10 includes a further evaporator or chiller 28 . The chiller 28 is provided parallel to the evaporator 22 in terms of flow. The chiller 28 can be used, for example, to cool an electrical component of the vehicle, but also to implement a water heat pump function using the waste heat from at least one electrical component. An expansion valve AE1 is connected upstream of the chiller 28 .

The refrigeration system 10 can also have an electrical heating element 30 which is designed, for example, as a high-voltage PTC heating element. The electric heating element 30 is used as an additional heater for a supply air flow L guided into the vehicle interior. The electric heating element 30 can be accommodated in an air conditioning unit 32 together with the heating register 26 and the evaporator 22 . In this case, the electrical heating element 30 can be arranged downstream of the heating register 26 .

In the 1 check valves R1 and R2 are also visible. Furthermore, some sensors pT1 to pT5 for detecting the pressure and/or temperature of the refrigerant are also shown. It is pointed out that the number of sensors and their arrangement is only shown here as an example. A refrigeration system 10 can also have fewer or more sensors. In the example shown, combined pressure/temperature sensors pT1 to pT5 are shown as sensors. However, it is just as conceivable that sensors that are separate from one another are used for measuring pressure or temperature and, if necessary, are also arranged spatially separately from one another along the refrigerant lines.

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

In AC operation of the refrigerant circuit 11, the refrigerant compressed to high pressure flows from the refrigerant compressor 12 when the shut-off valve A4 is 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. The refrigerant can flow to the expansion valve AE2 and into the interior evaporator 22 via a branch point Ab1 (evaporator section 22.1). In parallel or alternatively, the refrigerant can flow into the chiller 28 (chiller section 28.1) via a branch point Ab4 and the expansion valve AE1. The refrigerant flows from the evaporator 22 and/or the chiller 28 on the low-pressure side into the collector 24 and through the low-pressure section of the internal heat exchanger 20 back to the compressor 12.

In AC operation, the heating branch 16.1 or the secondary line 16 is shut off by means of the shut-off valve A3, so that hot refrigerant cannot flow through the heating register 26. To retrieve refrigerant from the inactive heating branch 16.1, the shut-off element designed as a shut-off valve A5 can be opened, so that the refrigerant can flow through the shut-off element A5 and the non-return valve R2, while it is closed at the same time Shut-off device A2, can flow in the direction of the collector 24.

In the 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.

To carry out the heating function by means of the chiller 28 to implement water heat pump operation, the refrigerant compressed by the refrigerant compressor 12 flows via the open shut-off valve A3 into the heating register 26. At the heating register 26, heat is given off to an inlet air flow FL routed into the vehicle interior. The refrigerant then flows via the open shut-off valve A1 and the branch point Ab1. It is expanded by means of the expansion valve AE1 in the chiller 28 to absorb waste heat from the electrical and/or electronic components arranged in a coolant circuit 28.2. With 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. In this case, via the shut-off valve A2 during water heat pump operation, refrigerant that has been removed can be sucked out of a bidirectional branch 14.1 or the primary line 14 and fed to the collector 24 via the check valve R2.

To carry out the heating function by means of the external heat exchanger 18 as a heat pump evaporator, the refrigerant compressed by the refrigerant compressor 12 flows via the open shut-off valve A3 to release heat to a supply air flow FL into the heating register 26. It is then released via the open shut-off valve A1 by means of the expansion valve AE3 in relaxes the outer heat exchanger 18 to absorb heat from the ambient air. The refrigerant then flows via a heat pump return branch 15 to the collector 24 and back to the refrigerant compressor 12. The expansion valves AE1, AE2 and AE4 remain closed, as does the shut-off valve A5.

An indirect delta connection can be implemented in that, when the shut-off valve A1 is open, the refrigerant compressed by the refrigerant compressor 12 is expanded into the chiller 28 by means of the expansion valve AE1, with no mass flow being generated at the same time on the coolant side, i.e. in the coolant circuit 28.2, i.e. the as Coolant fluid used, such as water or water-glycol mixture, remains on the coolant side of the chiller 28 or the chiller 28 is not actively flowed through by coolant. The expansion valves AE2, AE3 and AE4 remain closed with this switching variant.

In an after-heating or reheat operation, the supply air flow FL fed into the vehicle interior is first cooled by means of the evaporator 22 and thus dehumidified. With the heat transferred to the refrigerant by evaporation and dehumidification and the heat supplied to the refrigerant via the compressor 12, the supply air flow FL can be completely or at least partially reheated by means of the heating register 26.

For this purpose, the refrigeration system 10 , in particular the air conditioning unit 32 , has adjustable, in particular controllable and pivotable, temperature flaps 34 between the evaporator 22 and the heating register 26 . In the illustrated example, left and right temperature doors 34L and 34R (in 1 shown schematically) arranged. The temperature doors 34L, 34R can be adjusted or pivoted between an open position, referred to as the 100% position, and a closed position, referred to as the 0% position. Alternatively, it is also possible to connect the temperature flaps 34R, 34L downstream of the heating register 26.

In the 100% position, the entire supply air flow FL flowing through the evaporator 22 is routed via the heating register 26 and heated before it can flow into the passenger compartment of the vehicle. In the 0% position, the entire supply air flow FL flowing through the evaporator 22 flows in the bypass around the heating register 26 without heating and thus without absorbing heat into the passenger compartment.

In an x position of the temperature flaps 34L and 34R with 0%<x<100%, these temperature flaps are only partially open, so that only a partial air flow of the supply air flow FL flowing through the evaporator 22 is routed via the heating register 26. This heated partial air flow can then be mixed with the remaining, cooled and dehumidified partial air flow. The intake air flow FL heated in this way is supplied to the passenger compartment of the vehicle. By way of example, a 50% position indicates that the temperature flaps 34R and 34L are only half open, ie 50%.

The refrigeration system 10 has a sensor device 36 in the secondary line 16 downstream of the secondary line valve A3 and upstream of the heating register 26, which is set up to detect a hot gas temperature value representing the temperature of the gaseous refrigerant upstream of the heating register 26. The hot gas temperature value can be measured or detected directly or estimated indirectly based on other system parameters. For example, it is conceivable using the Sensoreinrich Device 36 to determine a pressure in the secondary line 16 and to draw conclusions about the hot gas temperature value. The sensor device 36 can be a pure temperature sensor or a combined temperature/pressure sensor, for example.

The air conditioner 32 is set up to conduct conditioned interior air KL to an interior 40 of the motor vehicle. This is illustrated in a simplified manner by the two curved arrows KL. It is clear that for this purpose channels connected to the air conditioning unit 32 are provided in the air conditioning unit 32 or in the interior 40 of the motor vehicle, through which the conditioned air KL can be conveyed to corresponding outflow nozzles.

The air conditioner has at least one opening 42 assigned to the interior 40 and by means of which the interior air can be sucked out of the interior 40 . The opening 42 can be connected to the air conditioning device 32 by means of a circulating air duct. The air conditioner 32 is set up or constructed in such a way that circulating air UL supplied from the interior 40 is supplied to the evaporator 22 . The evaporator can therefore be charged with circulating air UL and/or fresh air FL or a mixture of circulating air UL and fresh air FL. The intake temperature level upstream of the evaporator 22 must also be taken into account, which according to one embodiment is to be monitored with a temperature sensor in order to be able to control the switch-on time or the active integration of the evaporator 22 in the heat pump or reheat process.

An expansion valve AE5 is provided downstream of the evaporator. In this regard, it is pointed out that if the expansion valve AE5 is present, the in 1 Check valve R1 shown is omitted. The upstream expansion valve AE2 and the downstream expansion valve AE5 are thus assigned to the evaporator 22 . As a result, the evaporator 22 can be operated at an intermediate pressure level. The intermediate pressure level arises in particular between the expansion valves AE2 and AE5. A low-pressure level sets in downstream of the expansion valve AE5. The low pressure level downstream of the expansion valve AE5 is essentially the same low pressure level that the chiller 28 is adjusted to by means of the expansion valve AE1.

A sensor device, in particular a pressure sensor or a pressure/temperature sensor pT6, can be arranged in the line section arranged downstream between the expansion valve AE2 and the expansion valve AE5, but in particular between the evaporator 22 and the expansion valve AE5, in order to be able to appropriately adjust the pressure level to be set, in particular the intermediate pressure level.

According to the 2 Method 500 shown takes place during operation after the start (S501) of the refrigeration system 10 at a time not specified here, a transition to heating or heat pump operation (S502). Typically, the transition to S502 may depend on a measured outside temperature. For example, operation according to S502 can be stopped at temperatures below 10° C., in particular 5° C. or less.

According to S502, the heat pump operation is set in such a way that the refrigerant is routed from the refrigerant compressor 12 into the secondary branch 16. The refrigerant then passes through the heat exchanger that acts as a heat source, in particular the heating register 26.

According to step S503, the first expansion valve AE2 and the second expansion valve AE5 are set downstream of the heating register 26 in such a way that the evaporator 22 is operated at an evaporator temperature of more than 0° C. at a low pressure level or an intermediate pressure level, but also the intake temperature level of the air flow with e.g. 5°C is already in a temperature range > 0°C.

According to a step S504, either 100% circulating air originating from the interior 40 is routed to the evaporator 22, or the evaporator 22 is acted upon by a mixture of circulating air UL and fresh air FL. The mixing ratio of circulating air UL to fresh air FL can be, for example, approximately 70% to 95% circulating air to 30% to 5% fresh air FL. In the case of the method, the ratio of circulating air UL to fresh air FL in the air mixture acting on the evaporator 22 can also generally be adjusted.

According to a condition S505, the method is usually carried out from step S503, ie in particular the evaporator 22 is used for cooling and/or dehumidifying the circulating air UL and/or fresh air FL, when the interior temperature Tin in the motor vehicle is greater than 0°C.

Furthermore, it can be taken into account that an intake temperature level is set at the evaporator that allows cooling and dehumidification operation via the evaporator 22 .

According to a step S506, in the method 500 the chiller 28 arranged in parallel to the evaporator 22 in terms of flow can be the same be operated at the right time. According to step S507, the evaporator 22 and the chiller 28 can be operated at different pressure levels, in particular the chiller 28 at the low pressure level and the evaporator 22 at a higher intermediate pressure level.

As already mentioned above, the method 500 presented here and the refrigeration system 10 enable heat recovery from the interior air (circulating air) UL of the motor vehicle without releasing it unused or warm to the environment, as is the case in pure fresh air operation via the exhaust air ducts provided in the vehicle case is. In this case, the refrigeration system 10 can have an essentially unchanged structure without, for example, having to provide additional heat exchangers in exhaust air ducts for the interior air. The method 500 and the refrigeration system 10 can be used or operated accordingly, in particular when heating up a motor vehicle quickly, so that energy-efficient heating in the heat pump mode is possible. However, the method 500 or the refrigeration system 10 can also be used in so-called extended AC operation (cooling operation) when the interior (cabin) 40 of the motor vehicle is already warm, but the surroundings are cold. In such a case, a so-called post-heating operation (reheat) can be carried out at sub-zero temperatures in the environment, the method 500 being taken into account or used.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102015112123 A1 [0003]
• DE 102009048674 A1 [0003]
• DE 102014110360 A1 [0003]

Claims (12)

Method (500) for operating a refrigeration system (10) with a heat pump function for a motor vehicle, the refrigeration system (10) comprising: a refrigerant compressor (12) which can be connected or is connected to a primary line (14) and a secondary line (16); a directly or indirectly acting external heat exchanger (18) which is arranged in the primary line (14); an evaporator (22) which is arranged in the primary line (14); at least one further heat exchanger representing a heat source, in particular a heating register (26), which is arranged in the secondary line (16); a primary branch valve (A4) arranged between the refrigerant compressor (12) and the external heat exchanger (18); a secondary branch valve (A3) arranged between the refrigerant compressor (12) and the further heat exchanger, in particular a heating register (26), which represents a heat source; a first expansion valve (AE2) arranged upstream of the evaporator and a second expansion valve (AE5) arranged downstream of the evaporator; wherein the evaporator (22) is part of an air conditioning unit (32) for conditioning interior air for a motor vehicle, the method comprising the following steps: Setting (S502) a heat pump operation, in which the refrigerant is passed from the refrigerant compressor (12) into the secondary branch (16); Adjusting (S503) the first expansion valve (AE2) and the second expansion valve (AE5) so that the evaporator (22) is operated at an evaporator temperature of more than 0°C at a low pressure level or an intermediate pressure level, and Supplying (S504) circulating air (UL) originating from the interior to the evaporator (22), so that the evaporator (22) is subjected to pure circulating air (UL) or a mixture of circulating air (UL) and fresh air (FL). Method (500) according to claim 1 , wherein the evaporator (22) for cooling and/or dehumidifying the circulating air and/or fresh air is used (S505) when the interior temperature in the motor vehicle is greater than 0°C. Method (500) according to claim 1 or 2 , wherein the evaporator (22) is used for cooling and/or dehumidifying the circulating air and/or fresh air when the intake temperature level upstream of the evaporator (22) is greater than 0°C, in particular at least 5°C. The method (500) according to any one of the preceding claims, wherein a chiller (28) arranged fluidically parallel to the evaporator (22) is operated simultaneously (S506). Method (500) according to claim 4 , wherein the evaporator (22) and the chiller (28) are operated at different pressure levels (S507), in particular the chiller (28) at the low pressure level and the evaporator (22) at a higher intermediate pressure level. Method (500) according to one of the preceding claims, wherein the supply of pure circulating air (UL) or of a mixture of circulating air (UL) and fresh air (FL) is carried out alternately. Method (500) according to claim 6 , the switching from fresh air to recirculated air or the increase in the proportion of fresh air in the set mixture of recirculated air and fresh air or vice versa depending on an air quality measured in the interior and/or a carbon dioxide content or/and specified periods of time and/or a recorded number inmates is carried out. Refrigeration system (10) with a heat pump function for a motor vehicle, the refrigeration system (10) comprising: a refrigerant compressor (12) which can be connected or is connected to a primary line (14) and a secondary line (16); a directly or indirectly acting external heat exchanger (18) which is arranged in the primary line (14); an evaporator (22) which is arranged in the primary line (14); at least one further heat exchanger representing a heat source, in particular a heating register (26), which is arranged in the secondary line (16); a primary branch valve (A4) arranged between the refrigerant compressor (12) and the external heat exchanger (18); a secondary line valve (A3) arranged between the refrigerant compressor (12) and the further heat exchanger, in particular a heating register (26), which represents a heat source; a first expansion valve (AE2) arranged upstream of the evaporator and a second expansion valve (AE5) arranged downstream of the evaporator; the evaporator (22) being part of an air conditioning unit (32) for conditioning interior air for a motor vehicle, characterized in that the refrigeration system (10), in particular the air conditioning unit (32), has a circulating air supply (42) which is set up for this purpose , from the interior (40) originating circulating air (UL) to direct the evaporator (22), so that the evaporator (22) of pure circulating air or a mixture of circulating air (UL) and fresh air (FL) is applied. Refrigeration system (10) after claim 8 , characterized in that a sensor device (pT6), in particular a pressure/temperature sensor, is arranged downstream of the evaporator (22). Refrigeration system (10) after claim 8 or 9 , characterized in that flow-technically parallel to the evaporator (22) is arranged at least one further heat exchanger, in particular a chiller (28). Motor vehicle, in particular at least partially electrically operated motor vehicle, with a refrigeration system (10) according to one of Claims 8 until 10 , wherein in an interior (40) of the motor vehicle there is at least one intake opening (42) for interior air, which is fluidically connected to the circulating air supply (UL) of the air conditioning unit (32). motor vehicle after claim 11 , At least one carbon dioxide interior sensor and/or at least one occupant detection device being arranged in the interior.

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