DE102015222806A1 - HEATING SYSTEM AND METHOD FOR AIR-CONDITIONING A VEHICLE - Google Patents

Abstract

The invention relates to a heating system (2) for a vehicle, in particular for a hybrid vehicle, with a waste heat heating operation and an alternative heating operation and with an HT cooling circuit (4) for cooling an internal combustion engine (6) of the vehicle, the HT Cooling circuit (4) has a cooling circuit (8) and a heating circuit (10), which are hydraulically coupled to each other via a Heizkreisvorlauf (12) and a Heizkreisrücklauf (14), wherein in the cooling circuit (8) of the internal combustion engine (6) is arranged and in the heating circuit (10) a heating heat exchanger (18) and a heat source (20), for indoor heating. The heating circuit (10) is divided into a heating branch (26), in which the heating heat exchanger (18) is arranged, and in a return branch (28), for the return of coolant in the heating circuit (10), wherein in the return branch (28) is a passive Locking device (32) is arranged for automatically shutting off the return branch (28) in the waste heat heating operation. The heating system (2) is structurally particularly simple due to the special interconnection and manages with a reduced number of actively controlled and energized valves. Furthermore, a method for the air conditioning of a vehicle with a corresponding heat system (2) is specified.

Description

The invention relates to a heating system and a method for air conditioning a vehicle.

In the air conditioning of a vehicle usually its interior, also called passenger compartment, conditioned by means of a heating system, d. H. if necessary, heated or cooled. For this purpose, the heating system typically has a cooling unit, z. As a climate evaporator, which is connected to a refrigerant circuit, and a heating unit, often a heating heat exchanger, which is connected to a cooling circuit and is supplied with warm coolant.

In conventional vehicles with internal combustion engine, this is available throughout as a heat source. In alternative drive concepts, however, other solutions must be used regularly. The heat used for heating is then usually depending on the current driving mode of the vehicle from different heat sources, between which must be switched in a suitable manner. The Verschaltungsungs- and the control effort of the heating system are increased accordingly and the entire heating system is therefore more expensive and more expensive.

Against this background, it is an object of the invention to provide an improved heating system, which has the simplest possible interconnection and, in particular, is to be controlled as simply as possible, d. H. as easy as possible to switch between different companies. In particular, the heating system should be suitable for use in a hybrid vehicle. In addition, a method for the air conditioning of a vehicle by means of a corresponding heat system to be specified.

The object is achieved by a heating system with the features of claim 1 and by a method having the features of claim 9. Advantageous embodiments, developments and variants are the subject of the dependent claims. The remarks in connection with the heating system apply mutatis mutandis to the process and vice versa.

The heating system is for air conditioning of a vehicle, in particular a hybrid vehicle, and has for this purpose a waste heat heating operation and an alternative heating operation. The heating system further includes a HT refrigeration cycle, i. H. a high-temperature cooling circuit, for cooling an internal combustion engine of the vehicle, wherein the HT cooling circuit in turn has a cooling circuit and a heating circuit, which are hydraulically coupled to each other via a heating circuit and a Heizkreisrücklauf so that can be exchanged between these coolant. The coolant is, for example, water or a water / glycol mixture. The internal combustion engine is arranged in the cooling circuit and, in particular, a radiator is also connected to the cooling circuit for heat exchange with the surroundings of the vehicle. In the heating circuit, a heating heat exchanger is arranged, for interior heating, and a particular switchable heat source.

The heating heat exchanger is used primarily for heating air, which is supplied to the vehicle interior for heating the interior. The air is outdoor air, indoor air or a mixture of both, d. H.

Mixed air. The heating heat exchanger is thus generally designed as a coolant / air heat exchanger.

The heating circuit is connected at a first branch to the heating circuit flow and at a second branch to the heating circuit return and divided by the two branches into two branches, namely in a heating branch, in which the heating heat exchanger is arranged, and in a return branch, for the return of coolant in the heating circuit. In this case, the heating circuit is connected via the heating circuit flow in particular downstream of the internal combustion engine and upstream of the radiator to the cooling circuit, so that with respect to the flow direction of the coolant, the heating heat exchanger is connected in parallel to the radiator. Downstream of the internal combustion engine therefore a branch is formed in the cooling circuit, which leads on the one hand via the heating circuit flow to the heating circuit and on the other hand to the radiator, so that the waste heat from the engine can be advantageously distributed as needed in these two directions.

In the heating circuit, a heating circuit pump is further arranged, which is active in the alternative heating operation, so that coolant circulates in the heating circuit and is routinely passed through the heat source and the heating heat exchanger to supply heat from the heat source to the heating heat exchanger.

In the return branch upstream of the first branch and downstream of the second branch a passive locking device is arranged for automatically shutting off the return branch in the waste heat heating operation. "Passive" is generally understood in particular that no active or electronic control of the component concerned takes place, but this rather reacts automatically, automatically and passively to changing environmental conditions.

The invention is based in particular on the idea of reducing the number of valves, in particular of actively controlled valves, in the heating system as far as possible and in this way realizing a simplified and easier to control connection. It is possible to dispense with switching and shut-off valves as possible and instead comparatively simple and inexpensive locking devices are used primarily. Switching between various operating modes of the heating system, ie initially between the waste heat heating and the alternative heating operation is then advantageously essentially by switching on and off of the heating circuit pump, the coolant flow then automatically by the respectively generated pressure conditions in combination with the locking device and in particular deflected suitable without further switching operations. For redirecting the coolant is thus preferably dispensed with electrically controlled switching valves and passive components, namely the locking device are used instead. On a complex software control in particular for this locking device is advantageously dispensed with. Furthermore, there is no need for energizing corresponding valves, so that energy is advantageously saved during operation. Overall, the heating system is significantly less expensive, more energy efficient and also has a reduced space requirement. Due to the predominantly passive design of the heating system this is also very quiet, low maintenance and robust in operation.

The heating system is due to the possibility of switching in the heat supply of the heating heat exchanger especially for use in a hybrid vehicle, which indeed has an internal combustion engine, which is not operated continuously. Rather, the hybrid vehicle in addition to a combustion operation by means of the internal combustion engine on an electric driving operation in which the engine is switched off and the vehicle is driven only by means of an electric drive. A heating request during the electric driving operation can not be operated by waste heat of the engine. Instead, in this case, the alternative heating mode is switched over to supply the heating heat exchanger instead via the heat source arranged in the heating circuit. In combustion operation is then switched to the interior heating according to the waste heat heating mode.

In general, in a method for air conditioning of a vehicle by means of the heat system in the waste heat heating the heat exchanger exhaust heat of the engine supplied and the vehicle interior heated by the heating heat exchanger, even in alternative heating mode, the vehicle interior is heated by the heating heat exchanger, in this case, however the heat exchanger expediently supplied heat of the heat source. The main difference between waste heat heating operation and alternative heating operation thus consists in particular in the selection of the heat source for supplying the heating heat exchanger with heated coolant.

In waste heat heating mode, the heating circuit pump is usually switched off, d. H. deactivated, and the heating branch is coupled to the cooling circuit, so that coolant passes downstream of the engine via the heating circuit flow into the heating branch and to the heating heat exchanger. Downstream of the heating heat exchanger, the coolant is returned to the cooling circuit without passing through the return branch. For this purpose, the return branch is automatically shut off by means of the passive locking device in an advantageous manner.

In a first suitable variant, the heat source is arranged in the heating branch. This has the particular advantage that even in the waste heat heating operation by means of the heat source can be additionally heated. The heat source is in this case only used in the waste heat heating operation in addition to the heat supply, if the waste heat of the internal combustion engine is not sufficient to serve a given Heizanforderung. In a second suitable variant, however, the heat source is arranged in the return branch and is therefore not flowed through in the waste heat heating operation, which advantageously results in a lower pressure loss and less pump power is needed. In general, the heat source for supplying heat is suitably connected upstream of the heating heat exchanger to the cardiovascular system.

In alternative Heizbetieb the heating circuit is preferably operated by means of the heating circuit pump separately from the cooling circuit. As a result, an advantageous decoupling of the heating circuit and the cooling circuit is possible, so that in alternative heating operation no coolant exchange between the heating circuit and the cooling circuit, but the coolant is circulated in the heating circuit only there, whereby the vehicle interior is heated by the heat source and the heating heat exchanger particularly efficient.

For circulation of coolant in the cooling circuit, a cooling circuit pump is arranged in this particular, which is suitably turned on in the waste heat Helzbetrieb, that is activated to promote the coolant via the engine and by the heating branch. In alternative heating mode, however, the cooling circuit pump can remain switched off and is not needed, at least for the interior heating. Since the cooling circuit pump is needed regularly only when the Internal combustion engine is active, the cooling circuit pump is mechanically driven in a suitable variant of the internal combustion engine and is then in particular no electrically driven pump.

Suitably, a switch is then made between the waste heat heating operation and the alternative heating operation by activating or deactivating the heating circuit pump. Optionally, the cooling circuit pump is deactivated or activated accordingly, but otherwise in particular no further switching or switching operations are necessary so that the control of the heating system is particularly simple and is essentially passive and automatic. To switch from the waste heat heating mode in the alternative heating mode so the heating circuit pump is activated and the cooling circuit pump in particular deactivated. When switching in other direction, the heating circuit pump is deactivated and the cooling circuit pump in particular activated. A significant advantage is now in particular that is switched only by switching the pump between the two heating operations and the coolant flow is otherwise determined by the advantageous passive locking device, but no valve must be controlled.

The heat source is in a preferred embodiment, an electric heater, so that the alternative heating operation is an electrical heating operation. This is particularly advantageous in a hybrid vehicle in which is then switched in the electric driving operation for interior heating in the electric heating mode, d. H. is heated by electrical energy. The heater is for example designed as an electric water heater. The heat source is in a suitable and particularly simple embodiment, in particular no heat exchanger which is connected to a refrigeration circuit and is for example just no water-cooled condenser and no part of a heat pump. In principle, however, such embodiments of the heat source are conceivable.

Particularly preferred is an embodiment in which the locking device is a check valve. Such is particularly cost-effective and does not need to be actively controlled, but rather reacts automatically to changing pressure conditions in the HT cooling circuit and in the heating circuit. In a particularly compact embodiment, the check valve is integrated directly into a line hose, which forms the return branch itself or a portion of this.

The separate operation of the heating circuit in the alternative heating operation advantageously allows a simultaneous preheating of the internal combustion engine, since this is not connected in the alternative heating operation with the heating circuit. In an advantageous development, the heating system then has a preheating circuit and a preheating operation for preheating the internal combustion engine. When preheating then coolant downstream of the engine is not passed through the radiator, but returned via the Vorwärmkreis bypassing the radiator to a point upstream of the engine. The preheating circuit is therefore also referred to as an inner cooling circuit, the circle originally referred to only as a cooling circuit is then an outer cooling circuit.

The preheating operation is independent of the alternative heating mode adjustable due to the special interconnection of the HT cooling circuit and both operations can advantageously also be set simultaneously. To set the preheating operation, a valve is arranged in the cooling circuit, which has at least three ports, namely one each for the cooling circuit and the preheating, d. H. for the inner and the outer cooling circuit, as well as one for the internal combustion engine. The inner cooling circuit is then used to preheat the engine in the preheat mode and the outer cooling circuit is used to cool the engine in an engine cooling mode in which waste heat is dissipated through the radiator. Between the preheat mode and the engine cooling mode, only the valve is switched.

The cooling circuit pump is then advantageously arranged in both circles, d. H. both in the preheating and in the cooling circuit, so that advantageously by means of only one pump preheating and cooling of the internal combustion engine is realized. For this purpose, the cooling circuit pump is connected in particular between the valve and the internal combustion engine. The preheating circuit and the cooling circuit thus have a common line section, on which the internal combustion engine, the cooling circuit pump and the valve are arranged. Overall, therefore, the cooling circuit pump is arranged in the cooling circuit and expediently active in the waste heat heating mode and in the engine cooling mode, d. H. promotes coolant. The cooling circuit pump is also active in preheat mode.

Overall, in a preferred embodiment, the heating system has a waste heat heating operation, an alternative heating operation, a preheating operation, and an engine cooling operation. The alternative heating mode and the preheating mode are also adjustable at the same time. In general, the preheat mode is independent of the alternative heating mode adjustable. The engine cooling operation is simultaneously adjustable to the waste heat heating operation, so that heat, which is not required for heating is discharged through the radiator. The alternative heating mode and the waste heat heating mode are adjustable so far as that in the waste heat heating mode In addition, heat can still be provided via the heat source.

The totality of the active and inactive operations of the heating system determines its operating state at a given time. For example, a hybrid vehicle is initially operated in electric driving mode. If a heating request is now present, it is initially operated by switching on the alternative heating mode. Now, if the electric driving operation in the combustion mode changed, the preheating operation is first activated and preheated the internal combustion engine. If, meanwhile, a heating request is present, it will also be operated by means of the alternative heating operation or, depending on the general operating strategy, it will alternatively also be heated during preheating by means of the waste heat heating operation. When the internal combustion engine has reached the desired preheating temperature, the waste heat heating mode is activated, d. H. the waste heat of the internal combustion engine used for indoor heating, wherein the alternative heating operation is expediently terminated. Is it after that, d. H. especially with activated waste heat heating before excess heat, this is dissipated by switching on the engine cooling mode via the radiator to the environment. If there is a heating request in this situation, then in particular the waste heat heating mode is additionally switched on, in order first to use the waste heat of the internal combustion engine for heating the interior. If this is not enough, the heat source will still be activated to provide additional heat. Overall, therefore, a particularly flexible and efficient air conditioning is realized with a very simple design at the same time, especially HT cooling circuit.

In principle, it is conceivable to connect the valve either upstream or downstream of the internal combustion engine. Preferably, however, the valve is connected upstream of the internal combustion engine, since the thermal load is usually lower here. In the following, it is assumed that such an arrangement upstream of the internal combustion engine without limiting the generality. The cooling circuit pump is then arranged corresponding downstream of the valve.

In a first suitable variant, the valve is a thermal management module to which the heating circuit is connected switchable. In this case, "switchable" means, in particular, that the heating circuit is connected to a connection of the valve, which is adjustable and can at least be opened and closed. The thermal management module is in particular a mixing valve having a plurality, in particular three inputs, generally terminals, to which the cooling circuit, the preheating circuit and the heating circuit are connected. The heart circuit is in particular connected to the valve via the heating circuit return, so that coolant flows from the heating circuit upstream of the internal combustion engine into the cooling circuit. The inputs usually open into a mixing chamber, in which the different coolant flows are mixed. The thermal management module then further has a particular single output, i. H. in general, a further connection, which connects the mixing chamber with the cooling circuit, more precisely with the internal combustion engine with a corresponding arrangement of the valve upstream of the internal combustion engine.

The thermal management module is an active valve on a regular basis and is actively controlled, which ensures particularly high flexibility in air conditioning. Advantageously, the temperature of the coolant in the HT cooling circuit is thereby regulated as required. In particular, the connections are suitably activated and opened or closed as required.

In a second suitable variant, however, the valve is a thermostat, preferably a so-called map thermostat. In this embodiment, the valve is in particular not directly connected to the heating circuit return or - flow, but rather has in each case an input, generally connection, for the cooling circuit and the preheating circuit, and an output, generally connection to which the internal combustion engine is connected. The thermostat is characterized in particular by the fact that this does not need to be actively driven, but rather represents a passive switching element, which automatically assumes a suitable configuration. When switching on the internal combustion engine, this is then preheated initially in preheat mode. When a certain preheating temperature has been reached, the thermostat switches automatically and independently and the internal combustion engine is connected to the radiator, for heat dissipation to the environment, or alternatively with the heating branch, for interior heating. In this embodiment, the HT circuit thus comprises only two active components for adjusting the coolant flow, namely the heating circuit pump and the cooling circuit pump, whereas all the valves in the HT cooling circuit are passive components. As a result, the overall heating system is structurally particularly simple, inexpensive and low maintenance.

The heating circuit pump is arranged in particular depending on the configuration of the valve either in the return branch or in the heating branch. In a thermal management module, an arrangement of the heating circuit pump in both branches is possible. In an arrangement in the heating branch is in a possible variant also in the waste heat heating mode, the heating circuit pump additionally activated to adjust in particular a stronger flow of coolant through the heating branch, if one is needed. In contrast, in a thermostat as a valve, the heating circuit pump is suitably arranged in the return branch, in order in particular to prevent an undesired flow through the internal combustion engine.

In an embodiment with a thermostat, a further passive blocking device is advantageously arranged in the heating circuit flow, in particular a check valve, for shutting off the cooling circuit in the alternative heating mode. As a result, an unwanted backflow of coolant at the first branch in the heating circuit flow and thus in the cooling circuit in a simple manner and automatically prevented. The locking device automatically closes in the alternative heating mode due to the prevailing pressure in the HT cooling circuit pressure conditions. The heating circuit is then shut off from the cooling circuit and coolant in the heating circuit circulates only in this. When switching to the waste heat heating operation then change the pressure conditions, as the cardiovascular pump is disabled, so that the locking device opens and connects the cooling circuit with the heating branch.

Overall, due to the special interconnection in the entire HT cooling circuit, a reversal of the flow direction of the coolant when switching between different operations is dispensed with.

Embodiments of the invention will be explained in more detail with reference to a drawing. In each case schematically show:

1 a heating system,

2a - 2c each one operating state of the heating system 1 .

3 a variant of the heating system, and

4a - 4c each one operating state of the heating system 3 ,

In 1 is schematically a heating system 2 for a vehicle, not shown in detail, in particular a hybrid vehicle shown. The heating system 2 has a HT cooling circuit 4 on, for cooling an internal combustion engine 6 of the vehicle. The HT cooling circuit 4 again has a cooling circuit 8th and a heating circuit 10 on, which via a heating circuit flow 12 and a heating circuit return 14 hydraulically coupled with each other. The internal combustion engine 6 is in the cooling circuit 8th arranged, as well as a cooler 16 , for heat exchange with the environment of the vehicle. In the heating circuit 10 is a heating heat exchanger 18 arranged, for interior heating, and upstream of the heating heat exchanger 18 is a heat source 20 arranged, which is an electric heater in the embodiment shown. The heating circuit 10 is at a first junction 22 to the heating circuit flow 12 connected as well as at a second branch 24 to the heating circuit return 14 and through the two branches 22 . 24 in two branches 26 . 28 divided, namely in a heating branch 26 in which the heating heat exchanger 18 is arranged, and in a return branch 28 , for the return of coolant in the heating circuit 10 , Furthermore, in the heating circuit 10 , in 1 especially in the return branch 28 , a heating circuit pump 30 arranged. in the return branch 28 is also upstream of the first branch 22 and downstream of the second branch 24 a passive blocking device 32 arranged to automatically shut off the return branch 28 ,

In the cooling circuit 8th is upstream of the combustion engine 6 a cooling circuit pump 34 arranged, for the circulation of coolant in the cooling circuit 8th , In addition, the preheating of the engine is a Vorwärmkreis 36 formed, which downstream of the internal combustion engine 6 from the cooling circuit 8th branches off and coolant to a point upstream of the engine 6 returns. At this point here is a valve 38 arranged in which 1 is designed as a thermostat. The valve 38 then has two inputs E1, E2, the input E1 to the cooling circuit 8th is connected and the input E2 to the preheating circuit 26 , An outlet A of the valve 38 is in the direction of the internal combustion engine 6 to the cooling circuit 8th connected.

This in 1 shown heating system 2 has several operating modes, namely, a waste heat heating operation, an alternative heating operation, an engine cooling operation and a preheating operation. In waste heat heating mode and in alternative heating mode, the vehicle interior is replaced by the heating heat exchanger 18 heated. This waste heat of the combustion engine is in the waste heat heating operation 6 used in alternative heating mode, however, only heat of the heat source 20 , In engine cooling mode, waste heat of the internal combustion engine 6 over the radiator 16 dissipated. In preheat mode, coolant is used by the internal combustion engine 6 is heated, over the preheating circuit 36 again the internal combustion engine 6 fed to preheat this.

In the 2a to 2c is in each case an operating state of the heating system 2 out 1 shown, wherein in a given operating condition, several of the aforementioned operating modes can be active. The flowed through in the respective operating state of coolant line sections of the HT cooling circuit 4 are each shown reinforced.

2a shows the alternative heating operation, in which the heating circuit pump 30 is active and in the heating circuit 10 Coolant circulates. This is recurring via the heat source 20 and the heating heat exchanger 18 led, effectively heat the heat source 20 by means of the heating heat exchanger 18 is used for indoor heating. In this case, an inflow of coolant in the heating circuit flow 12 To avoid this is another locking device 40 arranged here also a check valve. The cooling circuit pump 34 is in 2a not active. The operating state shown is used in particular in an electric driving operation of the vehicle, if there is a heating request for the vehicle interior.

2 B shows starting from 2a in addition to the alternative heating mode, the preheating operation, in which the cooling circuit pump 34 is active and the valve 38 is switched such that coolant through the preheating circuit 36 is encouraged.

2c shows starting from 2 B switching between the alternative heating operation and the waste heat heating operation. The internal combustion engine 6 has reached a given preheat temperature and the valve 38 , which is designed here as a thermostat, automatically switches from input E2 to input E1, so that the cooling circuit pump 34 now coolant through the cooling circuit 8th promotes. The preheat operation is therefore deactivated. Downstream of the internal combustion engine 6 branches the heating circuit flow 12 from the cooling circuit 8th and leads to the heating circuit 10 heated coolant too. Through the locking device 32 automatically bypasses the heating heat exchanger 18 over the return branch 28 prevents and only the heating branch 26 served. If the waste heat of the internal combustion engine 6 is not sufficient, the heat source 20 additionally activated to provide more heat. The heating circuit pump 30 is not active.

In the embodiment of 1 and 2a to 2c is the heat source 20 in the heating branch 26 arranged. In a variant, not shown, the heat source 20 instead in the return branch 28 arranged and is therefore not flowed through in the waste heat heating operation, which advantageously results in a lower pressure loss and less pump power is needed. In the 1 shown arrangement in the heating branch 26 However, it has the advantage that even in the waste heat heating mode by means of the heat source 20 can be heated.

In 3 is a variant of the heating system 2 out 1 shown in which the valve 38 is designed as a thermal management module to which the Heizkreisrücklauf 14 connected via a third input E3. In addition, the heating circuit pump 30 here in the heating branch 26 arranged and not as in 1 in the return branch 28 , On the further locking device 40 was waived. Otherwise corresponds to the heating system 2 in 3 from that one 1 ,

4a shows the heating system 2 out 3 in alternative heating mode, where as in 2a only the heating circuit pump 30 is activated. The internal combustion engine 6 is also off and does not need to be refrigerated. The input E3 is closed.

In 4b becomes the heating system 2 as in 2 B additionally operated in preheat mode. The inputs E3 and E1 of the valve 38 are closed, so here too the heating circuit 10 separate from the preheating circuit 36 is operated and also the radiator 16 is not flowed through.

After preheating the valve switches 38 um and the input E2 is closed, in the presence of a heating request then a waste heat heating operation is possible, which then as in 4c shown is set. The input E3 is opened so that the heating branch 26 with the internal combustion engine 6 connected in series. The locking device 32 prevented as in 2c a bypass of the heating heat exchanger 18 over the return branch 28 , If necessary, additional heat is generated by means of the heat source 20 provided. The heating circuit pump 30 is not necessarily active, but is only connected, if an increased coolant flow is required.

Clearly visible in both variants of the heating system 2 in that this requires very little active components and expensive valves are largely dispensed with. The coolant flow in the entire HT cooling circuit 4 becomes decisive by switching the pumps on and off 30 . 34 and the automatic locking of the locking devices 32 . 40 certainly. In the embodiment of 3 and 4a to 4c In addition, also designed as a thermal management module valve 38 still active.

LIST OF REFERENCE NUMBERS

2

heating system

4

HT cooling circuit

6

internal combustion engine

8th

cooling circuit

10

heating circuit

12

Heating circuit

14

heating circuit

16

cooler

18

heating heat exchanger

20

heat source

22

first branch

24

second branch

26

heating branch

28

Return branch

30

Heating circuit pump

32

locking device

34

Cooling circuit pump

36

Vorwärmkreis

38

Valve

40

another locking device

A

output

E1, E2, E3

entrance

Claims (13)

Heating system ( 2 ) for a vehicle, in particular hybrid vehicle, with a waste heat heating operation and an alternative heating operation as well as with an HT cooling circuit ( 4 ), for cooling an internal combustion engine ( 6 ) of the vehicle, wherein - the HT cooling circuit ( 4 ) a cooling circuit ( 8th ) and a heating circuit ( 10 ), which communicate with each other via a heating circuit flow ( 12 ) and a heating circuit return ( 14 ) are hydraulically coupled, - in the cooling circuit ( 8th ) the internal combustion engine ( 6 ) is arranged and in the heating circuit ( 10 ) a heating heat exchanger ( 18 ) and a heat source ( 20 ), for interior heating, - the heating circuit ( 10 ) at a first branch ( 22 ) to the heating circuit flow ( 12 ) and at a second branch ( 24 ) to the heating circuit return ( 14 ) and the two branches ( 22 . 24 ) in two branches ( 26 . 28 ), namely in a heating branch ( 26 ), in which the heating heat exchanger ( 18 ) and in a return branch ( 28 ), for the return of coolant in the heating circuit ( 10 ), - in the heating circuit ( 10 ) a heating circuit pump ( 30 ) is arranged, which is active in the alternative heating mode, - in the return branch ( 28 ) upstream of the first branch ( 22 ) and downstream of the second branch ( 24 ) a passive blocking device ( 32 ) is arranged for automatically shutting off the return branch ( 28 ) in the waste heat heating mode. Heating system ( 2 ) according to the preceding claim, characterized in that the heat source ( 20 ) in the heating circuit ( 10 ) is an electric heater. Heating system ( 2 ) according to one of the preceding claims, characterized in that the locking device ( 32 ) is a check valve. Heating system ( 2 ) according to one of the preceding claims, characterized in that this is a preheating circuit ( 36 ) and a preheat operation, for preheating the internal combustion engine ( 6 ), and that in the cooling circuit ( 8th ) a valve ( 38 ) is arranged for adjusting the preheating operation. Heating system ( 2 ) according to the preceding claim, characterized in that the valve ( 38 ) a thermal management module is to which the heating circuit ( 10 ) in particular via the heating circuit return ( 14 ) is connected switchable. Heating system ( 2 ) according to claim 3, characterized in that the valve ( 38 ) is a thermostat. Heating system ( 2 ) according to the preceding claim, characterized in that in the heating circuit flow ( 12 ) another passive blocking device ( 40 ) is arranged, in particular a check valve, for shutting off the cooling circuit ( 8th ) in alternative heating mode. Heating system ( 2 ) according to one of the preceding claims, characterized in that in the cooling circuit ( 8th ) a cooling circuit pump ( 34 ) is arranged, which is active in the waste heat heating mode and in an engine cooling mode. Method for air conditioning a vehicle by means of a heating system ( 2 ) according to one of the preceding claims, wherein in a waste heat heating operation the heating heat exchanger ( 18 ) Waste heat of the internal combustion engine ( 6 ) is supplied and the vehicle interior by means of the heating heat exchanger ( 18 ) is heated, wherein the return branch ( 28 ) in the waste heat heating operation by means of the passive blocking device ( 32 ) is automatically shut off. Method according to the preceding claim, characterized in that in an alternative heating operation the heating heat exchanger ( 18 ) Heat of the heat source ( 20 ) is supplied and the vehicle interior by means of the heating heat exchanger ( 18 ) is heated, wherein the heating circuit ( 10 ) by means of the heating circuit pump ( 30 ) separated from the cooling circuit ( 8th ) is operated. Method according to the preceding claim, characterized in that switching between the waste heat heating operation and the alternative heating operation by the heating circuit pump ( 30 ) is activated or deactivated. Method according to one of the two preceding claims, characterized in that in a preheat operation of the internal combustion engine ( 6 ) is preheated by coolant downstream of the internal combustion engine ( 6 ) to a location upstream of the internal combustion engine ( 6 ) is returned. Method according to one of claims 9 to 11, characterized in that in an engine Cooling operation Waste heat of the internal combustion engine ( 6 ) via a cooler ( 16 ) is discharged.

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