DE102013106831A1 - Vehicle air conditioning system of a hybrid or electric vehicle - Google Patents

Abstract

The invention relates to a vehicle air conditioning system (10) of a hybrid or electric vehicle, comprising a refrigerant circuit (12), a compressor (14) for compressing a refrigerant (16), a condenser (18) for cooling and condensing the compressed refrigerant (16). , a pressure reduction unit (20) for decompressing the condensed refrigerant (16) and an evaporator (22) for heating and evaporating the decompressed refrigerant (16), a first cooling circuit (24) which is thermally coupled to the refrigerant circuit (12), and a pump (26) for circulating a first cooling liquid (28) and a heat exchanger (30) for cooling an electric drive train (31) of the hybrid or electric vehicle, and a second cooling circuit (32) which is connected to the refrigerant circuit (12) is thermally coupled and a pump (34) for circulating a second cooling liquid (36) and a heat exchanger (38) for heating Air (40) which can be supplied to a vehicle interior, the evaporator (22) being connected to the first cooling circuit (24) and being able to emit thermal energy to the refrigerant (16), and the condenser (18) being connected to the second cooling circuit (32) is and can absorb heat energy from the refrigerant (16).

Description

The invention relates to a vehicle air conditioner of a hybrid or electric vehicle, comprising a refrigerant circuit including a compressor for compressing a refrigerant, a condenser for cooling and condensing the compressed refrigerant, a pressure reducing unit for decompressing the condensed refrigerant, and an evaporator for heating and evaporating the decompressed refrigerant having.

Modern motor vehicles are now usually equipped with an air conditioner for air conditioning of the vehicle interior. These vehicle air conditioning systems are mainly operated with a refrigerant circuit according to the Carnot principle, in order to achieve a cooling of the vehicle interior at high outside temperatures. For heating the vehicle interior at low outside temperatures usually the waste heat of the motor vehicle internal combustion engine is used.

However, the waste heat of the vehicle engine is so low overall in electric vehicles and in hybrid vehicles during warm-up or temporary shutdown phases of the internal combustion engine, that a satisfactory heating of the vehicle interior is difficult. For this reason, an additional, electric heater is often used, but this is associated with additional energy and space requirements and additional equipment costs.

In order to improve the heating of the vehicle interior, it has already been proposed in the prior art to operate the vehicle air conditioning system provided for cooling the vehicle interior as a heat pump and thus to use the outside air as a heat source for heating the vehicle interior.

In very cold ambient air, however, it has proved difficult to ensure a continuous and satisfactory heating performance in heat pump operation, since the evaporator in this case easily ices up.

To solve this problem is in the US 2011/0167850 A1 proposed a vehicle air conditioning system having various heating modes, wherein both embodiments are described with a "direct" heat pump operation of the air conditioner and embodiments with an "indirect" heat pump operation of the air conditioner.

In direct heat pump operation of the heat exchanger for heating of the vehicle interior feedable air is flowed through directly by the refrigerant of the air conditioning circuit. Since the refrigerant is in the heat exchanger under high pressure and the heat exchanger is assigned as part of an "HVAC system" (heating / ventilation / air conditioning) the vehicle interior, complex protective measures are usually necessary in this case to prevent refrigerant from the Exits the heat exchanger and enters the vehicle interior. In addition, the flow through the heat exchanger with refrigerant in the cooling mode of the vehicle air conditioning affects the efficiency of the air conditioner, which leads to an increased energy requirement for the same cooling performance.

In the case of indirect heat pump operation, the heat exchanger for heating air that can be supplied to the vehicle interior is flowed through by the cooling liquid of a cooling circuit, wherein the cooling circuit is thermally coupled to the refrigerant circuit via a (further) heat exchanger and also serves to cool an internal combustion engine. However, in this cooling circuit, in particular during warm-up or temporary shutdown phases of the internal combustion engine, only a moderate transfer of heat energy between the cooling liquid and the vehicle interior feedable air, resulting in heating mode either insufficient heating or increased energy requirements.

The object of the invention is therefore to provide a structurally simple, compact and inexpensive vehicle air conditioning system, which can be operated particularly energy efficient both in the cooling mode and in the heating mode.

This object is achieved according to the invention by a vehicle air conditioning system of a hybrid or electric vehicle, comprising a refrigerant circuit comprising a compressor for compressing a refrigerant, a condenser for cooling and condensing the compressed refrigerant, a pressure reduction unit for decompressing the condensed refrigerant, and an evaporator for heating and vaporizing the decompressed refrigerant, a first cooling circuit which is thermally coupled to the refrigerant circuit and a pump for circulating a first cooling liquid and a heat exchanger for cooling an electric drive train of the hybrid or electric vehicle, and a second cooling circuit, which is thermally coupled to the refrigerant circuit is and a pump for circulating a second cooling liquid and a heat exchanger for heating of a vehicle interior feedable air, wherein the evaporator at d is connected to the first cooling circuit and can deliver heat energy to the refrigerant, and wherein the condenser to the second cooling circuit is connected and can absorb heat energy from the refrigerant.

The separate refrigerant and cooling circuits are fluidically decoupled and can thus be individually designed for each function to be performed. Thus, the first cooling circuit is specially designed to "collect" the heat energy of numerous smaller heat sources (power electronics, electric motor, battery, etc.) of the electric drive train of an electric or hybrid vehicle and uneven heat dissipation of the individual heat sources on its thermal capacity and thermal inertia of the first cooling circuit largely compensate, so that takes place in the evaporator, a very uniform heat transfer to the refrigerant. On the other hand, the second cooling circuit, which is likewise decoupled from the refrigerant circuit by fluid technology, can be tailored specifically to a particularly efficient transfer of heat between the second cooling fluid and the air that can be supplied to the vehicle interior. Finally, the refrigerant circuit ensures satisfactory heating or cooling of the vehicle interior by means of (adjustable) compressor power.

In one embodiment of the vehicle air conditioning system, the second cooling circuit for circulating the second cooling liquid has a coolant line with a line cross section A, where: 10 mm ² ≦ A ≦ 100 mm ² , in particular 20 mm ² ≦ A ≦ 60 mm ² . This small line cross-section A in the second cooling circuit allows in the heat exchanger good heat transfer between the second cooling liquid and the air supplied to the vehicle interior. This manifests itself by a high temperature difference of the second cooling liquid between a cooling liquid inlet and a cooling liquid outlet of the heat exchanger.

Furthermore, the pump has a delivery rate P in the second cooling circuit, wherein preferably: 50 dm ³ / h ≦ P ≦ 400 dm ³ / h, particularly preferably 120 dm ³ / h ≦ P ≦ 260 dm ³ / h. Due to this rather low flow in the second cooling circuit results, especially in conjunction with the above, small line cross-sections A, a high temperature drop of the second cooling liquid in the heat exchanger for heating the vehicle interior to be supplied air, the temperature difference is preferably above 20 ° C. This large temperature difference in the heat exchanger contributes to a particularly energy-efficient heat pump operation of the vehicle air conditioning system.

In particular, a line cross-section A of a coolant line and a delivery rate P of the pump in the second cooling circuit can be matched to one another such that the following applies for a flow rate v of the second coolant: 0.5 m / s ≦ v ≦ 2.0 m / s. In this range, the flow velocity v is large enough to ensure a largely constant and sufficient heat transfer and small enough to avoid excessive line wear due to erosion.

In a further embodiment of the vehicle air conditioning system, the refrigerant circuit is formed separately from the two refrigerant circuits, and the refrigerant is different from the refrigerant liquids. Because of these fluidly separate circuits without fluid connection different media can be used in the individual circuits. Suitable refrigerants are, for example, R 134 a, HFO 1234 yf or carbon dioxide. Suitable cooling fluids are, for example, water, oils or particularly preferably water / glycol mixtures.

Preferably, the first cooling circuit is formed separately from the second cooling circuit. Particularly preferably, these flow separated, separate cooling circuits are also thermally separated so that no direct heat transfer is possible between the two cooling circuits.

Despite the fluidically separate design of the cooling circuits, however, the first cooling liquid may be identical to the second cooling liquid. This reduces the number of cooling media used in the vehicle air conditioning system, which significantly simplifies the storage and filling of the vehicle air conditioning system.

In a further embodiment of the vehicle air conditioning system, the first cooling circuit has a cooler connected in parallel to the evaporator, in particular separately switchable cooler, wherein the first cooling liquid can flow through the radiator and thereby emit heat energy to the ambient air. Usually, the vehicle air conditioning system is equipped with a control unit which the Distribute the flow variably to the two line sections connected in parallel or restrict it to one of the two line sections. About this control unit, the vehicle air conditioning can be adapted with little effort to the particular desired function.

In a further embodiment of the vehicle air conditioning system, the second cooling circuit has a cooler connected in parallel to the heat exchanger, in particular separately switchable cooler, wherein the second cooling liquid can flow through the radiator and thereby emit heat energy to the ambient air. The vehicle air conditioning system is usually equipped with a control unit which can variably distribute the flow to the two line sections connected in parallel or restrict it to one of the two line sections. With this control unit, the vehicle air conditioning system can be adapted with little effort to the respective desired operating mode.

The evaporator through which the first coolant can flow is preferably a first evaporator and the upstream pressure reduction unit is a first pressure reduction unit, wherein the refrigerant circuit has a second evaporator with an upstream second pressure reduction unit connected in parallel with the first evaporator and the first pressure reduction unit through which the ambient air can flow. Particularly preferably, the pressure reduction units are each designed as expansion valves with shut-off function, so that the flow can be distributed over the pressure reduction units to the two line sections connected in parallel or limited to one of the two line sections. In this way, the vehicle air conditioner can be switched from a cooling mode to a heating mode with little effort, and vice versa.

According to one embodiment, the heat exchanger for heating the vehicle interior in the operation of the air conditioner can be traversed by both the second cooling liquid and the air supplied to the vehicle interior, wherein the cooling liquid is cooled by a temperature difference .DELTA.T _KF in the flow through the heat exchanger and the air to a temperature difference ΔT _{L is} heated, where: 0.3 <ΔT _KF / ΔT _L <1.1. Compliance with these temperature parameters contributes to extremely energy efficient heat pump operation of the vehicle air conditioning system.

According to a further embodiment, during the operation of the air conditioning system, the condenser can be flowed through by both the refrigerant and the second cooling liquid, the refrigerant, as it flows through the condenser, cooling by a temperature difference ΔT _KM and heating the cooling liquid by a temperature difference ΔT _KF . where: 0.5 <ΔT _KF / ΔT _KM <1.1. Compliance with these temperature parameters also contributes to extremely energy efficient heat pump operation of the vehicle air conditioning system.

The heat exchanger for heating the air supplied to the vehicle interior has a dimension t in the air flow direction and preferably comprises a plurality of parallel flat tubes, wherein two adjacent flat tubes have a center distance b, wherein between two adjacent flat tubes respectively at least one lamella extending in the flow direction of the second Cooling liquid is wave-shaped and on a wave crest in each case a first flat tube of the two adjacent flat tubes and at a trough a second flat tube of the two adjacent flat tubes touches, the lamella seen in the flow direction has a distance h between a wave crest and a trough, and where: 25 mm <t <60 mm, 4 mm <b <8 mm and 0.6 mm <h <1.2 mm. These design parameters of the heat exchanger cause a very good heat transfer from the second cooling liquid to the air that can be supplied to the vehicle interior.

The vehicle air conditioning system can be used for example in a hybrid vehicle with an internal combustion engine, wherein preferably a separate, third cooling circuit is provided which has a pump for circulating a third cooling liquid and a heat exchanger for cooling the internal combustion engine. This third cooling circuit is particularly preferably formed by the refrigerant circuit and the first and second cooling circuit thermally and fluidly separated, so in particular has no fluid connection to the other circuits. About this separate, third cooling circuit, the waste heat of the engine can be used to heat the vehicle interior with little effort. If the third cooling circuit supplies a sufficient heat output, the heat pump can be turned off or at least throttled in its performance, which in turn contributes to a particularly energy-efficient operation of the vehicle air conditioning.

For this purpose, the third cooling circuit preferably has a heat exchanger for heating air that can be supplied to the vehicle interior. As a result, an efficient transfer of heat from the third cooling liquid to the air that can be supplied to the vehicle interior can be realized so that the heat pump does not have to provide any or hardly any heating power for heating the vehicle interior.

Further features and advantages of the invention will become apparent from the following description of a preferred embodiment with reference to the drawings. In these show:

1 a schematic diagram of a vehicle air conditioning system according to the invention;

2 a temperature profile in a condenser and a heat exchanger for heating air supplied from a vehicle interior at different operating conditions of the vehicle air conditioning system according to the invention;

3 a Mollier diagram showing the state changes of a refrigerant in heating mode a vehicle air conditioning system according to the invention illustrated; and

4 a schematic perspective view of a heat exchanger for heating feedable from a vehicle interior air.

The 1 shows a vehicle air conditioning 10 a hybrid or electric vehicle, with a refrigerant circuit 12 , the one compressor 14 for compressing a refrigerant 16 , a capacitor 18 for cooling and condensing the compressed refrigerant 16 , a pressure reduction unit 20 for decompressing the condensed refrigerant 16 as well as an evaporator 22 for heating and vaporizing the decompressed refrigerant 16 comprising a first cooling circuit 24 that with the refrigerant circuit 12 thermally coupled and a pump 26 for circulating a first cooling liquid 28 and a heat exchanger 30 for cooling an electric drive train 31 of the hybrid or electric vehicle, and a second cooling circuit 32 that with the refrigerant circuit 12 thermally coupled and a pump 34 for circulating a second cooling liquid 36 and a heat exchanger 38 for heating air that can be supplied to a vehicle interior 40 having.

The refrigerant circuit 12 is a fluidically separate circuit without fluid connection to the cooling circuits 24 . 32 ,

The refrigerant 16 in the refrigerant circuit 12 is different from the cooling fluids 28 . 36 the cooling circuits 24 . 32 and mixes due to the fluidly separated configuration of the refrigerant circuit 12 not even with these coolants 28 . 36 , Suitable refrigerants are, for example, R 134 a, HFO 1234 yf or carbon dioxide.

For thermal coupling of the refrigerant circuit 12 with the first cooling circuit 24 is the evaporator 22 of the refrigerant circuit 12 to the first cooling circuit 24 connected, so the first coolant 28 the evaporator 22 flow through and heat energy to the refrigerant 16 can deliver.

For thermal coupling of the refrigerant circuit 12 with the second cooling circuit 32 is the capacitor 18 of the refrigerant circuit 12 to the second cooling circuit 32 connected, leaving the second coolant 36 the capacitor 18 flow through and heat energy from the refrigerant 16 can record.

According to 1 is the first cooling circuit 24 both fluidically and thermally separated from the second cooling circuit 32 educated. In other words, that means the two cooling circuits 24 . 32 separate circuits without fluid connection and without immediate heat transfer. About the refrigerant circuit 12 exists between the two cooling circuits 24 . 32 only an indirect thermal coupling.

Although the two cooling circuits 24 . 32 are separated by flow, is the first cooling liquid 28 preferably with the second cooling liquid 36 identical. The use of only a single coolant reduces the number of cooling media, which simplifies their storage and moreover when filling the vehicle air conditioner 10 is advantageous because there may be no confusion of cooling fluids. Suitable cooling liquids are, for example, water, oils or particularly preferably water / glycol mixtures.

The first cooling circuit 24 according to 1 one to the evaporator 22 connected in parallel, in particular separately switchable cooler 42 on, with the first cooling liquid 28 the cooler 42 flow through while heat energy to the ambient air 44 can deliver.

In addition, in the first cooling circuit 24 a control unit 46 provided over which the radiator 42 can be switched on or off separately. The control unit 46 in the present case comprises two shut-off valves, which a flow of the first cooling liquid 28 on parallel line sections 48 . 50 of the first cooling circuit 24 can distribute.

In a heating mode of the vehicle air conditioner 10 is the control unit 46 preferably switched so that the cooler 42 comprehensive line section 48 of the first cooling circuit 24 not from the first coolant 28 is flowed through. Thus, flows through the entire first coolant 28 the evaporator 22 and gives the over the heat exchanger 30 from the electric drive train 31 absorbed heat energy to the refrigerant 16 from.

Accordingly, the control unit 46 in a cooling mode of the vehicle air conditioner 10 preferably switched so that the evaporator 22 comprehensive line section 50 of the first cooling circuit 24 not from the first coolant 28 is flowed through. Thus, flows through the entire first coolant 28 the cooler 42 and gives the over the heat exchanger 30 from the electric drive train 31 absorbed heat energy to the ambient air 44 from.

Although the control unit 46 usually a line section 48 . 50 releases and the parallel connected, other line section 50 . 48 locks, of course, switch positions are conceivable in which both line sections 48 . 50 at least partially released.

The second cooling circuit 32 according to 1 one to the heat exchanger 38 connected in parallel, in particular separately switchable cooler 54 on, with the second cooling liquid 36 the cooler 54 flow through while heat energy to the ambient air 44 can deliver.

In addition, in the second cooling circuit 32 a control unit 56 provided over which the radiator 54 can be switched on or off separately. The control unit 56 is in the present case a three-way valve, which is a flow of the second cooling liquid 36 on parallel line sections 55 . 57 of the second cooling circuit 32 can distribute.

In a heating mode of the vehicle air conditioner 10 is the control unit 56 preferably switched so that the cooler 54 comprehensive line section 55 of the second cooling circuit 32 not from the second coolant 28 is flowed through. Thus flows through the entire second cooling liquid 28 the heat exchanger 38 and gives the over the capacitor 18 absorbed heat energy to the vehicle interior feedable air 40 from.

Accordingly, the control unit 56 in a cooling mode of the vehicle air conditioner 10 preferably switched so that a the heat exchanger 38 comprehensive line section 57 of the second cooling circuit 32 not from the second coolant 36 is flowed through. Thus flows through the entire second cooling liquid 36 the cooler 54 and gives the over the capacitor 18 absorbed heat energy to the ambient air 44 from.

Although the control unit 56 usually a line section 55 . 57 releases and the parallel connected, other line section 57 . 55 locks, of course, switch positions are conceivable in which both line sections 55 . 57 at least partially released.

In the event that, for example, under extreme conditions a heating power of the vehicle air conditioning 10 in heat pump mode is not sufficient for a satisfactory heating of the vehicle interior, the heat exchanger 38 an optional heater 52 be upstream of the second cooling fluid 36 heat. This heater 52 is preferably a self-regulating PTC heating element, but may alternatively be, for example, an electrical resistance heater.

In the refrigerant circuit 12 according to 1 is that of the first coolant 28 streamable evaporator 22 a first evaporator and the upstream pressure reduction unit 20 a first pressure reduction unit, wherein the refrigerant circuit 12 parallel to the first evaporator and the first pressure reduction unit one of the ambient air 44 permeable second evaporator 58 with an upstream second pressure reduction unit 60 having. The two pressure reduction units 20 . 60 are each designed in the present case as expansion valves with shut-off function. Alternatively, however, it is also conceivable that as a pressure reduction unit 20 . 60 in each case a prefabricated assembly of an expansion valve and a shut-off valve is used. In this way, the pressure reduction units can be 20 . 60 also for flow control of the refrigerant 16 use, so that additional flow control elements such as separate shut-off or check valves, can be omitted.

In the heating mode of the vehicle air conditioner 10 locks the second pressure reduction unit 60 preferably a second evaporator 58 comprehensive line section 62 of the refrigerant circuit 12 , Thus, the refrigerant decreases 16 exclusively from the electric drive train 31 provided by the hybrid or electric vehicle heat energy through the first evaporator 22 on.

Accordingly locks the first pressure reduction unit 20 in the cooling mode of the vehicle air conditioner 10 one the first evaporator 22 comprehensive line section 64 of the refrigerant circuit 12 , Thus, the refrigerant decreases 16 only heat energy from the air supplied to the vehicle interior 40 on, which leads to a desired cooling of the vehicle interior.

Although the pressure reduction units 20 . 60 usually a line section 62 . 64 release and the parallel connected, other line section 64 . 62 lock, of course, switch positions are conceivable in which both line sections 62 . 64 at least partially released.

According to 1 is in the refrigerant circuit 12 a refrigerant reservoir on the pressure side 65 provided upstream of the pressure reduction units 20 . 60 is arranged. The refrigerant reservoir 65 is therefore a high-pressure accumulator, preferably exclusively liquid refrigerant 16 to remove it in heating mode via the first pressure reduction unit 20 to the evaporator 22 and in the cooling mode via the second pressure reduction unit 60 to the evaporator 58 to lead. Of course, the refrigerant storage 65 alternatively also be a suction side arranged low-pressure accumulator, preferably exclusively gaseous refrigerant 16 is taken to the compressor 14 supply.

To a particularly energy-efficient heat pump operation of the vehicle air conditioning 10 to reach, has a coolant line 66 for circulating the second cooling liquid 36 in the second cooling circuit 32 a line cross section A, with 10 mm ² ≤ A ≤ 100 mm ² , in particular 20 mm ² ≤ A ≤ 60 mm ² .

Furthermore, the pump points 34 in the second cooling circuit 32 a delivery rate P on, with 50 dm ³ / h ≤ P ≤ 400 dm ³ / h, in particular 120 dm ³ / h ≤ P ≤ 260 dm ³ / h.

Particularly preferred are the line cross-section A of the coolant line 66 and the delivery rate P of the pump 34 in the second cooling circuit 32 coordinated so that a flow velocity v of the second cooling liquid 36 at 0.5 m / s ≤ v ≤ 2.0 m / s.

The small line cross-section A and the low flow in the second cooling circuit 32 allow in the heat exchanger 38 a good heat transfer between the second cooling liquid 36 and the air supplied to the vehicle interior 40 , This manifests itself by a high temperature drop of the second cooling liquid 36 between a cooling fluid inlet 67 and a coolant outlet 69 of the heat exchanger 38 and a particularly strong warming of the air 40 when flowing through the heat exchanger 38 ,

Due to the thermal coupling of the circuits 12 . 24 . 32 is the relatively low heat energy of the electric drive train 31 a hybrid or electric vehicle in the first cooling circuit 24 collect, to the refrigerant circuit 12 transferred, in heat pump operation of the refrigerant circuit 12 enlarge and finally to the second cooling circuit 32 leave to there over the heat exchanger 38 the air supplied to the vehicle interior 40 to heat. The heat energy of the electric drive train 31 is usually composed of the heat energy of several heat sources of the electric or hybrid vehicle together (eg power electronics, electric motor, battery).

At the same time, every single cycle can be due to the fluidic circulation separation 12 . 24 . 32 , in particular with regard to its cross-sections, flow rates and flow velocities, to the specific function of the respective circuit 12 . 24 . 32 to adjust.

This is the first cooling circuit 24 tailored to heat energy from the electric drive train as efficiently as possible 31 of the hybrid or electric vehicle and as needed via the radiator 42 or the evaporator 22 to the ambient air 44 or the refrigerant circuit 12 leave. The second cooling circuit 32 is tailored to the refrigerant circuit 12 over the capacitor 18 remove as much heat energy and if necessary on the cooler 54 or the heat exchanger 38 as efficiently as possible to the ambient air 44 or the air supplied to the vehicle interior 40 leave.

The between the cooling circuits 24 . 32 switched refrigerant circuit 12 On the other hand, it is specially designed for a customizable compressor output 14 a satisfactory heating or cooling capacity of the vehicle air conditioning system 10 to ensure for all possible boundary conditions.

If the vehicle air conditioning 10 in a hybrid vehicle with an internal combustion engine 68 optional, a separate, third cooling circuit can be used 70 be provided in the 1 indicated by dashed lines. In the illustrated embodiment, the third cooling circuit comprises 70 a pump 72 for circulating a third cooling liquid 74 and a heat exchanger 76 for cooling the internal combustion engine 68 ,

According to 1 indicates the third cooling circuit 70 a heat exchanger 78 for heating air that can be supplied to the vehicle interior 40 on. Parallel connected to the heat exchanger 78 is in the third cooling circuit 70 a particular separately switchable cooler 80 provided, wherein the third cooling liquid 74 the cooler 80 flow through while heat energy to the ambient air 44 can deliver.

In addition, in the third cooling circuit 70 a control unit 79 provided over which the radiator 80 can be switched on or off separately. The control unit 79 in the present case comprises two shut-off valves, which a flow of the third cooling liquid 74 on parallel connected line sections of the third cooling circuit 70 can distribute.

In a heating mode of the vehicle air conditioner 10 is the control unit 79 preferably switched so that the cooler 80 comprehensive line section of the third cooling circuit 70 not from the third coolant 74 is flowed through. Thus flows through the entire third cooling liquid 74 the heat exchanger 78 and gives the over the heat exchanger 76 from the combustion engine 68 absorbed heat energy to the vehicle interior feedable air 40 from.

Accordingly, the control unit 79 in a cooling mode of the vehicle air conditioner 10 preferably switched so that a the heat exchanger 78 comprehensive line section of the third cooling circuit 70 not from the third coolant 74 is flowed through. Thus flows through the entire third cooling liquid 74 the cooler 80 and gives the over the heat exchanger 76 from the combustion engine 68 absorbed heat energy to the ambient air 44 from.

Although the control unit 79 Usually a line section releases and the parallel connected, other line section locks, of course, switch positions are conceivable in which both line sections are at least partially released.

The heat exchanger 38 as well as the evaporator 58 and the optional heat exchanger 78 are part of an "HVAC system" (heating / ventilation / air conditioning), which is assigned to the vehicle interior and usually arranged in a ventilation duct for ventilation of the vehicle interior.

The third cooling circuit 70 is thermally and fluidly separated from the refrigerant circuit 12 and the first and second cooling circuits 24 . 32 trained, that is he has no fluid connection to one of the other circuits 12 . 24 . 32 on. About the separate, third cooling circuit 70 can with little effort the waste heat of the engine 68 be used for heating the vehicle interior. Unless the third cooling circuit 70 provides sufficient heating power can be located in the heat pump mode vehicle air conditioning 10 be turned off or at least throttled in their performance.

Overall, a vehicle air conditioning system results 10 whose operation is extremely energy efficient both in heating mode and in cooling mode.

The 2 shows temperature profiles in the capacitor 18 as well as in the heat exchanger 38 under different operating conditions of the vehicle air conditioner 10 , wherein the temperature T is plotted against the enthalpy E.

It becomes clear that the vaporous, superheated refrigerant 16 with an overheating temperature between 80 ° C and 110 ° C in the condenser 18 liquefied and as a liquid, supercooled refrigerant 16 with a subcooling temperature between 40 ° C and 50 ° C the capacitor 18 leaves. The preferred operating ranges of the superheated or super-cooled refrigerant 16 are according to 2 highlighted by cross-hatching. Also, in 2 fit line 81 for the temperature profile of the refrigerant 16 shown dotted.

Depending on the temperature profile of the refrigerant 16 the temperature of the second cooling liquid rises 36 in the condenser 18 starting from about 10-30 ° C to about 60 ° C. This preferred operating range for the second cooling fluid 36 is in 2 also highlighted by cross-hatching. The target temperature of the second coolant 36 in the condenser 18 is about 60 ° C, to a sufficient heating of the vehicle interior feedable air 40 to enable. This air 40 is according to 2 from about 0 ° C to about 55 ° C in the heat exchanger 38 heated, with an air outlet temperature of about 50 ° C can be considered as the minimum value for a satisfactory heating performance.

Preferably, the capacitor 18 during operation of the vehicle air conditioning system 10 both from the refrigerant 16 as well as the second coolant 36 be flowed through, wherein when flowing through the capacitor 18 the refrigerant 16 by a temperature difference .DELTA.T _KM cools and the second cooling liquid 36 heated by a temperature difference .DELTA.T _KF , where: 0.5 <.DELTA.T _KF / .DELTA.T _KM <1.1.

Incidentally, the heat exchanger 38 for heating the vehicle interior during operation of the vehicle air conditioning system 10 both from the second coolant 36 as well as from the vehicle interior air 40 be flowed through, which is flowing through the heat exchanger 38 the second cooling liquid 36 cooled by a temperature difference ΔT _KF and the air 40 heated by a temperature difference ΔT _KL , where: 0.3 <ΔT _KF / ΔT _L <1.1.

For comparison are in 2 also for conventional vehicle air conditioners with indirect heat pump operation temperature profiles for the second coolant 36 ' and the air that can be supplied to the vehicle interior 40 ' dashed lines. It becomes clear that the temperature of the second coolant 36 ' in the condenser or in the heat exchanger only changed by about 10 ° C and approximately between 30 ° C and 40 ° C. The air 40 ' can be heated at best from 0 ° C to about 40 ° C.

The larger temperature differences and the associated, better heating performance of the vehicle air conditioning 10 according to 1 are in particular due to the fact that the second cooling circuit 32 as a "low-flow circuit" with a small cross-section A and a highly efficient heat exchanger 38 is trained.

The 3 shows a Mollier diagram of the refrigerant circuit 12 in heating mode the Vehicle air conditioning 10 , wherein on the abscissa the enthalpy E and on the ordinate a pressure p of the refrigerant 16 is plotted logarithmically. There is an evaporation area 82 of the refrigerant 16 (here R134a) at a temperature of about -10 ° C and a corresponding refrigerant pressure of about 2 bar. The refrigerant 16 is then through the compressor 14 into a condensation area 84 compacted, in which the refrigerant 16 a temperature of about 55 ° C at a pressure of about 16 bar. Finally, the refrigerant 16 at the (first) pressure reduction unit 20 expanded so far that it is back in the evaporation area 82 lies.

The enthalpy E in the condenser 18 about 10% is distributed to a subcooling area, about 63% to a condensation area and about 27% to an overheating area of the refrigerant 16 (see also 2 ).

As a refrigerant 16 for the in 3 illustrated refrigerant circuit 12 In particular, the refrigerants R134a and HFO 1234 yf are suitable. Of course, however, other suitable refrigerants 16 , For example, carbon dioxide, in the refrigerant circuit 12 the vehicle air conditioner 10 be used.

The described refrigerant circuit 12 for vehicle air conditioning 10 is particularly suitable for hybrid and electric vehicles, with their "engine heat" no continuous, satisfactory heating of the vehicle interior can be guaranteed. The heating then takes place, as described above, via the heat pump operation of the vehicle air conditioning system 10 ,

The 4 shows a schematic perspective view of the heat exchanger 38 for heating the air which can be supplied to the vehicle interior 40 , To a temperature profile according to 2 with high temperature differences in the heat exchanger 38 To achieve, it has proved to be advantageous, the following dimensions for the heat exchanger 38 observed.

So has the heat exchanger 38 for heating the air which can be supplied to the vehicle interior 40 in the direction of air flow 86 a dimension t which is 25 mm <t <60 mm. Furthermore, the heat exchanger comprises 38 several parallel flat tubes 88 where two adjacent flat tubes 88 have a center distance b with 4 mm <b <8 mm. Between two adjacent flat tubes 88 each extends at least one lamella 90 in the flow direction 92 the second cooling liquid 36 is wavy and formed on a wave crest 94 in each case a first flat tube 88 the two adjacent flat tubes 88 as well as on a wave trough 96 a second flat tube 88 the two adjacent flat tubes 88 touches the lamella 90 in flow direction 92 seen a distance h between a wave crest 94 and a trough 96 where: 0.6 mm <h <1.2 mm.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• US 2011/0167850 A1 [0006]

Claims (15)

Vehicle air conditioning system of a hybrid or electric vehicle, with a refrigerant circuit ( 12 ), which is a compressor ( 14 ) for compressing a refrigerant ( 16 ), a capacitor ( 18 ) for cooling and condensing the compressed refrigerant ( 16 ), a pressure reduction unit ( 20 ) for decompressing the condensed refrigerant ( 16 ) and an evaporator ( 22 ) for heating and evaporating the decompressed refrigerant ( 16 ), a first cooling circuit ( 24 ) connected to the refrigerant circuit ( 12 ) is thermally coupled and a pump ( 26 ) for circulating a first cooling liquid ( 28 ) and a heat exchanger ( 30 ) for cooling an electric drive train ( 31 ) of the hybrid or electric vehicle, and a second cooling circuit ( 32 ) connected to the refrigerant circuit ( 12 ) is thermally coupled and a pump ( 34 ) for circulating a second cooling liquid ( 36 ) and a heat exchanger ( 38 ) for heating air that can be supplied to a vehicle interior ( 40 ), wherein the evaporator ( 22 ) to the first cooling circuit ( 24 ) and heat energy to the refrigerant ( 16 ), and wherein the capacitor ( 18 ) to the second cooling circuit ( 32 ) and heat energy from the refrigerant ( 16 ). Vehicle air conditioning system according to claim 1, characterized in that the second cooling circuit ( 32 ) for circulating the second cooling liquid ( 36 ) a coolant line ( 66 ) with a conductor cross-section (A), wherein the following applies: 10 mm ² ≦ A ≦ 100 mm ² , in particular 20 mm ² ≦ A ≦ 60 mm ² . Vehicle air conditioning system according to claim 1 or 2, characterized in that the pump ( 34 ) in the second cooling circuit ( 32 ) has a delivery rate (P), where: 50 dm ³ / h ≦ P ≦ 400 dm ³ / h, in particular 120 dm ³ / h ≦ P ≦ 260 dm ³ / h. Vehicle air conditioning system according to one of the preceding claims, characterized in that a line cross-section (A) of a coolant line ( 66 ) and a delivery rate (P) of the pump ( 34 ) in the second cooling circuit ( 32 ) are matched to one another such that for a flow velocity (v) of the second cooling liquid (v) 36 ): 0.5 m / s ≤ v ≤ 2.0 m / s. Vehicle air conditioning system according to one of the preceding claims, characterized in that the refrigerant circuit ( 12 ) separated from the two cooling circuits ( 24 . 32 ) is formed and the refrigerant ( 16 ) of the cooling liquids ( 28 . 36 ) is different. Vehicle air conditioning system according to one of the preceding claims, characterized in that the first cooling circuit ( 24 ) separated from the second cooling circuit ( 32 ) is trained. Vehicle air conditioning system according to one of the preceding claims, characterized in that the first cooling liquid ( 28 ) with the second cooling liquid ( 36 ) is identical. Vehicle air conditioning system according to one of the preceding claims, characterized in that the first cooling circuit ( 24 ) one to the evaporator ( 22 ) connected in parallel, in particular separately switchable cooler ( 42 ), wherein the first cooling liquid ( 28 ) the cooler ( 42 ) and thereby heat energy to the ambient air ( 44 ). Vehicle air conditioning system according to one of the preceding claims, characterized in that the second cooling circuit ( 32 ) one to the heat exchanger ( 38 ) connected in parallel, in particular separately switchable cooler ( 54 ), wherein the second cooling liquid ( 36 ) the cooler ( 54 ) and thereby heat energy to the ambient air ( 44 ). Vehicle air conditioning system according to one of the preceding claims, characterized in that the of the first cooling liquid ( 28 ) throughflowable evaporators ( 22 ) a first evaporator and the upstream pressure reduction unit ( 20 ) is a first pressure reduction unit, wherein the refrigerant circuit ( 12 ) parallel to the first evaporator and the first pressure reduction unit one of the ambient air ( 44 ) can be flowed through the second evaporator ( 58 ) with an upstream second pressure reduction unit ( 60 ) having. Vehicle air conditioning system according to one of the preceding claims, characterized in that the heat exchanger ( 38 ) for heating the vehicle interior during operation of the air conditioning system ( 10 ) from both the second cooling liquid ( 36 ) as well as from the vehicle interior air ( 40 ) can be flowed through, wherein during the flow through the heat exchanger ( 38 ) the cooling liquid ( 36 ) is cooled by a temperature difference ΔT _KF and the air ( 40 ) is heated by a temperature difference ΔT _L , where: 0.3 <ΔT _KF / ΔT _L <1.1. Vehicle air conditioning system according to one of the preceding claims, characterized in that the capacitor ( 18 ) during operation of the air conditioning system ( 10 ) both from the refrigerant ( 16 ) as well as the second cooling liquid ( 36 ) can be flowed through, wherein during the flow through the capacitor ( 18 ) the refrigerant ( 16 ) by one Temperature difference ΔT _KM cools and the cooling liquid ( 36 ) is heated by a temperature difference ΔT _KF , where: 0.5 <ΔT _KF / ΔT _KM <1.1. Vehicle air conditioning system according to one of the preceding claims, characterized in that the heat exchanger ( 38 ) for heating air that can be supplied to the vehicle interior ( 40 ) in the air flow direction ( 86 ) has a dimension (t) and a plurality of parallel flat tubes ( 88 ), wherein two adjacent flat tubes ( 88 ) have an axial distance (b), wherein between two adjacent flat tubes ( 88 ) at least one blade ( 90 ) extending in the direction of flow ( 92 ) of the second cooling liquid ( 36 ) is wave-shaped and on a wave mountain ( 94 ) each have a first flat tube of the two adjacent flat tubes ( 88 ) as well as at a wave trough ( 96 ) a second flat tube of the two adjacent flat tubes ( 88 ), the lamella ( 90 ) in the flow direction ( 92 ) seen a distance (h) between a wave crest ( 94 ) and a wave trough ( 96 ), and wherein 25 mm <t <60 mm, 4 mm <b <8 mm and 0.6 mm <h <1.2 mm. Vehicle air conditioning system according to one of the preceding claims for a hybrid vehicle with an internal combustion engine ( 68 ), characterized in that a separate, third cooling circuit ( 70 ), which is a pump ( 72 ) for circulating a third cooling liquid ( 74 ) and a heat exchanger ( 76 ) for cooling the internal combustion engine ( 68 ) having. Vehicle air conditioning system according to claim 14, characterized in that the third cooling circuit ( 70 ) a heat exchanger ( 78 ) for heating air that can be supplied to the vehicle interior ( 40 ) having.

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