Air conditioning system for a motor vehicle

Abstract

Air conditioning system for a motor vehicle, comprehensive - a first coolant circuit (10) with a coolant flow direction, - a thermoelectric pre-stage heat pump (12) with a hot side (W) and a cold side (K), the hot side (W) of which is thermally coupled to the first coolant circuit (10). - a thermoelectric final-stage heat pump (14) with a hot side (W) and a cold side (K), the cold side (K) of which is thermally coupled to the first coolant circuit (10) and is arranged upstream of the hot side (W) of the pre-stage heat pump (12), characterized in that the hot side (W) of the final-stage heat pump (14) is thermally coupled to the first coolant circuit (10) and is arranged downstream of the hot side (W) of the pre-stage heat pump (12) and upstream of the cold side (K) of the final-stage heat pump (14), so that coolant heated by heat exchange with the hot side (W) of the pre-stage heat pump (12) can be further heated by heat exchange with the downstream hot side (W) of the final-stage heat pump (14), wherein a liquid / gas heat exchanger is provided,which, as an interior heat exchanger (24), thermally couples the first coolant circuit (10) in the thermal influence area of ​​the hot side (W) of the final stage heat pump (14) with an airflow (26) that can be directed into the interior of the vehicle.

Description

[0001] The invention relates to an air conditioning system for a motor vehicle, comprising - a first coolant circuit with a coolant flow direction, - a thermoelectric pre-stage heat pump with a hot side and a cold side, the hot side of which is thermally coupled to the first coolant circuit. - a thermoelectric final stage heat pump with a hot side and a cold side, the cold side of which is thermally coupled to the first coolant circuit and is arranged upstream of the hot side of the pre-stage heat pump.

[0002] The invention further relates to an air conditioning system for a motor vehicle, comprising - a coolant circuit with a coolant flow direction, - a thermoelectric final stage heat pump with a hot side and a cold side coupled to the coolant circuit, the hot side of which is thermally coupled to an interior heat exchanger thermally coupled to the interior of the motor vehicle acting as a heat sink, and - a first thermoelectric pre-stage heat pump with a hot side and a cold side, the hot side of which is thermally coupled to the coolant circuit and arranged upstream of the cold side of the final stage heat pump.

[0003] Such air conditioning systems are known from DE 10 2010 002 018 A1. The above description approach relates to the same exemplary embodiment of the cited document and emphasizes different aspects. The above representation approach comes closest to a functional description.

[0004] The known air conditioning system utilizes a simple coolant circuit that is thermally coupled to both the warm side of the pre-stage heat pump and the cold side of the final-stage heat pump. Due to the simplicity of the coolant circuit, both coupling points can be described as either upstream or downstream relative to each other. The cold side of the pre-stage heat pump and the warm side of the final-stage heat pump are not coupled to the coolant circuit. Rather, the cold side of the pre-stage heat pump is thermally coupled to the outside air of the vehicle, and the warm side of the final-stage heat pump is thermally coupled to the inside air of the vehicle. During operation, the pre-stage heat pump extracts heat from the outside air on its cold side and pumps it to the warm side, where it is coupled into the coolant circuit.The coolant, preheated in this way, is further heated by heat exchange with an additional heat source, namely the waste heat from the vehicle's drive unit. Heat is extracted from the coolant, heated twice in this way, on the cold side of the final-stage heat pump. This heat is pumped to the warm side of the final-stage heat pump, where it is transferred to an air stream directed into the vehicle's interior. The vehicle's interior thus serves as a heat sink, into which heat is drawn from the outside air and the drive unit. The coolant, cooled on the cold side of the final-stage heat pump, flows back to the pre-stage heat pump, where it is reheated on the warm side, as described above.

[0005] A disadvantage of this known system is its low energy efficiency, which is largely due to the passive coupling of the additional heat source in a relatively high-temperature coolant circuit section. The temperature of the drive unit's waste heat must be correspondingly high to cause a coolant temperature increase between the hot side of the pre-stage heat pump and the cold side of the final-stage heat pump.

[0006] US 2004 / 0237541 A1 discloses a device for the propeller-free generation of a warm air flow for heating the interior of a motor vehicle. A horizontally extending, serpentine air duct with vertically oriented deflections of its curves is equipped with thermoelectric elements at the apex points of the curves. The thermocouples arranged at the lower apex points extend into the duct with their warm sides, and the thermocouples arranged at the upper apex points extend into the duct with their cold sides. As a result, air is heated at the lower apex points and caused to rise, while it is cooled and caused to fall at the upper apex points. The temperatures of the warm sides of the thermocouples at the lower apex points are staggered horizontally, increasing from the inlet to the outlet.This creates a continuous air flow through the duct, heating up from the inlet to the outlet.

[0007] DE 10 2006 042 160 A1 discloses an example of the generally known principle of the thermoelectric heat pump for the active transfer of heat between two fluid circuits thermally coupled via such a heat pump.

[0008] DE 10 2005 024 074 A1 discloses a system for generating electrical energy from heat sources of different temperature levels in a motor vehicle by means of a thermoelectric converter.

[0009] It is the object of the present invention to further develop a generic air conditioning system for motor vehicles in such a way that increased energy efficiency is achieved.

[0010] The object is achieved in conjunction with the features of the preamble of claim 1 in that the warm side of the final stage heat pump is thermally coupled to the coolant circuit and is arranged downstream of the warm side of the pre-stage heat pump and upstream of the cold side of the final stage heat pump, so that coolant heated by heat exchange with the warm side of the pre-stage heat pump can be further heated by heat exchange with the downstream warm side of the final stage heat pump, wherein a liquid / gas heat exchanger is provided which, as an interior heat exchanger, thermally couples the first coolant circuit in the thermal influence area of ​​the warm side of the final stage heat pump to an air flow that can be guided into the interior of the motor vehicle.

[0011] The object is further achieved in conjunction with the features of the preamble of claim 6 in that a second thermoelectric pre-stage heat pump is provided with a hot side and a cold side, - the cold side of which is thermally coupled to the coolant circuit and connected in parallel with the cold side of the first pre-stage heat pump which is thermally coupled to the coolant circuit, and • is coupled to the interior heat exchanger on the input side and • is thermally coupled to a heat source on the output side, and - whose warm side is thermally coupled to the coolant circuit and • on the input side, together with the warm side of the first pre-stage heat pump, it is thermally coupled to the cold side of the final stage heat pump and the heat source, and • is coupled on the output side to the warm side of the final stage heat pump.

[0012] Preferred embodiments of the invention are the subject of the dependent claims.

[0013] The invention varies the concept of cascading several thermoelectric heat pumps, preferably Peltier heat pumps, which is generally known from the prior art. While the prior art focuses on raising the temperature level of the final-stage heat pump using the coolant heated by the pre-stage heat pump by arranging the latter downstream and coupling its cold side to the latter's hot side, the cascading within the scope of the invention is primarily achieved by heating the coolant twice in series, first on the hot side of the pre-stage heat pump and then on the hot side of the final-stage heat pump.Nevertheless, the prior art concept of raising the temperature level of the final-stage heat pump is retained. However, this does not involve using, or only using (depending on the design) specifically heated coolant for this purpose, but rather the residual heat still contained in the coolant after its heat exchange with the destination, i.e., in particular, the vehicle interior. In this way, an increased temperature level at the "end-use point" and the utilization of residual heat can be achieved, which overall leads to increased energy efficiency and comfort.

[0014] This common inventive concept can be implemented in different ways, the subject matter of claims 1 to 5 being an air conditioning system with a substantially unbranched coolant circuit and the subject matter of claims 6 to 8 being an air conditioning system with a branched coolant circuit.

[0015] In the air conditioning system according to claim 1 with a substantially unbranched coolant circuit, the warm side of the final-stage heat pump is, in contrast to the prior art, thermally coupled to the coolant circuit, specifically downstream of the warm side of the pre-stage heat pump. The coolant heated on the warm side of the pre-stage heat pump is thus further heated on the warm side of the final-stage heat pump. The coolant, heated twice in this way, serves as a heat source for the heat exchange with the final consumption point, namely the vehicle interior. Specific configurations of this heat exchange will be discussed further below. Following the heat exchange with the interior, the coolant has cooled significantly but still contains usable residual heat. It is therefore fed to the cold side of the final-stage heat pump to raise its temperature level.Viewed in the direction of flow, the coolant thus passes through the warm side of the pre-stage heat pump, the warm side of the final stage heat pump (heat exchange with the vehicle interior), and the cold side of the final stage heat pump. The coolant, thus cooled to its maximum level, is then fed back to the warm side of the pre-stage heat pump to pass through the stations described above again.

[0016] Preferably, the cold side of the pre-stage heat pump is thermally coupled to a heat source. This is advantageously a waste heat reservoir from a drive unit, a battery's power electronics, an electric motor, and / or a brake of the motor vehicle. Other waste heat-producing components of the motor vehicle can also be used here. Depending on the design, the waste heat reservoir can be connected directly or, as is preferred due to the associated increased flexibility, via a separate, second coolant circuit.

[0017] In order to utilize the heat generated according to the invention in the interior of the motor vehicle, it is preferably provided that a liquid / gas heat exchanger is provided, which, as an interior heat exchanger, thermally couples the coolant circuit in the region of the warm side of the power stage heat pump with an air flow that can be directed into the interior of the motor vehicle. Typically, the heat exchanger will be a conventional water / air heat exchanger. The phrase "in the thermal sphere of influence" of the warm side of the power stage heat pump is not to be understood here in the sense of a purely spatial design. Rather, the phrase is to be understood functionally in such a way that the interior heat exchanger is to be arranged such that the coolant suffers no, or at least no significant, heat loss between the passage of the warm side of the power stage heat pump, where it reaches its maximum temperature, and the inlet into the interior heat exchanger.Accordingly, the double heat exchange, namely from the warm side of the final stage heat pump to the coolant and from this to the interior air flow, can be realized either in two components connected in series or in one integrated component.

[0018] In a preferred development of the invention, it is provided that the thermal coupling of the warm side of the final-stage heat pump with the coolant circuit is switchable such that the warm side of the final-stage heat pump can be bridged, and that a liquid-gas heat exchanger is provided which, as an interior heat exchanger, thermally couples the coolant circuit in the bridging region with an air flow that can be directed into the interior of the motor vehicle. This development of the invention results in the air conditioning system being able to be used not only for heating but also for cooling. For this purpose, the preliminary-stage heat pump is switched off so that no temperature gradient occurs between its cold side and its warm side. The final-stage heat pump, however, is operated normally; in particular, no voltage reversal is required. As the coolant passes the cold side of the final-stage heat pump in operation, it is cooled.Its passage through the warm side of the non-operating pre-stage heat pump does not result in any temperature change. Upstream of the warm side of the final-stage heat pump, the coolant is preferably bypassed around the warm side of the final-stage heat pump by means of a switching valve without thermal contact, so that there is no temperature change, and in particular no temperature increase, here either. The coolant, cooled in this way, then passes through the interior heat exchanger, where the interior serves as the heat source and is cooled. The coolant, heated in this way, then experiences further cooling as it passes through the stations described above on the cold side of the final-stage heat pump again. In this context, too, the statements made above in connection with the phrase "in the thermal influence zone" of the warm side of the final-stage heat pump apply analogously to the phrase "in the bridging zone".

[0019] In the embodiment according to claim 6 with a branched coolant circuit, the above-explained tasks of raising the temperature level of the final-stage heat pump on the one hand and heating the coolant twice on the other are distributed between two different pre-stage heat pumps. The task of utilizing residual heat, however, is fulfilled jointly by both pre-stage heat pumps. Thus, the cold sides of the two pre-stage heat pumps, which are connected in parallel on the inlet and outlet sides, are fed with coolant that has essentially lost its heat in an interior heat exchanger but still has a certain amount of residual heat. For this purpose, a corresponding coolant circuit branch is provided upstream of the cold sides of the pre-stage heat pumps. The coolant releases further heat on the cold sides of the pre-stage heat pumps. The cooled coolant flows are recombined downstream of the cold sides of the pre-stage heat pumps.The cold, combined coolant flow subsequently absorbs heat through heat exchange with a heat source, in particular, as preferably provided, with a waste heat reservoir of a drive unit, power electronics, and / or a brake of the motor vehicle. This heated coolant flow is combined with a similarly tempered coolant flow from a branch of the coolant circuit that has just undergone cooling on the cold side of the final-stage heat pump. This mixed coolant flow is fed to the hot sides of the two pre-stage heat pumps, for which purpose a corresponding branch of the coolant circuit is arranged upstream of them. The coolant portion passing through the hot side of the first pre-stage heat pump is heated here and then passes through the cold side of the final-stage heat pump to raise its temperature level.The coolant portion passing through the warm side of the second pre-stage heat pump is heated there and then reheated to a maximum temperature level as it subsequently passes through the warm side of the final-stage heat pump. The coolant, thus heated twice, is fed to the interior heat exchanger, through which it transfers its heat to the vehicle's interior.

[0020] The interior heat exchanger is preferably designed as a liquid / gas heat exchanger that thermally couples the coolant circuit in the thermal influence zone of the hot side of the final-stage heat pump with an air flow that can be directed into the interior of the vehicle. For details in this regard, reference is made to what was said above in connection with the unbranched embodiment.

[0021] Further features and advantages of the invention will become apparent from the following specific description and drawings.

[0022] They show: Fig. 1 a schematic representation of a first embodiment of an air conditioning system, Fig. 2 a schematic representation of a second embodiment of an air conditioning system.

[0023] The same reference symbols in the figures indicate the same or analogous elements.

[0024] Fig. Figure 1 shows a schematic representation of an embodiment with a substantially unbranched coolant circuit 10. The flow direction of the coolant in the coolant circuit 10 is indicated by arrows. The coolant flow is maintained by one or more coolant pumps (not shown).

[0025] Thermally coupled to the coolant circuit 10 are a pre-stage heat pump 12 and a final stage heat pump 14. Each of the thermoelectric heat pumps, which are preferably designed as Peltier heat pumps, has a hot side and a cold side, which are Fig. 1 are marked with "W" and "K" respectively. The thermal coupling to the coolant circuit 10 is achieved via heat exchanger elements 16. The specific design of the heat exchanger elements 16 is not important. In particular, they can be designed as separate elements or integrated into the heat pumps.

[0026] While the final-stage heat pump 14 is thermally coupled to the coolant circuit 10 on both sides, i.e., on its cold side K and its warm side W, the pre-stage heat pump 12 is thermally coupled to the coolant circuit 10 only on its warm side W. The cold side K of the pre-stage heat pump 12 is thermally coupled to a heat source 18, in particular a waste heat reservoir of the drive unit, a power electronics system, and / or a brake of the motor vehicle, for whose air conditioning the system shown is used. In the embodiment shown, this coupling takes place indirectly via an additional coolant circuit 20, to which, on the one hand, the cold side K of the pre-stage heat pump 12 and, on the other hand, the additional heat source 18 are coupled, each with corresponding heat exchangers 22.The provision of an additional coolant circuit, the coolant flow indicated by arrows being maintained by one or more coolant pumps (not shown), has the advantage that almost any path between the pre-stage heat pump 12 and the additional heat source 18 can be bridged. An alternative, direct coupling of the additional heat source 18 to the cold side K of the pre-stage heat pump 12 via a suitable heat exchanger would, however, have the advantage of a less complex structure. Finally, the coolant circuit 10 is thermally coupled to the interior of the motor vehicle via a heat exchanger 24 arranged downstream of the warm side W of the final-stage heat pump 14 and upstream of its cold side K. In the preferred embodiment, an air flow indicated by arrow 26, which flows through the heat exchanger 24 and is accordingly tempered, is directed into the interior of the motor vehicle.

[0027] The air conditioning system acc. Fig. 1 operates as follows: On the warm side W of the pre-stage heat pump 12, coolant is heated in the coolant circuit 10. The heat required for this is extracted from the additional coolant circuit 20 and, via this, from the heat source 18. The coolant, heated once in this way, flows on to the warm side W of the final-stage heat pump 14, where it undergoes further heating (see below for the essential source of the heat required for this). The coolant, heated twice in this way, flows through the heat exchanger 24 at maximum temperature, resulting in effective heating of the vehicle interior, which is perceived as comfortable due to the high temperature level. Due to the heat transfer to the interior air flow 26, the coolant cools down considerably. Nevertheless, it still contains usable residual heat. This is fed to the cold side K of the final-stage heat pump 14 to increase its operating temperature level.The maximum temperature of the coolant in the area of ​​the heat exchanger 24 can be correspondingly high.

[0028] The now twice cooled coolant is returned to the “beginning” of the process, ie to the warm side W of the pre-stage heat pump 12. In Fig. 1 is shown in dashed lines as a bypass 30 of the coolant circuit 10, which branches off from a controllable valve 28 located upstream of the warm side W of the final stage heat pump 14. This bypass flows downstream of the warm side W of the final stage heat pump 14 at the outlet point 32, which can be passively or actively controllable, back into the primary main circuit of the coolant circuit 10. The bypass 30 can thus be used to bridge the warm side W of the final stage heat pump 14. If, in such a circuit, only the final stage heat pump 14 is operated by applying an electrical voltage, whereas the pre-stage heat pump 12 is switched off, effective cooling of the vehicle interior can be achieved. In this circuit, the warm sides W of the heat pumps are passed without any significant temperature change. However, the coolant is cooled on the cold side K of the final stage heat pump 14.If the cooling is sufficient, the coolant in the heat exchanger 24 is then colder than the interior air flow 26, so that the latter is cooled in the heat exchanger 24 and contributes to cooling the vehicle interior.

[0029] Fig. Figure 2 shows a schematic representation of another embodiment of an air conditioning system, which is characterized by a branched coolant circuit 10. Also in Fig. 2, the coolant flow, which is maintained by coolant pumps (not shown), is marked by arrows. Regarding the individual elements of the air conditioning system of Fig. 2, reference is made to the above explanation of the elements with corresponding reference numerals in Fig. 1. In addition to the first pre-stage heat pump 12, the embodiment of Fig. 2 via a second pre-stage heat pump 13 with a hot side W and a cold side K. The essential connection of the individual elements will be described below.

[0030] To facilitate understanding, individual sections of the coolant circuit 10 are represented by different dashed lines according to their temperature level during operation. A solid line indicates the highest temperature level, a broad dashed line a lower temperature level, a narrow dashed line an even lower temperature level, and a dotted line a lowest temperature level. Please note that these only indicate very rough temperature levels for the purpose of better understanding, and under no circumstances should one assume exact temperature uniformity in similarly represented sections of the coolant circuit 10.

[0031] Comparable to the structure of the embodiment of Fig. 1, the coolant is heated on the warm side W of the first pre-stage heat pump 12. The coolant heated in this way is passed to the warm side W of the final stage heat pump 14 for further heating, where it is heated to its highest temperature level and brought into thermal contact with the interior air flow 26 in the heat exchanger 24. Downstream of the heat exchanger 24, the coolant circuit branches off at a branching point 33, which can be positively or actively controlled, so that the coolant containing residual heat is equally supplied to both cold sides K of the pre-stage heat pumps 12, 13 in order to raise their temperature operating level. The two partial flows of the coolant, which has been completely cooled in this way, are reunited at an outlet point 32 downstream of the cold sides K of the two pre-stage heat pumps 12, 13 and via a heat exchanger 22, comparable to the structure of the system of Fig. 1, thermally coupled to the heat source 18. In contrast to the embodiment according to Fig. 1, however, no separate coolant circuit 20 is provided for this purpose; rather, the heat source 18 is connected, as explained, via a branch of the coolant circuit 10.

[0032] The thus preheated coolant is fed equally to both hot sides W of the pre-stage heat pumps 12, 13, for which purpose the coolant circuit 10 is split at a further branching point 33 immediately upstream of the pre-stage heat pumps 12, 13. After passing the hot sides W of the pre-stage heat pumps 12, 13, the two coolant circuit branches run differently. While the branch passing the first pre-stage heat pump 12, as already explained above, leads to the hot side W of the final-stage heat pump 14, the branch passing the second pre-stage heat pump 13 leads to the cold side of the final-stage heat pump 14. It reaches the cold side at a similar temperature level to the first branch reaching the hot side W of the final-stage heat pump 14, so that its operating temperature level is significantly increased, resulting in a high maximum temperature of the coolant in the area of ​​the heat exchanger 24.The coolant cooled on the cold side K of the final stage heat pump 14 is combined with the coolant flow from the heat source 18 at a further outlet point 32 immediately downstream and, together with the coolant, passes through the two previously described branches which pass the warm sides W of the preliminary stage heat pumps 12, 13. LIST OF REFERENCE SYMBOLS 10 Coolant circuit 12 Pre-stage heat pump 13 Pre-stage heat pump 14 Power stage heat pump 16 heat exchangers 18 Heat source 20 additional coolant circuit 22 heat exchangers 24 heat exchangers 26 Interior airflow 28 Control valve 30 Bypass 32 Mouth 33 branching point W warm side of 12, 13, 14 K cold side of 12, 13, 14

Claims

[1] Air conditioning system for a motor vehicle, comprising - a first coolant circuit (10) with a coolant flow direction, - a thermoelectric pre-stage heat pump (12) with a hot side (W) and a cold side (K), the hot side (W) of which is thermally coupled to the first coolant circuit (10). - a thermoelectric final stage heat pump (14) with a hot side (W) and a cold side (K), the cold side (K) of which is thermally coupled to the first coolant circuit (10) and is arranged upstream of the hot side (W) of the pre-stage heat pump (12), characterized byin that the warm side (W) of the final stage heat pump (14) is thermally coupled to the first coolant circuit (10) and is arranged downstream of the warm side (W) of the pre-stage heat pump (12) and upstream of the cold side (K) of the final stage heat pump (14), so that coolant heated by heat exchange with the warm side (W) of the pre-stage heat pump (12) can be further heated by heat exchange with the downstream warm side (W) of the final stage heat pump (14), wherein a liquid / gas heat exchanger is provided which, as an interior heat exchanger (24), thermally couples the first coolant circuit (10) in the thermal sphere of influence of the warm side (W) of the final stage heat pump (14) to an air flow (26) which can be guided into the interior of the motor vehicle. [2] Air conditioning system according to claim 1, characterized bythat the thermal coupling of the warm side (W) of the final stage heat pump (14) with the first coolant circuit (10) is switchable such that the warm side (W) of the final stage heat pump (14) can be bridged, and that a liquid / gas heat exchanger is provided which, as an interior heat exchanger (24), thermally couples the first coolant circuit (10) in the bridging region with an air flow (26) that can be guided into the interior of the motor vehicle. [3] Air conditioning system according to one of the preceding claims, characterized by that the cold side (K) of the pre-stage heat pump (12) is thermally coupled to a heat source (18). [4] Air conditioning system according to claim 3, characterized by that the heat source (18) is a waste heat reservoir of a drive unit, a power electronics unit of a battery, an electric motor and / or a brake of the motor vehicle. [5] Air conditioning system according to one of claims 3 to 4, characterized in that the thermal coupling of the heat source (18) with the cold side (K) of the pre-stage heat pump (12) takes place via a separate, second coolant circuit (20). [6] Air conditioning system for a motor vehicle, comprising - a coolant circuit (10) with a coolant flow direction, - a thermoelectric final stage heat pump (14) with a hot side (W) and a cold side (K), the hot side (W) of which is thermally coupled to the coolant circuit (10) and an interior heat exchanger (24) thermally coupled to the interior of the motor vehicle acting as a heat sink, and - a first thermoelectric pre-stage heat pump (13) with a warm side (W) and a cold side (K) coupled to the coolant circuit (10), the warm side (W) of which is thermally coupled to the coolant circuit (10) and arranged upstream of the cold side (K) of the final stage heat pump (14), characterized by that a second thermoelectric pre-stage heat pump (12) with a hot side (W) and a cold side (K) is provided, - the cold side (K) of which is thermally coupled to the coolant circuit (10) and connected in parallel with the cold side (K) of the first pre-stage heat pump (13) which is thermally coupled to the coolant circuit (10) and • is coupled on the input side with the interior heat exchanger (24) and • is thermally coupled to a heat source (18) on the output side, and - whose warm side (W) is thermally coupled to the coolant circuit (10) and • on the input side, together with the warm side (W) of the first pre-stage heat pump (13), it is thermally coupled to the cold side (K) of the final stage heat pump (14) and the heat source (18), and • is coupled on the output side to the warm side (W) of the final stage heat pump (14). [7] Air conditioning system according to claim 6, characterized bythat the heat source (18) is a waste heat reservoir of a drive unit, a power electronics system and / or a brake of the motor vehicle. [8] Air conditioning system according to one of claims 6 to 7, characterized by that the interior heat exchanger (24) is designed as a liquid / gas heat exchanger which thermally couples the coolant circuit (10) in the thermal influence area of ​​the warm side (W) of the final stage heat pump (14) with an air flow (26) which can be guided into the interior of the motor vehicle.

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