DE102021111288A1 - Air conditioning device, in particular for a motor vehicle - Google Patents

Abstract

The present invention relates to an air conditioning device (10), in particular for a motor vehicle, comprising an air-guiding housing (11) with at least one air inlet (12) and at least one air outlet (13, 14, 15), a fan (16) and a heat exchanger arrangement ( 20, 20a, 20b, 30) which are arranged in the air-guiding housing (11) between the at least one air inlet (12) and the at least one air outlet (13, 14, 15). The heat exchanger arrangement (20, 20a, 20b, 30) comprises a first fluid-based heat exchanger (20, 20a, 20b) with an inlet tank (21) with at least one first inlet (23, 23a). The first heat exchanger (20) is integrated into a fluid circuit (40, 40') with a first fluid pump (48a). The air conditioner (10) according to the invention further comprises and a control device (50) by means of which the fluid circuit (40) can be controlled. The air conditioning device (10) according to the invention is characterized in that the temperature of the fluid at the first inlet (23) of the first heat exchanger (20, 20a, 20b) and the mass flow of the fluid in the first inlet (23, 23a ) can be changed in such a way that vertical temperature stratification (T1 - T8) can be set in the first heat exchanger (20, 20a, 20b).

Description

The present invention relates to an air conditioning device, in particular for a motor vehicle. Generic air conditioners include an air-guiding housing with at least one air inlet and at least one air outlet, a fan and a heat exchanger arrangement, which are arranged in the air-guiding housing between the at least one air inlet and the at least one air outlet. The heat exchanger arrangement typically includes at least one first fluid-based heat exchanger, which is integrated into a fluid circuit with a first fluid pump.

The air-guiding housing comprises several areas. Downstream of the at least one air inlet, a cold air path and a warm air path are typically generated by means of the heat exchanger arrangement, the associated air flows of which are distributed further downstream in a mixing and distribution zone to one or more air outlets according to the target temperatures. It is desirable to achieve a so-called temperature stratification, which is typically achieved by mixing flaps and air ducts in such a way that warmer air tends to be blown out further down (e.g. to the foot outlets) and cooler air higher up (e.g. via the manan flow or defrost channel).

The design of automotive air conditioners is influenced by the existence of traditionally existing internal combustion engines. Due to the change towards e-mobility without combustion engines, the cooling water of the combustion engine is no longer used as a heat source. As a result, there is a need to redefine the compromise between heating comfort and energy efficiency. Thermodynamically, the mixing of previously heated air on the one hand with air previously cooled in parallel is to be viewed critically. While this is suggested by the traditional mix and match approach, it negatively impacts energy efficiency.

It is the object of the present invention to specify an air conditioning device for a motor vehicle which offers an alternative approach to mixing warm/cold air.

According to the invention, this object is achieved by an air conditioning device with the features of claim 1 and by a method for controlling the same with the features of claim 9 . Advantageous training and further education result from the dependent claims.

The air conditioning unit according to the invention comprises a control device, by means of which the fluid circuit can be controlled, the temperature of the fluid at a first inlet of the first fluid-based heat exchanger and the mass flow into the first inlet being able to be changed by means of the control device in such a way that vertical temperature stratification can be set in the first heat exchanger . In other words, temperature stratification is generated via the flow rate generated by the first fluid pump, which reduces or eliminates the need for a further downstream mixture of colder and warmer air to achieve the air conditioning target. The temperature stratification therefore includes a more or less pronounced vertical temperature inhomogeneity at the first heat exchanger, with a horizontal component of this temperature inhomogeneity also being able to be present.

The design of the first fluid-based heat exchanger is a heating heat exchanger that is known per se. In the simplest case, the fluid circuit to which it is connected can even be the coolant circuit of an internal combustion engine, which is known per se. In the general case, however, the fluid circuit is not limited to this, but can also be fed by other heat and/or cold sources. In particular, indirect heat pumps are known which feed a fluid-based hot circuit and a fluid-based cold circuit via a refrigerant circuit.

In the simplest case, the fluid circuit consists of a single line loop with a temperature source and temperature sink, one of which is the first heat exchanger. Water or an aqueous solution, e.g. a water-glycol mixture, is typically used in the fluid circuit, but alternatively other fluids, e.g. oil, are also used.

The temperature can be controlled in any way. In the simplest form, control can take place according to a previously determined target control, in that the air conditioning system is controlled according to the desired air conditioning and external conditions according to fixed values or according to estimated values. In particular, a control circuit can also be provided, which controls the inlet temperature and the mass flow/flow rate through the first heat exchanger accordingly based on detected temperature signals. The temperature signals can be detected, for example, by sensors in the fluid circuit or in the air flow in the vicinity of the first heat exchanger. The control or regulation is carried out by the control device.

In the simplest case, the fluid circuit consists of only one main circuit. The temperature of this main circuit could, for example, by a different heat input through the heat source changeable. According to one embodiment of the invention, a secondary circuit and a valve device are provided in the fluid circuit, the mass flow of the fluid from the secondary circuit upstream of the first heat exchanger being adjustable by means of the valve device with a defined mixing ratio of the mass flow into the main circuit. In this case, the secondary circuit expediently has a different temperature level from the main circuit. It is fed, for example, by the cold circuit of an indirect heat pump mentioned above. By mixing the fluid at different temperatures, the desired temperature level can then be set in a very targeted manner. The first valve device can be configured as desired, for example as a proportional valve or as a timed switching valve with only one “open” and one “closed” switching position.

The mixing from the secondary circuit into the main circuit can take place passively, e.g. by the main circuit flowing past and "entrainment" by negative pressure from the secondary circuit. In a further embodiment, a second fluid pump is arranged in the secondary circuit, by means of which the mass flow of the secondary circuit can be controlled separately from the mass flow of the main circuit.

In order to be able to form vertical temperature stratification in the air-conditioning device in this way, it is also expedient for the first heat exchanger to comprise an inlet tank and an outlet tank, and for the fluid to flow through the first heat exchanger in a vertical direction. The inlet tank is then typically at the bottom and the outlet tank at the top, i.e. the flow through the first heat exchanger is from bottom to top. In principle, however, this can also happen the other way around, e.g. if, in a cooling mode, very cold fluid flows in from above and further down, due to slight warming, also creates vertical temperature stratification with the bottom warmer than the top. Flat tube heat exchangers are suitable as a design, without being restricted to this.

According to one embodiment of the invention, it is provided that the inlet tank has a second inlet and that the temperature of the fluid at the first and second inlet and the mass flow in the first and second inlet can be changed by means of the control device in such a way that vertical temperature stratification and horizontal zone formation are adjustable.

According to a further embodiment of the invention, it is provided that a second fluid-based heat exchanger with a third input is integrated into the main circuit of a fluid circuit and the first and second heat exchangers are arranged one behind the other in the air-conducting housing. The temperature of the fluid at least at the first and at the third inlet and the mass flow into the first and third inlet can then be changed independently of one another by means of the control device. As a result, two heating or cooling profiles can be placed one on top of the other, whereby these can also be reinforced. This expands the operating range of the heat exchanger assembly. If necessary, two smaller heat exchangers can be used, one of which can be switched off completely in a low-load situation. The second heat exchanger can also be integrated as a second layer in the first heat exchanger as a double heat exchanger.

A development of the invention is characterized in that the first heat exchanger is arranged in the air-conducting housing in such a way that the entire air flow flows through it and at least two air outlets are provided downstream of the first heat exchanger, which are aligned vertically to one another. As a result of the temperature stratification, the air conditioning unit can then be designed very compactly and without an additional mixing space with mixing flaps. Alternatively or additionally, the first heat exchanger can be arranged in the air-guiding housing in such a way that the first heat exchanger is partially flown around via a bypass. As a result, further zoning can be provided, for example for air conditioning the rear or a rear row of seats.

The method according to the invention for operating a motor vehicle air conditioning system with an aforementioned air conditioning unit is characterized in that an air conditioning request is detected, from which a profile of a target temperature stratification of the air flowing out of the air conditioning unit can be derived and the temperature at the inlet of the first heat exchanger and the flow rate through the first heat exchanger is controlled in such a way that an actual temperature stratification is established which lies within a predefined deviation from the target temperature stratification (tolerance corridor). The air temperature downstream of the first heat exchanger can be detected at at least a first and a second point arranged vertically to one another. The temperature at the inlet of the first heat exchanger is then increased if at the lower point the actual temperature is less than the sum of the target temperature and the predefined deviation at that point (i.e. when the actual temperature is lower than the target temperature taking into account the tolerance corridor). Conversely, the temperature at the entrance of the first heat exchanger is lowered if the actual temperature at the lower point is more than that sum of the target temperature and the predefined deviation at this point.

The flow rate is then increased if the actual temperature at the higher point is less than the sum of the target temperature and the predefined deviation at the point. Conversely, if the actual temperature at the higher point is more than the sum of the target temperature and the predefined deviation at the point, the flow rate will be decreased. In other words, a "stratification" can be derived as a target value from the difference between the higher and the lower temperature. The more stratification the driver wants, the lower the flow rate, or vice versa.

In this way, the advantages of the technical device features can be used for the purpose of efficient and comfort-enhancing air conditioning. The consideration of the tolerance corridor, which can also be zero in the borderline case, is helpful in order to avoid any oscillation or oscillation of the system.

• Die 1 zeigt schematisch den Prinzipaufbau eines Klimageräts, für welches die Erfindung vorteilhafterweise angewendet werden kann,
• die 2 und 3 zeigen schematisch eine erste und eine zweite Ausführungsvariante eines Fluidkreislaufes zur Verwendung in einem Klimagerät, insbesondere einem Klimagerät gemäß 1, gemäß einem ersten und einem zweiten Ausführungsbeispiel der Erfindung und
• die 4 bis 7 zeigen Ausführungsvarianten von Wärmetauschern, welche erfindungsgemäß in den mit Bezug zu den 2 und 3 beschriebenen Fluidkreisen einbindbar und als Wärmetauscher im luftführenden Kanal von Klimageräten, insbesondere gemäß 1, einsetzbar sind - mit Andeutung verschiedener Temperaturschichtungen.

The invention will now be based on exemplary embodiments and with reference to the 1 until 7 explained in more detail.

• the 1 shows schematically the basic structure of an air conditioner for which the invention can be advantageously applied,
• the 2 and 3 show schematically a first and a second embodiment of a fluid circuit for use in an air conditioner, in particular an air conditioner according to FIG 1 , according to a first and a second embodiment of the invention and
• the 4 until 7 show variants of heat exchangers, which according to the invention in with reference to 2 and 3 described fluid circuits can be integrated and as a heat exchanger in the air duct of air conditioning units, in particular according to 1 , can be used - indicating different temperature stratifications.

In the 1 is a schematic of the basic structure of an air conditioner 10 for a motor vehicle, for which the invention can be advantageously applied. The air conditioner 10 shown comprises, in a manner known per se, an air-guiding housing 11 with an air inlet 12 and three air outlets, namely a foot outlet 13, a man-line vent 14 and a defrost duct 15. The air inlet 12 can in turn have a number of inlet openings, in particular a fresh air flap and a recirculation flap (not shown). A blower 16 and a heat exchanger arrangement with a first fluid-based heat exchanger 20 and a second fluid-based heat exchanger 30 are also arranged in the air-conducting housing 11 . The first heat exchanger 20 is located downstream of the second heat exchanger 30 and is in a fluid circuit 40, 40 'included, which still with respect to the 2 and 3 will be dealt with in more detail.

The first heat exchanger 20 can be arranged in the air-conducting housing 11 in a manner known per se. In order to exploit the effect associated with the invention, the first heat exchanger 20 (and possibly also the second heat exchanger 30) is flowed through by the entire air flow, i.e. without the air flow being partially guided past the side of the heat exchanger 20, as will be explained in more detail below is explained. Alternatively, a cold air bypass (not shown) can be provided around the first heat exchanger 20, by means of which air pre-cooled by the second heat exchanger 30 can be routed past the first heat exchanger and mixed into the air flow downstream of it.

In the 2 a first embodiment of a fluid circuit 40 for use in the air conditioner 10 is shown schematically. The fluid circuit 40 consists of a self-contained main circuit in which a fluid pump 48a, the first fluid-based heat exchanger 20 of the air conditioning device 10 and a hot branch 44 are provided. Driven by the fluid pump 48a, a heat-storing fluid circulates in the fluid circuit 40, typically an aqueous-based fluid, eg, a 50:50 mixture of water and glycol. Alternatively, other fluids can be used, such as oil. A heat source 42 is connected in the warm branch 44 and supplies the fluid circuit 40 with warm fluid.

In a first variant, it can be provided that the outlet temperature of the heat source 42 can be changed, so that the temperature level in the fluid circuit 40 can be changed.

Alternatively or additionally, a cold branch 45 is provided with a cold source 43 which supplies the fluid circuit 40 with cool fluid. The cold circuit 45 (secondary circuit) branches off from the self-contained main circuit at branch point 41a and is reintegrated at mixing point 41b. The cold branch 45 is colder than the warm branch 44, so that a fluid with a temperature level between the warm circuit 44 and the cold circuit 45 can be set downstream of the mixing point 41b by mixing. The mixing ratio, ie the mass flow of the fluid, is controlled by the control valve 49a in the hot circuit 44 and the control valve 49b in the cold circuit 45 are set. The control valves 49a, 49b can be of any type and can be designed, for example, as proportional valves or as clocked closing valves. The fluid circuit 40, in particular the control valves 49a, 49b and the fluid pump 48a, can be controlled (open loop) or regulated (closed loop) by means of a control device 50.

The heat source 42 and the cold source 43 are preferably fed by a refrigeration machine/heat pump device, in particular by means of a refrigerant circuit (not shown), as is known per se from the prior art. The heat source 42 is then the condenser and the cold source 43 is the evaporator in such a refrigerant circuit. In order to operate the heat pump efficiently, the typical values for the heat source are 60°C and those for the cold source are 0°C.

Alternatively, the heat source and the cold source can also be provided differently. The heat can be supplied, for example, via the waste heat from an internal combustion engine. In this case, the heat source (at a system pressure > 1 bar) would typically be 90°C - 110°C warm.

A water-side temperature sensor 55 is also provided in the fluid circuit 40 . An air-side temperature sensor 51 is provided at an upper point near the first heat exchanger 20 and another air-side temperature sensor 52 is provided at a lower point near the first heat exchanger 20 . The temperature sensors 51, 52 can be provided at a suitable position, for example also at the outlets. The temperature sensors 51, 52, 55 are connected to the control device 50, so that the fluid pump 48a and the control valves 49a, 49b can be controlled on the basis of the temperature signals sent by these sensors, as will be explained in more detail below with reference to the method according to the invention.

In the 3 is a second embodiment of a fluid circuit 40 'for use in the air conditioner 10 is shown schematically. The fluid circuit 40' is an extension of the fluid circuit 40 and comprises a separate second cold branch 47 and a second hot branch 46, which branch off from the first cold branch 45 and the first warm branch 44 at the branching points 41c and 41e and reunite at the mixing point 41d , so that a second self-contained main circuit is formed, which merges with the first main circuit at the mixing point 41f downstream of the heat exchangers 20, 20'. Similar to the first main circuit, a fluid pump 48b, a further fluid-based heat exchanger 20', and the control valves 49c, 49d and a further water-side temperature sensor 56 are also provided in the second main circuit. The further heat exchanger 20' can be part of the heat exchanger arrangement of the air conditioning unit 10, for example the second heat exchanger 30. The heat exchangers 20, 20' can also be sections of a more complex heat exchanger 20a, 20b, as is the case with reference to FIGS 6 and 7 will be explained later.

Downstream from the mixing point 41d, a desired temperature level can again be adjusted separately by mixing the fluid. The mixing ratio is set analogously to the first main circuit by the control valve 49c in the hot circuit 46 and the control valve 49d in the cold circuit 47 by means of the control device 50 .

An air-side temperature sensor 53 is provided at an upper point near the second heat exchanger 20', and another air-side temperature sensor 54 is provided at a lower point near the second heat exchanger 20'. The temperature sensors 53, 54, 56 are also connected to the control device 50, so that the fluid pump 48b and the control valves 49c, 49d can be controlled on the basis of the temperature signals sent by these sensors, as will be explained in more detail below with reference to the method according to the invention .

In the 4 until 7 are variants of fluid-based heat exchangers 20, 20a, 20b, 30 shown, which according to the invention in with reference to 2 and 3 described fluid circuits 40, 40 'bindable and can be used as a heat exchanger in the air-carrying housing 11 of the air conditioner 10. The heat exchangers 20, 20a, 20b, 30 have in common that they have a bottom inlet tank 21, 31, a top outlet tank 22, 32 and an intermediate heat exchange core (in Figs 6 and 7 redundant reference symbols are partially omitted). In the case of automotive construction, flat-tube heat exchangers are typically used, without being restricted to this. The fluid flows through them from bottom to top, i.e. in a vertical direction, so that the prerequisite arises that the fluid cools down on the way up and forms temperature stratification.

The in the 4 and 5 The heat exchangers 20, 30 shown can be of a similar or the same design and each have a (single) first inlet 23, 33 in the inlet tank 21, 31 and an outlet 24, 34 in the outlet tank 22, 32.

According to the invention, different temperature stratifications T1, T2, which are symbolized by different hatchings, can be set in a targeted manner by means of the control device 50. The temperature of the fluid at the first inlet 23, 33 of the heat exchangers 20, 30 and the mass flow into the first inlet 23 is changed in such a way that a desired temperature stratification is established.

In the 6 For example, the inlet tank 21 of the heat exchanger 20a has a first inlet 23a at the lower left side and a second inlet 23b at the lower right side. The inlet tank 21 is divided in the middle by a partition 25a into two sub-tanks, so that the fluid flows through the left and right halves of the heat exchanger 20a differently and thus different temperature stratifications T3, T4 can form in the left and right halves. The separation can be implemented, for example, by a barrier in the inlet tank 21 or by a dummy flat tube.

In a further variant, the heat exchanger 20b ( 7 ) in addition to the features of the heat exchanger 20a from the 6 each have a second left and a second right inlet 23c, 23d, further partitions 25b, 25c being provided in the inlet tank 21. This means that four different temperature layers T5, T6, T7 and T8 can be set horizontally.

According to the invention, the temperature of the fluid at the various inputs 23a-23d and the mass flow into these inputs 23a-23d can be changed by means of the control device 50 in such a way that, in addition to vertical temperature stratification, horizontal zone formation can also be set.

A motor vehicle air conditioning system with an air conditioning unit 10 can then be operated as follows: If an air conditioning request is detected, e.g. via an input from a vehicle user via the operating device of the air conditioning system, a profile of a target temperature stratification of the air flowing out of the air conditioning unit can be derived from this. The temperature at the inlet of the first heat exchanger 20, 20a, 20b and the flow rate through the first heat exchanger 20, 20a, 20b are then controlled in such a way that an actual temperature stratification is set that comes close enough to the target temperature stratification. This is achieved by regulating the control device 50 with the temperature signals from the temperature sensors 51 - 56 as input and the flow rates of the fluid pumps 48a, 48b and the opening characteristics of the control valves 49a - 49d as the output (if these are optionally available).

The control method based on the simplest example of the heat exchanger 20 shown 4 with the simpler fluid circuit 40 according to 2 takes place as follows (the other temperature stratifications take place in an analogous manner via the other independently controllable partial circuits of the extended fluid circuit 40' and further inlets): The air temperature is recorded at the points of the temperature sensors 51, 52 lying one above the other. These provide indications of both the average temperature level and the specific formation of the temperature stratification.

The temperature at the inlet 23 of the first heat exchanger 20 is increased if, at the lower point across the temperature sensor 52, the actual temperature is less than the target temperature (taking into account a predefined deviation/tolerance) for that point. Conversely, the temperature at the input 23 is reduced if this actual temperature of the temperature sensor 52 is too high. As an alternative or in addition, regulation can take place on the basis of the temperature signals from the temperature sensor 55 . As mentioned, the increase/decrease in the temperature at the inlet 23 is achieved by controlling the mixture of the fluid from the hot branch 44 and the cold branch 45 via the control valves 49a, 49b.

The flow rate through the heat exchanger 20 is increased if at the higher point by the temperature sensor 51 the actual temperature is less than the target temperature (again allowing for a predefined deviation) at that point. The opposite would apply if the desired temperature of the temperature sensor 51 was too low, which is an indication that the increase in the temperature stratification was too low, whereupon the flow rate would be reduced. The increase/decrease of the flow rate is achieved by the fluid pump 48a as mentioned.

The present exemplary embodiments can be combined with one another as desired. The use of the fluid circuits 40, 40 'according to the invention 2 and 3 can be for any - be provided air conditioners - even known per se. The application for an air conditioner 10 according to 1 is advantageous because the first heat exchanger 20, 20a, 20b is arranged in the air-carrying housing 11 that this is traversed by the entire air flow. Furthermore, because downstream of the first heat exchanger 20, 20a, 20b there are at least two, in the case shown three, vertically offset air outlets 13, 14, 15, a mixing chamber with air flaps and other air guiding devices can either be dispensed with entirely, or at least simplified. The temperature control for the air outlets 13, 14, 15 is provided by the temperature stratification T1 - T8, such as them related to the 4 until 7 are indicated, automatically or is at least preferred.

The use of different heat exchangers 20, 20a, 20b can be adapted to both the requirements of the air conditioning unit 10 and to the design of the fluid circuit 40, 40' or possibly several separate fluid circuits (not shown). In particular, two separate heat exchangers 20, 20a, 20b can be arranged one behind the other and, for example, both cool or heat. As a result, the air conditioning performance could be increased, or vice versa, if necessary, smaller heat exchangers could be used because two are arranged one behind the other in the air flow. The heat exchangers 20a, 20b shown can also be designed as a divided component with two layers, i.e. the left half in the drawing can be in front of the right half in the air flow (or vice versa). Furthermore, the control according to the invention for setting a temperature stratification can also only be provided in one zone, e.g. only the left half of the air conditioning device 10 .

reference list

10

air conditioner

11

Air-conducting housing

12

air intake

13 - 15

air outlets

16

fan

20, 20a, 20b

first fluid-based heat exchanger

21

inlet tank

22

outlet tank

23a - 23d

inputs

24

Exit

25a - 25c

separation

30

second fluid-based heat exchanger

31

inlet tank

32

outlet tank

33

Entry

34

Exit

40, 40'

fluid circuit

41a - 41f

Branching points or mixing points

42

heat source

43

cold source

44, 46

warm branch

45.47

cold branch

48a, 48b

fluid pumps

49a - 49d

control valves

50

control device

51 - 54

Temperature sensors - air

55, 56

Temperature sensors - water

T1-T8

temperature stratification

Claims (9)

Air conditioning unit (10), in particular for a motor vehicle, comprising - an air-guiding housing (11) with at least one air inlet (12) and at least one air outlet (13, 14, 15), - a blower (16) and a heat exchanger arrangement (20, 20a , 20b, 30) which are arranged in the air-guiding housing (11) between the at least one air inlet (12) and the at least one air outlet (13, 14, 15), - the heat exchanger arrangement (20, 20a, 20b, 30) having a first Fluid-based heat exchanger (20, 20a, 20b) with an inlet tank (21) with at least one first inlet (23, 23a), and wherein the first heat exchanger (20) is integrated into a fluid circuit (40, 40') with a first fluid pump (48a), and - a control device (50), by means of which the fluid circuit (40) can be controlled, characterized in that - by means of the control device (50), the temperature of the fluid at the first inlet (23) of the first heat exchanger (20, 20a , 20b) and the mass flow of the fluid in the first input (23, 23a) can be changed in such a way that vertical temperature stratification (T1 - T8) can be set in the first heat exchanger (20, 20a, 20b). Air conditioner (10) after claim 1 , characterized in that a main circuit (44) and a secondary circuit (45) and a valve device (49a - 49d) are provided in the fluid circuit (40, 40'), the mass flow of the fluid from the Auxiliary circuit (45) upstream of the first heat exchanger (20, 20a, 20b) can be adjusted with a defined mixing ratio of the mass flow into the main circuit (44). Air conditioner (10) according to one of Claims 1 until 2 , characterized in that - the first heat exchanger (20, 20a, 20b) comprises an inlet tank (21) and an outlet tank (22) and - The fluid flows through the first heat exchanger (20, 20a, 20b) in the vertical direction. Air conditioning device (10) according to one of the preceding claims, characterized in that - the inlet tank (21) has a second inlet (23b) and - by means of the control device (50) the temperature of the fluid at the first and at the second inlet (23a, 23b) and the mass flow into the first and second inlet (23a, 23b) can be changed in such a way that vertical temperature stratification (T1 - T8) and horizontal zone formation (T3, T4) can be set. Air conditioning device (10) according to one of the preceding claims, characterized in that - a second fluid-based heat exchanger (20', 30) with a third input (33) is integrated into the main circuit (44, 46) of a fluid circuit (40'), - the first and the second heat exchanger (20, 20', 30) are arranged one behind the other in the air-conducting housing (11) and - by means of the control device (50), the temperature of the fluid at least at the first and at the third inlet (23, 23a, 33) and the mass flow into the first and third inlet (23, 23a, 33) can be changed independently of one another. Air conditioner (10) according to one of the preceding claims, characterized in that the first heat exchanger (20, 20a, 20b) is arranged in the air-conducting housing in such a way that the entire air flow flows through it and downstream of the first heat exchanger (20, 20a, 20b) at least two air outlets (13, 14, 15) are provided, which have a vertical orientation to one another. Air conditioner (10) according to one of Claims 1 until 5 , characterized in that the first heat exchanger (20, 20a, 20b) is arranged in the air-guiding housing in such a way that the flow partially flows around it via a bypass. Method for operating a motor vehicle air conditioning system with an air conditioning unit (10) according to one of the preceding claims, characterized in that - a request for air conditioning is detected, from which a profile of a desired temperature stratification of the air flowing out of the air conditioning unit can be derived and - the temperature at the inlet of the first heat exchanger (20, 20a, 20b) and the flow rate through the first heat exchanger (20, 20a, 20b) is controlled in such a way that an actual temperature stratification (T1 - T8) is set, which is within a predefined deviation from the target temperature stratification . procedure after claim 8 , characterized in that - the air temperature is detected downstream of the first heat exchanger (20, 20a, 20b) at at least a first and a second point (51, 52) arranged vertically to one another and - the temperature at the inlet (23, 23a) of the first heat exchanger (20, 20a, 20b) is increased/decreased if the actual temperature at the lower point (52) is less/more than the sum of the target temperature and the predefined deviation at this point (52), and - the flow rate is increased/decreased if at the higher point (51) the actual temperature is less/more than the sum of the target temperature and the predefined deviation at the point (52).

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