JP2016035377A - Compression cooling system and operation method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To create a compression cooling system as an air conditioning system which decreases a temperature in a vehicle and decrease a stoppage pressure acting on a compressor when the compression cooling system is not operated.SOLUTION: A compression cooling system 10 includes: a compressor 12; a gas cooler 14; an expansion device 16; and an evaporator 18. The compressor 12, the gas cooler 14, the expansion device 16, and the evaporator 18 are connected with each other by using lines in a circulation passage including a refrigerant. A first shutoff valve 34 is disposed at a downstream side of the compressor 12 and in front of the gas cooler 14. At least a second shutoff valve 36 is disposed at an upstream side of the compressor 12. Further, in an operation method of the compression cooling system 10, the second shutoff valve 36 is closed when the compression cooling system 10 is not operated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a compression cooling system according to the preamble of claim 1 and a method of operating the compression cooling system according to the preamble of claim 9.

  The compression cooling system is used as an air conditioning system for lowering the temperature inside the vehicle, particularly in a vehicle such as a passenger car or a passenger bus.

A general purpose compression refrigeration system for achieving this purpose comprises, inter alia, a compressor, a gas cooler, an expansion device, and an evaporator, which are connected to one another in a circuit. Present in the closed circuit is a refrigerant, such as carbon dioxide (CO ₂ ).

  A compression cooling system of this type is disclosed, for example, in EP 147 972 B1.

  Such a compression cooling system can also be found in WO 97/27437. WO 97/27437 also discloses a compression cooling system additionally comprising an intermediate heat exchanger.

  DE 10 2006 011 060 A1 discloses a system that additionally comprises a separate accumulator incorporated in the circuit between the evaporator and the heat exchanger.

  WO 94/14016 discloses a system with an additional expansion tube. In this case, the expansion pipe is connected to the circuit line between the expansion device and the evaporator.

  DE 10 2006 041 156 A1 discloses a system with an additional shut-off valve. A shut-off valve is incorporated in the line between the evaporator and the expansion device. When the compressor is switched off, the shut-off valve closes the line, and when the compressor is switched on, the shut-off valve opens the line.

During operation of a general-purpose compression cooling system, a relatively high operating pressure prevails downstream of the compressor and a relatively low pressure prevails upstream of the compressor. When the system is not in operation, pressure equalization occurs and a relatively high stop pressure is created in the circuit of the compression cooling system. In this case, the compressor must be designed for a relatively high stop pressure and must therefore be protected. In the case of a system according to EP 087576 having a certain filling (for example 260 g / m ³ ), a maximum pressure of 90.5 bar is achieved at a maximum temperature of 55 ° C. when the system is not operating according to EN 378. If triple safety is provided, the burst pressure should in this case be 271.5 bar.

EP 147 972 B1 WO 97/27437 DE 10 2006 011 060 A1 WO 94/14016 DE 10 2006 041 156 A1 EP087576

  The problem addressed by the present invention is to create a compression cooling system of the type described at the outset, where a reduced stop pressure acts on the compressor when the compression cooling system is not in operation.

  This object is achieved according to the invention by a compression cooling system having the features of claim 1.

  Advantageous configurations and developments of the invention are the subject of the dependent claims.

  A general-purpose compression cooling system includes a compressor, a gas cooler, and an expansion device and an evaporator, which are connected to each other using a line in a circulation path containing a refrigerant.

  According to the invention, the first shut-off valve is arranged downstream of the compressor and before the gas cooler, and at least one second shut-off valve is arranged upstream of the compressor. Accordingly, the second shut-off valve is disposed between the gas cooler outlet and the compressor inlet.

  If the system is in operation, both shut-off valves are opened. When the system is not in operation, both shut-off valves are closed and the compression cooling system is divided into two parts by the closed shut-off valve.

  In one part (meaning the high-pressure part), the refrigerant (preferably carbon dioxide) is in this case below an operating pressure of about 100 bar. In the other part (meaning the low pressure part), the refrigerant is in this case below a stop pressure of about 55 bar. Therefore, the stop pressure of the refrigerant (carbon dioxide) is below a critical pressure of about 73.8 bar.

  The system is operated, for example, at a high pressure of 100 bar and a suction pressure of 35 bar (this corresponds to evaporation at 0 ° C.). If the system is not in operation, the pressure initially remains the same. When all system parts are heated to 55 ° C. (maximum temperature when the system is not operating according to EN 378), the low pressure side pressure rises to about 50-60 bar. This is below the critical pressure of 73.8 bar and even lower than the system without a shut-off valve.

  The gas cooler is located in the high pressure section. The compressor is located in the low pressure section, so that when the compression cooling system is not in operation, a lower stop pressure is exerted on the compressor than in the case of compression cooling systems known in the prior art. Thus, the compressor can be protected from lower pressures and can therefore be realized in a lighter and less expensive manner.

  When the compression cooling system according to the present invention is not in operation, only a reduced stop pressure is present in the outlet line of the compressor. Thus, the compressor does not need to start under load.

  According to one advantageous development of the invention, the first shut-off valve is in the form of a check valve. The first check valve therefore automatically closes when the compressor is switched off and the pressure in the compressor drops and the pressure in the gas cooler is higher than in the compressor. The first check valve automatically opens when the compressor is switched on and the pressure behind the compressor increases. Therefore, clear control of the first shut-off valve is not necessary.

  The second shut-off valve is preferably in the form of a solenoid valve. Particularly advantageously, the second shut-off valve is connected to the compressor control and automatically closes when the compressor is switched off and opens automatically when the compressor is switched on.

  Advantageously, the intermediate heat comprising a first heat exchanger line arranged between the gas cooler and the expansion device and a second heat exchanger line arranged between the evaporator and the compressor. An exchange is installed. In this case, the second shut-off valve is preferably arranged between the first heat exchanger line and the expansion device. As a result, the stop pressure is particularly low.

  Advantageously, the accumulator is arranged between the evaporator and the compressor. In this case, the second shut-off valve is preferably arranged between the accumulator and the compressor. As a result, the stop pressure is particularly low.

  The problem is also solved by a method having the features of claim 9.

  In this case, the second shut-off valve automatically closes when the compressor is switched off, i.e. when the compression cooling system is not in operation.

  The second shut-off valve opens automatically when the compressor is switched on, i.e. when the compression cooling system is in operation.

  The invention is explained in more detail in the following text by means of advantageous exemplary embodiments shown in the figures. However, the invention is not limited to these exemplary embodiments. In the figure:

1 shows a schematic diagram of a compression cooling system according to a first exemplary embodiment. 1 shows a schematic cycle diagram in the form of a pH diagram of a compression cooling system according to a first exemplary embodiment. FIG. 2 shows a schematic diagram of a compression cooling system according to a second exemplary embodiment. FIG. 3 shows a schematic cycle diagram in the form of a pH diagram of a compression cooling system according to a second exemplary embodiment. 3 shows a schematic diagram of a compression cooling system according to a third exemplary embodiment. FIG. 4 shows a schematic cycle diagram in the form of a pH diagram of a compression cooling system according to a third exemplary embodiment.

The compression cooling system 10 according to the first exemplary embodiment comprises a compressor 12, a gas cooler 14, and an expansion device 16, and an evaporator 18, which are connected to each other in a circulation path using lines. ing. In this case, carbon dioxide (CO ₂ ) is present in the closed circuit as a refrigerant.

  Disposed on the line downstream of the compressor 12 and in front of the gas cooler 14 is a first shut-off valve 34. In this case, the first shut-off valve 34 is located immediately in front of the gas cooler 14.

  In this case, the first shut-off valve 34 has a check valve shape. When the compression cooling system 10 is in operation, the refrigerant that is compressed to the operating pressure by the compressor 12 can flow through the first shut-off valve 34 to the gas cooler 14. When the compression cooling system 10 is not in operation, the first shut-off valve 34 prevents the refrigerant from flowing back from the gas cooler 14 to the compressor 12.

  Arranged in the line upstream of the compressor 12 (in this case, between the gas cooler 14 and the expansion device 16) is a second shut-off valve 36. In this case, the second shut-off valve 36 is located behind the gas cooler 14. It can also be incorporated into the expansion device 16.

  In this case, the second shutoff valve 36 is in the shape of a solenoid valve. When the compression refrigeration system 10 is in operation, the second shut-off valve 36 opens and refrigerant can flow from the gas cooler 14 through the second shut-off valve 36 to the expansion device 16. When the compression cooling system 10 is not in operation, the second shut-off valve 36 closes to prevent refrigerant from continuing to flow from the gas cooler 14 to the expansion device.

  In this case, the compression cooling system 10 is operated at transcriticality. During operation, for example, an operating pressure of 100 bar and a temperature of 100 ° C. dominate downstream of the compressor 12. The refrigerant is in a supercritical state under these conditions. During operation, for example, a pressure of 34.9 bar and a temperature of 5 ° C. prevail upstream of the compressor 12. The refrigerant is in a gaseous state under these conditions.

  The refrigerant flows from the compressor 12 through the first shut-off valve 34 to the gas cooler 14 where it is cooled. From the gas cooler 14, the refrigerant flows through the open second shut-off valve 36 to the expansion device 16, where it expands to reduce pressure and temperature. In the process, the refrigerant becomes partially liquid and partially gas. From the expansion device 16, the refrigerant flows onto the evaporator 18, where the liquid fraction of the refrigerant evaporates again into a gas. The gaseous refrigerant coming out of the evaporator 18 is sucked by the compressor 12 and compressed to the operating pressure.

  Along with the pressure-enthalpy diagrams shown in FIGS. 1a, 2a and 3a, the respective states of the refrigerant (through which the refrigerant passes through the compression cooling system 10 according to the invention) are described in the following text: Briefly explained.

  1 represents a refrigerant as superheated gas at the inlet to the compressor 12. 1 'represents the state of the refrigerant as a vapor with a slightly liquid fraction at the outlet of the evaporator 18. 2 represents the refrigerant as the compressed gas at the outlet of the compressor 12, reference numeral 3 represents the refrigerant as the cooled supercritical gas at the outlet of the gas cooler 4, and the state 3 ′ is expanded. Represents a further cooled supercritical gaseous refrigerant at the inlet to the device 16 and reference numeral 4 represents an expanded refrigerant having liquid and vapor fractions at the outlet of expansion number 16 and at the inlet of the evaporator 18. 4 ′ represents the liquid phase of the refrigerant in the accumulator 24, and 4 ″ represents the gas phase of the refrigerant in the accumulator 24.

FIG. 1a shows the cycle in a pressure enthalpy diagram. In each case, the prevailing refrigerant pressure can be read from the isovolume line. Compression in the compressor 12 is performed from state 1 to state 2. Density changes from 92 g / ^{m 3} to 188 g / ^{m 3.} The low-pressure part of the compressor 12 occupies, for example, a ratio of 10.83% of the system volume, and the high-pressure part occupies a ratio of 0.40%. The pressure line to the gas cooler 14 accounts for 4.93% and the density corresponding to state 2 is 188 g / m ³ .

Behind the first shut-off valve 34, the refrigerant is cooled in the gas cooler 14 from state 2 to state 3. In this case, the density increases to 621 g / m ³ . The gas cooler 14 is subdivided into three parts with equal output. Mean density and the ratio of the system capacity, respectively, 219 g / ^{m 3} and 4.85% 317 g / ^{m 3} and 10.92%, which is 488 g / ^{m 3} and 30.91%. The hottest part of the gas cooler 14 requires a minimum area and a minimum amount for heat conduction because of the large temperature difference. The second shut-off valve 36 and the line to the expansion device account for 1.98% of the system capacity. The density corresponding to state 3 is 621 g / m ³ .

The expansion device 16 does not occupy much of the system capacity. Isoenthalpy expansion occurs from state 3 to state 4. A partially liquid refrigerant is evaporated in the evaporator 18 so that it again reaches state 1 at the outlet from the evaporator 18. The evaporator 18 is subdivided into three parts with equal output. The average density and proportion of system capacity is 156 g / m ³ and 7.22%, 124 g / m ³ and 7.22%, 101 g / m ³ and 8.24%, respectively. As a result of the constant evaporation temperature, all parts are approximately the same size. The suction line to the compressor 12 accounts for 12.49% of the system capacity. The density corresponding to state 1 is 92 g / m ³ .

The overall filling degree of the system is 268 g / m ³ . The isovolume line intersects the 55 ° C. isothermal line 42 under a pressure of 91.8 bar. The compressor 12 should be designed for this maximum stop pressure. As a result of the advantageous first embodiment comprising the shut-off valves 34 and 36, the system comprises a gas cooler 14 and a high pressure part 40 comprising a line between the gas cooler 14 and the second shut-off valve 36, and It is subdivided into a low pressure part 38. The high pressure section 40 accounts for 48.67% of the system capacity and has an average density or filling degree of 428 g / m ³ . The low pressure section 38 accounts for 51.33% and has an average density or average degree of 117 g / m ³ . The isobaric lines of the high and low pressure sections (40, 38) are drawn and intersect the 55 ° C. isothermal line 42 at 110.9 bar and 55.7 bar, respectively. This is the maximum stop pressure. In FIG. 1 a, the low pressure filling degree in the low pressure part 38 is represented by reference numeral 44; the high pressure filling degree in the high pressure part 40 is represented by reference numeral 46.

  When the compression cooling system 10 is not in operation, the second shut-off valve 36 is closed. In the gas cooler 14, the refrigerant is still lower than the operating pressure. In the rest of the compression refrigeration system 10, namely the expansion device 16, the evaporator 18, and the compressor 12, pressure equalization occurs where the refrigerant is below a lower stop pressure (eg 55.7 bar). .

  The first shut-off valve 34 (in this case in the form of a check valve) prevents the refrigerant from flowing back from the gas cooler 14 to the compressor 12, and thus the leveling between the gas cooler 14 and the compressor 12. Prevent pressure. The second shut-off valve 36 prevents refrigerant from flowing from the gas cooler 14 to the expansion device 16 and thus prevents pressure equalization between the gas cooler 14 and the expansion device 16.

  Therefore, when not in operation, the compression cooling system 10 is divided into a high pressure portion and a low pressure portion by the shutoff valves 34 and 36. In this case, the gas cooler 14 is located in the high-pressure part and the compressor 12 is located in the low-pressure part, where, for example, a maximum stop pressure of 55.7 bar prevails.

  In this case, when the compression cooling system 10 is not in operation, the expansion device 16 and the evaporator 18 are also located in the low pressure portion.

  In a first modification of the first exemplary embodiment, the second shut-off valve 36 is placed in a line between the expansion device 16 and the evaporator 18. In this case, when the compression cooling system 10 is not in operation, the expansion device 16 is located in the high pressure portion.

  In a second modification of the first exemplary embodiment, the second shut-off valve 36 is placed in a line between the evaporator 18 and the compressor 12. In this case, when the compression cooling system 10 is not in operation, the expansion device 16 and the evaporator 18 are located in the high pressure section.

  The compression cooling system 10 according to the second exemplary embodiment is similar to the compression cooling system 10 according to the first exemplary embodiment in terms of structure and functionality. Therefore, in particular, the differences are explained in the following text.

In addition to the compressor 12, the gas cooler 14, the expansion device 16, and the evaporator 18, the compression cooling system 10 according to the second exemplary embodiment additionally comprises an intermediate heat exchanger 28, which is circulated. They are connected to each other using lines in the road. In this case, carbon dioxide (CO ₂ ) is also present in the closed circuit as a refrigerant.

  The intermediate heat exchanger 28 includes a first heat exchanger line 13 and a second heat exchanger line 32. The first heat exchanger line 30 is located between the gas cooler 14 and the expansion device 16. The second heat exchanger line 32 is located between the evaporator 18 and the compressor 12.

  When the compression cooling system is in operation, the intermediate heat exchanger 28 reduces the refrigerant temperature before entering the expansion device 16 and increases the refrigerant temperature before entering the compressor 12.

  Disposed on the line downstream of the compressor 12 and in front of the gas cooler 14 is a first shut-off valve 34. The first shut-off valve 34 is in this case located immediately in front of the gas cooler 14.

  In this case, the first shut-off valve 34 is in the form of a check valve. When the compression cooling system 10 is in operation, the refrigerant compressed to the operating pressure by the compressor can flow to the gas cooler 14 through the first shut-off valve 34. When the compression cooling system 10 is not in operation, the first shut-off valve 34 prevents the refrigerant from flowing back from the gas cooler 14 to the compressor 12.

  Arranged in the upstream line of the compressor 12 (in this case, between the first heat exchanger line 30 of the intermediate heat exchanger 28 and the expansion device 16) is a second shut-off valve 36. In this case, the second shut-off valve 36 is located immediately behind the first heat exchanger line 30 of the intermediate heat exchanger 28.

  In this case, the second shut-off valve is in the shape of a solenoid valve. When the compression cooling system 10 is in operation, the second shut-off valve 36 opens and refrigerant can flow from the intermediate heat exchanger 28 through the second shut-off valve 36 to the expansion device 16. When the compression cooling system 10 is not in operation, the second shut-off valve 36 closes to prevent coolant from continuing to flow from the intermediate heat exchanger 28 to the expansion device 16.

  The compression cooling system 10 is in this case operated transcritical. During operation, for example, an operating pressure of 100 bar and a temperature of 100 ° C. dominate downstream of the compressor 12. The refrigerant is in a supercritical state under these conditions. During operation, for example, a pressure of 34.9 bar and a temperature of 5 ° C. prevail upstream of the compressor 12. The refrigerant is in a gaseous state under these conditions.

  The refrigerant flows from the compressor 12 through the first shut-off valve 34 to the gas cooler 14 where it is cooled. From the gas cooler 14, the refrigerant flows onto the first heat exchanger line 30 of the intermediate heat exchanger 28 where it is further cooled. From the first heat exchanger line 30 of the intermediate heat exchanger 28, the refrigerant flows through the open second shut-off valve 36 to the expansion device 16, where it expands to reduce pressure and temperature. In this process, the refrigerant is partially liquid and partially gas. From the expansion device 16, the refrigerant flows onto the evaporator 18, where the liquid fraction of the refrigerant evaporates again into a gas. From the evaporator 18, the refrigerant flows onto the second heat exchanger line 32 of the intermediate heat exchanger 28 where it is heated. The gaseous refrigerant coming out of the second heat exchanger line 32 of the intermediate heat exchanger 28 is sucked by the compressor 12 and compressed to the operating pressure.

FIG. 2a shows the cycle in a pressure enthalpy diagram. In each case, the prevailing refrigerant pressure can be read from the isovolume line. Compression in the compressor 12 is performed from state 1 to state 2. Density changes from 92 g / ^{m 3} to 188 g / ^{m 3.} The low pressure part of the compressor 12 occupies, for example, a ratio of 10.75% of the system capacity, and the high pressure part occupies a ratio of 0.39%. The pressure line to the gas cooler 14 accounts for 4.90% and the density corresponding to state 2 is 188 g / m ³ .

Behind the first shut-off valve 34, the refrigerant is cooled from state 2 to state 3 in the gas cooler 14. In this case, the density increases to 621 g / m ³ . The gas cooler 14 is subdivided into three parts with equal output. Mean density and the ratio of the system capacity, respectively, 219 g / ^{m 3} and 4.81% 317 g / ^{m 3} and 10.84%, which is 488 g / ^{m 3} and 30.68%. The hottest part of the gas cooler 14 requires a minimum area and a minimum amount for heat conduction because of the large temperature difference.

The line of the intermediate heat exchanger 28 to the first heat exchanger line 30 accounts for 0.14% of the system capacity. The density corresponding to state 3 is 621 g / m ³ . In the first heat exchanger line 30 of the intermediate heat exchanger 28, the refrigerant is further cooled to a state 3 ′ and a density of 690 g / m ³ . The first heat exchanger line 30 accounts for 0.34% of the system capacity and has an average density of 654 g / m ³ . The line to the second shutoff valve 36 and the expansion device 16 accounts for 1.83% of the system capacity. The density corresponding to state 3 ′ is 690 g / m ³ .

The expansion device 16 does not occupy much of the system capacity. Isoenthalpy expansion is performed from state 3 ′ to state 4. The partially liquid refrigerant is evaporated in the evaporator 18 and in the second heat exchanger line 32 of the intermediate heat exchanger 28. At the outlet from the evaporator 18, the state 1 ′ and an average density of 102 g / m ³ are reached again. The evaporator 18 is subdivided into three parts with equal output. Mean density and the ratio of the system capacity, respectively, 182 g / ^{m 3} and 7.50%, 139 g / ^{m 3} and 7.50%, a 112 g / ^{m 3} and 7.50%. As a result of the constant evaporation temperature, all parts are the same size. The evaporator 18 is filled better compared to the first embodiment.

The line between the evaporator and the second heat exchanger line 32 of the intermediate heat exchanger 28 accounts for 2.10% of the system capacity and the average density corresponding to state 1 ′ is 102 g / m ^3. It is. In the second heat exchanger line 32, the refrigerant is further evaporated and superheated to reach state 1 again. The second heat exchanger line 32 of the intermediate heat exchanger 28 occupies 0.42% of the system capacity and has an average density of 97 g / m ³ . The suction line to the compressor 12 accounts for 10.30% of the system capacity. The density corresponding to state 1 is 92 g / m ³ .

The overall filling degree of the system is 275 g / m ³ . The isotonic line intersects the 55 ° C. isotherm 42 under a pressure of 92.8 bar. The compressor 12 should be designed for this maximum stop pressure. As a result of the advantageous second embodiment comprising the shut-off valves 34 and 36, the system comprises the gas cooler 14, the first heat exchanger line 30 of the intermediate heat exchanger, and the gas cooler 14 and the second It is subdivided into a high-pressure part 40 and a low-pressure part 38 having a line with the shutoff valve 36. The high pressure section 40 accounts for 48.64% of the system capacity and has an average density or degree of filling of 432 g / m ³ . The low pressure section 38 accounts for 51.36% and has an average density or filling degree of 125 g / m ³ . The isobaric lines of the high and low pressure sections 40, 38 are drawn and intersect the 55 ° C isotherm 42 at 111.5 bar and 58.5 bar, respectively. This is the maximum stop pressure.

  When the compression cooling system 10 is not in operation, the second shut-off valve 36 is closed. In the gas cooler 14 and in the first heat exchanger line 30 of the intermediate heat exchanger 28, the refrigerant is still lower than the operating pressure. In the rest of the compression cooling system 10, namely the expansion device 16, the evaporator 18, the second heat exchanger line 32 of the intermediate heat exchanger 28, and the compressor 12, pressure equalization occurs and the refrigerant is there. Is lower than a lower stop pressure (eg 58.5 bar).

  The first shut-off valve 34 (in this case in the form of a check valve) prevents the refrigerant from flowing back from the gas cooler 14 to the compressor 12, and thus the leveling between the gas cooler 14 and the compressor 12. Prevent pressure. The second shutoff valve 36 prevents refrigerant from flowing from the first heat exchanger line 30 of the intermediate heat exchanger 28 to the expansion device 16, and thus the first heat exchanger line 30 of the intermediate heat exchanger 28. And pressure equalization between the expansion device 16 is prevented.

  Accordingly, when not in operation, the compression cooling system 10 is divided into a high pressure portion and a low pressure portion by the shut-off valves 34 and 36. In this case, the gas cooler 14 is located in the high-pressure part and the compressor 12 is located in the low-pressure part, where a stop pressure of, for example, 58.5 bar is prevailing.

  In this case, when the compression cooling system 10 is not in operation, the first heat exchanger line 30 of the intermediate heat exchanger 28 is also located in the high pressure section. In this case, the expansion device 16, the evaporator 18, and the second heat exchanger line 32 of the intermediate heat exchanger 28 are also located in the low pressure section when the compression cooling system 10 is not in operation.

  In a first modification of the second exemplary embodiment, the second shut-off valve 36 is disposed in a line between the gas cooler 14 and the first heat exchanger line 30 of the intermediate heat exchanger 28. Is done. In this case, the first heat exchanger line 30 of the intermediate heat exchanger 28 is located in the low pressure section when the compression cooling system 10 is not in operation.

  In a second modification of the second exemplary embodiment, the second shut-off valve 36 is placed in a line between the expansion device 16 and the evaporator 18. In this case, the expansion device 16 is located in the high pressure section when the compression cooling system 10 is not in operation.

  In a third modification of the second exemplary embodiment, the second shut-off valve 36 is placed in a line between the evaporator 18 and the second heat exchanger line 32 of the intermediate heat exchanger 28. The In this case, the expansion device 16 and the evaporator 18 are located in the high pressure section when the compression cooling system 10 is not in operation.

  In a fourth modification of the second exemplary embodiment, the second shut-off valve 36 is disposed in a line between the second heat exchanger line 32 of the intermediate heat exchanger 28 and the compressor 12. . In this case, the expansion device 16, the evaporator 18, and the second heat exchanger line 32 of the intermediate heat exchanger 28 are located in the high pressure section when the compression cooling system 10 is not in operation.

  The compression cooling system 10 according to the third exemplary embodiment is similar to the compression cooling system 10 according to the second exemplary embodiment in terms of structure and functionality. Therefore, in particular, the differences are explained in the following text.

The compression cooling system 10 according to the third exemplary embodiment additionally comprises an accumulator 24 in addition to the compressor 12, the gas cooler 14, the expansion device 16, the evaporator 18 and the intermediate heat exchanger 28. These are connected to each other using lines in the circulation path. In this case, carbon dioxide (CO ₂ ) is also present in the closed circuit as a refrigerant.

  In this case, the accumulator 24 is located between the evaporator 18 and the second heat exchanger line of the intermediate heat exchanger 28. The purpose of the accumulator 24 is to store an additional amount of refrigerant and, if necessary, drain it into the circuit of the compression cooling system 10.

  Disposed on the line downstream of the compressor 12 and in front of the gas cooler 14 is a first shut-off valve 34. In this case, the first shut-off valve 34 is located immediately in front of the gas cooler 14.

  In this case, the first shut-off valve 34 is in the form of a check valve. When the compression cooling system 10 is in operation, the refrigerant compressed to the operating pressure by the compressor can flow through the first shut-off valve 34 to the gas cooler 14. When the compression cooling system 10 is not in operation, the first shut-off valve 34 prevents the refrigerant from flowing back from the gas cooler 14 to the compressor 12.

  Arranged in a line upstream of the compressor 12 (in this case, between the intermediate heat exchanger 28 and the compressor 12) is a second shut-off valve 36. In this case, the second shut-off valve 36 is located immediately behind the intermediate heat exchanger 28.

  In this case, the second shut-off valve 36 is in the form of a solenoid valve. When the compression refrigeration system 10 is in operation, the second shut-off valve 36 is open and refrigerant can flow from the intermediate heat exchanger 28 through the second shut-off valve 36 to the compressor 12. When the compression cooling system 10 is not in operation, the second shut-off valve 36 is closed to prevent coolant from continuing to flow from the intermediate heat exchanger 28 to the compressor 12.

  The compression cooling system 10 is in this case operated transcritical. During operation, for example, an operating pressure of 100 bar and a temperature of 100 ° C. dominate downstream of the compressor 12. The refrigerant is in a supercritical state under these conditions. During operation, for example, a pressure of 34.9 bar and a temperature of 5 ° C. prevail upstream of the compressor 12. The refrigerant is in a gaseous state under these conditions.

  In contrast to the compression cooling system 10 according to the second exemplary embodiment, according to the third exemplary embodiment, refrigerant flows from the evaporator 18 to the accumulator 24 to During operation, it flows from there forward to the heat exchanger 28.

FIG. 3a shows a cycle in a passenger car air conditioning system with a pressure enthalpy diagram. In each case, the prevailing refrigerant pressure can be read from the isovolume line. Compression in the compressor 12 is performed from state 1 to state 2. Density varies from 92 g / ^{m 3} to 188 g / ^{m 3.} The low-pressure part of the compressor 12 occupies, for example, 16.17% of the system capacity, and the high-pressure part occupies 2.26%. The pressure line to the gas cooler 14 accounts for 1.89% and the density corresponding to state 2 is 188 g / m ³ .

Behind the first shut-off valve 34, the refrigerant is cooled from state 2 to state 3 in the gas cooler 14. In this case, the density increases to 621 g / m ³ . The gas cooler 14 is subdivided into three parts with equal output. Mean density and the ratio of the system capacity, respectively, 219 g / ^{m 3} and 1.60% 317 g / ^{m 3} and 3.62%, a 488 g / ^{m 3} and 10.44%. The hottest part of the gas cooler 14 requires a minimum area and a minimum amount for heat conduction because of the large temperature difference.

The line from the intermediate heat exchanger 28 to the first heat exchanger line 30 accounts for 1.22% of the system capacity. The density corresponding to state 3 is 621 g / m ³ . In the first heat exchanger line 30 of the intermediate heat exchanger 28, the refrigerant is further cooled to a state 3 ′ and a density of 690 g / m ³ . The first heat exchanger line 30 accounts for 1.65% of the system capacity and has an average density of 654 g / m ³ .

The line to the inflator 16 and the inflator 16 do not account for much of the system capacity. Isoenthalpy expansion is performed from state 3 ′ to state 4. The partially liquid refrigerant evaporates in the evaporator 18 and in the second heat exchanger line 32 of the intermediate heat exchanger 28. The average density of states 1 ′ and 102 g / m ³ is reached again at the outlet from the evaporator 18. The evaporator is subdivided into three parts with equal output. The average density and proportion of system capacity is 182 g / m ³ and 4.80%, 139 g / m ³ and 4.71%, 112 g / m ³ and 4.62%, respectively. As a result of the constant evaporation temperature, all parts are approximately the same size.

The line between the evaporator 18, the accumulator 24 and the second heat exchanger line 32 of the intermediate heat exchanger 28 occupies 5.03% of the system capacity, and the average density corresponding to state 1 ′ is 102 g / m ³ . The additional accumulator 24 accounts for 36.79% of the system capacity compared to the second embodiment. As a result, the ratio of gas cooler 14 and evaporator 18 in the system capacity is reduced accordingly. When the system is filled, the accumulator 24 contains about 30% liquid refrigerant from state 4 ′ and 70% gas refrigerant from state 4 ″. Thus, the average density is 346 g / m ³ .

In the second heat exchanger line 32, the refrigerant is further evaporated and superheated to reach state 1 again. The second heat exchanger line 32 of the intermediate heat exchanger 28 accounts for 1.68% of the system capacity and the average density is 97 g / m ³ . The suction line to the compressor 12 accounts for 3.50% of the system capacity. The density corresponding to state 1 is 92 g / m ³ .

The overall filling degree of the system is 275 g / m ³ . The isotonic line intersects the 55 ° C. isothermal line 42 under a pressure of 91.4 bar. The compressor 12 should be designed for this maximum stop pressure. As a result of the advantageous third embodiment comprising the shut-off valves 34 and 36, the system is subdivided into a low-pressure part 38 and a high-pressure part 40 comprising the compressor 12 and its direct connection line. The high pressure section 40 accounts for 76.17% of the system capacity and has an average density or degree of filling of 314 g / m ³ . The low pressure part 38 accounts for 23.83% and has an average density or filling degree of 109 g / m ³ . The isobaric lines of the high and low pressure sections 40, 38 are drawn and intersect the 55 ° C isotherm 42 at 98.3 bar and 52.9 bar, respectively. This is the maximum stop pressure.

When the compression cooling system 10 is not in operation, the second shut-off valve 36 is closed. In the gas cooler 14, the intermediate heat exchanger 28, the expansion device 16, the evaporator 18, and the accumulator 24 undergo pressure equalization, where the refrigerant is somewhat lower than the operating pressure. In the compressor 12, the refrigerant is below a lower stop pressure (for example up to 52.9 bar ).

  The first shut-off valve 34 (in this case in the form of a check valve) prevents the refrigerant from flowing back from the gas cooler 14 to the compressor 12, and thus the leveling between the gas cooler 14 and the compressor 12. Prevent pressure. The second shutoff valve 36 prevents refrigerant from flowing from the intermediate heat exchanger 28 to the compressor 12, and thus prevents pressure equalization between the first intermediate heat exchanger 28 and the compressor 12.

  Therefore, when not in operation, the compression cooling system 10 is divided into the high pressure section 40 and the low pressure section 38 by the shutoff valves 34 and 36. In this case, the gas cooler 14 is located in the high-pressure part 40 and the compressor 12 is located in the low-pressure part 38, where a stop pressure of, for example, 52.9 bar is prevailing.

  In this case, both heat exchanger lines of the intermediate heat exchanger 28, the expansion device 16, the evaporator 18, and the accumulator 24 are also located in the high pressure section when the compression cooling system 10 is not in operation.

  In a first modification of the third exemplary embodiment, the second shut-off valve 36 is placed in a line between the gas cooler 14 and the intermediate heat exchanger 28. In this case, both heat exchanger lines of the intermediate heat exchanger 28, the expansion device 16, the evaporator 18, and the accumulator are located in the low pressure section when the compression cooling system 10 is not in operation.

  In a second modification of the third exemplary embodiment, the second shut-off valve 36 is placed in a line between the intermediate heat exchanger 28 and the expansion device 16. In this case, the second heat exchanger line of the intermediate heat exchanger 28, the expansion device 16, the evaporator 18, and the accumulator 24 are located in the low pressure section when the compression cooling system 10 is not in operation.

  In a third modification of the third exemplary embodiment, the second shut-off valve 36 is placed in a line between the expansion device 16 and the evaporator 18. In this case, the second heat exchanger line of the intermediate heat exchanger 28, the evaporator 18, and the accumulator 24 are located in the low pressure section when the compression cooling system 10 is not in operation.

  In a fourth modification of the third exemplary embodiment, the second shut-off valve 36 is arranged in a line between the evaporator 18 and the accumulator 24. In this case, the second heat exchanger line of the intermediate heat exchanger 28 and the accumulator 24 are located in the low pressure section when the compression cooling system 10 is not in operation.

  In a fifth modification of the third exemplary embodiment, the second shut-off valve 36 is placed in a line between the accumulator 24 and the intermediate heat exchanger 28. In this case, the second heat exchanger line of the intermediate heat exchanger 28 is located in the low pressure section when the compression cooling system 10 is not in operation.

  The present invention is not limited to the exemplary embodiments described herein and the embodiments emphasized therein. Rather, many modifications are possible within the ability of those skilled in the art within the scope of the claims.

1 refrigerant state, superheated gas 2 compressed refrigerant state at the compressor outlet 3 refrigerant state, cooled supercritical refrigerant at the outlet of the gas cooler 3 'further cooled refrigerant, at the inlet to the expansion device Supercritical gas of 4 Refrigerant state, expanded liquid and vapor fraction 4 ′ Liquid phase refrigerant in accumulator 4 ″ Gas phase refrigerant in accumulator 10 Compression cooling system 12 Compressor 14 Gas cooler 16 Expansion device 18 Evaporator 24 Accumulator 28 Intermediate heat exchanger 30 First heat exchanger line 32 Second heat exchanger line 34 First shutoff valve 36 Second shutoff valve 38 Low pressure part 40 High pressure part 42 Isotherm (55 ° C.)
44 Low pressure filling degree 46 High pressure filling degree

Claims (13)

A compressor cooling system (12) comprising a compressor (12), a gas cooler (14), an expansion device (16), and an evaporator (18), which are connected to each other using a line in a circulation path containing refrigerant. 10)
A first shut-off valve (34) is disposed downstream of the compressor (12) and in front of the gas cooler (14);
At least one second shut-off valve (36) is located upstream of the compressor (12) and the two shut-off valves (34, 36) are sub-critical pressures when the system is not in operation. The low pressure part (38) in which the pressure is dominant and the high pressure part (40) in which the supercritical pressure is dominant are separated from each other,
Compression cooling system (10). A compression cooling system (10) according to claim 1,
The refrigerant is carbon dioxide,
Compression cooling system (10). A compression cooling system (10) according to claim 1 or 2,
The first shut-off valve (34) is in the shape of a check valve,
Compression cooling system (10). A compression cooling system (10) according to any one of claims 1 to 3,
The second shut-off valve (36) is in the form of a solenoid valve and / or an expansion device (16),
Compression cooling system (10). A compression cooling system (10) according to any one of claims 1 to 4,
A first heat exchanger line (30) disposed between the gas cooler (14) and the expansion device (16), and disposed between the evaporator (18) and the compressor (12). An intermediate heat exchanger (28) comprising a second heat exchanger line (32) to be provided,
Compression cooling system (10). A compression cooling system (10) according to claim 5,
The second shutoff valve (36) is arranged between the first heat exchanger line (30) and the expansion device (16),
Compression cooling system (10). A compression cooling system (10) according to any one of the preceding claims, wherein
An accumulator (24) is arranged between the evaporator (18) and the compressor (12),
Compression cooling system (10). A compression cooling system (10) according to claim 7,
The second shut-off valve (36) is arranged between the accumulator (24) and the compressor (12),
Compression cooling system (10). A compression cooling system (10) according to claim 1,
The compressor (12) is designed to produce a maximum operating pressure greater than the critical pressure, and is designed for a maximum stop pressure lower than the critical pressure of the refrigerant,
Compression cooling system (10). A compression cooling system (10) according to claim 1,
The compressor (12) is designed for a burst pressure corresponding to 1.5 to 3 times, preferably twice the critical pressure of the refrigerant,
Compression cooling system (10). A compressor cooling system (12) comprising a compressor (12), a gas cooler (14), an expansion device (16), and an evaporator (18), which are connected to each other using a line in a circulation path containing refrigerant. 10)
The compressor (12) is designed to produce a maximum working pressure greater than the critical pressure, and is designed for a maximum stop pressure lower than the critical pressure,
Compression cooling system (10). A method of operating a compression cooling system (10) according to any one of claims 1 to 11,
When the compression cooling system (10) is not in operation, the second shut-off valve (36) is closed,
Operation method of the compression cooling system (10). The method of claim 12, comprising:
When the compression cooling system (10) is in operation, the second shut-off valve (36) is opened,
Method.