DK181547B1

DK181547B1 - CO2 heat pump system or CO2 cooling system comprising an ejector unit and method for controlling the ejector unit of a CO2 heat pump system or a CO2 cooling system

Info

Publication number: DK181547B1
Application number: DKPA202200912A
Authority: DK
Inventors: Skaarup Nielsen Jacob; Gardø Christensen Kim; Holst Nielsen Mads; Lund Rasmussen Jonas
Original assignee: Fenagy As
Priority date: 2022-10-07
Filing date: 2022-10-07
Publication date: 2024-04-26
Also published as: US20240118003A1; CA3215349A1; DK202200912A1; EP4350248A1

Abstract

1. A C0₂ based system (20) being a heat pump system or a refrigeration system is disclosed. The system (20) comprises a plurality of ejectors (2, 2', 2'', 2''') are arranged in parallel. Each of the ejectors (2, 2', 2'', 2''') comprises a motive port (8) and a suction port (20). Each of the ejectors (2, 2', 2'', 2''') has a fixed geometry. A first actuated ball valve (4, 4', 4'', 4''') is arranged in front of the motive port (8). A second actuated ball valve (6, 6', 6'', 6''') is arranged in front of the suction port (10). The system (20) comprises a control unit (12) arranged and configured to control the activity of the ball valves (4, 4', 4'', 4''', 6, 6', 6'', 6''') on the basis of one or more predefined criteria.

Description

DK 181547 B1 1

Field of invention

The present invention relates to a heat pump or a refrigeration system applying vapor compression and an ejector cycle. The system comprises an ejector assembly as a pumping means for circulating low pressure refrigerant through the ejector cycle.

Prior art

Many prior CO> based heat pumps and refrigeration systems comprise one or more ejectors. An ejector comprises a primary nozzle (also named as motive nozzle), a suction chamber, a mixing chamber and a diffuser. The primary nozzle can be a convergent type or a convergent- divergent type. when the high pressure fluid (known as primary fluid or motive fluid) expands and accelerates through the primary nozzle, it flows out with high speed and hereby create a very low pressure region at exit plane of the nozzle. Accordingly, a pressure difference is created between the streams at the nozzle exit plane and the secondary fluid inlet. Thus, the secondary fluid is drawn through the suction chamber by the entrainment effect. Therefore, both fluids are mixed in the mix- ing chamber and flow through the diffuser hereby converting the kinetic energies of the mixture to pressure energy.

Typical prior art CO> based heat pumps and refrigeration systems com- prise variable ejectors that are configured to change geometry in order to regulate the flow. In these systems, a check valve is arranged next to the suction port of each ejector. The use of check valves is associat- ed to a risk for experiencing fluid leakage because check valves are not leak-tight.

DK 181547 B1 2

US20190111764A1 discloses a refrigeration cycle device that includes a compressor, a first branch portion, a radiator, a second branch portion, a first decompressor, a first evaporator, a second decompressor, a sec- ond evaporator, and an ejector. The first branch portion divides a flow of a refrigerant discharged from the compressor into one flow and an- other flow. The radiator radiates heat of the refrigerant of the one flow.

The second branch portion divides a flow of the refrigerant from the ra- diator into one flow and another flow. The first decompressor decom- presses the refrigerant of the one flow divided in the second branch portion. The second decompressor decompresses the refrigerant of the other flow divided in the second branch portion. A nozzle of the ejector decompresses and injects the refrigerant of the other flow divided in the first branch portion. The refrigerant suction port draws the refrigerant from the second evaporator. This solution is, however, associated with a risk of experiencing fluid leakage in front of the ports of the ejector.

Accordingly, it would be desirable to be able to provide an alternative solution that reduces or even eliminates the above-mentioned disad- vantages of the prior art. It is an object to reduce the risk of fluid leak- age in front of the port s of the ejector.

Summary of the invention

The object of the present invention can be achieved by a CO; based system as defined in claim 1 and by a method as defined in claim 7.

Preferred embodiments are defined in the dependent subclaims, ex- plained in the following description and illustrated in the accompanying drawings.

The system according to the invention is a CO; based system that com- prises one or more ejectors are arranged in parallel, wherein each of the ejectors comprises a motive port and a suction port, wherein each of the ejectors has a fixed geometry and that:

DK 181547 B1 3 c) a first actuated ball valve is arranged in front of the motive port and d) a second actuated ball valve is arranged in front of the suction port, wherein the system comprises a control unit arranged and configured to control the activity of the ball valves on the basis of one or more prede- fined criteria.

Hereby, it is possible to provide a CO; based heat pump or CO; based refrigeration system, in which the disadvantages of the prior art can be avoided. It is possible to reduce the risk for experiencing fluid leakage.

Moreover, it is possible to achieve an improved efficiency because the resistance induced by check valves used in front of the ports of the ejectors in the prior art can be reduced.

In an embodiment, the system is a heat pump.

In an embodiment, the system is a refrigeration system.

In an embodiment, the system comprises a plurality of ejectors ar- ranged in parallel. In an embodiment, the system comprises three or more ejectors arranged in parallel. In an embodiment, the system com- prises four or more ejectors arranged in parallel.

A motive line is connected to the motive port. By the phrase “in front of the motive port” is meant “in the motive line”.

A suction line is connected to the suction port. By the phrase “in front of the suction port” is meant “in the suction line”.

In an embodiment, the ejectors are high-pressure ejectors designed for high lift applications. Such ejectors are used to achieve the highest pos- sible pressure lift at a lower delivery rate. High-pressure ejectors are suitable for transporting superheated gas.

DK 181547 B1 4

The system according to the invention is a CO; based system that com- prises one or more ejectors arranged in parallel. If the system compris- es a single ejector only, this ejector is not arranged in parallel. Howev- er, if the system comprises several ejectors, the ejectors are arranged in parallel.

Each of the ejectors comprises a motive port and a suction port.

Each of the ejectors has a fixed geometry. Accordingly, the ejectors are not variable geometry ejectors.

A first actuated ball valve is arranged in front of the motive port and a second actuated ball valve is arranged in front of the suction port.

By the term “ball valve” is meant a shut-off valve. Accordingly, the “ball valve” may be a “butterfly valve”, a “ball valve” another valve that is capable of: a) in a first mode shutting-off a line and b) in a second mode being brought into an open configuration.

In an embodiment, the ball valve is a flow control device comprising a hollow, perforated and pivoting ball to control liquid flowing through it, wherein the ball valve is open when the ball's hole is in line with the flow inlet and closed when it is pivoted 90-degrees by a valve handle, blocking the flow.

The control unit is arranged and configured to control the activity of the ball valves on the basis of one or more predefined criteria. In an em- bodiment, the control unit is connected to the actuators of the ball valves via a wired connection. In an embodiment, the control unit is connected to the actuators of the ball valves via a wireless connection.

DK 181547 B1

In an embodiment, the system comprises: - a liquid-gas separator having an inlet port, a gas outlet port and a liquid outlet port; - a gas cooler having an inlet port and an outlet port; 5 - a high pressure valve arranged between the outlet port of the gas cooler and the inlet port of the liquid-gas separator; - a temperature sensor arranged to detect the temperature of the fluid leaving the gas cooler; - a pressure sensor arranged to detect the pressure of the fluid leav- ing the gas cooler; - an evaporator having an inlet port and an outlet port, wherein the suction ports of the ejectors are in fluid communication with the evaporator, wherein the inlet port of the evaporator is in fluid com- munication with the liquid outlet port of the liquid-gas separator; - a gas-by-pass valve arranged between the gas outlet port of the liquid-gas separator and the evaporator; - an intermediate temperature compressor arranged between the gas outlet port of the liquid-gas separator and the inlet port of the gas cooler; - a medium temperature compressor arranged between the gas out- let port of the liquid-gas separator and the inlet port of the gas cooler.

Accordingly, by applying a system according to the invention, it is pos- sible not to apply a check valve in front of the suction ports of the ejec- tors to prevent backflow. Therefore, the system according to the inven- tion reduces or even eliminates the risk for experiencing fluid leakage associated to the use of check valves (that are not leak-tight).

In an embodiment, the control unit is configured to detect the opening degree of the high-pressure valve, wherein the control unit is config- ured to open one or more of the actuated ball valves arranged in front

DK 181547 B1 6 of the motive ports of the ejectors if: - the control unit is in operation state and - the opening degree of the high pressure valve is equal to or higher than a predefined level of the opening degree of the high-pressure valve.

In an embodiment, the actuated ball valves are fully opened when they are opened.

In an embodiment, the actuated ball valves are fully closed when they are closed.

The predefined level may be a user defined input. The predefined level would typically be in the range 30-50%, preferably 30-40%. The user will typically provide an input directly to the control unit or indirectly to the control unit via an intermediate device (e.g. a smartphone, tablet or computer).

The control unit will typically be configured to determine the opening degree of the high-pressure valve. In an embodiment, the control unit is communicatively (via a wired connection or wirelessly) connected to a detection unit that is arranged and configured to detect the opening degree of the high-pressure valve.

In an embodiment, the control unit is configured to close one or more of the actuated ball valves arranged in front of the motive ports of the ejectors if: - the opening degree of the high pressure valve is equal to or less than a predefined level; - the pressure at outlet port of gas-cooler is equal to or less than a predefined setpoint pressure at the outlet port of the gas-cooler and - the suction ports for the respective ejectors are closed.

DK 181547 B1 7

In an embodiment, the predefined level is a user defined input. In an embodiment, the predefined level is in the range 7-12 %. In an embod- iment, the predefined level is in the range 8-10%. In an embodiment, the predefined level is 8 bars. In an embodiment, the predefined level is bars.

In an embodiment, the control unit is configured to determine the open- ing degree of the gas-by-pass valve and to open the actuated ball valves arranged in front of the suction ports of one or more of the ejec- 10 tors if: - the motive ports of the one or more of the ejectors are open; - the temperature of the fluid at the outlet port of the gas cooler is within a predefined temperature range; - the suction pressure at the intermediate temperature compressor is within a predefined range; - the opening degree of the gas-by-pass valve is below a predefined level and - the number of actively operated ejectors corresponds to a prede- fined number based on the number of actively operated medium temperature compressors.

It is important to underline that the control unit is configured to open the actuated ball valves arranged in front of the suction ports of one or more of the ejectors only if the capacity of the intermediate tempera- ture compressors is below 100 %. Hereby, it is ensured that suction ports of one or more additional ejector is only opened if the intermedi- ate temperature compressors have additional capacity.

The capacity of the intermediate temperature compressors is below 100 % when the intermediate temperature compressors can provide a high- er capacity. The capacity of the intermediate temperature compressors can be increased by activating an additional intermediate temperature

DK 181547 B1 8 compressor. If three out of four intermediate temperature compressors are active, the capacity is 75%. Accordingly, the capacity of the inter- mediate temperature compressors can be increased by activating the last intermediate temperature compressor so that all four intermediate temperature compressors are active.

In an embodiment, the control unit is configured to determine the open- ing degree of the gas-by-pass valve and to open the actuated ball valves arranged in front of the suction ports of one or more of the ejec- tors if the capacity of the intermediate temperature compressors is be- low 100 %:

In an embodiment, the predefined level is a user defined input.

In an embodiment, the system comprises a temperature sensor ar- ranged to detect the temperature of the fluid at the outlet port of the gas cooler.

By securing that the number of actively operated ejectors corresponds to a predefined number based on the number of actively operated me- dium temperature compressors, it is possible to ensure that the number of actively operated ejectors is selected in dependency of the compres- sor capacity.

In an embodiment, the control unit is configured to delay execution of opening and closing of the stop valves for a predefined delay time peri- od within a predefined range. In one embodiment, the predefined delay time period is within the range of 10-120 seconds. In one embodiment, the predefined delay time period is within the range of 15-90 seconds.

In one embodiment, the predefined delay time period is within the range of 20-60 seconds. In one embodiment, the predefined delay time period is within the range of 25-45 seconds. In one embodiment, the predefined delay time period is within the range of 25-35 seconds.

DK 181547 B1 9

In an embodiment, the control unit is configured to close the actuated ball valves arranged in front of the suction ports of one or more of the ejectors if either of the following constraints are met: - the temperature of the fluid leaving the gas cooler is not within a predefined temperature range limit; - the opening degree of the gas-by-pass valve exceeds a predefined level; - the number of actively operated ejectors exceeds a predefined number, wherein the predefined number is based on the number of actively operated medium temperature compressors.

The method according to the invention is a method for controlling a CO: based system being: a) a heat pump system or b) a refrigeration system, wherein the system comprises a plurality of ejectors are arranged in parallel, wherein each of the ejectors comprises a motive port and a suction port, wherein the method comprises the step of applying ejectors having a fixed geometry, wherein: c) a first actuated ball valve is arranged in front of the motive port and d) a second actuated ball valve is arranged in front of the suction port, wherein the method comprises the step of controlling the activity of the ball valves on the basis of one or more predefined criteria.

In an embodiment, the method applies a system comprising: - a liquid-gas separator having an inlet port, a gas outlet port and a liquid outlet port; - a gas cooler having an inlet port and an outlet port; - a high pressure valve arranged between the outlet port of the gas cooler and the inlet port of the liquid-gas separator;

DK 181547 B1 10 - a temperature sensor arranged to detect the temperature of the fluid leaving the gas cooler and - a pressure sensor arranged to detect the pressure of the fluid leav- ing the gas cooler.

In an embodiment, method comprises the following steps: - detecting the opening degree of the high-pressure valve; - opening one or more of the actuated ball valves arranged in front of the motive port motive ports of the ejectors if: a) the control unit is in operation state and b) the opening degree of the high pressure valve is equal to or higher than a predefined level.

The predefined level may be a user defined input. In an embodiment, the predefined level is within the range 30-50%. In an embodiment.

The predefined level is within the range 30-40%.

In an embodiment, one or more of the actuated ball valves arranged in front of the motive ports of the ejectors are closed if: - the opening degree of the high pressure valve is equal to or less than a predefined level; - the pressure at outlet port of gas-cooler is equal to or less than a predefined setpoint pressure at the outlet port of the gas-cooler and - the suction ports for the respective ejectors are closed.

The predefined level may be a user defined input. In an embodiment, the predefined level is within the range 8-12%. In an embodiment, the predefined level is within the range 8-10%.

In an embodiment, the method comprises the step of detecting the opening degree of the gas-by-pass valve, wherein the actuated ball valves arranged in front of the suction ports of one or more of the ejec- tors are being opened if:

DK 181547 B1 11 - the motive ports of the one or more of the ejectors are open; - the temperature of the fluid at the outlet port of the gas cooler is within a predefined temperature range; - the suction pressure at the intermediate temperature compressor is within a predefined range; - the opening degree of the gas-by-pass valve is below a predefined level and - the number of actively operated ejectors corresponds to a prede- fined number based on the number of actively operated medium temperature compressors.

In an embodiment, the method comprises the step of closing the actu- ated ball valves arranged in front of the suction ports of one or more of the ejectors if either of following constraints are met: - the temperature of the fluid leaving the gas cooler is no longer with- in a predefined temperature range limit; - the opening degree of the gas-by-pass valve exceeds a predefined level; - the number of actively operated ejectors exceeds a predefined number, wherein the predefined number is based on the number of actively operated medium temperature compressors.

In an embodiment, the temperature range limit is a user defined input.

In an embodiment, the predefined level (the opening degree of the gas- by-pass valve) is a user defined input. In an embodiment, the prede- fined level (the opening degree of the gas-by-pass valve) is within the range 20-35%. In an embodiment, the predefined level (the opening degree of the gas-by-pass valve) is within the range 25-35%. In an embodiment, the predefined level (the opening degree of the gas-by- pass valve) is 30%.

Description of the Drawings

DK 181547 B1 12

The invention will become more fully understood from the detailed de- scription given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

Fig. 1 shows a schematic diagram of a CO. based system (heat pump) according to the invention;

Fig. 2 shows a schematic diagram of an ejector according to the invention and

Fig. 3 shows a cross-sectional view of an ejector according to the invention.

Detailed description of the invention

Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a CO> based system of the present invention is illustrated in Fig. 1.

Fig. 1 is a schematic diagram of a CO; based system 20 constituting a heat pump 20. The heat pump 20 comprises a gas cooler 24 in fluid communication with an ejector assembly 52 comprising four ejectors 2, 20 2’, 2”, 2". The gas cooler 24 has an inlet port 66 and an outlet port 68.

The ejectors 2, 2, 2”, 2” are arranged in parallel. An outlet line 34 connects the gas cooler 24 and the motive ports of the ejectors 2, 2", 2”, 2". An actuated ball valve 4, 4’, 4”, 4”” is, however, arranged in front of each of the motive ports. It is important to underline that the number of ejectors 2, 2’, 2”, 2'” may be selected differently. The num- ber of ejectors 2, 2’, 2”, 2" can be any desired number equal to or larger than one.

The system 20 comprises a temperature sensor 74 arranged and con- figured to detect the temperature of the fluid leaving the gas cooler 24.

In one embodiment, the temperature sensor 74 is also configured to

DK 181547 B1 13 detect the pressure of the fluid leaving the gas cooler 24. In an embod- iment, the system 20 comprises a separate pressure sensor 76 config- ured to detect the pressure of the fluid leaving the gas cooler 24. The pressure sensor 78 may be arranged close to the temperature sensor 74. The pressure sensor may be arranged at the outlet port 68 of gas cooler 24.

The ball valves 4, 4’, 4”, 4”” are communicatively connected to a control unit 12. Accordingly, the control unit 12 can control the activity of the ball valves 4, 4’, 4”, 4'” and thus connect and disconnect the connection between the gas cooler 24 and each of the ejectors 2, 2’, 2”, 2" inde- pendently. The control unit 12 is communicatively connected to the temperature sensor 74 and the pressure sensor 76. Accordingly, the control unit 12 receives the temperature measurements made by the temperature sensor 74 and pressure measurements made by the pres- sure sensor 76.

The suction ports of the ejectors 2, 2', 2”, 2'” are connected to a line 36 that is in fluid communication with an evaporator 22 that receives fluid from a liquid-gas separator 14. The liquid-gas separator 14 comprises an inlet port 60, a gas outlet port 62 and a liquid outlet port 64. The evaporator has an inlet port 70 and an outlet port 72.

An expansion valve 30 is arranged at the line 38 extending between the evaporator 22 and the liquid-gas separator 14. The outlet port of each of the ejectors 2, 2’, 2”, 2'” is connected to the liquid-gas separator 14.

An actuated ball valve 6, 6’, 6”, 6” is arranged in front of each of the suction ports of the ejectors 2, 2', 2”, 2”. The ball valves 6, 6', 6”, 6" are communicatively connected to a control unit 12. Therefore, the con- trol unit 112 is configured to control the activity of the ball valves 6, 6’, 6”, 6'” and thus connect and disconnect the connection to the line 36.

DK 181547 B1 14

The liquid-gas separator 14 has a liquid outlet port that is connected to the line 38. The liquid-gas separator 14 has a gas outlet port that is connected to a line 46. The line 46 is connected to a pressure point 32 via a line 40, in which a gas-by-pass valve 28 is provided. The gas-by- pass valve 28 is a an activated valve. . The suction ports of the ejectors 2,2’, 2", 2'” are in fluid communication with the pressure point 32. Ac- cordingly, the ejectors 2, 2’, 2”, 27” have access to gas from the line 40 as well as the outlet port of the evaporator 22.

The heat pump 20 comprises an intermediate temperature compressor 16 that is arranged between the gas outlet of the liquid-gas separator 14 and the inlet port of the gas cooler 24. A line 48 extends between the line 46 and the intermediate temperature compressor 16. A line 50 extends between the intermediate temperature compressor 16 and the inlet port of the gas cooler 24.

The heat pump 20 comprises a medium temperature compressor 18 that is arranged between the intermediate temperature compressor 16 and the pressure point 32. A line 42 extends between the medium tem- perature compressor 18 and the line 50.

A high-pressure valve 26 arranged between the outlet port 68 of the gas cooler 24 and the inlet port 60 of the liquid-gas separator 14.

It is possible to apply several intermediate temperature compressors 16 and/or several medium temperature compressors 18 if a higher capaci- ty is needed.

Fig. 2 illustrates a schematic diagram of an ejector 2 according to the invention. The ejector 2 has a fixed geometry and comprises a motive port 8 and a suction port 10. A first actuated ball valve 4 is arranged in front of the motive port 8. A second actuated ball valve 6 is arranged in

DK 181547 B1 15 front of the suction port 10. The CO: based system according to the in- vention comprises a control unit 12 arranged and configured to control the activity of the ball valves 4, 6 on the basis of one or more prede- fined criteria.

Fig. 3 illustrates a cross-sectional view of an ejector 2 according to the invention. The ejector 2 is a high-pressure ejector 2. The ejector 2 comprises a motive port 8 and a suction port 10. The ejector 2 compris- es a nozzle 54, a mixing chamber 56 and a diffuser 58. The nozzle 54 converts the pressure energy of high pressure CO; to the velocity ener- gy in such a manner that the CO: is depressurized and is expanded by the nozzle 54 In the mixing chamber 56, high velocity CO: flow dis- charged from the nozzle 54 draws the vapor phase CO, which has been vaporized in the evaporator (see Fig. 1), into the mixing chamber 56 and is mixed with the vapor phase CO». In the diffuser 58, the CO: dis- charged from the nozzle 54 and the CO. drawn from the evaporator are mixed in such a manner that the velocity energy of the CO, is converted to the pressure energy to increase the pressure of the CO».

In an embodiment, the nozzle 54 has a throttled portion in its passage.

The throttled portion increases the velocity of the CO, which is dis- charged from the nozzle 54. In the mixing chamber 56, the CO: is mixed in such a manner that the sum of the kinetic momentum of the

CO» discharged from the nozzle 54 and the kinetic momentum of the

CO> drawn into the ejector 2 from the evaporator (see Fig. 1) is con- served. Accordingly, in the mixing chamber 56, the static pressure of the CO» is increased.

DK 181547 B1 16

List of reference numerals 2,2, 2", 2" Ejector 4,4' 4”, 4" Actuated ball valve 6,6’, 6”, 6" Actuated ball valve 8 Motive port

Suction port 12 Control unit 14 Liquid-gas separator 10 16 Intermediate temperature compressor 18 Medium temperature compressor 20 CO, based system (heat pump system or a refrigera- tion system) 22 Evaporator (refrigerant-air heat exchanger) 24 Gas cooler 26 High-pressure valve 28 Gas-by-pass valve 30 Valve 32 Pressure point 34, 36, 38 Line 40, 42, 44 Line 46, 48, 50 Line 52 Ejector assembly 54 Motive nozzle 56 Mixing chamber 58 Diffuser 60 Inlet port (of liquid-gas separator) 62 Gas outlet port (the liquid-gas separator) 64 Liquid outlet port (of liquid-gas separator) 66 Inlet port (of gas cooler) 68 Outlet port (of gas cooler) 70 Inlet port (of evaporator)

DK 181547 B1 17 72 Outlet port (of evaporator) 74 Temperature sensor 76 Pressure sensor

Claims

DK 181547 B1 18 Patent claim

1. CO>-based system (20) which is: a) a heat pump system or b) a cooling system, where the system (20) comprises one or more ejectors (2, 2”, 2”, 2”), which are placed in parallel, where each of the ejectors (2, 2', 2", 2") comprises a drive opening (8) and a suction opening (10), characterized in that each of the ejectors (2, 2', 2", 2'7 ) has a fixed geometry, and in that: c) a first activated ball valve (4, +, 4", 4") is placed in front of the drive opening (8) and d) a second activated ball valve (6, 6', 6") 6") is placed in front of the suction opening (10), where the system (20) comprises a control unit (12) which is arranged and — configured to control the ball valves (4, +, 4", 4", 6, 6', 6 ”, 6”) activity on the basis of one or more predefined criteria.

2. System (20) according to claim 1, wherein the system (20) comprises: - a liquid-gas separator (14) with an inlet opening (60), a gas outlet opening (62) and a liquid outlet opening (64); - a gas cooler (24) with an inlet opening (66) and an outlet opening (68); - a high-pressure valve (26) which is arranged between the outlet opening (68) of the gas cooler (24) and the inlet opening (60) of the liquid-gas separator (14); - a temperature sensor which is arranged to detect the temperature of the fluid leaving the gas cooler (24);

DK 181547 B1 19 - a pressure sensor which is designed to detect the pressure of the fluid leaving the gas cooler (24); - —an evaporator (22) with an inlet opening (70) and an outlet opening (72), where the suction openings (10) of the ejectors (2, 2", 2", 2") are in fluid connection with the evaporator (22), where the evaporator's ( 22) inlet opening (70) is in fluid communication with the liquid outlet opening (64) of the liquid-gas separator (14); - a gas bypass valve (28) placed between the gas outlet opening (62) of the liquid-gas separator (14) and the evaporator (22); - an intermediate temperature compressor (16) which is placed between the gas outlet opening (62) of the liquid-gas separator (14) and the inlet opening (66) of the gas cooler (24); - a medium temperature compressor (18) which is placed between the gas outlet opening (62) of the liquid-gas separator (14) and the inlet opening (66) of the gas cooler (24).

3. System (20) according to claim 2, wherein the control unit (12) is configured to detect the degree of opening of the high-pressure valve (26), wherein the control unit (12) is configured to open one or more of the activated ball valves (4, +, 4, 4”), which is placed in front of the drive openings (8) of the ejectors (2, 2, 2”, 2”), if: - — the control unit (12) is in operating mode - — the degree of opening of the high-pressure valve (26) corresponds to or is higher than a predefined level.

4. System (20) according to claim 3, wherein the control unit (12) is configured to close one or more of the activated ball valves (4, 4, 4", 4") located in front of the ejectors (2, 2', 2"). 2") drive openings (8) if: - — the degree of opening of the high-pressure valve (26) corresponds to or is less than a predefined level;

DK 181547 B1 20 - — the pressure at the outlet opening (68) of the gas cooler (24) corresponds to or is less than a predefined setting pressure at the outlet opening (68) of the gas cooler (24) and - — the corresponding ejectors (2, 2', 2", 2 ") suction openings (10) are closed.

5. System (20) according to claim 3 or 4, wherein the control unit (12) is configured to determine the degree of opening of the gas bypass valve (28) and to open the actuated ball valves (6, 6', 6", 6"), which is placed in front of the suction openings (10) in one or more of the ejectors (2, 2', 2”, 27”), if: - one or more of the ejectors (2, 2', 2”, 27) drive openings (10) are open; - the temperature of the gas cooler (24) outlet (68) is within a predefined temperature range; - the gas bypass valve (28) opening degree is below a predefined level, preferably a user-defined level; - the number of actively controlled ejectors (2, 2", 2", 2") corresponds to a predefined number based on the number of actively controlled medium temperature compressors (18); - the capacity of the intermediate temperature compressors (16) is below 100%.

6. System (20) according to claim 5, wherein the control unit (12) is configured to close the actuated ball valves (6, 6, 6”, 6) located in front of — the suction openings (10) in one or more of the ejectors ( 2, 2', 2”, 2”), if one of the following conditions is met: - —the temperature of the fluid leaving the gas cooler (24) is within a limit of a predetermined temperature range, exceeds (not within) - > the opening degree of the gas bypass valve (28) exceeds a predefined one

DK 181547 B1 21 level; - the number of actively controlled ejectors (2, 2', 2", 2") exceeds a predefined number, where the predefined number is based on the number of actively controlled medium temperature compressors (18).

7. Method for controlling a CO>-based system (20) which is: a) a heat pump system or b) a cooling system, where the system (20) comprises a plurality of ejectors (2, 2, 2", 2") , which are arranged in parallel, where each of the ejectors (2, 2', 2”, 2”) comprises a drive opening (8) and a suction opening (10), characterized in that the method includes the step of using ejectors (2, 2 ", 2", 2") with a fixed geometry, where: c) a first activated ball valve (4, +, 4", 4") is placed in front of the drive opening (8) and d) a second activated ball valve (6, 6 ', 6", 6") is placed in front of the suction opening (10), where the method includes the step of controlling the activity of the ball valves (4, H4,4',4",6,6, 6", 6") on the basis of one or several predefined criteria.

8. Method according to claim 7, wherein the system (20) comprises: - a liquid-gas separator (14) with an inlet opening (60), a gas outlet opening (62) and a liquid outlet opening (64); - a gas cooler (24) with an inlet opening (66) and an outlet opening (68); - a high-pressure valve (26) which is arranged between the outlet opening (68) of the gas cooler (24) and the inlet opening (60) of the liquid-gas separator (14); - a temperature sensor which is arranged to detect the temperature of the fluid leaving the gas cooler (24);

DK 181547 B1 22 - a pressure sensor which is arranged to detect the pressure of the fluid leaving the gas cooler (24); - a pressure sensor arranged to detect the pressure of the fluid leaving the gas cooler (24);

9. Method according to claim 8, wherein the method comprises the following steps: - detection of the degree of opening of the high-pressure valve (26); - opening of one or more of the activated ball valves (4, +, 4", 4"), which are placed in front of the drive openings (8) of the ejectors (2, 2', 2", 2"), if: a) the control unit ( 12) is in operating mode b) the degree of opening of the high-pressure valve (26) corresponds to or is higher than a predefined level.

10. Method according to claim 9, where one or more of the activated ball valves (4, 4, 4", 4"), which are placed in front of the drive openings (8) of the ejectors (2, 2", 2", 2"), are closed , if - the degree of opening of the high-pressure valve (26) corresponds to or is less than a predefined level; - the pressure at the outlet opening (68) of the gas cooler (24) corresponds to or is less than a predefined setting pressure at the outlet opening (68) of the gas cooler (24) and - the suction openings (10) of the corresponding ejectors (2, 2', 2", 2") are closed.

11. Method according to claim 10, wherein the method comprises the step of detecting the degree of opening of the gas bypass valve (28), where the activated ball valves (6, 6', 6", 6"), which are placed in front of the suction openings (10) in one or several of the ejectors (2, 2, 2”, 2”) are opened if: - — the drive openings (10) of one or more of the ejectors (2, 2', 2”, 2”) are open; - the temperature of the fluid at the outlet opening (68) of the gas cooler (24) is within

DK 181547 B1 23 for a predetermined temperature range; - the suction pressure at the intermediate temperature compressor (16) is within a predefined range; - the degree of opening of the gas bypass valve (28) is below a predefined level; - the number of actively controlled ejectors (2, 2', 2", 2") corresponds to a predefined number based on the number of actively controlled medium temperature compressors (18), and - the capacity of the medium temperature compressors (16) is below 100%.

12. Method according to claim 11, wherein the method comprises the step of closing the activated ball valves (6, 6', 6", 6"), which are placed in front of the suction openings (10) in one or more of the ejectors (2, 2', 2", 2"), if one of the following conditions is met: - the temperature of the fluid leaving the gas cooler (24) is no longer within a predefined limit of the temperature range; - —the degree of opening of the gas bypass valve (28) exceeds a predefined level; - —2the number of actively controlled ejectors (2, 2', 2", 2") exceeds a predefined number, where the predefined number is based on the number of actively controlled medium temperature compressors (18).