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 each other via a refrigerant circuit (50), wherein the occurrence of splash water (S) in an environment (U) of the ambient heat exchanger (20) is registered, wherein, upon the 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 measurement data from at least two sensors (70, 71, 72), characterized in thatthat measurement data from at least one camera sensor (70) and / or from at least one first rain sensor (71) are evaluated to detect splashing water (S) in the vicinity (U) of the ambient heat exchanger (20), and measurement data from at least one second rain sensor (72) arranged adjacent to the ambient heat exchanger (20) are evaluated to detect splashing water (S).

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 connected to each other via a refrigerant circuit. The invention further relates to a motor vehicle equipped with a heat pump.

[0002] Electrically powered vehicles often use heat pumps to heat the passenger compartment. In this process, 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 down to such an extent that the dew point of the surrounding air is reached, and frost forms on the surface of the heat exchanger.

[0003] Frost buildup increasingly ices the surface of the heat exchanger, thus preventing the heat pump from operating efficiently. To allow air to flow through the heat exchanger again, defrosting cycles are necessary, during which the iced-up heat exchanger is heated. Consequently, the ice melts, and air can flow through the heat exchanger once more. However, such defrosting cycles impair the efficiency and performance of the heat pump.

[0004] Especially in passenger cars, the ambient heat exchangers of the heat pump are located in the front engine compartment and are therefore susceptible to spray and road spray. During heating operation, the temperature of the ambient heat exchanger can drop below 0°C, which can cause the spray water that comes into contact with it to freeze.

[0005] Due to splashing water, the ambient heat exchanger can ice up faster than through exposure to resublimating humidity. This accelerated icing of the ambient heat exchanger by splashing water necessitates more frequent defrosting, thus reducing the efficiency of the heat pump.

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

[0007] DE 10 2014 102 078 A1 discloses a method for defrosting an ambient heat exchanger of a refrigerant circuit of an air conditioning system designed for a combined refrigeration 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] Patent JP 2016-120 760 A proposes an air conditioning system for a vehicle. This system includes a freezing unit, a control unit, and a weather information acquisition unit. A control unit determines whether it is raining. The control unit and the weather information acquisition unit acquire weather information about precipitation from a predetermined time in the past to the present. Furthermore, the air conditioning system for the vehicle has a heating mode for the freezing unit, which includes a first operation and a second operation. In the second operation, heating is carried out with a lower operating load on the compressor than in the first operation. In the heating mode, the air conditioning system for the vehicle performs the second operation if it is currently raining or if it has rained within a predetermined period within a range of the acquired weather information.

[0010] The invention is based on the objective of providing a method for preventing accelerated icing of heat pump evaporators due to exposure to splashing water. This objective is achieved by the features specified in claim 1. Further advantageous embodiments of the invention are described in the dependent claims.

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

[0012] According to the invention, the occurrence of splash water in the vicinity of the ambient heat exchanger is detected. The detection of the splash water can be continuous, on demand (e.g., 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 point 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 method prevents the heat pump from operating under conditions that do not allow for efficient 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 splashing 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 data transmission. Optionally, the control unit can be connected to at least one sensor via data transmission to receive operating parameters such as the temperature of the ambient heat exchanger, air temperature, operating status of the heat pump, speed of the refrigerant compressor, and the like.

[0016] Furthermore, the control unit can be connected to at least one sensor for registering splash water via a data transmission system.

[0017] If splashing water occurs, the heat pump can no longer be operated in the icing mode of the ambient heat exchanger or the external heat exchanger. This can be implemented particularly easily 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 freezing temperature of the splashing water.

[0018] Alternatively, the outside air can no longer be used as a heat source, and alternative heat sources can be used for heating. In this case, waste heat from drive components or an electric auxiliary heater can be provided, for example.

[0019] 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. Preferably, the waste heat can be directed to the area to be heated by at least one fan. With a vehicle-mounted heat pump, for example, the vehicle interior can be heated directly with the provided waste heat. This allows the heat pump to be deactivated or operated at a reduced output 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.

[0020] Icing of the ambient heat exchanger can be reliably prevented if the heat pump is deactivated when using heat from at least one alternative heat source for direct heating of the vehicle interior.

[0021] 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 that can be connected to the refrigerant circuit. In contrast to directly supplying heated air to an exemplary vehicle interior, the provided heat, or air heated by heat 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 located in the area 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, or in addition to, or in parallel with, the ambient heat exchanger which is affected by splashing water. When the ambient heat exchanger and at least one traction component heat exchanger are operated in parallel, the refrigerant flow through the first ambient heat exchanger can be throttled so that the evaporation temperature of the refrigerant is greater than 0°C, thus preventing icing of the first ambient heat exchanger.

[0022] The occurrence of splashing water is reliably detected by evaluating measurement data from at least one sensor. This detection can be achieved, for example, through optical monitoring of the surroundings or by recording vibrations caused by water droplets impacting surfaces. Such recording can be accomplished by evaluating measurement data from camera sensors, LiDAR sensors, rain sensors, and similar devices.

[0023] According to the invention, measurement data from at least one camera sensor and / or at least one first rain sensor are evaluated to detect splashing water in the vicinity of the ambient heat exchanger. This allows cameras already installed in many vehicles on a windshield to detect spray or rain using image recognition. Alternatively, rain sensors on the windshield can be used to register splashing water. Such sensors are already in use and can therefore serve as a reliable data source for identifying adverse operating conditions for the heat pump.

[0024] According to the invention, measurement data from at least one second rain sensor arranged adjacent to the ambient heat exchanger are evaluated to detect splashing water. This can preferably be achieved by a rain sensor at the same height as the ambient heat exchanger. This eliminates any discrepancy between the occurrence of spray at one position of the ambient heat exchanger and spray or splashing water at the position of the windshield.

[0025] In another embodiment, the occurrence of splashing water is detected by evaluating at least one parameter of a refrigerant compressor in the heat pump. Depending on the degree of icing of the ambient heat exchanger, the refrigerant compressor must operate at a higher capacity to provide sufficient 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 splashing water.

[0026] By evaluating at least one parameter of the heat pump's refrigerant compressor, the occurrence of splashing water can be detected particularly easily. This is achieved by determining the occurrence of splashing water based on a change in the ratio of the freezing and defrosting times of the ambient heat exchanger compared to a reference ratio. This allows the heat pump control system to internally identify rain or spray. Typical defrosting and operating times of the heat pump can be used in this analysis, along with significantly longer freezing and operating times.

[0027] A quotient of the time required for a typical operating process until the ambient heat exchanger freezes up and the time required for subsequent thawing of the ambient heat exchanger can be defined as a reference ratio.

[0028] When the surface of the ambient heat exchanger is exposed to spray or rain, 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 heat pump's control system can infer whether it is operating in spray or rain from the ratio of defrosting to freezing times. Such a deviation can be used to avoid inefficient operating conditions.

[0029] Another aspect of the invention relates to a motor vehicle equipped with a heat pump for carrying out a method according to the invention. An interior heat exchanger of the heat pump can be used 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.

[0030] 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 icing. This layer of frost or ice 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.

[0031] This process can prevent or slow down the accelerated formation of ice on the surface of the ambient heat exchanger caused by splashing water. To achieve this, the presence of splashing water, spray, or rain is detected, and measures are initiated, for example by the control unit, to slow down or prevent the icing of the ambient heat exchanger.

[0032] Exemplary embodiments of the invention are explained in more detail below with reference to the drawings. The drawings show: Fig. 1 a schematic representation of a motor vehicle according to the invention with a heat pump according to one embodiment, and Fig. 2 a schematic diagram of an air-side pressure loss coefficient of an ambient heat exchanger to illustrate accelerated icing by splashing water.

[0033] In the figures, the same constructive elements each have the same reference numerals.

[0034] 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, by way of example, to regulate the temperature in a passenger compartment 101 of the motor vehicle 100. The motor vehicle 100 is designed 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.

[0035] The heat pump 10 has an ambient heat exchanger 20, which is thermally coupled to the surrounding environment U or ambient air. This allows the ambient heat exchanger 20 to extract heat from the surrounding environment U during heating operation of the heat pump 10. The ambient heat exchanger 20 can, for example, be configured as an evaporator during heating operation of the heat pump 10.

[0036] 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.

[0037] The ambient heat exchanger 20 and the interior heat exchanger 40 are connected to each other via a refrigerant circuit 50. A refrigerant can be circulated through the refrigerant circuit 50 by means of a refrigerant compressor 51 to enable the extraction of heat from the environment U and the supply of heat to the passenger compartment 101.

[0038] By extracting heat from the environment U, the ambient heat exchanger 20 can ice up and thus lose its efficiency. To enable the continuous operation of the heat pump 10, the ambient heat exchanger 20 must be defrosted regularly. This is done by a [missing information - likely a specific device or component]. Fig. 2. Defrosting process A described in more detail.

[0039] To carry out the defrosting process A, for example the heat pump 10 can be operated in a direction reversed to the heating operation in order to briefly heat the ambient heat exchanger 20.

[0040] Rain and splash water S, which reaches the ambient heat exchanger 20, can cause an ice layer to form more quickly on the ambient heat exchanger 20 and impair the operation of the heat pump 10. This necessitates more frequent defrosting cycles A, which result in a shorter operating time and reduced energy efficiency of the heat pump 10.

[0041] 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 the heating or cooling capacity of the heat pump 10 by adjusting an operating state of the heat pump 10.

[0042] The control unit 60 is further connected to several sensors 70, 71, 72 via data transmission in order to register the occurrence of splash water S in the vicinity U of the ambient heat exchanger 20. This can preferably be done by receiving and evaluating measurement data from the sensors 70, 71, 72.

[0043] In the illustrated embodiment, the sensors 70, 71, 72 are configured as a camera sensor 70, a first rain sensor 71, and a second rain sensor 72. The camera sensor 70 and the first rain sensor 71 are arranged in the area of ​​a windshield 102 of the motor vehicle 100. The second rain sensor 72 is positioned adjacent to the ambient heat exchanger 20 in order to detect precise exposure of the ambient heat exchanger 20 to splash water S.

[0044] 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.

[0045] 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 designed as a vehicle component. In the illustrated embodiment, heat can be extracted from a power electronics unit 80 and a traction battery 81 of the motor vehicle 100 and used to directly heat the passenger compartment 101.

[0046] 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, instead of the ambient heat exchanger 20, which is affected by the splash water S, to the refrigerant circuit 50. An exemplary connection 22 of the traction component heat exchanger 21 to the refrigerant circuit 50 is shown schematically.

[0047] 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.

[0048] In the Fig.Figure 2 shows a schematic diagram of the air-side pressure loss coefficient ζ of the ambient heat exchanger 20 to illustrate accelerated icing due to the action of splashing water S. The air-side pressure loss coefficient ζ of the ambient heat exchanger 20 depends on a time or operating time t.

[0049] The air-side pressure drop coefficient ζ of the ambient heat exchanger 20 is a dimensionless measure of the pressure drop across the ambient heat exchanger 20 and serves to illustrate the consequences of icing. With increasing icing, the ambient heat exchanger 20 can extract less heat from the surroundings U, thus reducing the efficiency of the heat pump 10. To remove the icing from the ambient heat exchanger 20, defrosting processes A are initiated. A single defrosting process A can remove the icing from the ambient heat exchanger 20, causing the air-side pressure drop coefficient ζ to increase again. Exposure to splashing water S accelerates the icing process, necessitating more frequent defrosting processes A'.

[0050] 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.

[0051] The presence of splash water S can be detected by evaluating at least one parameter of the refrigerant compressor 51 of the heat pump 10 using the control unit 60. The presence of splash water S can be determined by comparing the ratio of a freezing time 92 and a defrosting time A' duration 94 of the ambient heat exchanger 20 to a reference ratio of a reference freezing time 93 and a reference defrosting time A duration 95 without the presence of splash water S.

[0052] A quotient of a time duration of a typical operating process or the reference freezing time 93 until the ambient heat exchanger 20 freezes and a duration 95 for a subsequent thawing or duration 95 of the defrosting process A of the ambient heat exchanger 20 can be defined as a reference ratio. Reference symbol list 100 motor vehicles 101 Passenger compartment 102 Windscreen 10 Heat pump 20 ambient heat exchangers 21 Traction Components - 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 action 92 Operating time / Freezing time with exposure to splashing water 93 Reference operating time / Reference freezing time 94 Duration of the defrosting process with exposure to splashing water 95 Duration of the reference defrost cycle ζ air-side pressure loss coefficient A (reference) defrosting process A' Defrosting process with splashing water S Splash water t time / operating time U surroundings 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), wherein 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 measurement data from at least two sensors (70, 71, 72), characterized bythat measurement data from at least one camera sensor (70) and / or from at least one first rain sensor (71) are evaluated to detect splash water (S) in the environment (U) of the ambient heat exchanger (20), and 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). [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 at least one parameter of a refrigerant compressor (51) of the heat pump (10). [6] Method according to claim 5, 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). [7] Motor vehicle (100) comprising a heat pump (10) for carrying out a method according to one of the preceding claims.

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