Device for distributing coolant in a motor vehicle air conditioning system

Abstract

Heat pump system for a vehicle with at least two heat exchangers (10, 12) through which coolant flows for heating and / or cooling the vehicle interior, and at least two separable coolant circuits (14, 16), at least one of which can be connected independently of the other coolant circuit (14, 16) to one, two or more heat exchangers (10, 12) so that, when connected to two or more heat exchangers (10, 12), the coolant flows through them sequentially, and the other coolant circuit (14, 16) can be connected to at least one heat exchanger (10, 12), characterized in that at least one check valve (2a, 4) is provided which prevents a backflow of coolant to a pump of a coolant circuit (14, 16).

Description

Technical area

[0001] The invention relates to a device for distributing the coolant in a motor vehicle having at least two coolant circuits and a refrigerant circuit. The coolant circuit, designed for combined operation in refrigeration system mode, heat pump mode, and reheating mode, has two coolant-to-air heat exchangers. To condition the supply air to the passenger compartment, the temperature level of the coolant in the coolant-to-air heat exchangers is provided by a refrigerant circuit. The refrigerant circuit typically has at least one compressor, an expansion element for expanding the refrigerant from a high to a low pressure level, a refrigerant-to-coolant heat exchanger operable as a condenser / gas cooler, and a refrigerant-to-coolant heat exchanger operable as an evaporator for transferring heat between the refrigerant of the refrigerant circuit and the coolant of the coolant circuit.

[0002] For the comfort of the occupants, a vehicle interior must be heated, cooled or dehumidified depending on the ambient temperature.

[0003] Heating electric vehicles, for example, poses particular challenges, as the waste heat from an engine is not available to the extent usual with combustion engines. Heat pump systems with secondary circuits used in this case, which operate with the refrigerant R744, for example, may be limited in their heating output.

[0004] With the principle of indirect heat transfer underlying the invention, the efficiency of the overall system in heat pump mode also depends significantly on the inlet temperature of the coolant in the refrigerant-to-coolant heat exchanger, which operates as a condenser / gas cooler. If the heat exchanger is designed as a counterflow heat exchanger, the refrigerant can ideally be cooled to the inlet temperature of the coolant in the heat exchanger. As the flow temperature of the coolant increases, the outlet temperature of the refrigerant from the heat exchanger also increases, thus reducing the transferred enthalpy difference in the heat exchanger.

[0005] Particularly when operating the air conditioning system in heat pump mode, coolant flow temperatures in the range of approximately 55°C to 60°C are desirable at very low ambient air temperatures in the range of -15°C to -20°C in order to condition the passenger compartment to a comfortable temperature in the shortest possible time. During this operation, the refrigerant ideally has a temperature above 55°C at the outlet of the refrigerant-to-coolant heat exchanger. However, to operate the air conditioning system more efficiently, the refrigerant must be cooled to temperatures well below the coolant flow temperature in order to achieve the greatest possible enthalpy difference.

[0006] The coolant circuit described above is typically operated at a coolant temperature above ambient and serves both to heat the vehicle interior and to dissipate heat to the environment. Similar challenges to those described above exist with a parallel coolant circuit that operates at a low temperature (usually below ambient) and primarily serves to cool the vehicle interior or vehicle components. Here, the coolant is cooled by the refrigerant in another refrigerant-to-coolant heat exchanger, and the higher the coolant inlet temperature, the higher the coefficient of performance (COP) of the heating / cooling system.

[0007] For refrigerant-to-air heat exchangers, there is also a requirement that the air conditioned downstream of the heat exchangers must exhibit only small temperature differences to avoid compromising occupant comfort. This requirement results in a maximum permissible temperature difference of the refrigerant between the inlet and outlet of the heat exchangers of approximately 10 to 15 K. State of the art

[0008] A conventional heat pump system is described in US Pat. No. 7,063,137 B2. However, this cannot solve the problems mentioned above.

[0009] DE 10 2016 006 682 A1 discloses a method for operating an air conditioning system of an electric or hybrid vehicle with a refrigerant circuit comprising an indirect evaporator, an indirect condenser, an expansion element and a refrigerant compressor, a thermal energy store, an ambient heat exchanger and / or at least one vehicle component which can be used selectively as a heat source or as a heat sink, wherein, selectively for providing thermal energy for heating or cooling a vehicle interior in a first preconditioning mode, thermal energy from the ambient air and / or the vehicle component used as a heat source is transferred to the thermal energy store by thermally coupling the thermal energy store to the condenser and the evaporator to the ambient heat exchanger and / or the vehicle component.or in a second preconditioning mode, thermal energy from the thermal energy storage device is transferred to the ambient air and / or the vehicle component used as a heat sink by thermally coupling the thermal energy storage device to the evaporator and the condenser to the ambient heat exchanger and / or the vehicle component. Furthermore, the invention relates to an air conditioning system for implementing the method according to the invention.

[0010] Other previously known embodiments of a heat pump system for a vehicle are disclosed, for example, in DE 10 2004 008 210 A1, on which the two-part subdivision of claim 1 is based, JP 2015 182 575 A, and JP 2003 214 794 A. Description of the invention

[0011] The invention is based on the object of improving the coefficient of performance or COP of a heat pump system with a secondary circuit without compromising the comfort of the vehicle occupants.

[0012] This object is achieved by a heat pump system having the features of claim 1. Further embodiments emerge from the dependent claims.

[0013] The heat pump system for a vehicle according to the invention has at least two coolant-to-air heat exchangers through which air flows for heating and / or cooling the vehicle interior. Furthermore, at least two separate coolant circuits are provided, of which at least one can be connected to one, two, or more coolant-to-air heat exchangers independently of the other coolant circuit, so that, when connected to two or more coolant-to-air heat exchangers, air flows through them one after the other, and the other coolant circuit can be connected to at least one coolant-to-air heat exchanger.

[0014] Furthermore, at least one check valve is provided which prevents a backflow of coolant to a pump of a coolant circuit.

[0015] The basic idea of ​​the invention is to flow through the two coolant-to-air heat exchangers sequentially during heating and / or cooling, so that, depending on the operating state, lower inlet temperatures of the coolant can be achieved upon entering the high-pressure side of the refrigerant-to-coolant heat exchanger, or higher inlet temperatures of the coolant can be achieved upon entering the low-pressure side of the refrigerant-to-coolant heat exchanger, where heat transfer from or to the refrigerant takes place. This is essentially achieved by the coolant heating up more rapidly in cooling mode by flowing through two coolant-to-air heat exchangers sequentially, and cooling down more rapidly in heating mode.This effect can be further enhanced because the serial flow through the coolant-to-air heat exchangers allows the coolant volume flow to be reduced at the same time without increasing the air-side temperature difference downstream of the last coolant-to-air heat exchanger.

[0016] Furthermore, the invention enables an operation in which one coolant-air heat exchanger cools the air and the other heats it in order to first dehumidify and then heat the air, ie a so-called reheat operation can be realized.

[0017] It should also be emphasized that the heat pump system according to the invention is independent of details of the refrigerant circuit, such as the refrigerant used, the number of evaporators, coolers, or condensers. In particular, cooling for the battery of an electric vehicle can also be provided. Furthermore, there may be additional heat sources and / or heat sinks. As explained in more detail below, the valves required for the described distribution and the specified switching options can be integrated into a single component.

[0018] The check valve according to the invention is provided in case the pump mentioned is not designed to be self-sealing when not in use.

[0019] As already indicated, the connection between the coolant circuits and the coolant-air heat exchangers can be formed in a single component in the form of a distributor.

[0020] Preferably, at least two, particularly preferably three 3 / 2-way valves are provided, each of which can be replaced by two shut-off valves.

[0021] Particularly diverse operating possibilities are achieved if a 3 / 2-way valve has a direct inflow from a first coolant circuit and an outflow towards the other coolant circuit, as will be described in more detail below with reference to the figures.

[0022] Furthermore, at least one 3 / 2-way valve is provided, which has a direct inflow from a heat exchanger, an outflow in the direction of one coolant circuit and an outflow in the direction of the other coolant circuit.

[0023] With regard to all valves, it should be emphasized that they can not only be provided as a single component in a distributor, but can also be provided at least partially at another location in the two coolant circuits.

[0024] In terms of an efficient design, it also offers advantages if both coolant circuits are connected to a common refrigerant circuit and a heat exchange takes place between the refrigerant circuit and both coolant circuits. Short description of the drawings

[0025] Preferred embodiments of the invention are explained in more detail below with reference to the drawings.

[0026] They show: Fig. 1 shows a first embodiment of the heat pump system according to the invention during heating; Fig. 2 shows the first embodiment of the heat pump system according to the invention during cooling; Fig. 3 shows the first embodiment of the heat pump system according to the invention during dehumidification; Fig. 4 shows a second embodiment of the heat pump system according to the invention during heating; Fig. 5 shows the second embodiment of the heat pump system according to the invention during cooling; Fig. 6 shows the second embodiment of the heat pump system according to the invention during dehumidification; Fig. 7 shows a third embodiment of the heat pump system according to the invention during heating; Fig. 8 shows the third embodiment of the heat pump system according to the invention during cooling; Fig. 9 the third embodiment of the heat pump system according to the invention during dehumidification. Detailed description of preferred embodiments of the invention

[0027] To the Fig. 1, it should first be explained with reference to the left-hand, central area that a refrigerant circuit, for example, with R 744 as the refrigerant, is provided, which has a compressor Comp, a refrigerant-to-coolant heat exchanger WGC for heating the coolant in a first coolant circuit 14, and a refrigerant-to-coolant heat exchanger Chiller for cooling a coolant in a second coolant circuit 16. Furthermore, an expansion valve EXV and an internal heat exchanger with integrated accumulator Accu / IHX are provided.Each coolant circuit shown in the top and bottom left-hand section has a (coolant-to-air heat exchanger) radiator LTR and two pumps, one of which is located immediately upstream of the radiator and the other in a line leading towards the coolant-to-air heat exchangers 10 and 12 shown on the right in the figure, which are referred to below as heat exchangers for the sake of simplicity. It should be noted that the first, always upstream, heat exchanger 10 primarily serves to cool / dehumidify the air, and the second, always downstream, heat exchanger 12 primarily serves to heat the air. The two heat exchangers 10, 12 belong to a heating, ventilation, and cooling system referred to as HVAC or air conditioning unit. The term "coolant distributor" refers to a coolant distributor of the embodiment shown, and "system" refers to the combination of the refrigerant and the two coolant circuits.It should also be noted that in all figures, arrows indicate the flow in the direction of the arrow.

[0028] Advantageously, both heat exchangers 10, 12 can be used for heating with a particularly high degree of efficiency, so that advantageously a particularly extensive cooling of the coolant in the first coolant circuit 14, which is the upper one in the figure, takes place if the flow of the coolant in this coolant circuit 14 takes place as follows.

[0029] The pump provided in the supply line to the heat exchanger 12 conveys the coolant toward this heat exchanger 12. By means of a 3 / 2-way valve designated 3, the coolant, after flowing through the heat exchanger 12, flows further toward the other coolant circuit 16 and there through the first heat exchanger 10. By means of a 3 / 2-way valve designated 1, the coolant is returned to the first coolant circuit 14, in particular through the heat exchanger WGC for reheating the coolant. In this case, no flow passes through the radiator LTR. Furthermore, in the second coolant circuit 16, the coolant flows only through the pump, the radiator LTR, and the cooler, but does not reach the heat exchangers 10, 12.

[0030] By having the air flow through the two heat exchangers 12, 10 one after the other, the above-described inventive effects can be achieved. The air flow through the heat exchangers 10, 12, on the one hand, and the coolant flow through the heat exchangers 10, 12, on the other hand, can be designed as a counterflow, crossflow, or cross / counterflow. The air fed into the interior of the vehicle is therefore heated in two stages. For the sake of completeness, it should be mentioned that in the embodiment shown, a shut-off valve or check valve 4 is provided. This is optional and prevents the coolant from flowing back to the pump. This is advantageous in the event that this pump is not sealed when switched off and would thus allow an unwanted bypass.

[0031] Fig. Figure 2 shows the case of a two-stage cooling of the air guided through the heat exchangers 10 and 12, in that the coolant of the second coolant circuit 16 is first, by the appropriate position of the 3 / 2-way valve 2 in the direction of the first coolant circuit 14, there through the second heat exchanger 12, by a position of the 3 / 2-way valve 3, which corresponds to the Fig. 1, back towards the second coolant circuit 16, there through the first heat exchanger 10 and from there through the appropriately switched 3 / 2-way valve 1 towards the pump of the second coolant circuit 16. Correspondingly, but inversely to the case described above, a two-stage cooling of the air to be fed into the vehicle interior and a particularly extensive heating of the coolant in the second coolant circuit 16 can thus be achieved. In this case, no flow passes through the radiator LTR of the second coolant circuit 16, and the coolant in the first coolant circuit 14 flows only through the heat exchanger WGC, the one pump and the radiator LTR, but not towards the heat exchangers.

[0032] In the Fig. 3, the coolant flows only in "its" coolant circuit. In other words, the coolant of the first coolant circuit 14 is passed through the second heat exchanger 12 and heats the air, while the coolant of the second coolant circuit 16 is passed through the first heat exchanger 10 and cools the air. By appropriately positioning the flaps 18 visible on the far right, which are used in the operating modes of the Fig. 1 and Fig. 2 are both closed to achieve a flow through the second heat exchanger 12, in the operation of Fig. 3, a mixing of cooled and heated air can take place. This advantageously dehumidifies the air and evens out the temperature. In other words, in this operating mode, the connections between the two coolant circuits 14, 16, which can be seen in the vertical direction in the figure, are not flowed through. Fig. In the operating mode shown in Figure 3, the coolant in the respective coolant circuit 14, 16 also flows through the radiator LTR.

[0033] The design of the Fig. 4 to 6 differs from that of the Fig. 1 to 3 by omitting the Fig. 1 to 3 with 2 and the shut-off valve 4. This advantageously saves costs. Instead of the 3 / 2-way valve 2, an optional shut-off valve 2a is provided, which prevents backflow to the pump of the second coolant circuit 16. However, the function of the shut-off valve 2a can also be performed by the pump arranged in the direction of the heat exchanger 10 and not directly upstream of the radiator LTR. Fig. The heating operation shown in Figure 4 does not differ from that shown in Fig. 1, so that reference can be made to it.

[0034] The Fig. The cooling operation shown in Figure 5 differs in that the coolant in the second coolant circuit 16 only flows through the first heat exchanger 10, and thus only a single-stage cooling takes place. Fig. 6 shows the dehumidification operation corresponds to the Fig. 3 and will therefore not be described again.

[0035] In the third embodiment according to Fig. 7 to 9 is the Fig. 1 to 6, the 3 / 2-way valve designated 1 is omitted, so that, as in Fig. 7, the heating operation is only carried out in one stage, and insofar as no flow of the coolant from the first coolant circuit 14 through the second coolant circuit 16 takes place. As shown in Fig. 8, however, a two-stage cooling operation is still possible, which in this respect Fig. 2 and does not need to be explained again. This also applies to the dehumidification operation according to Fig. 9, which corresponds to that of the Fig. 3 and Fig. 6. Compared to the shut-off valve 2a of the Fig. 4 to 6 is in the embodiment of the Fig.7 to 9, a shut-off valve 4 is provided to prevent backflow to the pump of the first coolant circuit 14.

[0036] Although two heat exchangers 10, 12 are shown in the figures, more heat exchangers may be provided. Furthermore, multiple heat pump systems, each with two or more heat exchangers, may be provided.

Claims

[1] Heat pump system for a vehicle with at least two heat exchangers (10, 12) through which flow passes for heating and / or cooling the vehicle interior, and at least two separable coolant circuits (14, 16), of which at least one can be connected independently of the other coolant circuit (14, 16) to one, two or more heat exchangers (10, 12), so that when connected to two or more heat exchangers (10, 12), flow passes through them one after the other, and the other coolant circuit (14, 16) can be connected to at least one heat exchanger (10, 12), characterized by that furthermore at least one check valve (2a, 4) is provided which prevents a backflow of coolant to a pump of a coolant circuit (14, 16). [2] Heat pump system according to claim 1, characterized by that the connection between the coolant circuits (14, 16) and the heat exchangers (10, 12) is carried out by means of a distributor. [3] Heat pump system according to claim 1 or 2, characterized by that at least two 3 / 2-way valves (1, 2, 3) or at least four shut-off valves are provided. [4] Heat pump system according to claim 3, characterized by that a 3 / 2-way valve (2) has a direct inlet from one coolant circuit (16) and an outlet in the direction of the other coolant circuit (14). [5] Heat pump system according to claim 3 or 4, characterized by that at least one 3 / 2-way valve (1, 3) has a direct inlet from a heat exchanger (10, 12), an outlet in the direction of one coolant circuit (14) and an outlet in the direction of the other coolant circuit (16). [6] Heat pump system according to one of the preceding claims, characterized by that both coolant circuits (14, 16) are connected to a common refrigerant circuit.

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