CO2 Heat Pump System or CO2 Refrigeration System Comprising an Ejector Assembly and Method for Controlling an Ejector Assembly of a CO2 Heat Pump System or a CO2 Refrigeration System

Abstract

A CO.sub.2 based system, such as a heat pump system or a refrigeration system, is disclosed. The system comprises a plurality of ejectors arranged in parallel. Each of the ejectors comprises a motive port and a suction port. Each of the ejectors has a fixed geometry. A first actuated ball valve is arranged in front of the motive port. A second actuated ball valve is arranged in front of the suction port. The system comprises a control unit arranged and configured to control the activity of the ball valves on the basis of one or more predefined criteria.

Claims

1. A CO.sub.2 based system comprising: one or more ejectors each having a motive port, a suction port, and a fixed geometry wherein 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; and a control unit arranged and configured to control the activity of the first actuated ball valve and the second actuated ball valve on the basis of one or more predefined criteria.

2. The system according to claim 1, further comprising two or more ejectors arranged in parallel.

3. The system according to claim 1, wherein the CO.sub.2 based system is a heat pump system or a refrigeration system.

4. The system according to claim 1, further 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; a temperature sensor arranged to detect a temperature of fluid leaving the gas cooler; a pressure sensor arranged to detect a pressure of the fluid leaving 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 communication with the liquid outlet port of the liquid-gas separator; a gas-bypass 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; and a medium temperature compressor arranged between the gas outlet port of the liquid-gas separator and the inlet port of the gas cooler.

5. The system according to claim 4, wherein the control unit is configured to detect an opening degree of the high-pressure valve and to open one or more of the first actuated ball valves arranged in front 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.

6. The system according to claim 5, wherein the control unit is configured to determine an opening degree of the gas-bypass valve and to open the second actuated ball valves arranged in front of the suction ports of one or more of the ejectors 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-bypass valve is below a predefined level; a number of actively operated ejectors corresponds to a predefined number based on a number of actively operated medium temperature compressors; and a capacity of the intermediate temperature compressors is below 100%.

7. The system according to claim 5, wherein the control unit is configured to close one or more of the first 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 the outlet port of the gas-cooler is equal to or less than a predefined setpoint pressure; and the suction ports for the respective ejectors are closed.

8. The system according to claim 7, wherein the control unit is configured to determine an opening degree of the gas-bypass valve and to open the second actuated ball valves arranged in front of the suction ports of one or more of the ejectors 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-bypass valve is below a predefined level; a number of actively operated ejectors corresponds to a predefined number based on a number of actively operated medium temperature compressors; and a capacity of the intermediate temperature compressors is below 100%.

9. The system according to claim 8, wherein the control unit is configured to close the second actuated ball valves arranged in front of the suction ports of one or more of the ejectors if any of following constraints is met: a temperature of the fluid leaving the gas cooler is outside the predefined temperature range; the opening degree of the gas-bypass valve exceeds the predefined level; the number of actively operated ejectors exceeds the predefined number that is based on the number of actively operated medium temperature compressors.

10. A method for controlling a CO.sub.2 based system having one or more ejectors having a motive port, a suction port, and a fixed geometry wherein 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, the method comprising: controlling the activity of the first actuated ball valve and the second actuated ball valve on the basis of one or more predefined criteria.

11. The method according to claim 10, further comprising two or more ejectors arranged in parallel.

12. The method according to claim 10, wherein the CO.sub.2 based system is a heat pump system or a refrigeration system.

13. The method according to claim 10, wherein the CO.sub.2 based 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; 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 a temperature of fluid leaving the gas cooler; a pressure sensor arranged to detect a pressure of the fluid leaving 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 communication with the liquid outlet port of the liquid-gas separator; a gas-bypass 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; and a medium temperature compressor arranged between the gas outlet port of the liquid-gas separator and the inlet port of the gas cooler.

14. The method according to claim 13, further comprising: detecting an opening degree of the high-pressure valve; opening one or more of the first actuated ball valves arranged in front of the 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.

15. The method according to claim 14, wherein one or more of the first 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 the outlet port of the gas-cooler is equal to or less than a predefined setpoint pressure; and the suction ports for the respective ejectors are closed.

16. The method according to claim 14, further comprising: detecting an opening degree of the gas-bypass valve, wherein the second actuated ball valves arranged in front of the suction ports of one or more of the ejectors are opened 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-bypass valve is below a predefined level; a number of actively operated ejectors corresponds to a predefined number based on a number of actively operated medium temperature compressors; and a capacity of the intermediate temperature compressors is below 100%.

17. The method according to claim 16, further comprising: closing the second actuated ball valves arranged in front of the suction ports of one or more of the ejectors if any of following constraints is met: the temperature of the fluid leaving the gas cooler is outside the predefined temperature range; the opening degree of the gas-bypass valve exceeds the predefined level; the number of actively operated ejectors exceeds the predefined number that is based on the number of actively operated medium temperature compressors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0099] The systems and methods will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative. In the accompanying drawings:

[0100] FIG. 1 shows a schematic diagram of a CO.sub.2 based system (heat pump) according to an embodiment;

[0101] FIG. 2 shows a schematic diagram of an ejector according to an embodiment; and

[0102] FIG. 3 shows a cross-sectional view of an ejector according to an embodiment.

DETAILED DESCRIPTION

[0103] Referring now in detail to the drawings for the purpose of illustrating embodiments of the present invention, a CO.sub.2 based system 20 of the present invention is illustrated in FIG. 1.

[0104] FIG. 1 is a schematic diagram of a CO.sub.2 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, 2, 2, 2. The gas cooler 24 has an inlet port 66 and an outlet port 68.

[0105] 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 emphasize that the number of ejectors 2, 2, 2, 2 may be selected differently. The number of ejectors 2, 2, 2, 2 can be any desired number equal to or larger than one.

[0106] The system 20 comprises a temperature sensor 74 arranged and configured to detect the temperature of the fluid leaving the gas cooler 24. In an embodiment, the temperature sensor 74 is also configured to detect the pressure of the fluid leaving the gas cooler 24. In an embodiment, the system 20 comprises a separate pressure sensor 76 configured to detect the pressure of the fluid leaving the gas cooler 24. The pressure sensor 76 may be arranged close to the temperature sensor 74. The pressure sensor may be arranged at the outlet port 68 of gas cooler 24.

[0107] 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 independently. 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 pressure sensor 76.

[0108] 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.

[0109] An expansion valve 30 is arranged in 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.

[0110] 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 control unit 12 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.

[0111] 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-bypass valve 28 is provided. The gas-bypass valve 28 is an activated valve. The suction ports of the ejectors 2, 2, 2, 2 are in fluid communication with the pressure point 32. Accordingly, the ejectors 2, 2, 2, 2 have access to gas from the line 40 as well as the outlet port of the evaporator 22.

[0112] 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.

[0113] 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 temperature compressor 18 and the line 50.

[0114] A high-pressure valve 26 is arranged between the outlet port 68 of the gas cooler 24 and the inlet port 60 of the liquid-gas separator 14.

[0115] It is possible to apply several intermediate temperature compressors 16 and/or several medium temperature compressors 18 if a higher capacity is needed.

[0116] FIG. 2 illustrates a schematic diagram of an ejector 2 according to an embodiment. 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 front of the suction port 10. The CO.sub.2 based system, in an embodiment, 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 predefined criteria.

[0117] FIG. 3 illustrates a cross-sectional view of an ejector 2 according to an embodiment. 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 comprises a nozzle 54, a mixing chamber 56 and a diffuser 58. The nozzle 54 converts the pressure energy of high pressure CO.sub.2 to the velocity energy in such a manner that the CO.sub.2 is depressurized and is expanded by the nozzle 54 in the mixing chamber 56. High velocity CO.sub.2 flow discharged from the nozzle 54 draws the vapor phase CO.sub.2, which has been vaporized in the evaporator (see FIG. 1), into the mixing chamber 56 where it is mixed with the vapor phase CO.sub.2. In the diffuser 58, the CO.sub.2 discharged from the nozzle 54 and the CO.sub.2 drawn from the evaporator are mixed in such a manner that the velocity energy of the CO.sub.2 is converted to the pressure energy to increase the pressure of the CO.sub.2.

[0118] In an embodiment, the nozzle 54 has a throttled portion in its passage. The throttled portion increases the velocity of the CO.sub.2, which is discharged from the nozzle 54. In the mixing chamber 56, the CO.sub.2 is mixed in such a manner that the sum of the kinetic momentum of the CO.sub.2 discharged from the nozzle 54 and the kinetic momentum of the CO.sub.2 drawn into the ejector 2 from the evaporator (see FIG. 1) is conserved. Accordingly, in the mixing chamber 56, the static pressure of the CO.sub.2 is increased.

LIST OF REFERENCE NUMERALS

[0119] 2, 2, 2, 2 Ejector [0120] 4, 4, 4, 4 Actuated ball valve [0121] 6, 6, 6, 6 Actuated ball valve [0122] 8 Motive port [0123] 10 Suction port [0124] 12 Control unit [0125] 14 Liquid-gas separator [0126] 16 Intermediate temperature compressor [0127] 18 Medium temperature compressor [0128] 20 CO.sub.2 based system (heat pump system or a refrigeration system) [0129] 22 Evaporator (refrigerant-air heat exchanger) [0130] 24 Gas cooler [0131] 26 High-pressure valve [0132] 28 Gas-bypass valve [0133] 30 Valve [0134] 32 Pressure point [0135] 34, 36, 38 Line [0136] 40, 42, 44 Line [0137] 46, 48, 50 Line [0138] 52 Ejector assembly [0139] 54 Motive nozzle [0140] 56 Mixing chamber [0141] 58 Diffuser [0142] 60 Inlet port (of liquid-gas separator) [0143] 62 Gas outlet port (the liquid-gas separator) [0144] 64 Liquid outlet port (of liquid-gas separator) [0145] 66 Inlet port (of gas cooler) [0146] 68 Outlet port (of gas cooler) [0147] 70 Inlet port (of evaporator) [0148] 72 Outlet port (of evaporator) [0149] 74 Temperature sensor [0150] 76 Pressure sensor