DE102021123256A1 - Vehicle thermal management system and method of operating the same - Google Patents

Abstract

A vehicle thermal management system for BEVs and a method of operating the same are provided, enabling faster cabin warm-up. By coupling thermal energy from the battery heater into the battery refrigerant circuit, heat in powertrain components or the battery (thermal mass) and/or ambient air in the heat pump assembly in combination with the heat boost mode is still present for a very short duration such as 1 to 5 minutes. In heat boost mode, a portion of the compressed refrigerant gas at the compressor outlet is directed to the inlet of the chiller via a thermal expansion valve to the inlet of the chiller to increase the suction pressure of the compressor, which in turn causes more waste heat to be generated by the compressor, which is lost to the Warming up the vehicle cabin is to be used. At the same time, low-temperature heat from the battery refrigerant circuit - whether the battery heater is activated or not - and/or low-temperature heat from the powertrain refrigerant circuit is coupled into the cooler in order to further increase the suction pressure of the compressor and thus shorten the warm-up time of the vehicle cabin.

Description

The invention relates to a vehicle heat management system according to claim 1 and a method of operating the same according to claim 11.

The complexity of thermal management systems in the automotive industry (PHEV & BEV) is increasing dramatically and the demand for cooling and heating is increasing dramatically. In conventional cars, the waste heat from the I/C motor is used to warm up or heat the passenger cabin. Battery electric vehicles (BEV) typically use a high voltage airside heater to heat the passenger cabin, causing packaging issues within the heating, ventilation, and air conditioning (HVAC) system and increasing costs.

1. a) Die thermische Masse weiterer Komponenten (wie Kompressor, Druckrohr, Akkumulator/Sammler/Wärmetauscher usw.) muss zusammen mit dem Erwärmen bzw. Heizen der Kabinenluft erwärmt werden;
2. b) Die Heizleistung hängt von der Leistungsaufnahme des Kompressors ab, die eine Funktion der Saugdichte, des Druckverhältnisses (Verhältnis von Auslass- zu Einlassdruck des Kompressors) und der Kompressordrehzahl ist;
3. c) Wenn der Kompressor vom Gleichgewichtspunkt bei niedriger Umgebungstemperatur gestartet wird, ist normalerweise der Saugdruck/Dichte niedrig und das Druckverhältnis ist niedriger, daher ist die Heizleistung des Kompressors sehr begrenzt;
4. d) Der Wärmeverlust an die Umgebung ist größer, wenn der Kompressor und das Druckrohr nicht wärmeisoliert sind.

To reduce the overall cost of the system and avoid packaging problems, an existing compressor is used as a heat source to heat the passenger cabin or battery, as in U.S. 2019/0070924 A1 disclosed. However, this approach introduces delays in warming up the cabin for the following reasons:

1. a) The thermal mass of other components (such as the compressor, pressure pipe, accumulator/collector/heat exchanger, etc.) must be heated together with the warming or heating of the cabin air;
2. b) The heating capacity depends on the power input of the compressor, which is a function of the suction density, the pressure ratio (ratio of compressor outlet to inlet pressure) and the compressor speed;
3. c) Normally, when the compressor is started from the equilibrium point in low ambient temperature, the suction pressure/density is low and the pressure ratio is lower, so the heating capacity of the compressor is very limited;
4. d) Heat loss to the environment is greater if the compressor and discharge pipe are not thermally insulated.

Even at very low ambient temperatures such as -20°C, the user demands rapid thermal comfort in the passenger cabin. Starting the system at very low ambient conditions, directly with high/target HVAC airflow, will result in a delay in warm-up and may also result in very limited/insufficient heat production from the compressor.

Accordingly, it is an object of the present invention to provide a vehicle thermal management system for BEVs that enables faster cabin warm-up. Furthermore, it is an object of the invention to provide a method for operating the vehicle heat management system to accelerate warm-up of the cabin.

These objects are achieved with a vehicle thermal management system according to claim 1 and with an operating method according to claim 9.

By coupling thermal energy from the battery heater into the battery refrigerant circuit, heat in powertrain components or the battery (thermal mass) and/or ambient air in the heat pump assembly in combination with the heat boost mode is still present for a very short duration such as 1 to 5 minutes. In heat boost mode, a portion of the compressed refrigerant gas at the compressor outlet is routed to the chiller inlet via a thermal expansion valve to the chiller inlet to increase the compressor suction pressure, which in turn causes more waste heat to be generated by the compressor to be used for warming up the vehicle cabin. At the same time, low-temperature heat from the battery refrigerant circuit - whether the battery heater is activated or not - and/or low-temperature heat from the powertrain refrigerant circuit is coupled into the cooler in order to further increase the suction pressure of the compressor and thus shorten the warm-up time of the vehicle cabin.

Preferably, a pre-conditioning of the vehicle cabin, a prior start of driving the vehicle by using criteria such as ambient temperature, required cabin temperature and available time for pre-conditioning the cabin is used to enable the most energy-efficient mode for increasing the warm-up rate of the vehicle cabin - claim 2.

The heating capacity depends on the power input of the compressor, which is a function of the suction density, the pressure ratio (ratio of compressor outlet to inlet pressure) and the compressor speed. The compressor discharge pressure is a function of the cabin condenser air outlet temperature, so to achieve a desired heating performance for the cabin, the airflow through the cabin condenser and the air outlet temperature should be controlled. Thus, in a preferred embodiment, airflow through the cabin condenser and cabin condenser air outlet temperature is controlled to maintain compressor suction and discharge pressure during heat boost mode to increase the heat production of the compressor and thus increase the warm-up speed of the cabin - claim 3.

In a preferred embodiment, the battery electric heater is positioned after or before the battery with a refrigerant bypass arrangement for the battery so that the battery is not in thermal communication with the battery electric heater. This quickly couples the full heating capacity of the electric battery heater to the radiator, resulting in increased compressor suction pressure and further increased cab warm-up speed. - Claim 4.

Preferably, the battery bypass is only activated for a limited period of time until a desired compressor inlet pressure is reached during heat boost mode of operation - claim 5.

The operation of the compressor with the compressor speed overshooting for a short duration, a few seconds, leads to a faster increase in the suction pressure/suction density at the compressor and thus to a faster increase in the compressor output and the cabin heating output - claim 6.

As already mentioned, the heating capacity depends on the compressor power input, which is a function of the suction density, the pressure ratio and the compressor speed. The compressor discharge pressure is a function of the cabin condenser air outlet temperature, so to achieve a desired heating performance for the cabin, the airflow through the cabin condenser and the air outlet temperature should be controlled. In some operating conditions it is preferable to use an air mix damper to achieve the desired HVAC air outlet temperatures - claim 7.

According to a further preferred embodiment, the control system causes the heat pump arrangement to operate in a heat pump mode, with the compressor operating in the efficient mode or in the heat boost mode or in a combination of heat pump mode and heat boost mode. With these different operating modes, the heating of the cabin can be optimized with regard to the ambient temperature, target cabin temperature and available waste heat sources. - Claim 8.

Method claim 9 is directed to the modes of operation of claim 8.

The warming up of the cabin is preferably started before the vehicle starts driving, so that the cabin is thermally pre-air-conditioned. Thus, when the driver enters the cabin, the cabin is already in a comfortable thermal condition - claim 10.

With the present invention, a faster warm-up rate of the cabin and a comparable warm-up performance as in a heat pump system with high-voltage air-side heating is achieved. Since no air heater is required, costs are reduced. Sleek HVAC packaging is also possible as the high voltage air heater is eliminated.

Preferred exemplary embodiments of the invention are described below with reference to the drawings.

The 1 until 3 illustrate a first embodiment of the present invention;

4 Figure 12 is a comparison of cabin warm-up of the prior art and the present invention;

The 5 until 7 represent a second embodiment;

8th and 9 Figure 12 illustrates the effect of matching the airflow into the HVAC 16 to the suction pressure of the compressor 12;

10 and 11 illustrate the effect of using an air mix door 90 provided in the HVAC 16 between the cabin evaporator 20 and the cabin condenser 14;

12 and 13 represent two different scenarios for the pre-air conditioning of the vehicle cabin before the vehicle starts driving.

The 1 until 3 12 illustrate the various modes of operation according to a first embodiment of a battery refrigerant circuit 4, a powertrain refrigerant circuit 6, a refrigerant circulation assembly 8, and a control system 10. The heat pump assembly 2 includes a compressor 12, a cabin condenser 14, used in a thermal ventilation and air conditioning system 16 for a vehicle cabin a radiator 18 for collecting thermal energy from the battery refrigerant circuit 4 and the powertrain refrigerant circuit, a cabin evaporator 20 located in the HVAC 16, and an exterior heat exchanger 22 operated as an evaporator in the heat pump assembly 2. The HVAC 16 also includes a cabin fan 24 for transporting the Heated or heated air into the vehicle cabin and for controlling the temperature of the cabin condenser 14 and thus the outlet pressure of the compressor 12. A first electric expansion valve 26 is arranged at the inlet of the cooler 18 and a second electric expansion valve 28 is arranged at the inlet of the cabin evaporator 20. A first pressure temperature sensor 30 is arranged at the outlet of the cooler 18 . A second pressure temperature sensor 34 is arranged at the outlet of the compressor 12 . A third pressure temperature sensor 34 followed by a check valve 35 is provided at the outlet of the cabin evaporator 20 . A refrigerant receiver 36, a cabin condenser 14, a compressor 12 are connected to the radiator 18, the cabin evaporator 20 and an outside heat exchanger 22 - all three are operated as evaporators - as known in compressor heat pumps. The refrigerant receiver 36 includes a plurality of valves and a refrigerant reservoir 38 stores liquid refrigerant from the cabin condenser 14 and provides the appropriate amount of liquid refrigerant to the radiator 18, the cabin evaporator 20 and/or the exterior heat exchanger 22 depending on whether the heat pump assembly 2 is in the refrigeration/air conditioning mode or in the heating mode. A fourth pressure temperature sensor 40 is provided at the outlet of the outdoor heat exchanger 22 . The outlet of the outdoor heat exchanger 22 can be connected to the inlet of the compressor 12 via a first isolation valve 42 .

The powertrain refrigerant circuit 6 connects a powertrain refrigerant pump 46 to at least one powertrain component 48 via a powertrain refrigerant 4-way valve 50 to a low temperature cooler (LTR) 52. The LTR 52 is provided adjacent to the exterior heat exchanger 22. A powertrain refrigerant bypass 54 connects the inlet of the powertrain refrigerant pump 46 to the powertrain refrigerant 4-way valve 50. The powertrain refrigerant circuit 6 can be thermally connected to the cooler 18 via the powertrain 4-way valve 50.

The battery refrigerant circuit 4 connects a battery refrigerant pump 56 to the battery 58 via a battery refrigerant 4-way valve 60 to the LTR 42. Between the battery 58 and the battery refrigerant pump 56, an electric battery heater 62 is provided. The battery refrigerant bypass 64 connects the inlet of the battery refrigerant pump 56 to the battery refrigerant 4-way valve 60. The battery refrigerant circuit 4 can be thermally connected to the cooler 18 via the battery refrigerant 4-way valve 60.

in the in 1 As illustrated in the heat pump mode of heat pump assembly 2 , low temperature heat coupled into exterior heat exchanger 22 and radiator 22 is radiated through cabin condenser 14 as high temperature heat into HVAC 16 . It can be seen that at low ambient temperatures, eg -20°C, there is a delay before the vehicle cabin begins to warm up, until waste heat from the compressor 12 and heat from the electric battery heater 52 is available.

To shorten this delay in warming up the cabin, a heat boost mode is applied, as in 2 shown. In addition to the in 1 In the components shown, a compressor bypass 70 connects the outlet of the compressor 12 to a 3-way block connection 74 at the inlet of the cooler 18. In the heat boost mode, the compressor bypass 70 diverts a portion of the hot compressed refrigerant gas back to the radiator 18 to increase the suction pressure of the compressor 12, which in turn causes more waste heat to be used by the compressor to warm up the vehicle cabin. At the same time, low-temperature heat from the battery refrigerant circuit 6 - with or without an activated battery heater 62 - and/or low-temperature heat from the powertrain refrigerant circuit 4 is coupled into the cooler 18 in order to further increase the suction pressure of the compressor 12 and thus to shorten the warm-up of the vehicle cabin.

The heat pump mode from 1 and the heat gain mode of 2 can also be combined like this in 3 is shown. In this combined mode, both the outdoor heat exchanger 22 and the chiller 18 are operated as evaporators in the heat pump assembly 2 .

• - Soll-Heizleistung von 6,5 kW
• - T_{air_in} = -20°C
• - Luftstrom: 270 kg/h
• - Wärmeverstärkungsmodus: p_d/p_s = 25bar/5bar Drehzahlbegrenzung des Kompressors: 8600rpm

The effect of this combination mode on the warm-up speed of the vehicle cabin at low ambient temperatures of -20°C is in 4 is shown comparing the heating energy/power in kW over time in seconds of the present invention - graph 80 - with a reference system - graph 82 - without applying measures of the present invention. For both in 4 The following conditions apply:

• - Target heating output of 6.5 kW
• - _{Tair_in} = -20°C
• - Air flow: 270 kg/h
• - Heat boost mode: p _d /p _s = 25bar/5bar Compressor speed limit: 8600rpm

That in the 5 until 7 illustrated second embodiment of the invention differs from the first embodiment according to the 1 until 3 merely by providing a battery refrigerant bypass 64. In the second embodiment, the battery refrigerant bypass 64 connects the outlet of the battery heater 62 to the battery refrigerant outlet of the battery 58 instead of the inlet of the battery refrigerant pump 56 to the battery refrigerant outlet of the battery 58. This allows the full heating capacity of the electric battery heater 62 can be immediately coupled to the radiator 18, causing an immediate increase in the suction pressure of the compressor 12 and further an increased warm-up rate of the cabin. This battery refrigerant bypass 64 is only activated for a limited period of time until a desired compressor inlet pressure is achieved during heat boost mode of operation.

The 8th and 9 represent a measure to further increase the warm-up rate of the vehicle cabin by optimizing the HVAC airflow caused by the cabin fan 24. Conventionally, the HVAC airflow is ramped up quickly to achieve the desired cabin airflow target. Using the same approach for heat boost mode will result in a delay in warm up and may also result in very limited/insufficient heat production from the compressor. The heating capacity depends on the power input of the compressor, which is a function of the suction density, the pressure ratio (ratio of compressor outlet to inlet pressure) and the compressor speed. The compressor discharge pressure is a function of the cabin condenser air outlet temperature, so to achieve a desired heating performance for the cabin, the airflow through the cabin condenser and the air outlet temperature should be controlled. By controlling the cabin fan 24, the airflow through the cabin condenser 14 and the cabin condenser air outlet temperature can be adjusted to the suction pressure of the compressor 12, as shown in FIG 8th shown. As a result, the compressor suction pressure and the compressor discharge pressure are gradually increased during the heat boost mode, causing the compressor 12 to produce increased heat - as in FIG 9 shown - and thus increases the warm-up speed of the cabin.

Operating the compressor 12 with compressor speed overshoot for a short duration, a few seconds, during the heat boost mode results in a faster increase in suction pressure/suction density at the compressor 12 and thus a faster increase in compressor power and cabin heating power.

As already mentioned, the heating capacity depends on the compressor power input, which is a function of the suction density, the pressure ratio and the compressor speed. The compressor discharge pressure is a function of the cabin condenser air outlet temperature, so to achieve a desired heating performance for the cabin, the airflow through the cabin condenser and the air outlet temperature should be controlled. In some operating conditions, it is advantageous to use an air mix door 90 to achieve desired HVAC air outlet temperatures. As in the 10 and 11 As illustrated, different cabin temperatures, or HVAC outlet air temperatures, T _set , are created using the air mix door provided between the cabin evaporator 20 and the cabin condenser 14 . In 10 _Tset = 75°C and in 11 _Tset = 50°C. In both cases the ambient temperature T _{air_in} is -20°C. In 10 the air flow into the HVAC 16 is 285 kg/h and T _set is 75°C, the air mix door 90 is closed and the air flow from the HVAC 16 into the vehicle cabin is 285 kg/h. In 11 the air flow into the HVAC 16 is 385 kg/h and T _set is 50°C, the air mix door 90 is open to a certain extent and the air flow from the HVAC 16 into the vehicle cabin is 385 kg/h.

The heat production of the compressor 12 depends on the compressor power input, which is a function of the suction density, ie pressure ratio (compressor discharge to inlet pressure ratio, p _d /p _s ) and compressor speed. Compressor discharge pressure p _d is a function of cabin condenser discharge air temperature, so to achieve a desired cabin heating performance, airflow through the cabin condenser 14 and discharge air temperature should be controlled to a saturation temperature of the desired compressor discharge pressure p _d . The air mix door 90 is used to achieve a desired cabin condenser air outlet temperature and a desired HVAC air outlet temperature into the cabin.

12 and 13 represent two different scenarios of preconditioning the vehicle cabin before the vehicle starts driving. Preconditioning means that the warming up of the cabin begins before the vehicle starts driving. The pre-conditioning of the vehicle cabin by using criteria such as ambient temperature, required cabin temperature and available time for Cabin preconditioning is used to select the most energy efficient mode of operation. Using ambient heat pump mode (as in 1 shown) for heating the passenger cabin is more efficient, but leads to a very slow warm-up of the cabin, and the required heating capacity cannot be achieved. Using heat boost mode (by using a compressor as a heat source, as in 2 shown) for heating the passenger cabin is less efficient, but warms up the cabin relatively faster and the required heating capacity can be achieved. Therefore, a combination of these modes is used to precondition the vehicle based on the time available.

In both scenarios, in the 12 and 13 are shown, an ambient temperature of -20°C and a desired cabin temperature of 22°C are assumed. The driver enters the desired cabin temperature and the start time of the journey via an app on a smartphone 100 . in 12 scenario A shown, the journey will start in 10 minutes. This is quite short, and to achieve the desired cabin temperature in those 10 minutes, the control system 10 selects the heat boost mode to warm up the cabin for 10 minutes. in 13 scenario B shown, the journey will start in 30 minutes. The control system selects a waiting time of 10 minutes, then selects heat pump mode for 15 minutes and then heat boost mode for 5 minutes to achieve the desired cabin temperature of 22°C at the entered time of vehicle start travel. Depending on the time available to drive, the ambient temperature, and the desired cabin temperature, the control system 10 selects the most energy efficient heating mode(s).

Reference List

2

heat pump arrangement

4

battery refrigerant circuit

6

Powertrain Refrigerant Circuit

8th

refrigerant circulation arrangement

10

control system

12

compressor

14

cabin condenser

16

Heat Ventilation and Air Conditioning (HVAC) System

18

cooler or chiller

20

cabin evaporator

22

Outer Heat Exchanger

24

cabin fan

26

First electric expansion valve

28

Second electric expansion valve

30

First pressure temperature sensor

32

check valve

34

Second pressure temperature sensor

35

Third pressure temperature sensor

36

refrigerant collector

38

coolant reservoir

40

Fourth pressure temperature sensor

42

First shut-off valve

46

Drive train refrigerant pump

48

Powertrain Component(s)

50

Powertrain Refrigerant 4-Way Valve

52

LTR - low temperature cooler

54

Powertrain Refrigerant Bypass

56

battery refrigerant pump

58

battery

60

Battery refrigerant 4-way valve

62

Electric battery heater

64

Battery refrigerant bypass

70

compressor bypass

72

Third electric expansion valve

74

3-way block connection

76

Second shut-off valve

80

Heat output versus time, present invention, combination mode

82

Heat output over time, reference mode, without invention

90

air mix door

100

smart phone

ps

suction pressure of 12

pd

discharge pressure of 12

pd/ps

pressure ratio of 12

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US20190070924A1 [0003]

Claims (11)

Vehicle thermal management system with: a heat pump assembly (2) including a compressor (12), a cabin condenser (14) and a radiator (18); a battery refrigerant circuit (56) thermally coupling a battery (58) and an electric battery heater (62); a powertrain refrigerant circuit (46) in thermal communication with at least one powertrain component (48), a control system (10) configured to, based on at least one of an ambient temperature, a cabin temperature and a desired travel start time: to control the heat pump arrangement (2) so that it is in one of the modes efficient mode, heat boost mode, or a combination of the efficient mode and the heat boost mode, wherein the compressor (12) generates more heat in the heat boost mode than in the efficient mode; and to control the heat pump assembly (2) to operate in a heat boost mode with or without activating the electric battery heater (62) and to cause the battery refrigerant circuit (54) and/or the powertrain Refrigerant circuit (46) for a limited period of time in thermal communication with the radiator (18). vehicle thermal management system claim 1 wherein in the heat boost mode a portion of the compressed refrigerant gas is routed from the compressor outlet via a compressor bypass (70) with a bypass expansion valve (72) to the inlet of the chiller (18) to increase the suction pressure of the compressor (12), which in turn causes more waste heat to be generated by the compressor (12) to be used to warm up the vehicle cabin. vehicle thermal management system claim 1 or 2 wherein the heat pump assembly (2) is caused to operate in the heat boost mode before the vehicle starts driving. A vehicle thermal management system as claimed in any preceding claim, further comprising a cabin fan (24) controlled by the control system (10) to cause increased inlet and outlet pressure of the compressor (12) during the thermal boost mode. The vehicle thermal management system of any preceding claim, wherein the battery electric heater (62) is positioned after or before the battery (58) with a battery refrigerant bypass (64) such that the battery (58) is not in thermal communication with the battery electric heater (62 ) is. vehicle thermal management system claim 5 wherein the battery refrigerant bypass (64) is activated for a limited period of time until a desired compressor inlet pressure is achieved during the heat boost mode. A vehicle thermal management system as claimed in any preceding claim, wherein the control system causes the compressor speed to increase during the thermal boost mode for a limited period of time at the beginning of the cabin warm-up. The vehicle thermal management system of any preceding claim, wherein the heat pump assembly (2) further includes a cabin evaporator (20) and an air mix door (90) connected between the cabin evaporator (20) and the cabin condenser (14) for directing ambient air into the vehicle cabin is arranged, wherein the control system (10) is configured to activate the air mix door (90) to control the air outlet temperature of the cabin condenser (14) to a saturation temperature of the desired compressor outlet pressure. A vehicle thermal management system as claimed in any preceding claim, wherein the control system (10) is configured to operate the heat pump assembly (2) in a heat pump mode with the compressor (12) in the efficient mode or in the heat boost mode or in a combination of heat pump mode and thermal boost mode is operated. Method for operating the vehicle thermal management system according to claim 9 to warm the vehicle cabin by selectively activating the heat pump mode, the heat boost mode, or a combination of the heat pump mode and the heat boost mode based on the ambient temperature, cabin temperature, and time available until the vehicle is desired to begin driving. procedure after claim 10 wherein warming up of the cabin is started before the vehicle starts running.

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