Vehicle air conditioning with reheat mode and vehicle with it

Abstract

Vehicle air conditioning system (1) with a refrigerant circuit (2) operable as a heat pump circuit with heating function and as a refrigeration circuit with cooling and dehumidification function, comprising: - a refrigerant compressor (4), two shut-off valves (14, 15) connected to the refrigerant compressor (4) on the high-pressure side, an evaporator (3), a refrigerant condenser / gas cooler (5) for dissipating heat extracted from a refrigerant into a vehicle environment by means of an air flow (L2), a first expansion element (6) associated with the evaporator (3) and a heat exchanger (7) for heating a passenger compartment, wherein the listed components (3, 4, 5, 6, 7) form the refrigerant circuit (2), wherein - a shut-off valve (14) for refrigeration system operation can be connected to the refrigerant condenser / gas cooler (5) via a branch point (2.1), and - the other shut-off valve (15) of the two shut-off valves (14, 15) for the heating function can be connected to the heat exchanger (7), characterized in that - a second expansion element (17) is arranged upstream of the refrigerant condenser / gas cooler (5), - a further shut-off valve (16) is arranged downstream of the heat exchanger (7) in such a way that, when the further shut-off valve (16) is open, the branch point (2.1) is connected to the first expansion element (6), and - when the further shut-off valve (16) is open, at least one partial refrigerant flow can be diverted downstream via the second expansion element (17) via the branch point (2.1) of the refrigerant circuit (2).

Description

[0001] The invention relates to a vehicle air conditioning system with a refrigerant circuit that can be operated as a heat pump circuit with heating function and as a refrigeration circuit with cooling and dehumidification function according to the preamble of patent claim 1. Furthermore, the invention relates to a vehicle with a vehicle air conditioning system according to the invention.

[0002] It is known that vehicles, especially motor vehicles, are equipped with an air conditioning system that can be switched from a cooling mode to a heating mode and vice versa.

[0003] Furthermore, vehicle air conditioning systems are known whose refrigerant circuit has an indirect condenser designed as a refrigerant-to-coolant heat exchanger, which, in heating mode, heats the air of the vehicle interior via a condenser-side coolant circuit and the heater core integrated downstream there. In addition to at least one front evaporator, electrified vehicles require a separate coolant circuit for conditioning and temperature control of the energy storage device, which is usually implemented as a high-voltage battery. Such a coolant circuit can be coupled to the refrigerant circuit by means of a heat exchanger, whereby such a heat exchanger is itself also designed as an evaporator for cooling an air stream or as a so-called chiller for cooling water.

[0004] The use of the refrigerant circuit of a vehicle air conditioning system in heat pump mode to heat the passenger compartment is also known. When connected or functioning as a heat pump, the refrigerant circuit is capable of heating an air or water stream or coolant stream and transferring this heat directly or indirectly to the air in the passenger compartment.

[0005] A generic vehicle air conditioning system with an integrated heat pump system for cooling and heating is known from DE 101 63 607 A1. In heat pump operation, the energy is introduced indirectly into the air flow for the vehicle cabin via heat transfer fluids. This is achieved using a liquid-to-air heat exchanger, the so-called heating heat exchanger in the vehicle's air conditioning unit. To heat the air flow, the refrigerant is cooled and, if necessary, condensed, and to cool the air flow, the refrigerant is evaporated and heated. In this known vehicle air conditioning system, during refrigerant system operation, the refrigerant compressed by a refrigerant compressor is expanded via a gas cooler and an internal heat exchanger via a first expansion valve into an evaporator. The refrigerant then flows back to the refrigerant compressor via the low-pressure side.In heating mode, the refrigerant compressed by the refrigerant compressor is passed through a refrigerant-to-coolant heat exchanger, where part of the refrigerant's heat is transferred to a coolant circuit for heating the passenger compartment. It then flows through the internal heat exchanger into the first expansion valve, where it is expanded into the evaporator. The refrigerant is then expanded by a second expansion valve into a refrigerant-to-heat exchanger for heat absorption, where heat from the engine coolant is added to the refrigerant. Finally, the refrigerant flows back to the refrigerant compressor via the low-pressure side and the internal heat exchanger.

[0006] From the subsequently published DE 11 2014 005 360 T5, a vehicle air conditioning system with a refrigerant circuit with an integrated heat pump, a heating circuit, and a coolant circuit is known. The heating circuit comprises a heating heat exchanger arranged in an air conditioning unit, a coolant-refrigerant heat exchanger for thermal coupling with the coolant circuit, and a heating pump. In the coolant circuit, the refrigerant compressed by a refrigerant compressor is passed through the coolant-refrigerant heat exchanger in all operating modes, i.e., both in refrigeration system operation for cooling or dehumidifying the air flow supplied to the vehicle interior and in heating mode.In dehumidification mode, the refrigerant is fed through an upstream branch point of the coolant-refrigerant heat exchanger, first via an expansion device to the condenser and then to the refrigerant compressor, and secondly via a bypass that can be closed off by an expansion device to the evaporator, where it absorbs heat from the air flow supplied to the vehicle interior. The refrigerant flowing through the condenser absorbs heat from the vehicle's ambient air.

[0007] Reheat operation of a vehicle air conditioning system is characterized by the fact that the air flowing into the passenger compartment via the air conditioning unit and the heat exchangers located there is first dehumidified (i.e., cooled) and then heated to the desired outlet temperature. Reheat operation typically occurs at an ambient temperature of approximately 5 to 25 °C and a correspondingly increased relative humidity.

[0008] Combustion-engine-powered vehicles dissipate approximately 50% of their waste heat into the environment via the cooling water. This waste heat can also be used to heat the vehicle, especially during reheat operation.

[0009] Electric vehicles dissipate almost 100% of their waste heat through the cooling water, but at a significantly lower temperature. This temperature is usually so low that the waste heat can only be used for heating to a limited extent, or not at all. Therefore, electric heating is required.

[0010] One energy-efficient method involves providing the required heat using a heat pump process. The refrigerant evaporates in the air conditioning unit's evaporator or, for example, additionally via at least one water-refrigerant heat exchanger, the so-called chiller, which can be used either to cool an energy storage device or to extract heat from other electronic components to operate a heating process. The refrigerant condenses for heating operation not in the condenser at the front of the vehicle, but either in an internal condenser / gas cooler via the cooling water of the heating circuit or in an air-charged heating register in the air conditioning unit. In both cases, the air is reheated after the evaporator.

[0011] Ideally, the heat absorbed by at least one evaporator together with the power transferred into the refrigerant via the compressor corresponds exactly to the heat flow transferred into the cooling water and subsequently from the cooling water (via the heating heat exchanger) or from the refrigerant via the heating register, which must be applied to set the required comfort heat for the cabin supply air, taking into account the heat transfer losses that occur.

[0012] If there is a heating output deficit, an additional heat source, such as a chiller, would have to be used, and if there is a heating output surplus, an additional heat sink (condenser / gas cooler) would have to be provided.

[0013] Since a heat pump process is a closed-loop process, the power supplied to a vehicle air conditioning system by the compressor and heat supply to at least one evaporator must be dissipated again to a condenser / gas cooler. If there is an imbalance in the cooling and heating requirements, usually resulting in a power surplus on the hot side, the vehicle air conditioning system becomes unstable and the high pressure rises until the system is throttled down due to the high pressure limit being reached, or in extreme cases, high pressure drops and the air conditioning system shuts down.

[0014] Alternatively, it would be possible to provide the condenser or gas cooler as an additional heat sink next to the heating gas cooler or heating condenser. However, in this case, a rapid drop in high pressure is to be expected, as the pressure level in the system will adjust to the condensation pressure dictated by the ambient temperature, which in turn would be below the pressure required to transfer heat into the air flow through a heating coil or into the cooling water.

[0015] The object of the invention is therefore to further develop a vehicle air conditioning system of the type mentioned above in such a way that a stable and easily controllable heat pump process is achieved.

[0016] This object is achieved by a vehicle air conditioning system having the features of patent claim 1.

[0017] Such a vehicle air conditioning system with a refrigerant circuit that can be operated as a heat pump circuit with heating function and as a refrigeration circuit with cooling and dehumidification function comprises: - a refrigerant compressor, two shut-off valves connected to the refrigerant compressor on the high-pressure side, an evaporator, a refrigerant condenser or a gas cooler for discharging heat extracted from a refrigerant into a vehicle environment by means of an air flow, a first expansion valve associated with the evaporator and a heat exchanger for heating a passenger compartment, wherein the listed components form the refrigerant circuit, wherein - that a shut-off valve for refrigeration system operation can be connected to the refrigerant condenser / gas cooler via a branch point, - the other of the two shut-off valves for the heating function can be connected to the heat exchanger, is characterized according to the invention in that - a second expansion device is installed upstream of the refrigerant condenser / gas cooler, - a further shut-off valve is connected downstream of the heat exchanger in such a way that, when the further shut-off valve is open, the branch point is connected to the first expansion device, and - when the further shut-off valve is open, at least a partial refrigerant flow can be diverted downstream via the branch point of the refrigerant circuit via the second expansion device.

[0018] In this vehicle air conditioning system according to the invention, the excess energy in the heating circuit is dissipated in the heat pump process via the condenser / gas cooler, which is set to an intermediate pressure level via a second expansion element.

[0019] This ensures that the heat pump process remains stable and easily controllable. The high pressure level can be maintained at a stable target value. Neither pressure increases nor system shutdowns due to overheating are to be expected. Heat can continue to be transferred from the refrigerant circuit to the heating circuit to the required extent, as the heat flow can be regulated according to a setpoint, and excess heat is transferred to the environment.

[0020] According to a preferred embodiment of the invention, the heat exchanger of the refrigerant circuit is designed as a refrigerant-heating medium heat exchanger for coupling to a heating circuit, and a heating heat exchanger is arranged in the heating circuit to perform the heating function. Instead of the refrigerant-heating medium heat exchanger, a heat exchanger designed as a heating register can be used, which is arranged in an air conditioning unit of the vehicle's air conditioning system and is directly surrounded by air to heat the passenger compartment.

[0021] In the event of a heat deficit, a chiller with a third expansion element is connected in parallel to the evaporator and the first expansion element. The chiller is coupled to a coolant circuit containing a heat source, e.g., electronic components, and a low-temperature cooler. This allows heat to be extracted from this heat source and made available to the refrigeration circuit and, if necessary, the cooling circuit as heating energy.

[0022] Advantageously, according to the further development, the second expansion element is designed with an opening diameter corresponding to the pipe diameter in the upstream and downstream sections of the second expansion element. Alternatively, according to the further development, a bypass valve is connected in parallel with the second expansion element. This allows pressure losses to be compensated if the flow cross-section of the second expansion element is insufficient for the normal cooling mode of the vehicle air conditioning system.

[0023] Such a vehicle air conditioning system according to the invention is suitable for use in all vehicle types.

[0024] The invention is described in detail below using exemplary embodiments with reference to the accompanying figures. They show: Fig. 1 is a circuit diagram of a vehicle air conditioning system as a first embodiment according to the invention, and Fig. 2 a circuit diagram of a vehicle air conditioning system as a second embodiment of the invention.

[0025] The vehicle air conditioning system 1 according to Fig. 1 comprises a refrigerant circuit 2, a heating circuit 8 and a coolant circuit 10.

[0026] The refrigerant circuit 2 consists of an evaporator 3, a refrigerant compressor 4, a refrigerant condenser or gas cooler 5, a first expansion element 6 designed as an expansion valve, and a refrigerant-heating medium heat exchanger 7. Two shut-off valves 14 and 15 are provided on the high-pressure side of the refrigerant compressor 4. When the shut-off valve 15 is closed, the shut-off valve 14 is opened for refrigeration system operation, and the shut-off valve 15 is opened for heating operation when the shut-off valve 14 is closed.

[0027] The heating circuit 8 consists of the heat exchanger 7, with water as the heating medium, a water pump 18, a heating element 19 and a heating heat exchanger 9.

[0028] The evaporator 3 and the heating heat exchanger 9 are housed in an air conditioning unit 1.1 of the vehicle air conditioning system 1.

[0029] During refrigeration system operation of the refrigerant circuit 2, the refrigerant compressed to a high pressure p1 by the refrigerant compressor 4 is fed via the open shut-off valve 14 to the refrigerant condenser or gas cooler 5 arranged in the front area of the vehicle via a second expansion element 17 designed as an expansion valve, with maximum dethrottlement at the pressure level p2 ≤ p1. After condensation of the refrigerant in the refrigerant condenser or gas cooler 5, the refrigerant is expanded to a pressure p3 via a check valve 24 and the first expansion element 6 in the evaporator 3, where p3 < p2 ≤ p1. The heat extracted from the refrigerant by the refrigerant condenser or gas cooler 5 is dissipated into the vehicle environment via an air flow L2. The air flow L1 fed to the evaporator 3 is cooled by the evaporator and fed to the passenger compartment of the vehicle. For this purpose, an air flap 1.11 of the air conditioning unit 1.1 is set so that this air flow L1 is not or not completely guided over the heating heat exchanger 9.

[0030] The second expansion element 17, with its flow cross-section, should be designed so that it causes virtually no pressure losses during normal refrigeration system operation (AC mode). Therefore, the opening diameter should ideally correspond to the diameter of the air conditioning line in the supply and discharge sections leading to the refrigerant condenser or gas cooler 5. Alternatively, it would also be possible to connect a switchable bypass valve 25 in parallel with the second expansion element 17 for dethrottling, as shown in Fig. 1 is shown in dashed lines.

[0031] Between the shut-off valve 14 and the second expansion element 17 is a branch point 2.1 of the refrigerant circuit 2, which is connected downstream via a shut-off valve 16 to the first expansion element 6 and upstream to the heat exchanger 7. During refrigeration system operation, this shut-off valve 16 is closed, so that the compressed refrigerant is fed to the refrigerant condenser or gas cooler 5 via the second expansion element 17.

[0032] For heating and reheating operation of the vehicle air conditioning system 1, the compressed refrigerant is fed to the heat exchanger 7, which is designed as a refrigerant-water heat exchanger, via the open shut-off valve 15 when the shut-off valve 14 is closed. This heat exchanger 7, together with the water pump 18, the heating element 19, and the heating heat exchanger 9 arranged in the air conditioning unit 1.1, forms the heating circuit 8 downstream.

[0033] In reheat mode of the vehicle air conditioning system 1, the heat transferred from the evaporator 3 to the refrigerant, together with the drive power introduced into the refrigerant by the refrigerant compressor 4, is transferred via the heat exchanger 7 to the heating circuit 8, so that the air flow L1 supplied to the passenger compartment is reheated at the heating heat exchanger 9 after being cooled at the evaporator 3. For this purpose, the air flap 1.11 of the air conditioning unit 1.1 takes the Fig. 1, so that the air flow L1 is completely guided over this heating heat exchanger 9.

[0034] To avoid excess power on the hot side of the refrigerant circuit 2 during reheat operation of the vehicle air conditioning system 1, when the shut-off valve 16 is closed, the refrigerant is not fed to the first expansion element 6, but rather expanded via the second expansion element 17 into the refrigerant condenser or gas cooler 5. The excess heat bound in the refrigerant is thus transferred to the air flow L2 via the refrigerant condenser or gas cooler 5 and dissipated by it. This allows heat to be partially transferred to the heating circuit 8 via the heat exchanger 7 during reheat operation of the refrigerant circuit 2.

[0035] In this case, the air damper 1.11 in the air conditioning unit 1.1 assumes an intermediate position, so that not the entire air volume flows through the heating heat exchanger 9. Instead, two partial volume flows are established via the heating heat exchanger 9 and past the heating heat exchanger 9, which are mixed together again downstream and result in the desired intermediate temperature.

[0036] According to Fig. 1, the vehicle air conditioning system 1 also includes a coolant circuit 10 with a low-temperature cooler 13 exposed to the air flow L2, which is connected in the flow direction to a coolant pump 20, a chiller 12, a heat source 11, and a shut-off valve 22. A further shut-off valve 23 bypasses the low-temperature cooler 13. The chiller 12, together with a third expansion element 21 designed as an expansion valve, which ideally has an integrated shut-off function, is connected in parallel to the series circuit comprising the evaporator 3 and the first expansion element 6. A high-voltage battery and / or electrical components, such as electric motors or power electronics, serve as the heat source 11, for example.

[0037] The chiller 12 serves, among other things, to transfer the heat transferred from the heat source 11 to the coolant in the coolant circuit 10 to the refrigerant circuit 2 in the event of a heating deficit. In this function, the chiller 12 works together with the third expansion element 21 as an evaporator. This heat is then transferred via the heat exchanger 7 to the heating circuit 8, and thus the air flow L1 is ultimately heated by means of the heating heat exchanger 9. In this function of the chiller 12, depending on the temperature level in the coolant circuit 10, the shut-off valve 22 is closed and the shut-off valve 23 is open, or vice versa, the shut-off valve 22 is open and the shut-off valve 23 is closed.

[0038] If the chiller 12 is not required for heating support, the third expansion element 21 and the shut-off valve 23 are closed, but the shut-off valve 42 is open, so that the heat from the heat source 11 is dissipated to the outside via the low-temperature cooler 13 via the air flow L2.

[0039] In addition, there may be a need for the chiller 12 if active battery cooling is required, ie the cooling capacity of the low-temperature cooler 13 is no longer sufficient on its own to dissipate the heat generated in the heat source 11 from the coolant circuit 10.

[0040] The embodiment of a vehicle air conditioning system 1 according to the invention according to Fig. 2 differs from that according to Fig. 1 in that the heat exchanger 7, a refrigerant-to-air heat exchanger, is designed as a so-called heating register and is arranged in the air conditioning unit 1.1. The heating circuit 8 is therefore not coupled to the refrigerant circuit 2, but has an alternative heat source 11.1 instead of the heat exchanger 7.

[0041] With this heating circuit 8 according to Fig. 2, the heat from heat source 11.1 can optionally be used to heat air flow L1 by means of heat exchanger 9. There are various options for arranging heat exchanger 7. For example, air flow L1 can be routed downstream of evaporator 3 either via heat exchanger 9 and then via heat exchanger 7, or conversely, first via heat exchanger 7 and then via heat exchanger 9. It would also be possible to route air flow L1 only via the evaporator and heat exchanger 7, dispensing with heat exchanger 9.

[0042] Otherwise, the function corresponds to that in Fig. 2 shown vehicle air conditioning system 1 of that according to Fig. 1. Reference symbol 1 vehicle air conditioning system 1.1 Air conditioning unit of the vehicle air conditioning system 1 1.11 Air flap 2 Refrigerant circuit of the vehicle air conditioning system 1 2.1 Branch point of the refrigerant circuit 2 3 Evaporator of the refrigerant circuit 2 4 Refrigerant compressor of refrigerant circuit 2 5 Refrigerant condenser, gas cooler 6 first expansion organ 7 heat exchangers 8 Heating circuit 9 Heating circuit heat exchanger 8 10 Coolant circuit 11 Heat source 11.1 Heat source of the heating circuit 12 Chiller of the coolant circuit 10 13 Low-temperature cooler of the coolant circuit 10 14 Shut-off valve 15 Shut-off valve 16 Shut-off valve 17 second expansion organ 18 Water pump of the heating circuit 8 19 Heating element of the heating circuit 8 20 Coolant pump of the coolant circuit 10 21 third expansion organ 22 Coolant circuit shut-off valve 10 23 Coolant circuit shut-off valve 10 24 Check valve 25 Bypass valve

Claims

[1] Vehicle air conditioning system (1) with a refrigerant circuit (2) operable as a heat pump circuit with heating function and as a refrigeration circuit with cooling and dehumidification function, comprising: - a refrigerant compressor (4), two shut-off valves (14, 15) connected to the refrigerant compressor (4) on the high-pressure side, an evaporator (3), a refrigerant condenser / gas cooler (5) for dissipating heat extracted from a refrigerant into a vehicle environment by means of an air flow (L2), a first expansion element (6) associated with the evaporator (3) and a heat exchanger (7) for heating a passenger compartment, wherein the listed components (3, 4, 5, 6, 7) form the refrigerant circuit (2), wherein - a shut-off valve (14) for refrigeration system operation can be connected to the refrigerant condenser / gas cooler (5) via a branch point (2.1), and - the other shut-off valve (15) of the two shut-off valves (14, 15) for the heating function can be connected to the heat exchanger (7), characterized by , that - a second expansion element (17) is arranged upstream of the refrigerant condenser / gas cooler (5), - a further shut-off valve (16) is arranged downstream of the heat exchanger (7) in such a way that, when the further shut-off valve (16) is open, the branch point (2.1) is connected to the first expansion element (6), and - when the further shut-off valve (16) is open, at least one partial refrigerant flow can be diverted downstream via the second expansion element (17) via the branch point (2.1) of the refrigerant circuit (2). [2] Vehicle air conditioning system (1) according to claim 1, characterized by , that - the heat exchanger (7) of the refrigerant circuit (2) is designed as a refrigerant-heating medium heat exchanger for coupling to a heating circuit (8), and - a heating heat exchanger (9) is arranged in the heating circuit (8) to carry out the heating function. [3] Vehicle air conditioning system (1) according to claim 1, characterized by that the heat exchanger (7) of the refrigerant circuit (2) is designed as a refrigerant-air heat exchanger. [4] Vehicle air conditioning system (1) according to one of the preceding claims, characterized by , that - a chiller (12) with a third expansion element (21) is connected in parallel to the evaporator (3) and the first expansion element (6), and - the chiller (12) is coupled to a coolant circuit (10) which has a heat source (11) and a low-temperature cooler (13). [5] Vehicle air conditioning system (1) according to one of the preceding claims, characterized by that the second expansion element (17) is designed with an opening diameter corresponding to the pipe diameter in the upstream and downstream sections of the second expansion element (17). [6] Vehicle air conditioning system (1) according to one of claims 1 to 4, characterized by that a bypass valve (25) is connected in parallel to the second expansion element (17). [7] Vehicle with a vehicle air conditioning system (1) according to one of the preceding claims.

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