DE102021129842A1 - vehicle air conditioning - Google Patents

Abstract

A vehicle air conditioning system with a heat pump/chiller for heating and cooling and dehumidifying the air in the vehicle cabin and a method for operating this vehicle air conditioning system are specified, which works with waste heat from the compressor when heating up the vehicle cabin at cold outside temperatures and operates the chiller as a Heat exchanger allows. In order to increase the efficiency of heat pumps/refrigerating machines, it is known to use an internal heat exchanger (10) to heat or overheat the cold refrigerant flow after the evaporator device (4) with the warm refrigerant flow after the condenser device (8). According to the invention, the first bypass line (22) is now fed not to the evaporator inlet but to the heat-absorbing side of the internal heat exchanger. The structure of the internal heat exchanger (10) is thus used to mix the hot partial refrigerant flow from the first bypass line (22) with the cold two-phase refrigerant flow from the evaporator device (4) and to break up refrigerant droplets. Alternatively, the internal structure of the evaporator device (4) can also be used to break up drops of refrigerant.

Description

The invention relates to a vehicle air conditioning system with a heat pump/refrigerating machine for heating and for cooling and dehumidifying the air in the vehicle cabin according to claim 1 and a method for operating the vehicle air conditioning system according to claim 10 or 11.

From the U.S. 2019/0070925 A1 and the JP 2014-226979 A vehicle air conditioning systems with a heat pump/refrigerating machine for heating and for cooling and dehumidifying the air in the vehicle cabin of an electric vehicle are known. These vehicle air conditioning systems both include a heating condenser for heating the air in the vehicle cabin, an external condenser for dissipating waste heat to the environment, a cabin evaporator for cooling the air in the vehicle cabin, an external evaporator, which is referred to as a chiller, with the cabin evaporator and the chiller is preceded by an expansion device and a refrigerant compressor. It is known from both publications to operate the refrigerant compressor in an ineffective mode when the electric vehicle is started at cold outside temperatures, in which the compressor generates more waste heat. This waste heat is then used to heat the vehicle cabin. This is done in that a partial flow of the compressed hot refrigerant gas is fed via a bypass line with an expansion element together with the two-phase refrigerant flow after the expansion element in the chiller path to the low-pressure inlet of the compressor. The cabin evaporator is inactive in this mode because the air in the vehicle cabin is to be heated and not cooled. However, it must be ensured that the refrigerant flow into the compressor has a high vapor content and therefore a low liquid content. In addition, the refrigerant flow must not show any separation of gas and liquid, as refrigerant droplets would damage the compressor.

In the U.S. 2019/0070925 A1 the partial flow returned via the bypass line is mixed with the two-phase flow of refrigerant from the chiller in a low-pressure collector, so that large drops of refrigerant are sufficiently broken up. Compared to a high-pressure collector, the volume of a low-pressure collector is larger. In addition, the low-pressure collector must be designed for high refrigerant mass flows while fulfilling its function of separating the liquid and gaseous phase, which leads to a complex structure with a larger volume. Both are disadvantageous for the limited space available.

In the JP 2014-226979 A the connection point of the bypass line with hot partial flow of refrigerant gas and the two-phase flow after the EXV is in the chiller path between EXV and chiller in the chiller path and the mixing and comminution of refrigerant droplets takes place in the refrigerant channels of the chiller, which have a fine structure. The disadvantage here is that the chiller is exposed to the high temperatures of the hot refrigerant gas flow fed via the bypass line and in this mode cannot act as a heat exchanger, but only as a line with a mixing function.

Starting from the JP 2014-226979 A It is therefore the object of the invention to specify a vehicle air conditioning system which, when heating up the vehicle cabin when the outside temperatures are cold, uses waste heat from the compressor and enables the chiller to be operated as a heat exchanger. It is also the object of the invention to specify a method for operating this vehicle air conditioning system.

This problem is solved by the features of claims 1 or 9 and 10.

In order to increase the efficiency of heat pumps/refrigeration machines, it is known to use an internal heat exchanger to heat or overheat the cold refrigerant flow downstream of the evaporator device using the warm refrigerant flow downstream of the condenser device. According to the invention, a first bypass line is now fed not to the evaporator inlet but to the low-pressure side of the internal heat exchanger. The structure of the internal heat exchanger is thus used to mix the hot refrigerant partial flow from the first bypass line with the cold two-phase refrigerant flow from the evaporator device and to break up refrigerant droplets. Alternatively, the internal structure of the evaporator device can also be used to break up refrigerant droplets.

The advantageous configurations according to claim 2 relate to the configuration of the condenser device in the form of a heating condenser for heating the vehicle cabin and an external condenser for dissipating waste heat.

The advantageous configurations according to claim 3 relate to the configuration of the evaporator device in the form of a cabin evaporator for cooling the air in the vehicle cabin and an external evaporator or chiller for absorbing waste heat or heat from the environment in parallel connection.

According to the advantageous embodiment according to claim 4, the external capacitor is a Coolant circuit connected to an air/liquid heat exchanger. A mixture of glycol and water is used as the coolant.

According to the advantageous embodiment according to claim 5, the chiller can be connected to a heat source or a heat sink via a coolant circuit. The heat sink could be a vehicle battery that is heated when the outside temperature is cold. Vehicle components or the environment can be used as a heat source. In terms of process technology, this different use of the chiller is illustrated by claims 10 and 11.

The internal heat exchanger essentially leads to an improvement in the coefficient of performance of the refrigeration machine in cooling mode. In the heating mode considered here, the internal heat exchanger does not lead to any improvement in the coefficient of performance and it only serves to mix and homogenize the two-phase mixture from the chiller path and the hot refrigerant gas from the first bypass line. According to the preferred embodiment according to claim 6, when the shut-off valve of the second bypass on the high-pressure side of the internal heat exchanger is open, the heat exchange in the internal heat exchanger is reduced. Due to the missing or extremely reduced heat exchange in the inner heat exchanger, the control of the vehicle air conditioning system during the starting process is simplified.

In the variant according to claim 7, the mixing point of the two-phase mixture from the chiller path and the hot refrigerant gas from the bypass line is at the chiller inlet. In order to prevent heat transfer in the inner heat exchanger, a second bypass line is provided on the high-pressure side of the inner heat exchanger. This simplifies the control of the vehicle air conditioning system during the starting process.

The heat transfer in the internal heat exchanger can be deactivated via the three-way valve according to claim 8 in the heating mode considered here, which further simplifies the control of the vehicle air conditioning system during the starting process.

According to a cheaper variant, a simple shut-off valve is used in the second bypass instead of the three-way valve - claim 9.

Further details, features and advantages of the invention result from the following description of a preferred embodiment of the invention.

• 1a ein Blockschaltbild einer ersten Ausführungsform der Erfindung;
• 1b die schematische Darstellung der ersten Ausführungsform im p-h-Diagramm mit Regelstruktur;
• 2 eine erste Betriebsart der ersten Ausführungsform veranschaulicht im p-h-Diagramm;
• 3 eine zweite Betriebsart der ersten Ausführungsform veranschaulicht im p-h-Diagramm;
• 4 ein Blockschaltbild einer zweiten Ausführungsform der Erfindung;
• 5 ein Blockschaltbild einer dritten Ausführungsform der Erfindung;
• 6a ein Blockschaltbild einer vierten Ausführungsform der Erfindung; und
• 6b die schematische Darstellung der vierten Ausführungsform im p-h-Diagramm mit Regelstruktur.

It shows

• 1a a block diagram of a first embodiment of the invention;
• 1b the schematic representation of the first embodiment in the ph diagram with control structure;
• 2 a first mode of operation of the first embodiment illustrated in the ph diagram;
• 3 a second mode of operation of the first embodiment illustrated in the ph diagram;
• 4 a block diagram of a second embodiment of the invention;
• 5 a block diagram of a third embodiment of the invention;
• 6a a block diagram of a fourth embodiment of the invention; and
• 6b the schematic representation of the fourth embodiment in the ph diagram with control structure.

1a shows a block diagram of a first embodiment of the invention with a refrigeration circuit 2 in which an evaporator device 4, a refrigerant compressor 6, a condenser device 8, an internal heat exchanger 10 and an expansion device 12 are integrated. The evaporator device includes a cabin evaporator 40 for cooling a vehicle cabin 14 with a cabin evaporator inlet 40-1 and a cabin evaporator outlet 40-2 and an external evaporator or chiller 42 with a chiller inlet 42-1 and a chiller outlet 42-2. The cabin evaporator 40 and the chiller 42 are connected in parallel in the refrigeration circuit 2 . The chiller outlet 42-2 and the cabin evaporator outlet 40-2 open into a common line 19. The condenser device 8 includes a heating condenser 80 with a heating condenser inlet 80-1 and a heating condenser outlet 80-2 and an external condenser 82 for dissipating waste heat to the environment an input 82-1 and an output 82-2. The heating condenser outlet 80-2 is connected to the inlet 82-1 of the external condenser 82 via the first expansion element 18, ie the heating condenser 80 and the external condenser 82 are connected to one another in series in the refrigeration circuit 2. The external condenser 82 also includes a high pressure receiver 82-3 from which the outlet 82-2 of the external condenser 82 leads out. The expansion device 12 comprises a second expansion element 122 which is connected upstream of the chiller 42 and a third expansion element 123 which is connected upstream of the cabin evaporator 40 . The interior heat exchanger 10 includes a high pressure side 10-1 and a low pressure side 10-2. The high-pressure side 10-1 is traversed by a condensate line 20, which branches off from the outlet 82-2 of the external condenser 82 and in the second and third expansion organ 122, 123 opens. The common line 19 passes through the low-pressure side 10-2; the common line 19 is connected to the low-pressure inlet 6-1 of the refrigerant compressor. Heat is thus transferred from the condensate in the condensate line 20 to the two-phase mixture in the common line 19 by the internal heat exchanger 10 . A first bypass line 22 with a fourth expansion element 24 branches off from the high-pressure outlet 6-2 of the refrigerant compressor 6 and opens into the common line 19 upstream of the low-pressure side 10-2 of the internal heat exchanger 10 in the direction of flow. A check valve 26 is connected on the input side to the cabin evaporator outlet 40- 2 and connected to the common line 19 on the output side. The check valve 26 prevents the hot refrigerant gas from the first bypass line 22 or the two-phase mixture from the chiller 42 from getting into the cabin evaporator that is not active when the vehicle cabin 14 is heated.

1b illustrates the warm-up phase of the cabin when the vehicle starts with low outside temperatures in the ph diagram. The chiller 42 and the cabin evaporator 40 are inactive and therefore only represent one line. The path of the cabin evaporator 40 is closed by the third expansion element 123 . The two-phase mixture from the second expansion element 122 is mixed with the hot partial flow of refrigerant gas from the bypass line 22 in the low-pressure side 10-2 of the internal heat exchanger 10, so that at the low-pressure inlet 6-1 of the refrigerant compressor there is a homogeneous flow of refrigerant with very small drops of refrigerant, or ideally no drops at all . The partial flow of refrigerant gas that is not recirculated is fed to the heating condenser 80 through which the air in the vehicle cabin flows. This causes the air to heat up. The condensed refrigerant from the heating condenser 82 or the high-pressure collector 83 is further cooled in the high-pressure side 10 - 1 of the internal heat exchanger 10 and expanded in the first expansion element 122 .

The temperature of the air emerging from the heating condenser 80, air to the vehicle cabin, is controlled by means of a first control device 14 by changing the speed of the refrigerant compressor 6. By means of a second control device 15, the suction pressure of the refrigerant compressor 6 at the low-pressure inlet 6-1 is controlled by changing the degree of opening of the fourth expansion element 24. By means of a third control device 16, the overheating SH after the low-pressure side 10-2 of the inner heat exchanger is controlled to 10 by changing the degree of opening of the second expansion element 122.

Since the inactive chiller 42 is not required as a mixing device and hot refrigerant gas flows through it, heat can be extracted from or supplied to the chiller 42 by a coolant circuit. 2 illustrates the case in which heat is extracted from the chiller 42 via a coolant circuit and is supplied to a battery. In other words, the chiller 42 is used as a component that gives off heat to the battery, contrary to its heat-absorbing function as an evaporator. How out 2 can be seen, the expanded, two-phase refrigerant is condensed again after the second expansion element 122 and supercooled and mixed in the low-pressure side 10-2 of the inner heat exchanger 10 with the hot partial flow of refrigerant gas from the bypass line 22 and superheated. When the second bypass around the high-pressure side of the internal heat exchanger is open, a higher performance of the chiller is possible in order to give off heat to the cooling circuit and, for example, the battery, due to the higher entry enthalpy without subcooling through the internal heat exchanger.

3 illustrates the case in which waste heat from the environment or from vehicle components is supplied to the chiller 42 via the coolant circuit. The chiller 42 operates in its usual function as an evaporator. The refrigerant is not completely vaporized and is present at the chiller outlet 42-2 in two phases, but with a higher vapor content than at the chiller inlet 42-1.

4 shows a second embodiment with a second bypass line 30 with a shut-off valve 32, which short-circuits the internal heat exchanger 10 on the high-pressure side. The internal heat exchanger 10 essentially leads to an improvement in the coefficient of performance of the refrigeration machine in the cooling mode. In the heating mode considered here, the internal heat exchanger 10 does not lead to an improvement in the coefficient of performance and it only serves to mix and homogenize the two-phase mixture from the chiller 42 and the hot refrigerant gas from the first bypass line 22 on the low-pressure side. When the shut-off valve 32 is open, the majority of the refrigerant flow in the condensate line 20 is therefore routed past the internal heat exchanger 10 . Due to the missing or significantly reduced heat exchange in the inner heat exchanger 10, the control of the vehicle air conditioning system is simplified during the starting process.

5 Fig. 13 shows a third embodiment of the invention, which differs from the second embodiment in that the shut-off valve 32 has been replaced by a three-way valve 34. In this way, the heat transfer of the internal heat exchanger can be completely deactivated in the heating mode considered here, which is the rule Management of the vehicle air conditioning system during the starting process is further simplified.

6a Fig. 12 shows a fourth embodiment of the invention, which differs from the third embodiment 5 differs in that the first bypass line 22 with the fourth expansion element 24 does not open into the common line 19 but into the chiller inlet 42-1. In order to prevent heat transfer in the indoor heat exchanger 10, a second bypass line 30 is provided on the high-pressure side of the indoor heat exchanger 10. This simplifies the control of the vehicle air conditioning system during the starting process.

6b illustrates the warm-up phase of the cabin when the vehicle starts with low outside temperatures in the ph diagram. The cabin evaporator 40 is inactive and the path of the cabin evaporator 40 is closed by the third expansion element 123 . The internal heat exchanger 10 essentially leads to an improvement in the coefficient of performance of the refrigeration machine in the cooling mode. In the heating mode considered here, the internal heat exchanger 10 does not lead to any improvement in the coefficient of performance and it is only used for additional mixing and homogenization of the two-phase mixture from the chiller 42.

The control is analogous to that based on 1b explained regulation 1b . The temperature of the air emerging from the heating condenser 80, air to the vehicle cabin, is controlled by means of a first control device 14 by changing the speed of the refrigerant compressor 6. By means of a second control device 15, the suction pressure of the refrigerant compressor 6 at the low-pressure inlet 6-1 is controlled by changing the degree of opening of the fourth expansion element 24. By means of a third control device 16, the overheating SH after the low-pressure side 10-2 of the internal heat exchanger 10 is controlled by changing the degree of opening of the second expansion element 122. A fourth control device 17 adjusts the undercooling SC after the heating condenser 18 by changing the degree of opening of the first expansion element 18 .

Reference List

SH

overheating

SC

hypothermia

2

Refrigerant circulation

4

evaporator device

40

cabin evaporator

40-1

cabin evaporator inlet

40-2

cabin evaporator outlet

42

external evaporator, chiller

42-1

chiller input

42-2

chiller outlet

6

refrigerant compressor

6-1

low pressure inlet

6-2

high pressure outlet

8th

condenser device

80

heating condenser

80-1

heating condenser input

80-2

heating condenser output

82

external condenser

82-1

External condenser input

82-2

External capacitor output

83

high-pressure collector

10

internal heat exchanger

10-1

high pressure side

10-2

low pressure side

12

expansion device

122

second expansion organ

123

third expansion organ

14

first control device

15

second control device

16

third control device

17

fourth control device

18

first expansion organ

19

common line

20

condensate line

22

first bypass line

24

fourth expansion organ

26

check valve

30

second bypass line

32

shut-off valve

34

three-way valve

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

• US 2019/0070925 A1 [0002, 0003]
• JP 2014226979 A [0002, 0004, 0005]

Claims (11)

Vehicle air conditioning system with a heat pump/refrigeration machine, which has a refrigerant circuit (2) and which can be operated to heat a vehicle cabin (14) and to cool and dehumidify the vehicle cabin (14), comprising: - an evaporator device (4) which has an evaporator inlet (40 -1, 42-1) and an evaporator outlet (40-2, 42-2), - a refrigerant compressor (6) which has a high-pressure outlet (6-2) and a low-pressure inlet (6-1), the low-pressure inlet ( 6-1) is connected to the evaporator outlet (40-2, 42-2), - a refrigerant condenser device (8) which has a condenser inlet (80-1) and a condenser outlet (82-2), the condenser inlet (80- 1) is connected to the high-pressure outlet (6-2), - an expansion device (12, 122, 123), which is connected upstream of the evaporator device (4), and - a first bypass line (22), which runs from the high-pressure outlet (6-2 ) branches off, for supplying a partial flow of the compressed refrigerant via a second expansion device (24) to the evaporator outlet (40-2, 42-2) or the evaporator inlet (40-1, 42-1), characterized by - an internal heat exchanger (10 ), which is arranged between the condenser outlet (82-2) and the first expansion device (12, 122, 123) on the one hand and the low-pressure inlet (6-1) and evaporator outlet (40-2, 42-2) on the other. vehicle air conditioning claim 1 , characterized in that the condenser device (8) comprises a heating condenser (80) for heating the vehicle cabin (14) and an external condenser (82), which are connected in series via a first expansion element (18), the heating condenser (80) is connected to the high-pressure outlet (6-2) and the external condenser (82) via the outlet (82-2) to the internal heat exchanger (10). vehicle air conditioning claim 1 or 2 , characterized in that the evaporator device (4) has a cabin evaporator (40) for cooling the air in the vehicle cabin (14) and an external evaporator or chiller (42), which are connected in parallel, and that the expansion device (12) has a second and the third expansion element (122, 123) comprises that the second expansion element (122) is connected upstream of the chiller (42) and that the third expansion element (123) is connected upstream of the cabin evaporator (40). vehicle air conditioning claim 2 or 3 , characterized in that an air/liquid heat exchanger is connected to the external condenser (82) via a first coolant circuit. Vehicle air conditioning according to one of the preceding claims 3 until 4 , characterized in that the chiller (42) is connected to a second coolant circuit for dissipating or absorbing heat. Vehicle air conditioning system according to one of the preceding claims, characterized in that a second bypass line (30) with a valve device (32; 34) is arranged between the condenser outlet (82-2) and the expansion device (12) in order to close the condenser outlet (82-2) to be connected directly and/or via the internal heat exchanger (10) to the expansion device (12). Vehicle air conditioning according to one of the preceding claims 3 until 6 , characterized in that the first bypass line (22) is connected to the chiller inlet (42-1). Vehicle air conditioning, after claim 6 or 7 , characterized in that the valve device is an adjustable three-way valve (34). Vehicle air conditioning, after claim 6 or 7 , characterized in that the valve means is a shut-off valve (32). Method for operating an air conditioning system according to one of the preceding claims 3 until 9 that the chiller (42) emits heat to a vehicle battery in the heating mode via a coolant circuit. Method for operating an air conditioning system according to one of the preceding claims 3 until 9 that the chiller (42) absorbs waste heat in heating mode via a coolant circuit.

Images