Refrigeration system with heat pump function for a motor vehicle with a sensor device arranged on the high-pressure side downstream of an internal heat exchanger, and a method for operating such a refrigeration system.

Abstract

A refrigeration system (10), in particular with a heat pump function, for a motor vehicle (200) with an internal combustion engine or at least partially electric drive is described. The refrigeration system (10) comprises a refrigerant circuit (11) with a refrigerant compressor (12); a first heat exchanger (18), in particular a gas cooler or condenser; a second heat exchanger (22), in particular an evaporator; and an internal heat exchanger (20). A first sensor device (pT7) for detecting a refrigerant pressure and / or a refrigerant temperature is arranged in the refrigerant circuit (11) on the high-pressure side downstream of the internal heat exchanger (20) and upstream of the second heat exchanger (22). Furthermore, a method for operating such a refrigeration system is described.

Description

[0001] The invention relates to a refrigeration system, in particular with a heat pump function, for a motor vehicle with an internal combustion engine or at least partially electric drive, wherein the refrigeration system comprises a refrigerant circuit with a refrigerant compressor; a first heat exchanger, in particular a gas cooler or condenser; a second heat exchanger, in particular an evaporator; and an internal heat exchanger. The invention further relates to a method for operating such a refrigeration system.

[0002] Such a refrigeration system is described, for example, in DE 10 2020 133 101 A1, in particular in the section therein. Fig. 8, and DE 10 2019 126 850 A1 is known.

[0003] In such known refrigeration systems (also known as AC systems) or refrigeration systems combined with a heat pump function (also known as AC / HP systems), sensor devices for detecting refrigerant pressure and / or temperature are typically located directly downstream of the refrigerant compressor and on the low-pressure side between the second heat exchanger (evaporator) and the refrigerant compressor. In supercritical refrigeration systems, such as those operating with refrigerant R744, an (additional) such sensor device may also be located directly downstream of the first heat exchanger (gas cooler).

[0004] In refrigeration systems designed in this way, it is not possible to determine the enthalpy before entering the second heat exchanger (evaporator), so that no conclusions can be drawn about the enthalpy and thus the outlet condition at the outlet of the second heat exchanger.

[0005] The object underlying the invention is seen as being to provide a refrigeration system in which the above disadvantages can be avoided and improved operation of the refrigeration system is made possible taking enthalpy into account.

[0006] This problem is solved by a refrigeration system and a method for operating a refrigeration system with the features of the respective independent patent claim. Advantageous embodiments with expedient further developments are specified in the dependent patent claims.

[0007] A refrigeration system, particularly one with a heat pump function, is proposed for a motor vehicle with an internal combustion engine or at least partially electric drive. The refrigeration system comprises a refrigerant circuit with a refrigerant compressor; a first heat exchanger, particularly a gas cooler or condenser; a second heat exchanger, particularly an evaporator; and an internal heat exchanger. It is provided that a first sensor device for detecting refrigerant pressure and / or temperature is arranged in the refrigerant circuit on the high-pressure side downstream of the internal heat exchanger and upstream of the second heat exchanger.

[0008] By arranging the sensor device in this section of the refrigeration system, it is possible to draw conclusions about the enthalpy at the inlet of the second heat exchanger, in particular the evaporator, based on the recorded temperature and / or pressure values ​​of the refrigerant.

[0009] In this context, it is important to consider that the refrigeration system must be in an operating state where the measured pressure and temperature allow for the determination of a unique material property value for the enthalpy. Preferably, this should be a subcooled or supercritical state.

[0010] In the refrigeration system, an expansion device can be assigned to the second heat exchanger upstream, with the first sensor device being arranged upstream of the expansion device. Such an arrangement of the sensor device is permissible because the enthalpy generally does not change due to the expansion of the refrigerant upstream of the second heat exchanger or evaporator.

[0011] In the refrigeration system, the refrigerant circuit can have a third heat exchanger, in particular a chiller, which is arranged parallel to the second heat exchanger with respect to the direction of flow of refrigerant in the refrigerant circuit, wherein the first sensor device is arranged upstream of the third heat exchanger.

[0012] In this configuration, a further expansion element can be assigned to the third heat exchanger upstream, with the first sensor device being arranged upstream of the further expansion element.

[0013] By arranging the sensor device upstream of the third heat exchanger or its expansion element, an input-side enthalpy for the third heat exchanger can also be determined.

[0014] In the refrigeration system, a second sensor device for detecting refrigerant pressure and / or refrigerant temperature can be arranged downstream of the refrigerant compressor and upstream of the first heat exchanger in the refrigerant circuit.

[0015] In the refrigeration system, a third sensor device for detecting refrigerant pressure and / or refrigerant temperature can be arranged downstream of the first heat exchanger and upstream of the inner heat exchanger in the refrigerant circuit.

[0016] In a refrigeration system, the first heat exchanger can have a first heat exchanger section or at least one flux, particularly for cooling and / or condensing the refrigerant, and in particular a subcooling section, particularly for subcooling the refrigerant. Subcooling of the refrigerant can only occur in the case of subcritical system operation, particularly on the high-pressure side of the system. Such a configuration of the first heat exchanger can be provided, in particular, when using R744 as the refrigerant.

[0017] The refrigeration system can have a control unit that is connected to the first sensor device. This allows the control unit to receive and process measured values ​​from the first sensor device.

[0018] The control unit can also be connected to other components of the refrigeration system, such as the refrigerant compressor, the expansion device(s), and other sensor devices, so that the refrigeration system can be operated or controlled in different operating modes by means of the control unit.

[0019] A method for operating a refrigeration system described above is also proposed, wherein the method comprises the following steps: recording a refrigerant pressure value and a refrigerant temperature value using the first sensor device; determining an inlet enthalpy of the refrigerant before entering the second heat exchanger and / or the third heat exchanger as a function of the refrigerant pressure and refrigerant temperature values ​​recorded using the first sensor device.

[0020] The procedure may also include the following steps: Recording a refrigerant pressure value and a refrigerant temperature value using the third sensor device; Determining the enthalpy converted on the high-pressure side of the refrigerant circuit as a function of the refrigerant pressure and refrigerant temperature values ​​recorded by the first sensor device and the third sensor device.

[0021] Using the refrigeration system and method described above, it is possible to determine, ascertain, or estimate the outlet enthalpy at the heat exchanger(s) based on the inlet enthalpy and the power dissipated at the second and / or third heat exchanger(s). Based on this outlet enthalpy, the following information, for example, can be determined or conclusions drawn: power distribution in the respective heat exchanger, superheating of the refrigerant after passing through the respective heat exchanger, and undercharging of the refrigerant circuit or system.

[0022] A motor vehicle with an internal combustion engine and / or at least partially electric drive, in particular also a purely electric vehicle, may be equipped with a refrigeration system described above, which can be operated in particular according to the procedure described above.

[0023] Further advantages and details of the invention will become apparent from the following description of embodiments with reference to the figures. These show: Fig. 1. A simplified and schematic representation of a refrigeration system of a motor vehicle; Fig. 2 a simplified representation of a method for operating a refrigeration system.

[0024] In Fig. Figure 1 is a schematic and simplified representation of an embodiment of a refrigeration system 10 for a motor vehicle. The refrigeration system 10 comprises a refrigerant circuit 11, which can be operated in both refrigeration mode (also referred to as AC mode) and heat pump mode. In the embodiment shown, the refrigeration system 10 comprises a refrigerant compressor 12, an external heat exchanger 18, an internal heat exchanger 20, an evaporator 22, and a refrigerant accumulator or receiver 24. The external heat exchanger 18 can be configured as a condenser or a gas cooler. In particular, the external heat exchanger 18, in the embodiment shown, allows bidirectional flow.

[0025] The evaporator 22 is shown here as an example of a front evaporator for a vehicle. The evaporator 22 also represents other possible evaporators in a vehicle, such as rear evaporators, which can be arranged parallel to each other in terms of airflow. In other words, the refrigeration system 10 includes at least one evaporator 22.

[0026] A shut-off valve A4 is arranged downstream of the compressor 12. An expansion valve AE2 is provided upstream of the evaporator 22.

[0027] Within the scope of this description, the section from the compressor 12 to the external heat exchanger 18, to the internal heat exchanger 20 and to the evaporator 22 in the entire refrigerant circuit 11 of the refrigeration system 10 is referred to as the primary circuit 14.

[0028] The refrigeration system 10 further comprises a heating coil 26 (also referred to as a heating condenser or hot gas cooler). A shut-off valve A3 is arranged upstream of the heating coil 26. A shut-off valve A1 is arranged downstream of the heating coil 26. Furthermore, an expansion valve AE4 is arranged downstream of the heating coil 26.

[0029] Within the scope of this description, the section of the entire refrigerant circuit of the refrigeration system 10 from the compressor 12 to the heating coil 26, to the expansion valve AE4, and to a branch Ab2 is referred to as the secondary circuit 16. The secondary circuit 16 comprises a heating branch 16.1, which extends from the shut-off valve A3 via the heating coil 26 to the shut-off valve A1. The secondary circuit 16 also includes a reheat branch 16.2, which is fluid-connected upstream to the heating coil 26 and downstream to the external heat exchanger 18. The secondary circuit 16, or rather the reheat branch 16.2, connects to the primary circuit 14 at branch Ab2.

[0030] The refrigeration system 10 includes an additional evaporator or chiller 28. Chiller 28 is arranged parallel to evaporator 22 in terms of flow direction. Chiller 28 can, for example, be used to cool an electrical component of the vehicle, or to implement a water-source heat pump function by utilizing the waste heat from at least one electrical component. An expansion valve AE1 is installed upstream of chiller 28.

[0031] The refrigeration system 10 can also include an electric heating element 30, which is, for example, designed as a high-voltage PTC heating element. The electric heating element 30 serves as an auxiliary heater for an intake air stream L directed into the vehicle interior. The electric heating element 30 can be housed together with the heating coil 26 and the evaporator 22 in an air conditioning unit 32. The electric heating element 30 can be arranged downstream of the heating coil 26.

[0032] The refrigeration system 10 with heat pump function shown here as an example is intended in particular for a motor vehicle 200, which is shown here in simplified form as a dashed rectangle, with internal combustion engine or at least partially electric drive.

[0033] The refrigeration system 10 therefore comprises the refrigerant circuit 11 with the refrigerant compressor 12, a first heat exchanger 18 (or external heat exchanger), in particular a gas cooler or condenser, a second heat exchanger 22 (evaporator) and the internal heat exchanger 20. In the refrigerant circuit 11, a first sensor device pT7 for detecting a refrigerant pressure and / or a refrigerant temperature is arranged on the high-pressure side downstream of the internal heat exchanger 20 and upstream of the second heat exchanger 22.

[0034] As mentioned above, the expansion element AE2 is assigned upstream to the second heat exchanger 22 or evaporator, with the first sensor device pT7 being arranged upstream of the expansion element AE2.

[0035] In the refrigeration system 10, the refrigerant circuit 11 can have the third heat exchanger 28, in particular a chiller, which is arranged parallel to the second heat exchanger 22 (evaporator) with respect to the flow direction of refrigerant in the refrigerant circuit 11, wherein the first sensor device pT7 is arranged upstream of the third heat exchanger 28.

[0036] As mentioned above, the expansion element AE1 is assigned to the third heat exchanger 28 or chiller upstream, with the first sensor device pT7 being arranged upstream of the expansion element AE1.

[0037] The refrigeration system 10 can have a second sensor device pT1 in the refrigerant circuit 11 for detecting a refrigerant pressure and / or a refrigerant temperature downstream of the refrigerant compressor 12 and upstream of the first (outer) heat exchanger 18 or gas cooler.

[0038] In the refrigeration system 10, a third sensor device pT5 for detecting a refrigerant pressure and / or a refrigerant temperature can be arranged in the refrigerant circuit 11 downstream of the first (outer) heat exchanger 18 and upstream of the inner heat exchanger 20.

[0039] The first (outer) heat exchanger may include a first heat exchanger section (not shown here). This section may be designed as a gas cooler and may have at least a single-flow design. As a condenser, the first heat exchanger may include at least a single-flow condensation section and, if necessary, a subcooling section.

[0040] Furthermore, the refrigeration system 10 has a control unit 50 which is connected to the first sensor device pT7. The control unit 50 is also connected to the other components (actuators, sensors) of the refrigeration system 10, so that desired operating modes of the refrigeration system 10 can be set or controlled by means of the control unit 50.

[0041] The refrigeration system 10 can also include a sensor device pT2 arranged on the low-pressure side upstream of the internal heat exchanger 20 for detecting a refrigerant pressure and / or a refrigerant temperature.

[0042] Alternatively, such a sensor device pT2, should a refrigerant storage unit 24 and an internal heat exchanger 20 be designed as a combination component, can be installed downstream of the internal heat exchanger 20 and thus upstream of the compressor 12.

[0043] In the Fig. Figure 1 also shows optional check valves Rn (n = integer). Furthermore, the refrigeration system may also have other sensor devices not shown here.

[0044] In Fig. Figure 2 shows a simplified method 500 for operating a refrigeration system 10 described above, wherein the method 500 in particular comprises the following steps.

[0045] According to step S501, a refrigerant pressure value and a refrigerant temperature value are recorded using the first sensor device pT7.

[0046] According to step S502, the inlet enthalpy of the refrigerant is determined before entering the second heat exchanger 22 and / or the third heat exchanger 28 as a function of the refrigerant pressure and refrigerant temperature values ​​recorded by the first sensor device pT7.

[0047] According to step S503, a refrigerant pressure value and a refrigerant temperature value can be detected using the third sensor device pT5.

[0048] According to step S504, the enthalpy converted on the high-pressure side in the refrigerant circuit 11 can be determined as a function of the refrigerant pressure and refrigerant temperature values ​​recorded by the first sensor device pT7 and the third sensor device pT5.

[0049] The first sensor device pT7, in conjunction with the third sensor device pT5 (especially for AC processes), enables a balancing of the converted enthalpy for the high-pressure side section of the internal heat exchanger 20 on the high-pressure side of the refrigerant circuit 11, especially for load cases with subcooling after the gas cooler.

[0050] This enthalpy value is equivalent in magnitude to the low-pressure side section of the internal heat exchanger 20. With a further pressure-temperature sensor (not shown) possibly arranged between the internal heat exchanger 20 and the compressor, the inlet enthalpy of the refrigerant to the refrigerant storage tank 24 can be calculated using this sensor and the determined enthalpy conversion of the internal heat exchanger 20. Consequently, the inlet state of the refrigerant entering the refrigerant storage tank 24 can be determined, and thus the refrigerant quality, i.e., the vapor content present, can also be determined.

[0051] Using the method 500 described above, the inlet enthalpy upstream of at least one evaporator 22 and / or chiller 28 can be determined based on recorded pressure / temperature values ​​and material properties of the refrigerant used during supercritical operation and / or when subcooling is ensured during subcritical operation.

[0052] Based on the inlet enthalpy and the power dissipated at the evaporator 22 and / or chiller 28, the outlet enthalpy at the heat exchangers 22 and 28 can be determined. The outlet enthalpy allows conclusions to be drawn about the power distribution in a given heat exchanger, about superheating of the refrigerant after the heat exchanger, or about underfilling of the refrigerant circuit 11 or system.

[0053] The described method can also be applied to the actual heat pump operation of a refrigeration system. In this case, the pressure-temperature sensor pT4, located downstream of the heating coil 26, is used to determine the enthalpy of the refrigerant leaving the heat exchanger. Based on a heat balance across a chiller 28 in the water-source heat pump mode of the refrigeration system 10 and the inlet enthalpy to the chiller 28, the outlet state of the refrigerant can be determined or estimated.

[0054] If the refrigeration system 10 operates in reheat mode without using the reheat loop 16.2, and thus with parallel flow through the first heat exchanger 18 and the heating coil 26 – meaning that after compressor 12 the refrigerant mass flows are split into a first mass flow flowing through the first heat exchanger 18 and a second mass flow flowing through the heating coil 26 – then, if both partial mass flows are recombined in a section of the branches Ab1 and Ab8, and thus before flowing through the expansion elements AE1 and / or AE2, the resulting enthalpy at the inlet of the subsequently flowed heat exchangers 22 and / or 26 is determined by the respective mass flow fractions flowing through the heat exchangers. For example, if both heat exchangers 26 and 28 are flowed through with equal mass flows, a mixed enthalpy results as the average of the two individual enthalpies.In another example, if the first heat exchanger 18 is supplied with 75% and the heating coil 26 with 25% of the total mass flow provided by the compressor 12, the resulting “effective” enthalpy at the heat exchangers 22 and / or 28 can be determined or estimated as 75% of the difference between the enthalpy exiting the first heat exchanger 18 and the heating coil 26.

[0055] If the refrigeration system 10 is equipped with an internal heat exchanger 20, its effect in a reheat mode with the parallel flow through the heat exchangers 18 and 26 described above is reduced with increasing mass flow proportion via the heating register 26 until it is completely eliminated at 100% mass flow via the heating register 26. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2020 133 101 A1

[0002] DE 10 2019 126 850 A1

[0002]

Claims

[1] Refrigeration system (10), in particular with heat pump function, for a motor vehicle (200) with internal combustion engine or at least partially electric drive, wherein the refrigeration system (10) has a refrigerant circuit (11) with a refrigerant compressor (12); a first heat exchanger (18), in particular a gas cooler or condenser; a second heat exchanger (22), in particular an evaporator; an internal heat exchanger (20); characterized by , that in the refrigerant circuit (11) a first sensor device (pT7) for detecting a refrigerant pressure and / or a refrigerant temperature is arranged on the high-pressure side downstream of the inner heat exchanger (20) and upstream of the second heat exchanger (22). [2] Refrigeration system (10) according to claim 1, characterized by, that an expansion element (AE1) is associated upstream of the second heat exchanger (22), wherein the first sensor device (pT7) is arranged upstream of the expansion element (AE1). [3] Refrigeration system (10) according to claim 1 or 2, characterized by , that the refrigerant circuit (11) has a third heat exchanger (28), in particular a chiller, which is arranged parallel to the second heat exchanger (22) with respect to the direction of flow of refrigerant in the refrigerant circuit (11), wherein the first sensor device (pT7) is arranged upstream of the third heat exchanger (28). [4] Refrigeration system (10) according to claim 3, characterized by , that a further expansion element (AE1) is associated upstream of the third heat exchanger (28), wherein the first sensor device (pT7) is arranged upstream of the further expansion element (AE1). [5] Refrigeration system (10) according to any of the preceding claims, characterized by, that in the refrigerant circuit (11) a second sensor device (pT1) for detecting a refrigerant pressure and / or a refrigerant temperature is arranged downstream of the refrigerant compressor (12) and upstream of the first heat exchanger (18). [6] Refrigeration system (10) according to any of the preceding claims, characterized by , that in the refrigerant circuit (11) a third sensor device (pT5) for detecting a refrigerant pressure and / or a refrigerant temperature is arranged downstream of the first heat exchanger (18) and upstream of the inner heat exchanger (20). [7] Refrigeration system (10) according to any of the preceding claims, characterized by , that the first heat exchanger (18) has a first heat exchanger section and in particular a subcooling section. [8] Refrigeration system (10) according to any of the preceding claims, characterized bythat it has a control unit (50) which is connected to the first sensor device (pT7). [9] Method (500) for operating a refrigeration system (10) according to any one of the preceding claims, wherein the method comprises the following steps: Acquisition (S501) of a refrigerant pressure value and a refrigerant temperature value by means of the first sensor device (pT7); Determine (S502) an inlet enthalpy of the refrigerant before entering the second heat exchanger (22) and / or the third heat exchanger (28) as a function of the refrigerant pressure and refrigerant temperature values ​​detected by the first sensor device (pT7). [10] Method (500) according to claim 9, wherein the method (500) further comprises the following steps: Acquisition (S503) of a refrigerant pressure value and a refrigerant temperature value using the third sensor device (pT5); Determining the enthalpy converted on the high-pressure side of the refrigerant circuit as a function of the refrigerant pressure and refrigerant temperature values ​​recorded by the first sensor device (pT7) and the third sensor device (pT5).

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