Splash-water-dependent control of a heat pump

Abstract

Method for operating a heat pump (10), in particular in a motor vehicle (100), with an ambient heat exchanger (20) and an interior heat exchanger (40), which are connected to one another via a refrigerant circuit (50), characterized in that an occurrence of splash water (S) in an environment (U) of the ambient heat exchanger (20) is registered, wherein, upon a registered occurrence of splash water (S), the heat pump (10) is operated to heat the interior heat exchanger (40) with an evaporation temperature in the ambient heat exchanger (20) above a freezing temperature of the splash water (S) or heat from at least one alternative heat source (80, 81) is used to directly or indirectly heat the interior heat exchanger (40), wherein the occurrence of splash water (S) is registered by evaluating at least one parameter of a refrigerant compressor (51) of the heat pump (10).wherein the occurrence of splash water (S) is determined based on a change in a ratio of a freezing time (92) and a defrosting time (94) of the ambient heat exchanger (20) compared to a reference ratio (93, 95).

Description

[0001] The invention relates to a method for operating a heat pump, particularly in a motor vehicle, comprising an ambient heat exchanger and an interior heat exchanger, which are connected to each other via a refrigerant circuit. Furthermore, the invention relates to a motor vehicle with a heat pump.

[0002] Heat pumps are often used to heat the passenger compartment in electrically powered vehicles. The heat required to heat the passenger compartment is extracted from the vehicle's surroundings and transferred to the passenger compartment. During this process, a heat exchanger thermally coupled to the vehicle's surroundings cools to such an extent that the temperature falls below the dew point of the ambient air, and frost forms on the surface of the heat exchanger.

[0003] Due to the formation of frost, the surface of the heat exchanger increasingly ices over, thus preventing efficient operation of the heat pump. To allow air to flow through the heat exchanger again, defrost cycles or defrosting processes are necessary, during which the frozen heat exchanger is heated up. Consequently, the ice melts, and air can flow through the heat exchanger again. However, such defrosting cycles impair the efficiency and performance of the heat pump.

[0004] Especially in passenger cars, the heat pump's ambient heat exchangers are located in the front engine compartment and are therefore vulnerable to spray and splash water. During heating operation of the heat pump, the temperature of the ambient heat exchanger can drop below 0°C, which can cause the splash water that reaches the ambient heat exchanger to freeze.

[0005] Due to splashing water, the ambient heat exchanger can freeze up faster than due to the effects of resublimating humidity. Accelerated icing of the ambient heat exchanger due to splashing water requires more frequent defrosting, thus reducing the efficiency of the heat pump.

[0006] DE 10 2013 110 224 A1 discloses a method for operating an air conditioning system for conditioning the air of a passenger compartment of a motor vehicle, in particular of a motor vehicle with an insufficient heat source from the drive.

[0007] DE 10 2014 102 078 A1 relates to a method for defrosting an ambient heat exchanger of a refrigerant circuit of an air conditioning system designed for a combined refrigeration system and heat pump mode.

[0008] From DE 10 2018 117 097 A1, a heat exchanger arrangement for an air conditioning system of a motor vehicle for conditioning the supply air for a passenger compartment with a refrigerant circuit and a coolant circuit is known.

[0009] JP 2016-120 760 A1 proposes an air conditioner for a vehicle. It includes a freezing device, a controller, and a weather information acquisition part. A control unit determines whether it is raining. The control unit and the weather information acquisition part acquire weather information about precipitation from a predetermined time in the past to the present time. Furthermore, the vehicle air conditioner has, as the heating mode of the freezing device, a heating mode comprising a first operation and a second operation in which heating is performed with an operating load on a compressor that is lower than in the first operation. In the heating mode, the vehicle air conditioner performs the second operation if it is currently raining or if it has rained within a predetermined period of time within a range of the acquired weather information.

[0010] The invention is based on the object of creating a method for preventing accelerated icing of heat pump evaporators due to the effects of splash water. This object is achieved by the features specified in claim 1. Further advantageous embodiments of the invention are described in the subclaims.

[0011] According to one aspect of the invention, a method for operating a heat pump, in particular in a motor vehicle, is provided. The heat pump has an ambient heat exchanger and an interior heat exchanger, which are connected to one another via a refrigerant circuit. The interior heat exchanger and the ambient heat exchanger of the heat pump can also be configured as a first heat exchanger and a second heat exchanger, respectively. Depending on the operating state of the heat pump, one heat exchanger can function as a condenser and one heat exchanger as an evaporator.

[0012] According to the invention, the occurrence of splash water in the environment of the ambient heat exchanger is recorded. The splash water can be recorded continuously, as needed, for example, based on weather data, or at regular intervals.

[0013] If splash water is detected, the heat pump is operated to heat the interior heat exchanger with an evaporation temperature in the ambient heat exchanger above the freezing temperature of the splash water. Alternatively, heat from at least one alternative heat source is used instead of the ambient heat exchanger to directly or indirectly heat the vehicle interior.

[0014] This process can prevent heat pump operation under conditions that do not permit efficient heat pump operation. By detecting spray, rain, or splashing water, the increased risk of icing on the ambient heat exchanger can be identified and the heat pump's control system can be adjusted accordingly.

[0015] The detection of splash water and the regulation or control of the heat pump can be carried out by a control unit that can be connected to the heat pump via a data transmission line. Optionally, the control unit can be connected to at least one sensor via a data transmission line to receive operating parameters, such as the temperature of the ambient heat exchanger, air temperature, the operating state of the heat pump, the speed of the refrigerant compressor, and the like. Furthermore, the control unit can be connected to at least one sensor for detecting splash water.

[0016] If splash water occurs, the process prevents the heat pump from operating in freezing mode with the ambient heat exchanger or the outdoor heat exchanger. This can be implemented particularly easily from a technical perspective if the evaporation temperature in the ambient heat exchanger is selected such that the surface temperature of the ambient heat exchanger does not fall below the solidification or freezing temperature of the splash water.

[0017] Alternatively, the outside air heat source can be eliminated and alternative heat sources can be used for heating. The waste heat can be provided, for example, by drive components or an electric auxiliary heater.

[0018] In one embodiment, heat from at least one vehicle component, in particular a drive component, traction battery and / or power electronics, is used as an alternative heat source for directly heating the vehicle interior. This allows, for example, waste heat generated by the vehicle component to be used as a heat source. The waste heat can preferably be guided to the area to be heated by at least one fan. With a vehicle-mounted heat pump, for example, a vehicle interior can be heated directly with the provided waste heat. This allows the heat pump to be deactivated or operated at a reduced power to prevent the ambient heat exchanger from icing up. In this case, the vehicle component can also be an auxiliary heater that serves exclusively to provide waste heat.

[0019] Icing of the ambient heat exchanger can be reliably prevented if the heat pump is deactivated when heat from at least one alternative heat source is used to directly heat the vehicle interior.

[0020] According to a further embodiment, heat from at least one vehicle component, in particular a drive component, traction battery, and / or power electronics, is used as an alternative heat source for indirectly heating the vehicle interior by heating at least one traction component heat exchanger connectable to the refrigerant circuit. In contrast to a direct supply of heated air into an exemplary vehicle interior, the heat provided or air heated by power loss can also be used to heat another ambient heat exchanger. This allows the heat pump to continue operating with the connected traction component heat exchanger. The traction component heat exchanger can be arranged in the region of one or more drive components of the vehicle.In particular, the traction component heat exchanger can be connected to the refrigerant circuit instead of the ambient heat exchanger affected by splash water, or in addition to or in parallel with it. When the ambient heat exchanger and the at least one traction component heat exchanger are operated in parallel, a refrigerant flow through the first ambient heat exchanger can be throttled such that the evaporation temperature of the refrigerant is greater than 0°C to prevent icing of the first ambient heat exchanger.

[0021] The occurrence of splash water can be detected in a technically robust manner if it is registered by evaluating measurement data from at least one sensor. Detection of splash water can be achieved, for example, by optically monitoring the surrounding area or by registering vibrations caused by the impact of water droplets. Such registration can be achieved by evaluating measurement data from camera sensors, LIDAR sensors, rain sensors, and the like.

[0022] According to a further embodiment, measurement data from at least one camera sensor and / or at least one rain sensor is evaluated to detect spray water in the vicinity of the ambient heat exchanger. This allows the cameras already installed in many vehicles to detect spray or rain on a windshield using image recognition. Alternatively, rain sensors on the windshield can be used to register spray water. Such sensors are already in use and can thus serve as a reliable data source for detecting adverse operating conditions for the heat pump.

[0023] A discrepancy between the occurrence of spray at a position of the ambient heat exchanger and spray or splash water at the position of the windshield can be eliminated by evaluating measurement data from at least one rain sensor located adjacent to the ambient heat exchanger to detect splash water. This can preferably be achieved by a rain sensor at the level of the ambient heat exchanger.

[0024] According to the invention, the occurrence of splash water is detected by evaluating at least one parameter of a refrigerant compressor of the heat pump. Depending on the degree of icing of the ambient heat exchanger, the refrigerant compressor must be operated at a higher power to provide heat output to the indoor heat exchanger. This power consumption of the refrigerant compressor can be used to determine the degree of icing and also to detect splash water.

[0025] By evaluating at least one parameter of the heat pump's refrigerant compressor, the occurrence of splash water is detected particularly easily from a technical perspective. The occurrence of splash water is determined based on a change in the ratio of the freezing time to the defrosting time of the ambient heat exchanger compared to a reference ratio. This allows the heat pump control system to detect rain or spray internally. Typical times for defrosting and operating cycles of the heat pump can be used in a ratio with freezing and operating cycles that are significantly longer than defrosting cycles.

[0026] A quotient of a time duration of a normal operating process until the ambient heat exchanger freezes up and a time duration for subsequent thawing of the ambient heat exchanger can be defined as a reference ratio.

[0027] When spray or rain hits the surface of the ambient heat exchanger, this ratio decreases compared to the reference ratio, as the operating time until the ambient heat exchanger freezes is shortened. Based on this change, the ratio of defrost times to freeze times can be used to determine whether the heat pump is operating in spray or rain. This deviation can be used to avoid inefficient operating conditions.

[0028] A further aspect of the invention relates to a motor vehicle having a heat pump for implementing a method according to the invention. An interior heat exchanger of the heat pump can serve to cool or heat the interior of the motor vehicle. Alternatively, the interior heat exchanger can also be used to heat or cool vehicle components, such as traction batteries or power electronics.

[0029] When the vehicle interior is heated, an ambient heat exchanger connected to the interior heat exchanger via a refrigerant circuit is cooled. Over time, frost can form on the surface of the ambient heat exchanger. Splashing water can further accelerate the icing of the ambient heat exchanger. The layer of frost or ice on the surface of the ambient heat exchanger reduces the efficiency of the heat pump and impairs the heating performance of the interior or passenger compartment. In particular, efficiency is reduced by the more frequent need to defrost the ambient heat exchanger.

[0030] This process can prevent or slow down the accelerated formation of ice on the surface of the ambient heat exchanger caused by splashing water. The occurrence of splashing water, spray, or rain is detected, and measures are initiated, for example, by the control unit to slow or prevent the icing of the ambient heat exchanger.

[0031] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. They show: Fig. 1 a schematic representation of a motor vehicle according to the invention with a heat pump according to an embodiment, and Fig. 2 a schematic diagram of an air-side pressure loss coefficient of an ambient heat exchanger to illustrate accelerated icing by splash water.

[0032] In the figures, the same structural elements have the same reference numerals.

[0033] The Fig. Figure 1 shows a schematic side view of a motor vehicle 100 with a heat pump 10 for air treatment according to one embodiment. The heat pump 10 serves, for example, to adjust a temperature in a passenger compartment 101 of the motor vehicle 100. The motor vehicle 100 is configured as a passenger car. The heat pump 10 can be used analogously in any motor vehicle 100, such as trucks, buses, agricultural vehicles, and the like.

[0034] The heat pump 10 has an ambient heat exchanger 20, which is thermally coupled to an environment U or ambient air. This allows the ambient heat exchanger 20 to extract heat from the environment U during heating operation of the heat pump 10. The ambient heat exchanger 20 can be configured, for example, as an evaporator during heating operation of the heat pump 10.

[0035] Furthermore, the heat pump 10 has an interior heat exchanger 40. The interior heat exchanger 40 is thermally connected to the passenger compartment 101 in order to heat or cool the passenger compartment 101 depending on the operating state of the heat pump 10.

[0036] The ambient heat exchanger 20 and the interior heat exchanger 40 are fluidly connected to each other via a refrigerant circuit 50. A refrigerant can be conveyed through the refrigerant circuit 50 by means of a refrigerant compressor 51 to enable heat to be extracted from the environment U and supplied to the passenger compartment 101.

[0037] By extracting heat from the environment U, the ambient heat exchanger 20 can ice up and thus lose its efficiency. To enable continuous operation of the heat pump 10, the ambient heat exchanger 20 must be defrosted regularly. This is done by a Fig. 2 defrosting process A described in more detail.

[0038] To carry out the defrosting process A, for example, the heat pump 10 can be operated in a direction opposite to the heating operation in order to briefly heat the ambient heat exchanger 20.

[0039] Rain and splash water S that reach the ambient heat exchanger 20 can cause a layer of ice to form more quickly on the ambient heat exchanger 20 and impair the operation of the heat pump 10. This requires more frequent defrosting processes A, which result in a shortened operating time and reduced energy efficiency of the heat pump 10.

[0040] A control unit 60 can be connected to the refrigerant compressor 51 and configured to control the heat pump 10. In particular, the control unit 60 can implement requirements for a heating or cooling capacity of the heat pump 10 by adjusting an operating state of the heat pump 10.

[0041] The control unit 60 is further connected to a plurality of sensors 70, 71, 72 in a data-conducting manner in order to register the occurrence of splash water S in the environment U of the ambient heat exchanger 20. This can preferably be done by receiving and evaluating measurement data from the sensors 70, 71, 72.

[0042] In the illustrated embodiment, sensors 70, 71, 72 are configured as a camera sensor 70, a first rain sensor 71, and a second rain sensor 72. Camera sensor 70 and first rain sensor 71 are arranged in the region of a windshield 102 of motor vehicle 100. Second rain sensor 72 is positioned adjacent to ambient heat exchanger 20 in order to precisely detect the application of spray water S to ambient heat exchanger 20.

[0043] If the control unit 60 detects an effect of splash water S on the ambient heat exchanger 20, the heat pump 10 can be operated to heat the interior heat exchanger 40 with an evaporation temperature in the ambient heat exchanger 20 above a freezing temperature of the splash water S in order to prevent icing of the ambient heat exchanger 20.

[0044] Alternatively, at least one alternative heat source 80, 81 can be used to directly or indirectly heat the interior heat exchanger 40. For example, heat can be extracted from at least one heat source 80, 81 configured as a vehicle component. In the illustrated embodiment, heat can be extracted from a power electronics system 80 and a traction battery 81 of the motor vehicle 100 and used to directly heat the passenger compartment 101.

[0045] For indirect heating of the passenger compartment 101, the alternative heat source 80, 81 can be used with the aid of a traction component heat exchanger 21. For this purpose, the traction component heat exchanger 21 can be connected in series with the ambient heat exchanger 20 or to the refrigerant circuit 50 instead of the ambient heat exchanger 20, which is affected by the splash water S. An exemplary connection 22 of the traction component heat exchanger 21 to the refrigerant circuit 50 is shown schematically.

[0046] The traction component heat exchanger 21 can extract the heat required for heating the passenger compartment 101 from the heat sources 80, 81 and can thus be used to bridge or relieve the ambient heat exchanger 20.

[0047] In the Fig.2 shows a schematic diagram of an air-side pressure loss coefficient ζ of the ambient heat exchanger 20 to illustrate accelerated icing due to the action of splash water S. The air-side pressure loss coefficient ζ of the ambient heat exchanger 20 depends on a time or operating time t.

[0048] The air-side pressure loss coefficient ζ of the ambient heat exchanger 20 is a dimensionless measure of the pressure loss at the ambient heat exchanger 20 and serves to illustrate the consequences of icing. As icing increases, the ambient heat exchanger 20 can extract less heat from the environment U and thus reduces the efficiency of the heat pump 10. To eliminate icing of the ambient heat exchanger 20, defrosting processes A are initiated. A defrosting process A can eliminate icing of the ambient heat exchanger 20, so that the air-side pressure loss coefficient ζ increases again. Due to the effect of splash water S, the degree of icing is reached more quickly, so that more frequent defrosting processes A' are necessary.

[0049] The diagram shows a reference curve 90 in normal operation or without impairment of the ambient heat exchanger 20 by splash water S and a curve 91 of the air-side pressure loss coefficient ζ with impairment of the ambient heat exchanger 20 by splash water S.

[0050] The occurrence of splash water S can be detected by the control unit 60 evaluating at least one parameter of the refrigerant compressor 51 of the heat pump 10. The occurrence of splash water S can be determined based on a change in a ratio of a freezing duration 92 and a duration 94 of the defrosting process A' of the ambient heat exchanger 20 compared to a reference ratio of a reference freezing duration 93 and a duration 95 of the reference defrosting process A without the influence of splash water S.

[0051] A quotient of a time duration of a normal operating process or the reference freezing time 93 until the ambient heat exchanger 20 freezes up and a duration 95 for subsequent thawing or duration 95 of the defrosting process A of the ambient heat exchanger 20 can be defined as a reference ratio. List of reference symbols 100 motor vehicles 101 Passenger compartment 102 Windshield 10 heat pump 20 ambient heat exchangers 21 traction component heat exchangers 22 Connection of the traction component heat exchanger 40 interior heat exchangers 50 Refrigerant circuit 51 refrigerant compressors 60 control unit 70 Camera sensor / Sensor 71 first rain sensor / sensor 72 second rain sensor / sensor 80 Power electronics / alternative heat source 81 Traction battery / alternative heat source 90 Reference curve of the air-side pressure loss coefficient ζ 91 Curve of the air-side pressure loss coefficient ζ with splash water effect 92 Operating time / freezing time with splash water exposure 93 Reference operating time / Reference freezing time 94 Duration of defrosting process with splash water exposure 95 Duration of the reference defrost process ζ air-side pressure loss coefficient A (reference) defrosting process A' Defrosting process with splash water effect S Splash water t Time / Operating time U Environment of the ambient heat exchanger

Claims

[1] Method for operating a heat pump (10), in particular in a motor vehicle (100), with an ambient heat exchanger (20) and an interior heat exchanger (40), which are connected to one another via a refrigerant circuit (50), characterized bythat an occurrence of splash water (S) in an environment (U) of the ambient heat exchanger (20) is registered, wherein when a registered occurrence of splash water (S) the heat pump (10) is operated to heat the interior heat exchanger (40) with an evaporation temperature in the ambient heat exchanger (20) above a freezing temperature of the splash water (S) or heat from at least one alternative heat source (80, 81) is used to directly or indirectly heat the interior heat exchanger (40), wherein the occurrence of splash water (S) is registered by evaluating at least one parameter of a refrigerant compressor (51) of the heat pump (10), wherein the occurrence of splash water (S) is determined based on a change in a ratio of a freezing time (92) and a defrosting time (94) of the ambient heat exchanger (20) compared to a reference ratio (93, 95). [2] Method according to claim 1, wherein heat from at least one vehicle component, in particular a drive component, a traction battery (81) and / or a power electronics unit (80), is used as an alternative heat source (80, 81) for directly heating a passenger compartment (101). [3] Method according to claim 2, wherein when heat from the at least one alternative heat source (80, 81) is used for direct heating of the interior heat exchanger (40), the heat pump (10) is deactivated. [4] Method according to claim 1, wherein heat from the at least one vehicle component, in particular the drive component, the traction battery (81) and / or the power electronics (80), is used as an alternative heat source (80, 81) for indirectly heating the passenger compartment (101) by heating at least one traction component heat exchanger (21) connectable to the refrigerant circuit (50). [5] Method according to one of claims 1 to 4, wherein the occurrence of splash water (S) is registered by evaluating measurement data from at least one sensor (70, 71, 72). [6] Method according to one of claims 1 to 5, wherein measurement data from at least one camera sensor (70) and / or from at least one rain sensor (71, 72) are evaluated to detect splash water (S) in the environment (U) of the ambient heat exchanger (20). [7] Method according to claim 6, wherein measurement data from at least one second rain sensor (72) arranged adjacent to the ambient heat exchanger (20) are evaluated to detect splash water (S). [8] Motor vehicle (100) comprising a heat pump (10) for carrying out a method according to one of the preceding claims.

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