EP4072875A1

EP4072875A1 - Reheating method for operating a refrigeration system for a motor vehicle, refrigeration system, and motor vehicle having a refrigeration system of this type

Info

Publication number: EP4072875A1
Application number: EP20785471.2A
Authority: EP
Inventors: Dirk Schroeder; Christian Rebinger; Helmut Rottenkolber
Original assignee: Audi AG
Current assignee: Audi AG
Priority date: 2019-12-09
Filing date: 2020-09-28
Publication date: 2022-10-19
Also published as: CN114746298A; WO2021115655A1; DE102019133546A1

Abstract

The invention relates to a reheating method (500) for operating a refrigeration system (10) for a motor vehicle, the refrigeration system (10) comprising: a refrigerant compressor (12), which can be or is connected to a primary run (14) and a secondary run (16); an external heat exchanger (18), which is arranged in the primary run (14); an evaporator (22), which is arranged in the primary run (14); a heating condenser (26), which is arranged in the secondary run (16); at least one movable temperature flap (34L, 34R), which is arranged between the evaporator (22) and the heating condenser (26) with respect to a supply air flow direction (L); at least one shut-off valve (AE4, A1; R3, R4), which is arranged downstream of the heating condenser (26) in the secondary run (16); the reheating method comprising the following steps: setting the at least one shut-off valve (AE4, A1; R3, R4) to a position in which, downstream of the heating condenser (26), refrigerant flows into the evaporator (22) while bypassing the external heat exchanger (18); and incorporating at least one additional heat sink, in particular of a chiller (28) operating as a water heat pump and/or of the external heat exchanger (18) operating as an air heat pump evaporator, which heat sink is arranged fluidically in parallel or in series with the evaporator (22). The invention further relates to a refrigeration system (10) and to a motor vehicle having a refrigeration system of this type.

Description

Post-heating method for operating a refrigeration system for a motor vehicle, refrigeration system and motor vehicle with such a refrigeration system

DESCRIPTION:

The invention relates to a reheating method (RH II) for operating a Käl teanlage with 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 comprises a refrigerant compressor which can be or is connected to a primary branch and a secondary branch; an external heat exchanger which is arranged in the primary märstrang; an evaporator, which is net angeord in the primary line; a heating register, which is arranged in the secondary line; at least one movable temperature flap, which is arranged in relation to a supply air flow direction before or after the heating register; and at least one shut-off element which is arranged downstream of the heating register in the secondary branch.

Such a refrigeration system with a heat pump function is described, for example, in DE 10 2018 213 232.1, which was not yet published at the time the present application was submitted.

Further background information on refrigeration systems or heat pumps can be found, for example, in the publications DE 101 26 257 A1, DE 10 2015010 552 B3 and DE 102015012995 B1.

In a reheating process, which is also referred to in technical jargon as reheat, reheat operation, reheat process, the air conditioning of a vehicle interior is the one that is cooled and dehumidified by the evaporator Air brought to ei ne desired blow-out temperature by at least partial heating by means of the heating register.

The heating register is a heat source in which the heat stored in the refrigerant is transferred to another medium, such as air, water, a water-glycol mixture and the like. The heating register can be designed as a heating condenser or heating gas cooler if (ambient) air flows through it directly as cabin air, which absorbs the emitted heat. The heating register can be performed as a fluid heat exchanger if it is flowed through or around by a fluid other than (ambient) air, such as water, water-glycol mixture or the like, with the heat stored in the refrigerant the fluid is dispensed. In the case of the design as a fluid heat exchanger, a further heat transfer then takes place from the heated fluid to the (ambient) air. In this respect, a fluid heat exchanger indirectly heats (ambient) air as the cabin air flow.

At least one temperature flap can be used in the air flow path between the evaporator and the heating register (i.e. upstream of the heating register) that is completely closed (0% open position or closed position) when the air is cooled and not heated into the vehicle interior should. When the temperature flap is fully open (100% open position), essentially all of the air flow from the evaporator is passed over the heating register and heated. If the temperature flap is partially opened, part of the air is passed over the heating register and the other part of the air is passed around the heating register and is not heated, so that a mixture of heated and cooled air is formed downstream of the heating register, which is then sent to the Vehicle interior is fed. The adjustable temperature flap can alternatively also be arranged downstream of the heating register. The object on which the invention is based is seen in specifying a reheating method that enables optimized operation of the refrigeration plant.

This object is achieved by a Nachheizverfahren with the features of claim 1, by a refrigeration system with the features of Pa tentanspruchs 9 and by a motor vehicle with the features of Pa tentanspruchs 15. Advantageous embodiments with appropriate further training are given in the dependent claims.

A post-heating method is therefore proposed for operating a refrigeration system for a motor vehicle, the refrigeration system comprising: a refrigerant compressor which can be or is connected to a primary branch and a secondary branch; an external heat exchanger which is arranged in the primary train; an evaporator which is arranged in the primary line; a heating register, which is arranged in the secondary line; at least one movable temperature flap, which is arranged in front of or after (upstream or downstream) the heating register with respect to a supply air flow direction; at least one shut-off device which is arranged downstream of the heating register in the secondary branch; the post-heating process comprising the following steps:

Setting the at least one shut-off element in a position in which refrigerant flows into the evaporator downstream of the heating register, bypassing the external heat exchanger, and

Incorporation of at least one additional heat sink arranged fluidically parallel or in series with the evaporator, in particular a chiller working as a water heat pump evaporator and / or the external heat exchanger working as an air heat pump evaporator.

Such a post-heating process can be used in particular when an increasing heating requirement is determined that can no longer be achieved by itself the heat transferred to the refrigerant at the evaporator and via the compressor can be covered. By integrating at least one additional heat sink, heat can be extracted from the coolant used as a heat source, such as water, water-glycol mixture, (ambient) air. This increases the temperature and the pressure of the refrigerant in the refrigeration system, so that the heating output made possible by the refrigeration system, together with the compressor drive output, increases. Such a method also enables the reheating mode or reheat mode to be achieved through a compact interconnection of the refrigeration system with a few active components.

In the post-heating process, the ambient temperature can be recorded and the process can be carried out when the ambient temperature is up to 15 ° C, in particular in a range from about 0 ° to 15 °, ie down to a lower ambient temperature that just allows refrigeration system operation allowed. This can ensure that the described interconnection of the refrigeration system with an additionally integrated heat sink is carried out when the operating and ambient conditions are favorable for such a post-heating operation.

The at least one further heat sink can be incorporated by opening an expansion valve connected upstream of the heat sink in question. In particular, such an expansion valve can be opened step by step or incrementally.

The post-heating process can include the following steps:

Setting the temperature flap in a target open position;

Maintaining the target opening position of the temperature flap;

Gradual opening or gradual closing of the expansion valve depending on the heating requirement, which is determined using a refrigeration system parameter, until a certain pressure level is set on the high-pressure side of the heating condenser and / or until the expansion valve has reached a maximum or minimum opening position. The reheating process Reheat II (RH II) presented here can build directly on the functionality of the reheating process Reheat I (RH I) contained in a parallel application. All functionalities of the reheating process Reheat I (RH I) can be taken over and the heating output of the system can be increased by integrating at least one additional evaporator.

The post-heating process can thus be carried out with the temperature flaps essentially kept constant or open by directly influencing the pressure and temperature conditions in the refrigeration circuit. Since the post-heating process described here can be ended when the expansion valve reaches a corresponding position, or operation can be switched to another post-heating process.

In the post-heating process, several heat sinks can be integrated in combination, with the respective expansion valves of the relevant heat sinks being opened or closed.

The target opening position of the temperature flap can be set to a value between 60% to 90%, in particular to a value between 70% and 85%, based on a maximum opening position of 100%.

In the post-heating process, an expansion valve upstream of the evaporator can always be kept in an open position, which can be set or adjusted depending on the required or required cooling capacity (dehumidification requirement), among other things. In other words, refrigerant always flows through the evaporator during this post-heating process, regardless of which other heat sink (s) is or are involved. As a result, the air to be supplied to a vehicle interior is always dehumidified.

After the expansion valve of the relevant (additional) heat sink (evaporator) has reached its maximum opening position, an electrical cal heating module can be switched on. This makes it possible to respond to a further increase in heating demand. The maximum opening position should assume a sensible and justifiable value that does not necessarily have to correspond to 100% opening, but can also be less than 100%.

A refrigeration system for a motor vehicle is also proposed, with a refrigerant compressor which can be or is connected to a primary line and a secondary line; an external heat exchanger which is arranged in the primary train; an evaporator which is arranged in the primary line; a heating register which is arranged in the secondary line; at least one movable temperature flap which is arranged upstream or downstream of the heating register with respect to a direction of supply air flow; at least one shut-off device, which is arranged downstream of the heating register in the secondary branch; The refrigeration system is set up to be operated in a post-heating operation described above, and in such post-heating operation the refrigerant flows through the following components of the refrigeration system one after the other starting from the refrigerant compressor: heating register in the secondary line, evaporator in the primary line and, in terms of flow, a parallel or in Row to the Ver evaporator arranged heat sink, in particular a chiller working as a water heat pump evaporator and / or the external heat exchanger working as an air heat pump evaporator.

The external heat exchanger can have a bidirectional flow. Air heat pump operation can be enabled here by means of the refrigeration system. Depending on the implemented system design and line routing, the external heat exchanger can also have a monodirectional flow.

A shut-off valve can be arranged between the heating register and the evaporator and an expansion valve can be arranged between the heating register and the external heat exchanger. Both the shut-off valve and the expansion valve represent a respective shut-off device that is used to carry out the reheating process. With such a configuration, the post-heating process can be carried out with the shut-off valve open and the expansion valve closed, so that refrigerant can flow from the heating register directly to the evaporator.

Alternatively, a non-return valve can be arranged between the heating register and the evaporator. The check valve is also a shut-off device that is used to carry out the reheating process. Such a check valve enables refrigerant to flow through from the heating register in the direction of the evaporator, with flow through or also back flow in the opposite direction being prevented. Furthermore, the external heat exchanger can have a monodirectional flow. In such a configuration of the refrigeration system, an air heat pump operation can still be represented, but a reheating operation via a series connection of the heating register and the external heat exchanger is not possible because a fluidic connection or line between the heating register and the external heat exchanger is dispensed with. In this respect, such a configuration represents a simplification of a refrigeration system, which can, however, continue to be operated with the post-heating method.

As stated above, the external heat exchanger can have a monodirectional or bidirectional flow, depending on the embodiment of the refrigeration system. In a monodirectional variant, the refrigerant always flows through the external heat exchanger in the same direction or in the same way in refrigeration system operation and in air heat pump mode. In a bidirectional variant, the external heat exchanger in refrigeration system operation is flowed through by refrigerant in a different or different direction (opposite) than in air heat pump mode. With regard to the outer heat exchanger, it should also be noted that - similar to the heating register - it can transfer heat to or from the (ambient) air both directly (as a gas condenser or gas cooler) and indirectly (as a fluid heat exchanger) . An expansion valve, which is configured to set an intermediate pressure level on the evaporator, can be arranged downstream of the evaporator. This can counteract icing of the evaporator, because the pressure in the evaporator can be set so that icing due to condensing water from the evaporator supply air can be excluded while other low-pressure side system sections can be operated at a lower pressure level.

A motor vehicle can be equipped with a refrigeration system described above. The motor vehicle can in particular be an electric vehicle. In the case of 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.

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

1 shows a schematic and simplified circuit diagram of a refrigeration system for a motor vehicle;

FIG. 2 shows a flow diagram of an exemplary implementation of the Nachheizver process, in particular by means of the refrigeration system described in FIG. 1;

3 shows a schematic and simplified circuit diagram of an embodiment of a refrigeration system for a motor vehicle for performing the heating process after;

Fig. 4 is a schematic and simplified circuit diagram of an embodiment form of a refrigeration system for a motor vehicle for performing the heating process after. In Fig. 1, an embodiment of a refrigeration system 10 for a motor vehicle is shown schematically and simplified. The refrigeration system 10 comprises 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 external heat exchanger 18, an internal heat exchanger 20, an evaporator 22 and an accumulator or refrigerant collector 24. The external heat exchanger 18 can be designed as a condenser or gas cooler. In particular, the external heat exchanger 18 in the embodiment shown is bidirectional through flow bar.

The evaporator 22 is shown here by way of example as a front evaporator for a vehicle. The evaporator 22 also represents other evaporators that are possible in a vehicle, such as, for example, rear evaporators, which can be arranged fluidically parallel to one another. In other words, the refrigeration system 10 thus comprises 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.

In the context of this description, in the entire refrigerant circuit 11 of the refrigeration system 10, 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 branch 14.

The refrigeration system 10 further comprises a meat register 26 (also referred to as a meat condenser or meat gas cooler). A shut-off valve A3 is arranged upstream of the meat register 26. A shut-off valve A1 is arranged downstream of the meat register 26. Furthermore, an expansion valve AE4 is arranged downstream of the fleece condenser 26. In the context of this description, in the entire refrigerant circuit of the refrigeration system 10, 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. The secondary branch 16 comprises 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 branch 16 further comprises a reheating branch or reheat branch 16.2, which can be fluidly connected to the heating register 26 upstream and to the external heat exchanger 18 downstream. Since the secondary branch 16 or the reheat branch 16.2 opens into the primary branch 14 at a branch point Ab2.

The refrigeration system 10 comprises a further evaporator or chiller 28. The chiller 28 is provided in 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 serves as an auxiliary heater for a supply air flow L routed into the interior of the vehicle. The electric heating element 30 can be accommodated in an air conditioner 32 together with the heating register 26 and the evaporator 22. The electrical heating element 30 can be arranged downstream of the heating register 26.

In FIG. 1, check valves R1 and R2 can also be seen. Furthermore, some sensors pT1 to pT5 for detecting pressure and / or temperature of the refrigerant are also shown. It should be noted that the number of sensors or their arrangement is shown here only 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. But it is just as conceivable that separate sensors are used for the measurement of pressure or temperature and, if necessary, are also arranged spatially separated 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 high-pressure refrigerant flows from the refrigerant compressor 12 into the external heat exchanger 18 with the shut-off valve A4 open. From there, it flows to the high-pressure section of the internal heat exchanger 20 and the fully open expansion valve AE3. The refrigerant can flow via a branch point Ab1 to the expansion valve AE2 and into the interior evaporator 22 (evaporator section 22.1). In parallel or alternatively, the refrigerant can flow into the chiller 28 via a branch point Ab4 and the expansion valve AE1 (chiller section 28.1). From the evaporator 22 and / or the chiller 28, the refrigerant flows on the low-pressure side into the collector 24 and through the low-pressure section of the inner heat exchanger 20 back to the compressor 12.

In AC operation, the heating branch 16.1 or the secondary branch 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 valve designed as a shut-off valve A5 can be opened so that the refrigerant can flow in the direction of the collector 24 via the shut-off element A5 and the check valve R2 while the shut-off element A2 is closed at the same time.

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 a water heat pump operation, the refrigerant flows through the Denser 12 compressed refrigerant into the heating register 26 via the open shut-off valve A3. At the heating register 26, heat is given off to a supply air flow L guided into the vehicle interior. The refrigerant then flows through the opened 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. In 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, refrigerant stored in the water heat pump mode can be extracted from a bidirectional branch 14.1 or the primary branch 14 via the shut-off valve A2 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 means of the refrigerant compressor 12 flows through the open shut-off valve A3 to give off heat to a supply air stream L in the heating register 26 Expansion valve AE3 relaxed in 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, while at the same time no mass flow is generated on the coolant side, i.e. in the coolant circuit 28.2, e.g. Fluid used as a coolant, such as water or a 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 a reheating or reheating mode, the supply air flow L fed into the vehicle interior is initially 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 L can be heated completely or at least partially again by means of the Heizregis age 26.

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

In the 100% position, the entire supply air flow L flowing through the evaporator 22 is guided over 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 L 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 in each case only a partial air flow of the supply air flow L flowing through the evaporator 22 is passed over the heating register 26. This heated partial air flow can then be added to the remaining, cooled and dehumidified partial air flow. The supply air flow L heated in this way is supplied to the passenger compartment of the vehicle. For example, a 50% position indicates that the temperature flaps 34R and 34L are only half open, that is to say 50%. A reheating or reheat operation of the refrigerant circuit 11 or the Käl teanlage 10 is carried out depending on the heat balance in different Wei se.

An operating method 500 that is possible for reheating or reheating operation is explained below by way of example using the flow chart in FIG. 2 and with reference to the refrigeration system 10 shown in FIG. 1 and its components. Such an operating method is usually implemented as a control program in a control device for the refrigeration system or for air conditioning in a vehicle.

A post-heating operation is considered, in which the refrigerant flows from the compressor 12 via the opened shut-off valve A3 to the meat register 26 (meat condenser or meat gas cooler). The expansion valve AE4 is closed and the shut-off valve A1 is open, so that the refrigerant can flow into the evaporator 22 via the expansion valve AE2. In terms of flow, the chiller 28 is integrated as a further heat sink. Accordingly, the expansion valve AE1 is also in an open position. For further consideration it is assumed that the expansion valve AE3 is closed. The after-heating operation is thus achieved with an interconnection of the refrigeration system 10 with as few active components as possible.

The integration of the chiller 28 can take place via a system-side compulsory requirement based on the existing need for cooling at least one floch voltage component or as a meat requirement requirement to generate additional meat performance at the meat register 26, which is functionally equivalent to a "voluntary" floch voltage component cooling.

According to the post-heating method 500 shown in FIG. 2, after the start (S501) of the refrigeration system 10, a transition to post-heating operation takes place at a point in time not specified here, which is referred to here as Reheat II (S502). One possible condition that must be met in order to start the after-heating operation (S502) can be, for example measured ambient temperature. The reheating process can be activated in particular when the ambient temperature is up to 15 ° C. is, in particular from about 0 ° C to 15 ° C.

In the post-heating process 500, the two temperature flaps 34L, 34R in this application are set to a target opening position TKso. TKso can be a specific opening value or, as shown in FIG. 2 at 502a, can be a range from an upper opening limit value TKo to a lower opening limit value TKu. When operating the refrigeration system 10, at least one refrigeration system parameter is used to determine whether the heating requirement is constant, increasing or decreasing. A variable or refrigeration system parameter used here as an example is the temperature flap opening TKan requested by a control unit. If a larger temperature flap opening TKan is required, the heating requirement increases. If a smaller temperature flap opening TKan is required, the heating requirement is reduced. For the following description, it is pointed out that a temperature flap opening TKan requested by the system in the reheating method considered here does not necessarily lead to a corresponding adjustment of the actual opening position or actual opening position TKis of the temperature flaps 34L, 34R.

As already mentioned, it is assumed that the temperature flaps are in an actual open position TKis, which is in the range from TKo to TKu. According to step S503, it is checked whether a required temperature flap opening TKan is less than the upper opening limit value TKo and greater than the lower opening limit value TKu. If this is the case, according to step S504 the temperature flaps 34L, 34R can be adjusted in their actual open position TKis, which is indicated by the two arrows in step S504. The refrigeration circuit and / or the peripherals influencing the climatic conditions remain unchanged. If the condition of step S503 is not met, a check is made in S505 to determine whether the requested temperature flap opening is greater than the upper opening limit value TKo. Outside these limits takes place on the part of the refrigeration circuit and / or the change in the The periphery influencing climatic conditions has a change and thus a reaction to the changed requirements and boundary conditions.

If this is not the case, the requested opening position TKan is less than the lower opening limit value TKu (S506). This means that the heating requirement is falling and that the temperature flaps 34L, 34R should actually be closed further. According to the post-heating method 500 described here, however, the temperature flaps are not closed any further. Rather, it is checked in step S507 whether the expansion valve AE1 connected upstream of the chiller 28 has already been set to a minimum value, in particular is closed. If this is the case, it can be checked in S512 whether the ambient temperature T_U is higher than a predetermined comparison temperature value T_x. Depending on the result of the test in S512, another post-heating mode is selected or the refrigeration system is switched to another post-heating mode, which are designated here with RH I or RH III (S513, S514).

If the expansion valve AE1 is not set to its minimum value in accordance with S507, it is closed further in accordance with S507. This reduces the volume flow Vs_Vdi to be provided by the compressor. The pressure and temperature of the refrigerant also decrease accordingly (S509).

If the minimum adjustable position of the expansion valve is not yet enough, and if the heating requirement continues to fall, which is determined by checking the conditions in S510 and S511, the expansion valve is closed again in accordance with S508. As long as the heating requirement is falling, steps S 506, S507, S508, S509, S510, S511 are run through several times.

A check takes place in S510 as to whether the requested temperature flap opening TKan is greater than the upper opening limit value TKo. If this is not the case, S511 checks whether the requested temperature flap opening is in the target range, that is between TKo and TKu. If it does, will it is assumed that the set position of the expansion valve AE1 is suitable and can essentially be maintained (S526). As a result, according to S527, the pressure pHD and also the hot gas temperature tHG are kept essentially constant.

If the demand for heating increases, the method is carried out as follows on the basis of steps S503 and S505 already mentioned above. If it is determined in S505 that the requested temperature flap opening TKan is greater than the upper opening limit value TKo, this means that the heating requirement is increasing and that the temperature flaps 34L, 34R would actually have to be opened further. However, according to the method described here, the temperature flaps are not (yet) opened any further. Rather, the expansion valve AE1 is opened in step S515. By opening the expansion valve AE1, the supply of heat from the chiller 28 to the refrigeration circuit is enabled or increased. As a result, according to S516, the volume flow Vs_Vdi to be provided by the compressor 12 increases. The pressure and temperature of the refrigerant also increase accordingly.

In S517 it is checked whether the high pressure pHD and / or the hot gas temperature tHG present in the refrigeration system 10 has reached a maximum value. If this is not the case, S518 checks whether the requested temperature flap opening TKan is greater than the upper opening limit value TKo. If this is the case, S519 checks whether the expansion valve AE1 has already been set to a maximum possible opening value. If the maximum adjustable opening position of the expansion valve AE1 has not yet been reached, a branch is made again to S515 and the expansion valve AE1 is opened further (step by step or incrementally).

As long as the heating requirement is increasing, steps S515, S516, S517, S518, S519 are run through several times.

If it is determined in S517 that a maximum pressure pHD and / or a maximum hot gas temperature tHG has been reached and thus a further increase in output via the refrigeration circuit is ruled out, an increase takes place. branch to S524. In S524 it is checked whether the electric heating element 30 is already in operation with full power. If this is not the case, in S525 the electrical heating element 30 is switched on or its output or heat dissipation to the cabin air flow is increased. If, according to S521, the requested temperature flap opening TKan is still above the upper opening limit value TKo, the heating power or heat output of the electrical heating element 30 is increased further (S525). If the condition in S521 is no longer met due to a falling heating requirement, the heating power or heat output of the electrical heating element 30 is reduced again in accordance with S522. If the electrical heating element 30 is no longer active, which is checked in S523, a branch is made to steps S510 and S511, so that if the heating falls or has fallen, the pressure must be adjusted again by setting, in particular closing the opening position of the expansion valve AE1 ( S508) can be reached. If the condition in S524 is met, the refrigeration system 10 is switched to another operating mode or reheating mode, which is referred to here as an example with DWP-RH (S528). However, it can be assumed that with the maximum set waste heat via the refrigeration circuit and with maximum heating output, set via an electrical auxiliary heater, the system can have reached its heating output limits and is therefore operated to the limit.

In addition to the measures described above for carrying out the reheating process, the methods from the reheating process Reheat I (RH I) contained in a parallel notification can be used to vary the performance of the evaporator. In particular, the amount of supply air L supplied to the evaporator 22 can be adjusted in order to influence the heating performance. Fresh air or circulating air or a mixture of fresh air and circulating air can be used as the supplied air. Alternatively, the target temperature of the air after the evaporator can be changed within the limits defined and permitted by the control unit. This change is based in particular on the need for dehumidification. The reheating process shown in Fig. 2 was described using the example of the additional Lich integrated chiller with its upstream expansion valve AE1. It should be noted that the method can also be carried out by means of the external heat exchanger 18 and with the expansion valve AE3 open or adjustable. In this case, the external heat exchanger 18 is provided fluidically parallel to the evaporator 22 and operates as an air heat pump evaporator. Correspondingly, AE3 could also stand at all points in FIG. 2 where AE1 is mentioned. It is also conceivable that both the chiller 28 and the external heat exchanger 18 are integrated together as heat sinks. Accordingly, the opening positions of AE1 and AE3 would then be checked or adjusted in accordance with the method shown in FIG.

FIG. 3 shows an embodiment of a refrigeration system 110, with which the reheating method Re-heat II described above with reference to FIG. 2 can also be carried out. The refrigeration system 110 according to this embodiment is structurally simplified compared to the refrigeration system shown in FIG. 1. 10. As can be seen from FIG. 3, only one connection to the evaporator 22 or the chiller 28 is provided downstream of the heating register 26. The refrigeration system 110 has no after-heating branch or reheat branch 16.2 (FIG. 1). Correspondingly, the external heat exchanger 18 can no longer be connected in series with the heating register 26.

In order to be able to carry out the post-heating process described above with the simplified refrigeration system 110, a check valve R3 is arranged between the heating register 26 and the expansion valve AE2 or the expansion valve AE1. The check valve R3 allows refrigerant to flow from the heating register 26 to the evaporator 22 according to the reheating method described above, but prevents refrigerant flow in the opposite direction, i.e. when the refrigeration system is operating in AC mode. In Fig. 3 an expansion valve AE5 is also shown downstream of the evaporator 22 in dashed presen- tation. Such an expansion valve AE5 can be arranged in all of the embodiments of the refrigeration system 10, 110 (FIGS. 1, 3, 4) shown here instead of the check valve R1 shown. By arranging the expansion valve AE5 downstream of the evaporator 22, an intermediate pressure level can be achieved on the evaporator 22 who is above the icing limit. Any additional heat sink that is integrated can be operated at a low low pressure level.

Fig. 4 shows the simplified refrigeration system with a further possible adaptation. Instead of the expansion valve AE3 still present in FIG. 3, a check valve R4 can be provided, which is arranged between the internal heat exchanger 20 and the evaporator 22 or chiller 28. The check valve R4 is flowed through by Käl temittel in AC operation of the refrigeration system 110. In a Fleizbetrieb the check valve R4 prevents a refrigerant flow from Fleizregister 26 to the floch pressure side of the inner heat exchanger 20. The above-described reheating process (FIG. 2) can also be carried out with this further simplified configuration of the refrigeration system 110.

With regard to the adapted structure of the refrigeration system 110 according to FIGS. 3 and 4, it is also pointed out that with such a configuration switching to another after-heating method RH III illustrated in steps S513 and S525 is not possible, but rather system-side adaptations SYS are made Need to become.

The post-heating process described above with reference to FIG. 2 can be carried out, for example, with the following values. TKso can be set from 60% to 90%, in particular to a value between 70% and 85%, based on the maximum open position of 100%. For example, TKu can be 78% and TKo can be 82%, so that TKso covers a range from 78% to 82%. The selection of suitable opening limit values TKu and TKo can, in particular, depend on the individual Shafts of the refrigeration system used can be selected, the range from TKu to TKo should be chosen rather narrow, in particular so that the quotient TKu / TKo is greater than or equal to 0.8. For the above example with TKu = 78% and TKo = 82%, the quotient is 0.95.

The post-heating process described in the context of this application can be achieved by integrating further heat sinks, such as, for example, the chiller 28 and / or external heat exchanger 18. The possibility of a simplified structure of the refrigeration system 110 can also be considered.

In summary, the reheating process Reheat II (RH II) presented here is a reheating operation that is based on a reheating process Reheat I (RH I) contained in a parallel application, with an additional evaporator and thus an additional heat sink (here, for example, a chiller) is involved.

However, if instead of the "voluntary" integration of the chiller to cover the heating requirement there is a "forced integration" of the chiller, i.e. active battery cooling is required by thermal management, the process described for the stepped release of the chiller must not be pursued any further. An excess heating requirement can then be compensated for by changing to a Nachheizver contained in a parallel application Reheat III (RH III).

Claims

PATENT CLAIMS:

Post-heating method (500) for operating a refrigeration system (10) for a motor vehicle, 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); an external heat exchanger (18) which is arranged in the primary branch (14); an evaporator (22) which is arranged in the primary line (14); a heating register (26) which is arranged in the secondary line (16); at least one movable temperature flap (34L, 34R) which, with respect to a supply air flow direction (L), is arranged upstream or downstream of the heating register (26); at least one shut-off element (AE4, A1; R3, R4) which is arranged downstream of the heating register (26) in the secondary branch (16); the post-heating process comprising the following steps:

Setting the at least one shut-off element (AE4, A1; R3, R4) in a position in which refrigerant flows into the evaporator (22) downstream of the heating register (26), bypassing the external heat exchanger (18), and

Integration of at least one additional heat sink, arranged fluidically parallel or in series with the evaporator (22), in particular a chiller (28) working as a water heat pump evaporator and / or the external heat exchanger (18) working as an air heat pump evaporator.

Post-heating method (500) according to claim 1, wherein the ambient temperature is detected and the method is carried out when the ambient temperature is up to 15 ° C, in particular in a range from about 0 ° to 15 °.

Post-heating method (500) according to claim 1 or 2, wherein the integration of the at least one further heat sink (18, 28) by opening a Nes of the relevant heat sink (18, 28) upstream expansion valve (AE1, AE3) takes place.

4. Post-heating method according to claim 3, further comprising the steps of: setting the temperature flap (34L, 34R) in a target

Open position (TKso);

Maintaining (502a) the target opening position (TKso) of the temperature flap (34L. 34R);

Step-by-step opening (S515) or step-by-step closing (S508) of the expansion valve (AE1, AE3) depending on the heating requirement, which is determined using a refrigeration system parameter (TKan), until a predetermined pressure level is set on the high-pressure side of the heating register (26) or / and until the expansion valve (AE1, AE3) has reached a maximum or minimum opening position (S507, S519).

5. Nachheizverfahren (500) according to claim 3 or 4, wherein several heat sinks (18, 28) are integrated in combination, the respective expansion valves (AE1, AE3) of the respective heat sinks (18, 28) are opened or closed.

6. Nachheizverfahren (500) according to claim 4 or 5, wherein the target opening position (TKso) of the temperature flap (34L, 34R) is set to a value between 60% to 90%, in particular to a value between 70% and 85%, based on a maximum open position of 100%.

7. Post-heating method (500) according to one of the preceding claims, wherein an expansion valve (AE2) connected upstream of the evaporator (22) is always held in an open position, which is adjustable as a function of the prevailing pressure level.

8. Nachheizverfahren (500) according to one of the preceding claims, wherein after reaching a maximum open position (S519) of the expansion valve (AE1, AE3) of the relevant heat sink (18, 28), an electrical heating module (30) is switched on (S525).

9. A refrigeration system (10) for a motor vehicle, with a refrigerant compressor (12) which can be or is connected to a primary line (14) and a secondary line (16); an external heat exchanger (18) which is arranged in the primary train (14); an evaporator (22) which is arranged in the primary line (14); a heating register (26) which is arranged in the secondary line (16); at least one movable temperature flap (34L. 34R) which is arranged with respect to a supply air flow direction (L) before or after the Heizregis ter (26); at least one shut-off element (AE4, A1 ,; R3, R4) which is arranged downstream of the heating register (26) in the secondary branch (16); wherein the refrigeration system (10) is set up to be operated in a Nachheizbe drive according to one of the preceding claims, and wherein in such a Nachheizbe the refrigerant from the refrigerant compressor (12) successively flows through the following components of the refrigeration system (10): heating register (26) in the secondary branch, evaporator (22) in the primary branch and, in terms of flow technology, a heat sink arranged in parallel or in series with the evaporator (22), in particular a chiller (28) working as a water heat pump evaporator and / or the external heat exchanger working as an air heat pump ( 18).

10. Refrigeration system (10) according to claim 9, wherein the external heat exchanger (18) can be flown through bidirectionally.

11. Refrigeration system (10) according to claim 9 or 10, wherein between the heating register (26) and the evaporator (22) a shut-off valve (A1) is angeord net and wherein between the heating register (26) and the external heat exchanger (18) Expansion valve (AE4) is arranged.

12. Refrigeration system (10) according to claim 9, wherein a check valve (R3) is arranged between the heating register (26) and the evaporator (22).

13. A refrigeration system (10) according to claim 12, wherein the outer heat transfer ger (18) can flow through unidirectionally and is separated from the heating register (26). 14. Refrigeration system according to one of the preceding claims, wherein downstream of the evaporator (22) an expansion valve (AE5) is arranged, which is configured to set an intermediate pressure level on the evaporator (22). 15. Motor vehicle with a refrigeration system (10) according to one of claims 9 to 14.