CN113291116A

CN113291116A - Splash-related regulation of a heat pump

Info

Publication number: CN113291116A
Application number: CN202110193485.0A
Authority: CN
Inventors: J.韦斯托泽; J-C.阿尔布雷赫特
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 2020-02-24
Filing date: 2021-02-20
Publication date: 2021-08-24
Also published as: DE102020104739A1

Abstract

In order to provide a method for operating a heat pump (10), in particular in a motor vehicle (100), having an ambient heat exchanger (20) and an interior heat exchanger (40), which method prevents the icing of the heat pump evaporator from accelerating due to the effect of splash water, it is proposed that the occurrence of splash water (S) in the surroundings (U) of the ambient heat exchanger (20) is detected, wherein the heat pump (10) for heating the interior heat exchanger (40) is operated at an evaporation temperature in the ambient heat exchanger (20) which is higher than the freezing temperature of the splash water (S) or the passenger compartment (101) is directly or indirectly heated by the heat of at least one alternative heat source (80, 81) when the occurrence of splash water (S) is detected.

Description

Splash-related regulation of a heat pump

Technical Field

The invention relates to a method for operating a heat pump, in particular in a motor vehicle, having an ambient heat exchanger and an interior heat exchanger which are connected to one another by a refrigerant circuit. The invention also relates to a motor vehicle having a heat pump.

Background

In electrically driven vehicles, heat pumps are commonly used to heat the passenger compartment. The heat required for heating the passenger compartment is taken from the vehicle surroundings and transferred into the passenger compartment. In the process, the heat exchanger thermally coupled to the vehicle environment is cooled such that the condensation point of the air is below the vehicle surroundings and frost forms on the surface of the heat exchanger.

Due to the formation of frost, the surface of the heat exchanger is increasingly frozen and thus hampers an efficient operation of the heat pump. In order to re-enable the heat exchanger to be flowed through by air, a defrost cycle or defrost process is required, in which the frozen heat exchanger is heated. Thus, the ice melts and the heat exchanger can be flowed through again by the air. But such defrost cycles compromise the efficiency and performance of the heat pump.

Especially for passenger cars, the ambient heat exchanger of the heat pump is arranged in the front engine compartment and is therefore susceptible to water droplets and splashed water. In the heating operation of the heat pump, the temperature of the ambient heat exchanger may drop below 0 ℃, so that splashing water that reaches the ambient heat exchanger may freeze.

Due to the splashed water, the ambient heat exchanger may freeze more rapidly than due to the influence of the re-sublimating air moisture. The freezing of the ambient heat exchanger is accelerated by the splashed water, and thus the ambient heat exchanger needs to perform the defrosting process more frequently, and thus the efficiency of the heat pump is lowered.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for preventing the icing of the heat pump evaporator from accelerating due to the influence of splashing water. The object is achieved according to the invention by a method for operating a heat pump, in particular in a motor vehicle, having an ambient heat exchanger and an interior heat exchanger which are connected to one another by a refrigerant circuit, wherein the occurrence of splash water in the surroundings of the ambient heat exchanger is detected, wherein, when the occurrence of splash water is detected, the heat pump for heating the interior heat exchanger is operated at an evaporation temperature in the ambient heat exchanger which is higher than the freezing temperature of the splash water, or the interior heat exchanger is directly or indirectly heated by the heat of at least one alternative heat source. The object is also achieved according to the invention by a motor vehicle having a heat pump for carrying out the method described above.

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 by a refrigerant circuit. The interior heat exchanger and the ambient heat exchanger of the heat pump can also be designed as a first heat exchanger and as a second heat exchanger. Depending on the operating state of the heat pump, one heat exchanger can act as a condenser and one heat exchanger as an evaporator.

According to the invention, the presence of splash water in the surroundings of the ambient heat exchanger is detected. The detection of splashing water can be carried out continuously or at regular time intervals, if desired, for example due to weather data.

Upon detection of the presence of splash water, the heat pump for heating the interior space heat exchanger is operated at an evaporation temperature in the ambient heat exchanger that is higher than the freezing temperature of the splash water. Alternatively, the vehicle interior space is heated directly or indirectly using the heat of at least one alternative heat source instead of the ambient heat exchanger.

By means of the method, the heat pump can be prevented from operating under operating conditions which do not allow efficient heat pump operation. By detecting spray, rain or splash water, an increased risk of icing to the ambient heat exchanger can be detected and the regulation of the heat pump can be adjusted accordingly.

The detection of the splash water and the regulation or control of the heat pump can be carried out by a controller, which can be connected to the heat pump in a data-transmitting manner. Optionally, the controller may be connected in data transmission with at least one sensor, for example, to receive operating parameters such as the temperature of the ambient heat exchanger, the air temperature, the operating state of the heat pump, the rotational speed of the refrigerant compressor, etc. Furthermore, the controller can be connectable in data-transmitting manner to at least one sensor for detecting splash water.

In the event of splash water, the heat pump can no longer be operated in icing mode of the ambient heat exchanger or of the external heat exchanger by means of the method described. This can be achieved particularly easily technically if the evaporation temperature in the ambient heat exchanger is selected such that the surface temperature of the ambient heat exchanger is not below the condensation or freezing temperature of the splash water.

Alternatively, instead of using outside air as a heat source, an alternative heat source may be used for heating. Here, the waste heat can be provided, for example, by the drive component or by an electric heater.

In one embodiment, the heat of at least one vehicle component, in particular a drive component, a traction battery and/or power electronics, as an alternative heat source is used for directly heating the vehicle interior. It is thus possible to use, for example, the heat loss generated by the vehicle components as a heat source. Preferably, the lost heat may be transported to the area to be heated by at least one fan. For a vehicle-side heat pump, the vehicle interior can be directly heated, for example, with the heat loss provided. Thus, the heat pump may be deactivated or run at reduced power in order to prevent icing of the ambient heat exchanger. The vehicle component can also be an electric heater, which is used only to provide the waste heat.

When the heat from at least one alternative heat source is used for directly heating the interior heat exchanger, the heat pump is deactivated, as a result of which icing of the ambient heat exchanger can be reliably prevented.

According to a further embodiment, the heat of at least one vehicle component, in particular a drive component, a traction battery and/or a power electronics device, as an alternative heat source is used for indirectly heating the vehicle interior by heating at least one traction component heat exchanger connectable to the refrigerant circuit. Instead of feeding the heated air directly into the exemplary vehicle interior, the supplied heat or the air heated by the lost power can also be used to heat a further ambient heat exchanger. The heat pump can therefore continue to operate via the switched-in traction means heat exchanger. The traction means heat exchanger can be arranged here in the region of one or more drive means of the vehicle. The traction means heat exchanger can in particular replace an ambient heat exchanger which is damaged by splashing water or be connected to the refrigerant circuit additionally or in parallel thereto. When the ambient heat exchanger and the at least one traction means heat exchanger are operated in parallel, the refrigerant flow through the first ambient heat exchanger may be throttled such that the evaporation temperature of the refrigerant is greater than 0 ℃, in order to avoid freezing of the first ambient heat exchanger.

The occurrence of splash water is detected by evaluating the measurement data of the at least one sensor, whereby the occurrence of splash water can be determined technically reliably. The detection of the occurring splashing water can be carried out, for example, by optical monitoring of the surroundings or by detecting vibrations due to the collision of water droplets. Such detection can be performed by evaluating measurement data of a camera sensor, a LIDAR sensor, a rain sensor, etc.

According to a further embodiment, the measurement data of at least one camera sensor and/or at least one rain sensor are evaluated in order to identify splashed water in the surroundings of the ambient heat exchanger. Thus, cameras that have been mounted on windshields in many vehicles are able to recognize water foam or rain through image recognition. Alternatively a rain sensor on the windscreen may be used to detect the splashed water. Such sensors are already in use and can therefore be used as a reliable data source for determining unfavorable operating conditions for the heat pump.

The measurement data of at least one rain sensor arranged adjacent to the ambient heat exchanger is evaluated in order to detect splashed water, whereby differences between spray on the location of the ambient heat exchanger and spray or splash water on the location of the windshield can be eliminated. This may preferably be achieved by a rain sensor at the level of the ambient heat exchanger.

According to a further embodiment, the presence 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 needs to be operated at a higher power in order to provide thermal power to the interior heat exchanger. This power consumption of the refrigerant compressor may be used to determine the degree of icing and may also be used to detect splashed water.

The occurrence of splash water is determined on the basis of a change in the ratio of the freezing time period to the defrosting time period of the ambient heat exchanger relative to a reference ratio, whereby the occurrence of splash water can be detected particularly simply technically by evaluating at least one parameter of the refrigerant compressor of the heat pump. Thus, the determination of rain or spray can be made internally by the heat pump regulation. The usual times for the defrosting process and the operating process for the heat pump in connection with a freezing process or operating process that is significantly longer than the defrosting process can be used here.

The quotient of the usual operating time period until the ambient heat exchanger freezes and the time period for the subsequent defrosting of the ambient heat exchanger can be defined as the reference ratio.

In the case where water foam or rainwater is applied to the surface of the ambient heat exchanger, the ratio is decreased as compared with the reference ratio because the operation process until the ambient heat exchanger is frozen is shortened. Based on this change, when adjusting the heat pump, it can be inferred from the ratio of the defrost time to the freeze time that the heat pump is operating with spray or rain. Such deviations may be used to avoid inefficient operating conditions.

A further aspect of the invention relates to a motor vehicle having a heat pump for carrying out the method according to the invention. The interior heat exchanger of the heat pump can be used to cool or heat the interior of the motor vehicle. Alternatively, the interior space heat exchanger can also be used for heating or cooling vehicle components, such as traction batteries or power electronics.

In a heating operation of the vehicle interior, the ambient heat exchanger, which is coupled to the interior heat exchanger via the refrigerant circuit, cools. In this case, frost is formed on the surface of the ambient heat exchanger over time. Splashing water may also accelerate freezing of the ambient heat exchanger. The efficiency of the heat pump is reduced due to the frost or ice layer on the surface of the ambient heat exchanger, and the heating power of the interior space or passenger compartment is impaired. Efficiency is reduced due to the need to perform the defrosting process of the ambient heat exchanger particularly more frequently.

By means of which it is possible to prevent or slow down the acceleration of the ice formation on the surface of the ambient heat exchanger due to the effect of the splashing water. For this purpose, the occurrence of splashed water, spray or rain is detected and measures are initiated, for example by a controller, for slowing down or preventing icing of the ambient heat exchanger.

Drawings

Embodiments of the invention are described in detail below with the aid of the figures. In the drawings:

fig. 1 shows a schematic illustration of a motor vehicle according to the invention, having a heat pump according to one embodiment;

FIG. 2 shows a schematic diagram of the pressure loss coefficient of the air side of the ambient heat exchanger to illustrate accelerated icing due to splashing water.

In the drawings, the same structural elements have the same reference numerals, respectively.

Detailed Description

Fig. 1 shows a schematic side view of a motor vehicle 100 with a heat pump 10 for air treatment according to an embodiment. The heat pump 10 is illustratively used to regulate the temperature in the passenger compartment 101 of the motor vehicle 100. The motor vehicle 100 is designed as a passenger car. The heat pump 10 may be similarly used with any motor vehicle 100, such as a truck, bus, farm vehicle, or the like.

The heat pump 10 has an ambient heat exchanger 20 which is thermally coupled to the ambient U or ambient air. Thus, in the heating operation of the heat pump 10, the ambient heat exchanger 20 may take heat from the ambient U. In the heating operation of the heat pump 10, the ambient heat exchanger 20 can be designed, for example, as an evaporator.

Furthermore, the heat pump 10 has an interior space heat exchanger 40. The interior space 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.

The ambient heat exchanger 20 and the interior space heat exchanger 40 are fluidly connected to each other by a refrigerant circulation circuit 50. Refrigerant can be conveyed through the refrigerant circuit 50 by means of the refrigerant compressor 51, in order to be able to extract heat from the environment U and to transfer the heat into the passenger compartment 101.

As a result of extracting heat from the environment U, the ambient heat exchanger 20 may freeze and thus fail. In order to enable the heat pump 10 to operate permanently, the ambient heat exchanger 20 needs to be periodically de-iced. This is achieved by the defrost process a described in detail in fig. 2.

To perform the defrosting process a, the heat pump 10 may be operated in the opposite direction to the heating operation, for example, to briefly heat the ambient heat exchanger 20.

Since rain water and splashed water S reach the ambient heat exchanger 20, a layer of ice can form relatively quickly on the ambient heat exchanger 20 and impair the operation of the heat pump 10. A more frequent defrost process a is therefore required, which leads to a shortened operating time and a reduced energy efficiency of the heat pump 10.

A controller 60 may be connected to the refrigerant compressor 51 and may be provided for controlling the heat pump 10. The control 60 can in particular fulfill the requirements for the heating power or the cooling power of the heat pump 10 in the form of an adjustment of the operating state of the heat pump 10.

The controller 60 is also connected to a plurality of

sensors

70, 71, 72 in a data-transmitting manner in order to record the presence of splashed water S in the surroundings U of the ambient heat exchanger 20. This can preferably be achieved by receiving and evaluating the measurement data of the

sensors

70, 71, 72.

In the embodiment shown, the

sensors

70, 71, 72 are designed 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 region of a windshield 102 of the motor vehicle 100. The second rain sensor 72 is positioned adjacent the ambient heat exchanger 20 to accurately determine that the ambient heat exchanger 20 is being subjected to the splash water S.

If it is determined by the controller 60 that the splashed water S has an influence on the ambient heat exchanger 20, the heat pump 10 for heating the interior space heat exchanger 40 can be operated at an evaporation temperature in the ambient heat exchanger 20 which is higher than the freezing temperature of the splashed water S, in order to prevent the ambient heat exchanger 20 from freezing.

Alternatively, at least one

alternative heat source

80, 81 may be used to directly or indirectly heat the interior space heat exchanger 40. For example, the heat of at least one

heat source

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

Alternative heat sources

80, 81 may be used to indirectly heat passenger compartment 101 via traction component heat exchanger 21. For this purpose, the traction means heat exchanger 21 can be connected in series with the ambient heat exchanger 20 or, instead of the ambient heat exchanger 20 being damaged by the splashing water S, with the refrigerant circuit 50. An exemplary connecting line 22 of the traction means heat exchanger 21 to the refrigerant circuit 50 is schematically illustrated.

Here, the traction means heat exchanger 21 can extract the heat required for heating the passenger compartment 101 from the

heat sources

80, 81 and can therefore be used to bridge the ambient heat exchanger 20 or to reduce the load on the ambient heat exchanger 20.

Fig. 2 shows a schematic diagram of the pressure loss coefficient ζ on the air side of the ambient heat exchanger 20 for illustrating accelerated icing due to the influence of the splash water S. The pressure loss coefficient ζ on the air side of the ambient heat exchanger 20 varies with time or operating time t.

The pressure loss coefficient ζ at the air side of the ambient heat exchanger 20 is a dimensionless value 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 may extract less heat from the ambient environment U and thus reduce the efficiency of the heat pump 10. To eliminate the icing of the ambient heat exchanger 20, the defrost process a is initiated. The defrosting process a can remove the ice formation of the ambient heat exchanger 20, and the air-side pressure loss coefficient ζ increases again. The degree of icing is reached more quickly due to the influence of the splashing water S, so that a more frequent defrosting process a' is required.

The figure shows a reference curve 90 for the air-side pressure loss coefficient ζ in normal operation or in the case of a damage of the ambient heat exchanger 20 by the spray water S and a curve 91 for the case of a damage of the ambient heat exchanger 20 by the spray water S.

The presence of splash water S may be detected by an evaluation of at least one parameter of the refrigerant compressor 51 of the heat pump 10 by the controller 60. The occurrence of splash water S can be determined by a change in the ratio of the freezing time period 92 to the defrosting process a' time period 94 of the ambient heat exchanger 20 relative to a reference ratio of the reference freezing time period 93 to the reference defrosting process a time period 95.

The reference ratio can be defined as the quotient of the usual operating period or reference freezing period 93 until the ambient heat exchanger 20 freezes and the subsequent defrosting period 95 or defrosting period a 95 of the ambient heat exchanger 20.

List of reference numerals

100 motor vehicle

101 passenger compartment/vehicle interior space

102 windshield

10 Heat pump

20 environment heat exchanger

21 traction element heat exchanger

22 connecting pipeline of traction part heat exchanger

40 internal space heat exchanger

50 refrigerant circulation circuit

51 refrigerant compressor

60 controller

70 camera sensor

71 first rain sensor

72 second rain sensor

80 Power electronics/alternative Heat Source

81 traction battery/alternative heat source

Reference curve of pressure loss coefficient ζ at 90 air side

Curve of pressure loss coefficient ζ on air side under influence of 91 splash water

Run/freeze duration under splash-water influence of 92

93 reference run duration/reference freeze duration

Duration of defrost process under influence of 94 splashed water

95 reference defrost process duration

Pressure loss coefficient of Zeta air side

Reference defrost Process

Defrost process under influence of A' splash water

S splash water

time/running time

Ambient of the U-ambient heat exchanger

Claims

1. Method for operating a heat pump (10), in particular in a motor vehicle (100), the heat pump (10) having an ambient heat exchanger (20) and an interior heat exchanger (40) which are connected to one another by means of a refrigerant circuit (50), characterized in that the presence of splash water (S) in the surroundings (U) of the ambient heat exchanger (20) is detected, wherein, when the presence of splash water (S) is detected, the heat pump (10) for heating the interior heat exchanger (40) is operated at an evaporation temperature in the ambient heat exchanger (20) which is higher than the freezing temperature of the splash water (S), or the interior heat exchanger (40) is directly or indirectly heated by means of the heat of at least one alternative heat source (80, 81).

2. Method according to claim 1, wherein the heat of at least one vehicle component, in particular a drive component, a traction battery (81) and/or a power electronics (80), as an alternative heat source (80, 81) is used for directly heating the passenger compartment (101).

3. The method according to claim 2, wherein the heat pump (10) is deactivated when the inner space heat exchanger (40) is directly heated with heat from at least one alternative heat source (80, 81).

4. Method according to claim 1, wherein the heat of at least one vehicle component, in particular a drive component, a traction battery (81) and/or a power electronics (80), as an alternative heat source (80, 81) is used for indirectly heating the vehicle interior (101) by heating at least one traction component heat exchanger (21) connectable to the refrigerant circuit (50).

5. Method according to any one of claims 1 to 4, wherein the occurrence of splashed water (S) is detected by evaluating measurement data of at least one sensor (70, 71, 72).

6. Method according to any one of claims 1 to 5, wherein measurement data of at least one camera sensor (70) and/or at least one rain sensor (71, 72) are evaluated in order to identify splashed water (S) in the surroundings (U) of the ambient heat exchanger (20).

7. A method according to claim 6, wherein measurement data of at least one second rain sensor (72) arranged adjacent to the ambient heat exchanger (20) is evaluated in order to identify splashed water (S).

8. The method according to any one of claims 1 to 7, wherein the presence of splash water (S) is detected by evaluating at least one parameter of a refrigerant compressor (51) of the heat pump (10).

9. The method of claim 8, wherein the presence of splash water (S) is determined based on a change in a ratio of a freeze period (92) to a defrost period (94) of the ambient heat exchanger (20) relative to a reference ratio (93, 95).

10. A motor vehicle (100) having a heat pump (10) for implementing the method according to any one of the preceding claims.