Heating and air conditioning of different temperature levels of a vehicle and method therefor

Abstract

The invention relates to a heating and air conditioning installation for a vehicle, having a first heating circuit and a cooling circuit and a refrigerant circuit, which comprises at least a compressor, an expansion element, an external heat exchanger which can be operated as an evaporator in a heat pump mode, a first heat exchanger on the high-pressure side and a second heat exchanger on the low-pressure side which can be connected for an air conditioning mode, wherein the first heat exchanger is also connected to the first heating circuit and the second heat exchanger is also connected to the cooling circuit, wherein the heating and air conditioning installation comprises a second heating circuit, wherein the refrigerant circuit comprises a third heat exchanger on the high-pressure side which is arranged downstream in the refrigerant flow direction relative to the first heat exchanger, which is also connected to the second heating circuit, wherein the refrigerant of the refrigerant circuit and the heating liquid of the second heating circuit are directly and / or indirectly thermally coupled by means of a heat exchange connection in the third heat exchanger. The invention also relates to a related control method and a vehicle having the same.

Description

TECHNICAL FIELD

[0001] The invention relates to a heating and air conditioning installation for a vehicle. The heating and air conditioning installation has a first heating circuit for heating comprising at least one pump and a cooling circuit comprising at least one pump and a refrigerant circuit comprising at least a compressor, an expansion element, an external heat exchanger which can be operated as an evaporator in a heat pump operation, a first heat exchanger on the high-pressure side and a second heat exchanger on the low-pressure side which is at least for an air conditioning operation and which is connected or connectable, wherein the first heat exchanger is also connected to the first heating circuit and the second heat exchanger is also connected to the cooling circuit, and in the first heat exchanger the refrigerant of the refrigerant circuit and the heating liquid of the first heating circuit are directly and / or via an optional first latent heat storage medium thermally coupled or thermally couplable by a heat exchange connection, and in the second heat exchanger the refrigerant of the refrigerant circuit and the cooling liquid of the cooling circuit are directly and / or via an optional second latent heat storage medium thermally coupled or thermally couplable by a heat exchange connection, wherein the heating and air conditioning installation is designed for a vehicle. Such an air conditioning installation comprises a first heating circuit for heating and a cooling circuit and a refrigerant circuit comprising at least a compressor, an expansion element, an external heat exchanger which can be operated as an evaporator, a first heat exchanger on the high-pressure side and a second heat exchanger on the low-pressure side which is at least for an air conditioning operation and which is connected or connectable, wherein the first heat exchanger is also connected to the first heating circuit and the second heat exchanger is also connected to the cooling circuit.

[0002] The invention also relates to a method for controlling such a heating and air conditioning installation and a vehicle having such a heating and air conditioning installation. In particular, an electric or hybrid vehicle has such an installation, in particular for cooling or heating the air of the interior space of the vehicle. The battery of the electric or hybrid vehicle is also cooled, as a rule, by means of the installation.

[0003] The components of the refrigerant circuit are connected to refrigerant lines in order to flow the refrigerant in the circuit. In the compressor, the refrigerant is heated by compression and reaches a high pressure and is de-pressurized again in the expansion element, wherein the refrigerant cools. BACKGROUND

[0004] It is known for cooling installations for vehicles which are able to provide even three different temperature levels. Thus, EP 3023609 A1 discloses a cooling installation for a vehicle having a high-temperature coolant circuit, a medium-temperature coolant circuit and a low-temperature coolant circuit for cooling components of the vehicle at three different temperature levels. However, disadvantageous here is that the cooling liquid is only cooled by air in all three circuits. Furthermore, no heating is provided in the cooling system there. WO 2018 / 009122 A1 discloses a cooling installation for a hybrid vehicle having three coolant circuits which are able to be operated at three different temperature levels, however, wherein the high-temperature coolant circuit only has an air cooling device in order to cool the internal combustion engine with the cooling liquid cooled thereby. Heating is not provided with the cooling installation there.

[0005] While the installation disclosed in US 2006 / 0032623 A1 is able to cool and heat air, the cooling installation has only a heating circuit and a switchable cooling or heating circuit in addition to the refrigerant circuit, so that the possibility does not exist that three temperature levels can be operated simultaneously therefrom. The heating and air conditioning installation disclosed in US 2012 / 0031140 A1 having a refrigerant circuit and three heating or cooling liquid circuits connected thereto via heat exchangers is only able to be operated simultaneously at a maximum of two temperature levels. The first high-temperature cooling liquid circuit is only used there for indirectly cooling the refrigerant with external air. Figure 6

[0006] While the installation disclosed in DE 10 2018 212 693 A1 is able to be operated at three different temperature levels, however, wherein the refrigerant circuit comprises only one condenser / gas cooler on its high-pressure side for heat exchange with a heating liquid of the heating circuit having one temperature level. In the high-temperature coolant circuit there, the temperature increase is mainly achieved by the waste heat of the internal combustion engine, so that the high-temperature level is not easily settable to be constant and for this the waste heat of the motor is required.

[0007] The heating and air conditioning installation disclosed in DE 10 2010 051 976 A1 is also able to be operated at three different temperature levels, however, wherein in the heating operation the heat for evaporation is only able to be obtained from the interior of the installation or vehicle. While the heating and air conditioning installation shown in US 2008 / 0041071 A1 is able to be operated at three temperature levels, no cooling circuit is contained, so that the refrigerant circuit has an evaporator in the air handling unit, which conflicts with a compact implementation of the refrigerant.

[0008] ​The facility for a vehicle disclosed in US 2017 / 0297414 A1 is able to be operated at three different temperature levels, but the refrigerant circuit does not contain an external heat exchanger.

[0009] A cooling device for a battery is disclosed in DE 102011105366 A1, which has a cooling circuit for the battery, which is thermally coupled to the air conditioning circuit of the vehicle via a latent heat store.

[0010] The circuit system for a vehicle disclosed in DE 102018129393 A1 and DE 102017118425 A1 has only one heating circuit connected to the refrigerant circuit and one cooling circuit connected to the refrigerant circuit.

[0011] The problem on which the invention presented herein is based is therefore that in the hitherto known heating and air conditioning facilities for a vehicle, heating and cooling at different temperature levels by means of the refrigerant circuit of the facility is not sufficient. It is therefore to be provided for an improved heating and air conditioning facility for a vehicle, in particular with regard to heating and cooling at different temperature levels.

[0012] The invention presented herein is based on the corresponding problem of a vehicle having such a heating and air conditioning facility. Furthermore, the invention presented herein is based on the corresponding problem of a method for controlling such a heating and air conditioning facility in a vehicle. SUMMARY

[0013] The problem underlying the invention presented herein is solved by the features specified hereinafter. The problem is solved by a heating and air conditioning installation having a first heating circuit for heating comprising at least one pump and having a cooling circuit comprising at least one pump and having a refrigerant circuit comprising at least a compressor, an expansion element, an external heat exchanger which can be operated as an evaporator in a heat pump operation, a first heat exchanger on the high-pressure side and a second heat exchanger on the low-pressure side which is accessed or can be accessed at least for an air conditioning operation, wherein the first heat exchanger is also connected to the first heating circuit and the second heat exchanger is also connected to the cooling circuit and in the first heat exchanger the refrigerant of the refrigerant circuit and the heating liquid of the first heating circuit are directly and / or via a possible first latent heat storage medium thermally coupled or can be thermally coupled by a heat exchange connection and in the second heat exchanger the refrigerant of the refrigerant circuit and the cooling liquid of the cooling circuit are directly and / or via a possible second latent heat storage medium thermally coupled or can be thermally coupled by a heat exchange connection, wherein the heating and air conditioning installation is designed for a vehicle, wherein the heating and air conditioning installation comprises a second heating circuit for heating comprising at least one pump, the refrigerant circuit comprises a third heat exchanger on the high-pressure side which is arranged downstream with respect to the first heat exchanger in a predefined refrigerant flow direction and the third heat exchanger is also connected to the second heating circuit, wherein in the third heat exchanger the refrigerant of the refrigerant circuit and the heating liquid of the second heating circuit are directly and / or via a possible third latent heat storage medium thermally coupled or can be thermally coupled by a heat exchange connection.

[0014] The heating and air conditioning installation has the advantage that for heating the second heating circuit can be operated at a lower temperature level than the first heating circuit. Furthermore, the cooling circuit can be operated at a third, even lower temperature level. The refrigerant of the refrigerant circuit is advantageously used as a heat source and as a cold source for this purpose. There is no need for the waste heat of the drive motor of the vehicle to be used as an additional heat source. The respective temperature levels can be set constant by means of the heating and air conditioning installation for heating and cooling. In the heat pump operation, i.e. in the heating operation, the external heat exchanger of the refrigerant circuit can advantageously be operated as an evaporator. Thereby, the heat required for evaporation can be obtained directly from the outside air. The operation of the installation is uncomplicated and relatively cost-effective, in particular due to the only one refrigerant circuit. The heat exchangers of the refrigerant circuit do not have to be located directly in the air handling region of the interior space of the vehicle, which allows a more compact design of the refrigerant circuit.

[0015] The external heat exchanger is a heat exchanger which exchanges heat with the outside air.

[0016] The latent heat storage medium is a heat storage medium which can store latent heat. However, this does not exclude that sensible heat can be stored therein. Typically, the latent heat storage medium is composed of a phase change material.

[0017] Advantageous design proposals, improvements and refinements of the respective subject matter of the application are given herein.

[0018] Preferably, the first heat exchanger in the refrigerant circuit is configured as a desuperheater for a first temperature level, and the third heat exchanger in the refrigerant circuit is configured as a subcooler for a lower second temperature level. Thus, the simultaneous heating by means of two heating circuits at different temperature levels can be achieved in a simple manner via the heat exchange of the high-pressure side of the refrigerant circuit.

[0019] According to an advantageous design proposal, the first heat exchanger and / or the second heat exchanger and / or the third heat exchanger are also configured as latent heat stores with a respective latent heat storage medium, and their latent heat storage medium(s) are thermally coupled or thermally couplable via the heat exchange connection on the one hand to the refrigerant of the refrigerant circuit and on the other hand to the respective cooling liquid or heating liquid of the respective cooling circuit or the first or second heating circuit. Thus, cold or heat is effectively stored in the respective first, second and / or third heat exchanger. Said cold or heat can then be output, for example, to the respective cooling or heating liquid of the respective cooling circuit or the first or second heating circuit. Thus, the thermal management is more flexible. Part load operation of the facility is also improved thereby. For example, when the refrigerant circuit is switched off, heating or cooling can continue by means of the stored heat or cold.

[0020] Embodiments of the heating and air conditioning facility according to the application are also advantageous in which the first heat exchanger and / or the second heat exchanger and / or the third heat exchanger are configured as tube-fin heat exchangers. Latent heat storage media such as xylitol or paraffin can be easily introduced into such heat exchangers, so that an indirect thermal coupling via the respective latent heat storage medium between the refrigerant of the refrigerant circuit and the heating liquid or cooling liquid of the respective heating or cooling circuit is achieved.

[0021] According to a further advantageous design proposal of the heating and air conditioning facility according to the application, the first heat exchanger and / or the second heat exchanger and / or the third heat exchanger are configured as plate heat exchangers. In such liquid-refrigerant heat exchangers, a direct thermal coupling of the heating liquid or cooling liquid and the refrigerant of the refrigerant circuit via the plates as a direct heat exchange connection is particularly effective.

[0022] Preferably, the refrigerant circuit is configured such that it can be operated transcritically with a refrigerant. Thus, a smooth temperature profile can be achieved in the refrigerant circuit at the high-pressure side at constant pressure. In particular, for this purpose, CO2 is suitable as a low-cost and harmless refrigerant for the refrigerant circuit.

[0023] According to an advantageous design, the heating and air-conditioning installation according to the application is designed in such a way that the heating and air-conditioning installation can be operated in such a way that in the first heat exchanger the refrigerant of the refrigerant circuit has a maximum temperature of more than 40°C, while in the third heat exchanger the refrigerant has a maximum temperature in the range of 15°C up to 40°C, the limits included. Thus, the first and second heating circuits can be operated at significantly different temperature levels, wherein the temperature level of the first heating circuit is very suitable for heating by means of a convector, while the temperature level of the second heating circuit is very suitable for heating by means of an air-liquid heat exchanger in the area of the vehicle roof.

[0024] It is preferred that the external heat exchanger of the heating and air-conditioning installation is arranged downstream of the third heat exchanger in the intended refrigerant flow direction and is designed in such a way that the external heat exchanger air-refrigerant heat exchanger can be operated as an evaporator for a heat pump operation and as a gas cooler for an air-conditioning operation. Thus, the external heat exchanger enables a heat exchange of the refrigerant with the outside air in the air-conditioning operation and the heat pump operation of the heating and air-conditioning installation. It is particularly advantageous here that an embodiment in which the external heat exchanger has two separate refrigerant lines in two refrigerant line bundles, wherein in one refrigerant line bundle an expansion element is arranged upstream of the external heat exchanger in the intended refrigerant flow direction and in the other refrigerant line bundle a second expansion element is arranged downstream of the external heat exchanger in the intended refrigerant flow direction and a second heat exchanger is arranged further downstream and the two refrigerant line bundles are at least alternatively switchable in a parallel connection to each other by means of at least one valve arranged downstream of the third heat exchanger in the intended refrigerant flow direction. Thus, one refrigerant line is arranged in the external heat exchanger separately from the other for the evaporator operation, while the other refrigerant line is arranged for the gas cooler operation of the external heat exchanger. It is preferred that the external heat exchanger in the refrigerant circuit can be operated as a hybrid heat exchanger simultaneously as an evaporator and a gas cooler and the size proportion of the refrigerant flow can be adjusted by means of the two refrigerant line bundles. Thus, the heating and air-conditioning installation can advantageously be operated in an adjustable hybrid operation between a pure heat pump operation and a pure air-conditioning operation. The adjustment takes place here, for example, in the refrigerant circuit immediately downstream of the third heat exchanger via an adjustable three-way valve.

[0025] According to an advantageous refinement of the heating and air-conditioning installation according to the application, the first heating circuit further comprises at least one convector for positioning in the floor region of the vehicle interior and / or at least one air-liquid heat exchanger for heating air of the driver's seat region. It is thus ensured that the convector and / or the driver's seat heat exchanger are operated with sufficiently hot heating liquid. Preferably, the second heating circuit further comprises at least one air-liquid heat exchanger for positioning in the roof region for heating air of the vehicle interior or of a region of the vehicle interior. The sufficient heating of the air is thus achieved with not too hot heating liquid.

[0026] According to an advantageous design, the cooling circuit further comprises at least one air-liquid heat exchanger for cooling air for the vehicle interior or for a region of the vehicle interior. The air in the vehicle interior can thus be efficiently cooled.

[0027] According to an advantageous refinement of the heating and air-conditioning installation according to the application, the heating and air-conditioning installation comprises a regulating device for controlling the heating and air-conditioning installation. The installation can thus be controlled automatically. Preferably, the regulating device is designed to control the switching of the refrigerant circuit between air-conditioning operation and heat pump operation and to control the pumps of the first and second heating circuits and of the cooling circuit in terms of pump power and / or to control the respective temperatures of the respective heating and cooling liquids by means of the measurement data of the temperature sensors and / or to control the power of the compressor and / or to control the expansion element(s). The installation can thus be controlled particularly flexibly and automatically.

[0028] According to an advantageous embodiment, the first and third heat exchangers are part of a heat exchanger unit, which as a compact construction type saves space and material.

[0029] Finally, the features of the embodiments of the heating and air-conditioning installation according to the application can essentially be freely combined with one another and are not combined in the order present in the description, as long as the features are independent of one another and do not exclude one another.

[0030] The problem underlying the vehicle according to the application presented herein is solved by a vehicle, in particular a bus or a rail vehicle, having a heating and air-conditioning installation according to the application. The above explanations regarding the heating and air-conditioning installation according to the application apply accordingly with regard to further advantages and advantageous embodiments and refinements. It is particularly advantageous to have an electric or hybrid vehicle having a heating and air-conditioning installation according to the application.

[0031] The problem underlying the method according to the application given herein is solved by a method for controlling a heating and air conditioning installation according to the application in a vehicle for heating and / or cooling air for one or more vehicle interior spaces or vehicle interior space regions, in which, for heating, a first heating circuit is operated at a higher temperature level than a second heating circuit. Thus, heating is advantageously carried out at two different temperature levels at the same time by means of the refrigerant circuit via the heating liquid, wherein cooling at a third temperature level is additionally possible.

[0032] As regards further advantages and advantageous embodiments and improvements, the above explanations in this respect regarding the heating and air conditioning installation according to the application apply accordingly. BRIEF DESCRIPTION OF DRAWINGS

[0033] Embodiments of the application are set forth according to the drawings.

[0034] The drawings show:

[0035] Figure 1 A block diagram showing one embodiment of a heating and air conditioning installation for a vehicle;

[0036] Figure 2 A block diagram showing another embodiment of a heating and air conditioning installation for a vehicle;

[0037] Figure 3 One embodiment of a first heat exchanger which is also configured as a latent heat store;

[0038] Figure 4 A pressure-enthalpy diagram showing a cycle with a refrigerant circuit in the case of operation of one embodiment of a heating and air conditioning installation according to the application;

[0039] Figure 5 A block diagram showing one embodiment of a first heating circuit of a heating and air conditioning installation according to the application;

[0040] Figure 6 A block diagram showing one embodiment of a second heating circuit of a heating and air conditioning installation according to the application;

[0041] Figure 7 A vehicle with a heating and air conditioning installation according to the application; and

[0042] Figure 8 A flow chart showing one embodiment of a method for controlling a heating and air conditioning installation according to the application. DETAILED DESCRIPTION

[0043] All drawings are to be understood as schematic. The drawings are not drawn true to scale in order to improve the clarity of the figures.

[0044] In Figure 1 a block diagram of one embodiment of a heating and air conditioning installation 1 for a vehicle is shown. The refrigerant circuit 3 has a compressor 5 which compresses the refrigerant. In this case it is an electrically driveable, optionally adjustable in terms of its rotational speed, compressor 5. It is also conceivable that the compressor 5 is able to be driven by the drive motor of the vehicle. The refrigerant is CO2, which operates trans-critically in the refrigerant circuit 3. The compressed refrigerant flows at high pressure and high temperature from the output of the compressor 5 through the refrigerant line into a first heat exchanger 7, which is provided as a desuperheater in the refrigerant circuit 3. The first heat exchanger is a liquid- refrigerant heat exchanger in the embodiment of a plate heat exchanger. It is also conceivable that another suitable type of heat exchanger. A first heating circuit 9 is also connected on the first heat exchanger 7, the heating liquid of which is water or for example a water-glycol mixture. In the first heat exchanger 7, which is constructed as a plate heat exchanger, the refrigerant of the refrigerant circuit is directly thermally coupled with the heating liquid of the first heating circuit 9 via a heat exchange connection. The heating liquid, which is heated there by means of the maximum temperature of the hot refrigerant of over 40°C in the heating operation of the heating and air conditioning installation 1, is circulated in the first heating circuit 9 by means of a pump 11, which is constructed as an adjustable water pump in this case, and is conveyed to a convector 13 in order to heat the air of the vehicle interior, which can be positioned or is positioned for example in the floor region of the vehicle interior.

[0045] A third heat exchanger 15 is provided on the high-pressure side, downstream of the first heat exchanger 7 in the direction of flow of the refrigerant, connected by refrigerant lines. The third heat exchanger is configured as a subcooler. The third heat exchanger is a liquid-refrigerant heat exchanger in the configuration of a plate heat exchanger. Another suitable type of heat exchanger is also conceivable. The third heat exchanger 15 is also connected to the second heating circuit 17, so that a thermal coupling between the refrigerant of the refrigerant circuit and the heating liquid of the second heating circuit 17 is present in the heat exchange connection. During the heating operation of the heating and air-conditioning installation 1, the maximum temperature of the refrigerant in the third heat exchanger 15 is in the range between 15°C and 40°C, inclusive of the boundary values, i.e. lower than the temperature in the first heat exchanger 7. The heating liquid of the second heating circuit 17 is therefore not as hot as the heating liquid of the first heating circuit 9, which enables simultaneous heating by means of the heating and air-conditioning installation 1 at two different temperature levels. The heating liquid of the second heating circuit 17 is water or, for example, a water-glycol mixture, and does not necessarily have to be of the same type as the heating liquid of the first heating circuit 9. By means of the second heating circuit 17, the heating medium is pumped by means of a pump 19, which is configured as a water pump that is adjustable in this case, and is conveyed to an air-liquid heat exchanger 21 in order to heat the air of the vehicle interior, which can be positioned or is positioned, for example, in the roof region of the vehicle interior.

[0046] In a conceivable variant, the first heat exchanger 7 and the third heat exchanger 15 downstream of it can be configured as part of a heat exchanger unit.

[0047] In the refrigerant circuit 3, there is a branch 23 immediately downstream of the third heat exchanger 15 in the refrigerant flow direction on the high-pressure side, which divides into two refrigerant line bundles 25a and 25b. The refrigerant line bundle 25a provided especially for the heat pump operation, i.e. the heating operation, of the heating and air-conditioning installation 1 is guided through an optional first internal heat exchanger 27 to a first expansion element 29, which is used especially for expanding the refrigerant. In this case, the first expansion element 29 is configured as an adjustable expansion valve, which can also be used as a shut-off valve. It is also conceivable to provide a shut-off valve and a thermostatic expansion valve in series in the refrigerant circuit 3. In the refrigerant line bundle 25a on the low-pressure side downstream of the first expansion element 29, there is a refrigerant line 33 which is guided through an external heat exchanger 31, which serves as an evaporator region. The cooled refrigerant flowing through the external heat exchanger 31 is evaporated by expansion when exchanging heat with the outside air. In this case, the external heat exchanger 31 is an air-refrigerant heat exchanger, which is configured for the heat exchange of outside air and refrigerant of the refrigerant circuit 3. The refrigerant line bundle 25a continues on the low-pressure side from the external heat exchanger 31 through the optional first internal heat exchanger 27 to the input of the compressor 5, wherein the two refrigerant line bundles 25a and 25b are combined again before this. The other refrigerant line bundle 25b provided especially for the air-conditioning operation of the heating and air-conditioning installation 1 is guided in the refrigerant flow direction on the high-pressure side from the branch 23 to a switchable valve 35 and again through a second refrigerant line 37 of the external heat exchanger 31, which serves as a gas cooler region. The refrigerant flowing through there is further cooled by heat exchange with the outside air. Thus, the external heat exchanger 31 can be operated as an evaporator in one refrigerant line bundle 25a and as a gas cooler in the other refrigerant line bundle 25b. The two refrigerant lines 33 and 37 run separately in the external heat exchanger 31.

[0048] It is also conceivable to provide a variant with two external heat exchangers 31, wherein one external heat exchanger can be operated as an evaporator and the other external heat exchanger can be operated as a gas cooler.

[0049] The refrigerant line bundle 25b, which is provided for the air conditioning operation, continues from the external heat exchanger 31 on the high-pressure side through the optional internal second heat exchanger 39 to a second expansion element 41, which in this case is configured as an adjustable expansion valve. It is also conceivable that another common suitable type of expansion element 41 is provided. In the refrigerant circuit 3 on the low-pressure side downstream of the second expansion element 41, a second heat exchanger 43 is provided, which is connected via refrigerant lines, in which the refrigerant flowing there through is evaporated, which is pre-cooled by expansion. In this case, the second heat exchanger 43 is a liquid-refrigerant heat exchanger, which is configured as a plate heat exchanger, which is also connected to a cooling circuit 45. In the second heat exchanger 43, the refrigerant of the refrigerant circuit 3 is thermally coupled or thermally couplable to the cooling liquid of the cooling circuit 45 by means of a heat exchange connection. In the air conditioning operation of the heating and air conditioning installation 1, the cooling liquid is cooled there and is conveyed to an air-liquid heat exchanger 49, which is also provided in the cooling circuit 45, by means of an adjustable pump 47 integrated in the cooling circuit 45, which, for example, can be positioned or has been positioned in the roof region of the vehicle interior. It is also conceivable that a larger number of air-liquid heat exchangers 49 for cooling in the cooling circuit 45. It is also conceivable that heat exchangers for cooling vehicle components, for example a battery, are also integrated in the cooling circuit 45. Thus, it is possible to heat and cool by means of the heating and air conditioning installation 1 in three different temperature levels via the first heating circuit 9, the second heating circuit 17 and the cooling circuit 45, which are all thermally coupled to the refrigerant circuit 3, wherein this can even be achieved at the same time.

[0050] The refrigerant line bundle 25b, which is provided for the air conditioning operation, continues from the second heat exchanger 43 through the optional internal second heat exchanger 39 on the low-pressure side back to the input of the compressor 5.

[0051] The heating and air conditioning installation 1 is provided for a vehicle, for example a bus or a rail vehicle. Such a vehicle can be, for example, a hybrid vehicle or a purely electric vehicle.

[0052] The heating and air conditioning installation 1 is controlled by means of a regulating device 50. In this case, the regulating device comprises a processor for automatic control. The processor regulates the two expansion elements 29 and 41, the valves 35, the pumps 11, 19 and 47 and the power of the compressor 5.

[0053] The regulating device is configured to receive measurement signals of temperature sensors, which are not shown in Figure 1 , for example for the outside air temperature and the vehicle interior temperature.

[0054] In Figure 2A block diagram of another embodiment of a heating and air conditioning system 1 for a vehicle is shown. The heating and air conditioning system 1 corresponds to... Figure 1 The heating and air conditioning system shown in the figure, however, includes first, second, and third heat exchangers 7, 43, and 15, which also constitute latent heat storage tanks. Reference numerals and components indicated by reference numerals correspond to... Figure 1 The reference numerals and components are shown in the accompanying drawings. Thus, on a compressor 5, two expansion elements 29 and 41, a switchable valve 35, an external heat exchanger 31 that can operate as both an evaporator and a gas cooler, and a refrigerant circuit 3 including two internal heat exchangers 27 and 39 are thermally coupled via a first heat exchanger 7 of a first heating circuit 9, a third heat exchanger 15 of a second heating circuit 17, and a second heat exchanger 43 of a cooling circuit 45.

[0055] A variant with two external heat exchangers 31 is also conceivable, one of which can operate as an evaporator and the other as a gas cooler.

[0056] The first heat exchanger 7 includes a first latent heat storage medium 14, which is disposed between the refrigerant line and the heating liquid line of the first heat exchanger 7. The first heat exchanger is configured as a tube-blade heat exchanger. Another type of heat exchanger with a first latent heat storage medium 14 is also conceivable, such as a plate heat exchanger with a first latent heat storage medium layer 14 located between a layer guiding the refrigerant and a layer guiding the heating liquid. In this case, the first latent heat storage medium 14 is paraffin wax as a phase change material, with a melting point in the range of approximately 60°C. Another first latent heat storage medium 14 suitable for the high-temperature region of the first heat exchanger 7 is also conceivable, such as sugar alcohols, especially xylitol, or hydrides with sufficiently high melting temperatures. The refrigerant of the refrigerant circuit 3 is thermally coupled to the heating liquid of the first heating circuit 9 in the first heat exchanger 7 via the first latent heat storage medium 14.

[0057] The second heat exchanger 43 includes a second latent heat storage medium 14a, which is disposed between the refrigerant line and the cooling liquid line of the second heat exchanger 43. The second heat exchanger is configured as a tube-blade heat exchanger. Another type of heat exchanger with a second latent heat storage medium 14a is also conceivable. In this case, the second latent heat storage medium 14a of the second heat exchanger 43 is water, allowing the second heat exchanger 43 to be used as an ice reservoir. Another second latent heat storage medium 14a suitable for the low-temperature region of the second heat exchanger 43 is also conceivable, such as an aqueous salt solution. The refrigerant of the refrigerant circuit 3 is thermally coupled to the cooling liquid of the cooling circuit 17 in the second heat exchanger 43 via the second latent heat storage medium 14a.

[0058] The third heat exchanger 15 contains a third latent heat storage medium 14b which is arranged between the refrigerant line and the heating liquid line of the third heat exchanger 15. The third heat exchanger is configured as a tube-fin heat exchanger. It is also conceivable that another type of heat exchanger with a third latent heat storage medium 14b. In this case, the third latent heat storage medium 14b of the third heat exchanger 15 is a paraffin with a melting temperature of approximately 40°C which is lower than the latent heat storage medium in the first heat exchanger 7. It is also conceivable that another third latent heat storage medium 14b which is suitable for the medium temperature range of the third heat exchanger 15 as a phase change material, such as a hydrogenated salt with a melting temperature of approximately 40°C. The refrigerant of the refrigerant circuit 3 is thermally coupled via the third latent heat storage medium 14b in the third heat exchanger 15 to the heating liquid of the second heating circuit 17.

[0059] The heating and air conditioning installation 1 is controlled by means of a regulating device 50. In this case, the regulating device comprises a processor for automatic control. The processor regulates the power of the two expansion elements 29 and 41, the valves 35, the pumps 11, 19 and 47 and the compressor 5. The regulating device is configured to receive measurement signals about the stored heat and cold in the latent heat storage media 14, 14a and 14b of the first, second and third heat exchangers 7, 43 and 15 and measurement signals of temperature sensors which are not shown in Figure 2 for the outside air temperature and the temperature of the vehicle interior.

[0060] It is also conceivable as a variant of the heating and air conditioning installation 1 according to the application a hybrid form of the embodiments shown in Figure 1 and Figure 2 , i.e. such that only one or two of the first, second and third heat exchangers 7, 43 and 15 are configured as latent heat stores, for example only the third heat exchanger 15 with the third latent heat storage medium 14b.

[0061] In Figure 3One embodiment of the first heat exchanger 7, which is also configured as a latent heat store, is shown in Fig. 1. In this case, the first heat exchanger is a tube-vane heat exchanger. A tubular refrigerant line 8 for the refrigerant of the refrigerant circuit is guided through a first latent heat storage medium 14 in a lower region of the first heat exchanger 7, which in this case is a paraffin having a high melting temperature in the range from 60° to 100°C. A tube 10 for the heating liquid of the first heating circuit likewise extends through the first latent heat storage medium 14 in an upper region of the first heat exchanger 7 parallel to the refrigerant line 8. A plurality of plate-like vanes 12 arranged parallel to one another are located in a plane perpendicular to the longitudinal axes of the refrigerant line 8 and of the tube 10 for the heating liquid. The plate-like vanes are composed of a good heat-conducting material, for example aluminum or copper. The vanes 12 are in heat-conducting connection with the refrigerant line 8 and with the tube 10 for the heating liquid and also with the first latent heat storage medium 14.

[0062] In principle, the second and third heat exchangers can also be configured in the same way as the first heat exchanger 7, with the use of latent heat storage media suitable for the respective predetermined temperature range, for example water in the second heat exchanger and paraffin having a melting temperature of approximately 40°C in the third heat exchanger.

[0063] In Figure 4A pressure-enthalpy diagram with a cycle of the refrigerant circuit in operation of an embodiment of the heating and air conditioning installation according to the application is shown in Fig. 1. The isotherms are plotted in the right-hand part of the diagram. The refrigerant is CO2. By compression in the compressor, the CO2 reaches a high pressure and a high temperature from point E to point A. In this case, the cooling of the refrigerant CO2 on the line from point A to point C is in a smooth temperature change curve from 90°C down to 15°C at a constant high pressure of about 90 bar. Here, the refrigerant CO2 remains above the critical point. The high pressure of the refrigerant CO2 above the critical point is achieved, for example, by means of a corresponding liquid level displacement in the refrigerant circuit. From the refrigerant CO2 in the first heat exchanger, heat is emitted to the heating liquid of the first heating circuit, which is the high temperature circuit, in the temperature range (HT) from about 65°C down to about 43°C on the line between point A to point B. In this case, the heating liquid is water. Since the heating liquid in the first heating circuit is above 40°C in operation, the heat emission is limited so that the temperature of the refrigerant CO2 in the first heat exchanger cannot fall below the 40°C isotherm. In the third heat exchanger, the refrigerant further emits heat on the high pressure side to the heating liquid of the second heating circuit in the medium temperature range (MT) between 40°C and 15°C on the line between point B to point C. With the expansion following in the cycle plotted in the expansion element, the pressure of the refrigerant drops sharply to point D and its temperature drops significantly in an adiabatic manner. On the low pressure side from point D to point E, in the cycle plotted in the diagram, the enthalpy of the refrigerant is increased, in particular by evaporation, for example in an external heat exchanger, until finally in the circuit in the diagram again point E is reached. Point E in the refrigerant circuit corresponds to the state of the refrigerant at the input of the compressor.

[0064] In Figure 5A block diagram of one embodiment of a first heating circuit 9 of a heating and air conditioning installation according to the application is shown in Fig. 1. In the first heating circuit 9, a heating liquid is circulated in the heating operation by means of a pump 11. The heating liquid is water or a water-glycol mixture. Other suitable heating liquids are also conceivable. The first heating circuit 9 is a high-temperature circuit. The heating liquid is operated at a temperature level of more than 40°C. For this purpose, the first heating circuit 9 is connected to a first heat exchanger 7. The first heat exchanger is incorporated in the refrigerant circuit of the heating and air conditioning installation as a desuperheater directly after the output of the compressor, so that the compressed refrigerant, for example CO2, is particularly hot there in order to exchange heat with the heating liquid. In this case, the first heat exchanger 7 is a liquid-refrigerant heat exchanger which is designed as a plate heat exchanger. A design variant as a heat exchanger with a first latent heat storage medium, for example a sugar alcohol, is also conceivable. In this variant, the first heat exchanger 7 is also a latent heat store. The pump 11 is an adjustable electric pump. The pump pumps the heating liquid in the first heating circuit 9 through the first heat exchanger 7 and then, if the electric auxiliary heater 51 is switched on, through the electric auxiliary heater 51, which can be switched on if the heating liquid is to be additionally heated. Along the flow direction of the heating liquid after the electric auxiliary heater 51, the liquid line branches at a first branch 53, wherein one liquid line bundle 55a runs to an adjustable valve 57 for regulating the flow quantity through the downstream convector 13. The convector 13 is designed to be able to be positioned in the floor region of the vehicle interior. This liquid line bundle 55a is guided from the output of the convector 13 back to the input of the pump 11. After the branch 53 at the three-way valve 59, the other liquid line bundle 55b branches into two switchable line branches, wherein one of the line branches runs directly to the input of the pump 11, while the other line branch still runs through a driver's seat heat exchanger 61 before it reaches the input of the pump 11 in order to heat the region of the driver's seat. In this case, the three-way valve 59 can be adjusted. The three-way valve is designed in such a way that the two line branches 5 branching off from it can be opened and closed independently of one another in order to flow the heating liquid through. The first heating circuit 9 can be controlled by adjusting the pump 11, the valve 57, the auxiliary heater 51 and the three-way valve 59.

[0065] In Figure 6A block diagram of one embodiment of a second heating circuit 17 of a heating and air conditioning installation according to the application is shown in Fig. 2. In the second heating circuit 17, a heating liquid is circulated in the heating operation by means of a pump 19. The heating liquid is water or a water-glycol mixture. Other suitable heating liquids are also conceivable. The second heating circuit 17 is a medium-temperature circuit. The temperature level is lower than that of the first heating circuit. The maximum pre-start temperature of the heating liquid is at 40°C or below. The post-start temperature is operated at a temperature level in the range of 15°C to 30°C, inclusive. To this end, the second heating circuit 17 is connected to a third heat exchanger 15. Said third heat exchanger is incorporated in the refrigerant circuit of the heating and air conditioning installation as a subcooler behind the first heat exchanger on the high-pressure side, so that the compressed refrigerant, for example CO2, is not as hot there for heat exchange with the heating liquid as in the first heat exchanger. In this case, the third heat exchanger 15 is a liquid-refrigerant heat exchanger which is designed as a plate heat exchanger. A design variant as a heat exchanger with a third latent heat storage medium, for example paraffin, is also conceivable. In this variant, the third heat exchanger 15 is also a latent heat storage. The pump 19 is an adjustable electric pump. Said pump pumps the heating liquid in the second heating circuit 17 through the third heat exchanger 15 and then through an electric auxiliary heater 65 which can be switched on if the heating liquid is to be additionally heated. Along the flow direction of the heating liquid, behind the electric auxiliary heater 65, the liquid line branches at an adjustable three-way valve 67. One liquid line bundle 69a leads from the output of the three-way valve 67 directly back to the input of the pump 19. The other liquid line bundle 69b extends to two air-liquid heat exchangers 21 of a roof unit 70 which is provided for heating the air of the vehicle interior and which can be positioned or is positioned in or on the roof of the vehicle interior. Other numbers of air-liquid heat exchangers 21 are also conceivable depending on the power intensity and spatial relationship of the heating and air conditioning installation. After passing through the air-liquid heat exchangers 21, in the second heating circuit 15, the liquid line extends back to the input of the pump 19. By adjusting said pump 19, auxiliary heater 65 and three-way valve 67, the second heating circuit 17 can be controlled.

[0066] In Figure 7 A vehicle 81 is shown in Fig. 1 with a heating and air conditioning installation 1 according to the application. The heating and air conditioning installation 1 corresponds, for example, to one of the embodiments shown in Figure 1 or Figure 2 The vehicle 81 is a bus. The bus has a purely electric drive. A hybrid drive is also conceivable, for example. The refrigerant circuit 3 and its components are designed, for example, as in one of the embodiments shown in Figure 1The components described in 2 are located in the area of the roof 83. For heat exchange of the refrigerant with the outside air, an outside heat exchanger is located directly below the ventilation unit 85 on the roof 83. A first heating circuit 9, which is thermally connected on the high-pressure side via a first heat exchanger to the refrigerant circuit 3, leads through a convector 13 in the floor area of the passenger compartment 87, which is used to heat the air in the passenger compartment 87. The first heating circuit 9 and its components, such as in particular the pump, correspond to those described in Figure 1 and 2 . The first heating circuit is a high-temperature circuit.

[0067] A second heating circuit 17, which is thermally connected on the high-pressure side via a third heat exchanger to the refrigerant circuit 3, leads to an air-liquid heat exchanger 21 in the roof area of the passenger compartment 87, which is used to heat the air of the passenger compartment 87. The second heating circuit 17 and its components, such as in particular the pump, correspond to those described in Figure 1 and 2 . The second heating circuit is a medium-temperature circuit.

[0068] A cooling circuit 45, which is thermally connected on the low-pressure side via a second heat exchanger to the refrigerant circuit 3, leads to an air-liquid heat exchanger 49, which is also in the roof area of the passenger compartment 87, which is used to cool the air of the passenger compartment 87. The cooling circuit 45 and its components, such as in particular the pump, correspond to those described in Figure 1 and 2 . The cooling circuit is a low-temperature circuit.

[0069] The heating and air conditioning installation 1 is controlled by means of a regulating device 50. To this end, the regulating device receives measurement signals from an outside air temperature sensor 89 and a vehicle interior space temperature sensor 91.

[0070] A rail vehicle, for example a tram, can also be considered as a vehicle 81 with a heating and air conditioning installation 1 according to the application.

[0071] A flow chart of one embodiment of a method for controlling a heating and air conditioning installation according to the application of a vehicle, for example a bus, is shown in Figure 8 . The heating and air conditioning installation corresponds to that described in Figure 1As shown in the middle. Control takes place by means of a regulating device. In a first method step 100, the regulating device receives measurement data from temperature sensors for the temperature of the outside air and the temperature of the air in the vehicle interior, in particular in the passenger area. In a second method step 110, on the basis of the measured temperatures and a preset desired temperature, the regulating device decides whether the heating and air conditioning facility should remain in operation or be put into operation. If not, the heating and air conditioning facility is stopped as long as it is still in operation, and the method is restarted after a waiting time of, for example, one second. If, however, the result in the method step 110 is that the heating and air conditioning facility is switched on or remains switched on, it is decided in a next method step 120 whether the heating and air conditioning facility should be operated in a heat pump operation for heating or in an air conditioning operation for cooling. As long as the result of the heat pump operation is "yes", a valve which is embodied as a shut-off valve between the third heat exchanger and the gas cooler region of the outside heat exchanger in the refrigerant circuit is closed in a method step 130 for this purpose, a first expansion element for expansion of the refrigerant before the evaporator region of the outside heat exchanger is opened, and the compressor of the refrigerant circuit is switched on or remains switched on. In addition, the pump of the cooling circuit is switched off or remains switched off.

[0072] In a next method step 140, the pump of the first heating circuit which is a high-temperature circuit is switched on. As a result, a heating liquid flows through the first heating circuit at a temperature level of at least 40°C and, in turn, also through the convector in the floor region of the vehicle interior, which heats the air there, in a manner by heat exchange with hot refrigerant at high pressure which exceeds 40°C in the first heat exchanger which is embodied as a desuperheater. The refrigerant is CO2.

[0073] In a method step 150, the pump of the second heating circuit is switched on. As a result, the heated heating liquid of the second heating circuit is circulated in the third heat exchanger which is embodied as a subcooler in the refrigerant circuit after the first heat exchanger, by means of an air-liquid heat exchanger in the roof region of the vehicle interior. There, the air of the vehicle interior is heated. The heating liquid, for example water, of the second heating circuit has a lower temperature level than the first heating circuit. The temperature of the heating liquid of the second heating circuit is located here between 15°C and 40°C. In the third heat exchanger, the temperature of the refrigerant at high pressure has already fallen into the range between 15°C and 40°C, so that the heating liquid of the second heating circuit is not heated to a higher temperature on heat exchange. It is also conceivable that the method steps 130, 140 and 150 do not take place one after the other, but simultaneously in parallel.

[0074] The method is then restarted after a waiting time of, for example, one second.

[0075] If, however, in the method step 120 the result of the air-conditioning run for cooling is "no", then in the subsequent method step 130A the first expansion element before the evaporator region of the external heat exchanger is closed and the valve, which is configured as a shut-off valve, is opened between the third heat exchanger and the gas cooler region of the external heat exchanger, and the compressor of the refrigerant circuit is switched on or remains switched on. Furthermore, the pumps of the first and second heating circuits are switched off or remain switched off. In step 140A the pump of the cooling circuit, which serves as a low-temperature circuit, is switched on or remains switched on. As a result, a cooling liquid circulates therein and flows through the second heat exchanger, which serves as an evaporator, in which the cooling liquid is cooled by means of heat exchange with the cold refrigerant of the refrigerant circuit, which evaporates on the low-pressure side. In this case, the cooling liquid is a glycol-water mixture. The cooling liquid, after its cooling, continues to flow through the air-liquid heat exchanger in the roof region of the vehicle interior, and there cools the air of the vehicle interior.

[0076] After a waiting time of, for example, one second, the method is restarted.

[0077] The method accordingly also operates the heating and air-conditioning installation shown in Figure 2 , however, wherein in the heat exchange from the refrigerant to the heating liquid of the first and second heating circuits and in the heat exchange from the refrigerant to the cooling liquid of the cooling circuit, an intermediate step of storing heat or cold in the respective latent heat storage medium of the first, second and third heat exchanger takes place.

Claims

1. A heating and air-conditioning installation (1) having a first heating circuit (9) for heating comprising at least one pump (11) and a cooling circuit (45) comprising at least one pump (47) and a refrigerant circuit (3) comprising at least a compressor (5), an expansion element, an external heat exchanger (31) which can be operated as an evaporator in a heat pump mode, a first heat exchanger (7) on the high-pressure side and a second heat exchanger (43) on the low-pressure side which is connected or connectable at least for air-conditioning operation, wherein the first heat exchanger (7) is also connected to the first heating circuit (9) and the second heat exchanger (43) is also connected to the cooling circuit (45), and in the first heat exchanger (7) the refrigerant of the refrigerant circuit (3) is thermally coupled to the heating liquid of the first heating circuit (9) by a heat exchange connection directly or via a first latent heat storage medium (14), and in the second heat exchanger (43) the refrigerant of the refrigerant circuit (3) is thermally coupled to the cooling liquid of the cooling circuit (45) by a heat exchange connection directly or via a second latent heat storage medium (14a), wherein the heating and air-conditioning installation (1) is designed for a vehicle, characterized in that - the heating and air-conditioning installation (1) comprises a second heating circuit (17) for heating comprising at least one pump (19), - the refrigerant circuit (3) comprises a third heat exchanger (15) on the high-pressure side which is arranged downstream in a predetermined refrigerant flow direction with respect to the first heat exchanger (7), - the third heat exchanger (15) is also connected to the second heating circuit (17), wherein in the third heat exchanger (15) the refrigerant of the refrigerant circuit (3) is thermally coupled to the heating liquid of the second heating circuit (17) by a heat exchange connection directly or via a third latent heat storage medium (14b), - the external heat exchanger (31) is arranged downstream of the third heat exchanger (15) in the predetermined refrigerant flow direction and is designed such that the external heat exchanger (31) can be operated as an evaporator as an air-refrigerant heat exchanger for the heat pump mode and as a gas cooler for air-conditioning operation, - the external heat exchanger (31) has two separate refrigerant lines (33, 37) of two refrigerant line bundles (25a, 25b), wherein in one refrigerant line bundle (25a) the expansion element (29) is arranged upstream of the external heat exchanger (31) in the intended refrigerant flow direction and in the other refrigerant line bundle (25b) a second expansion element (41) is arranged downstream of the external heat exchanger (31) in the intended refrigerant flow direction and a second heat exchanger (43) is arranged more downstream and the two refrigerant line bundles (25a, 25b) are alternatively switchable in a parallel connection to one another by means of at least one valve (35) arranged downstream of the third heat exchanger (15) in the intended refrigerant flow direction, and - the external heat exchanger (31) in the refrigerant circuit (3) is capable of operating as a hybrid heat exchanger both as an evaporator and as a gas cooler and the size proportion of the refrigerant flow can be adjusted by means of the two refrigerant line bundles (25a, 25b).

2. The heating and air conditioning installation (1) according to claim 1, characterized in that the first heat exchanger (7) in the refrigerant circuit (3) is designed as a desuperheater for a first temperature level and the third heat exchanger (15) in the refrigerant circuit (3) is designed as a subcooler for a second temperature level, wherein the second temperature level is lower than the first temperature level.

3. The heating and air conditioning installation (1) according to claim 1 or 2, characterized in that the first heat exchanger (7) and / or the second heat exchanger (43) and / or the third heat exchanger (15) are also designed as a latent heat store with a corresponding latent heat storage medium (14, 14a, 14b) and the latent heat storage medium (14, 14a, 14b) of the latent heat store is thermally coupled, on the one hand, to the refrigerant of the refrigerant circuit (3) and, on the other hand, the latent heat storage medium of the second heat exchanger (43) is thermally coupled to the cooling liquid of the cooling circuit (45) and / or the latent heat storage medium of the first heat exchanger (7) is thermally coupled to the heating liquid of the first heating circuit (9) and / or the latent heat storage medium of the third heat exchanger (15) is thermally coupled to the heating liquid of the second heating circuit (17).

4. The heating and air conditioning installation (1) according to claim 1 or 2, characterized in that the first heat exchanger (7) and / or the second heat exchanger (43) and / or the third heat exchanger (15) are designed as a tube-fin heat exchanger or as a plate heat exchanger.

5. The heating and air conditioning installation (1) according to claim 1 or 2, characterized in that the refrigerant circuit (3) is designed in such a way that the refrigerant circuit can be operated transcritically with a refrigerant.

6. The heating and air conditioning installation (1) according to claim 5, characterized in that the refrigerant of the refrigerant circuit (3) is CO2.

7. The heating and air-conditioning installation (1) according to claim 1 or 2, characterized in that the first heating circuit (9) further comprises at least one convector (13) for positioning in the floor region of the vehicle interior (87) and / or also at least one air-liquid heat exchanger (61) for heating air of the driver's seat region, and the second heating circuit (17) further comprises at least one air-liquid heat exchanger (21) for positioning in the region of the vehicle roof (83) for heating air of the vehicle interior (87) or of a vehicle interior region.

8. The heating and air-conditioning installation (1) according to claim 1 or 2, characterized in that the cooling circuit (45) further comprises at least one air-liquid heat exchanger (49) for cooling air for the vehicle interior (87) or for a vehicle interior region.

9. The heating and air-conditioning installation (1) according to claim 1 or 2, characterized in that the heating and air-conditioning installation comprises a regulating device (50) for controlling the heating and air-conditioning installation (1).

10. The heating and air-conditioning installation (1) according to claim 9, characterized in that the regulating device (50) is designed for controlling the switching of the refrigerant circuit (3) between air-conditioning operation and heat pump operation and controlling the pumps (11, 19) of the first heating circuit (9) and of the second heating circuit (17) and the pump (47) of the cooling circuit (45) in terms of pump power, and / or controlling the respective temperature of the respective heating and cooling liquid by means of the measurement data of a temperature sensor, and / or controlling the power of the compressor (5), and / or controlling one or more of the expansion element (29) and the second expansion element (41).

11. The heating and air-conditioning installation (1) according to claim 1 or 2, characterized in that the first heat exchanger (7) and the third heat exchanger (15) are designed as part of a heat exchanger unit.

12. A vehicle (81) having a heating and air-conditioning installation (1) according to any one of claims 1 to 11.

13. The vehicle (81) according to claim 12, characterized in that the vehicle is a bus or a rail vehicle.

14. The vehicle (81) according to claim 12, characterized in that the vehicle is an electric or hybrid vehicle.

15. A method for controlling a heating and air-conditioning installation (1) according to any one of claims 1 to 11 for heating and / or cooling air for one or more vehicle interiors (87) or vehicle interior regions in a vehicle (81) according to any one of claims 12 to 14, wherein, for heating, the first heating circuit (9) is operated at a higher temperature level than the second heating circuit (17) at the same time.

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