Refrigeration system

Abstract

A refrigeration system (1) has A) an ejector circuit (3) comprising: Aa) a high pressure compressor unit (2) comprising at least one compressor (2a, 2b, 2c, 2d); Ab) a heat rejecting heat exchanger/gas cooler (4); Ac) an ejector (6); Ad) a receiver (8) having a gas outlet (8b) which is connected to an inlet of the high pressure compressor unit (2). B) a normal cooling temperature flowpath (5) comprising in the direction of flow of the refrigerant: Ba) a normal cooling temperature expansion device (10) fluidly connected to a liquid outlet (8c) of the receiver (8); Bb) a normal cooling temperature evaporator (12); Bc) an ejector secondary inlet line (68) with an ejector inlet valve (26) fluidly connecting an outlet (12b) of the normal cooling temperature evaporator (12) to a suction inlet (6b) of the ejector (6); and Bd) a normal cooling temperature flowpath valve unit (22) configured for fluidly connecting the inlet of the high pressure compressor unit (2) selectively either to the gas outlet (8b) of the receiver (8) or to the outlet (12b) of the normal cooling temperature evaporator (12); C) a freezing temperature flowpath (7) comprising in the direction of flow of the refrigerant: Ca) a freezing temperature expansion device (14) fluidly connected to the liquid outlet (8c) of the receiver (8); Cb) a freezing temperature evaporator (16); Cc) a freezing temperature compressor unit (18) comprising at least one freezing temperature compressor (18a, 18b); and Cd) a freezing temperature flowpath valve unit (20) configured for fluidly connecting the outlet of the freezing temperature compressor unit (18) selectively either to the inlet of the high pressure compressor unit (2) or to the ejector inlet valve (26).

Claims

1. A refrigeration system comprising A) an ejector circuit comprising in the direction of flow of a circulating refrigerant: Aa) a high pressure compressor unit comprising at least one compressor; Ab) a heat rejecting heat exchanger/gas cooler; Ac) an ejector having a primary inlet fluidly connected to the outlet(s) of the heat rejecting heat exchanger/gas cooler; a secondary inlet; and an outlet, which is fluidly connected to Ad) a receiver having a gas outlet which is connected to an inlet of the high pressure compressor unit; B) a normal cooling temperature flowpath comprising in the direction of flow of the refrigerant: Ba) a normal cooling temperature expansion device fluidly connected to a liquid outlet of the receiver; Bb) a normal cooling temperature evaporator; Bc) an ejector secondary inlet line with an ejector inlet valve fluidly connecting an outlet of the normal cooling temperature evaporator to the secondary inlet of the ejector; and Bd) a normal cooling temperature flowpath valve unit configured for fluidly connecting the inlet of the high pressure compressor unit selectively either to the gas outlet of the receiver or to the outlet of the normal cooling temperature evaporator; C) a freezing temperature flowpath comprising in the direction of flow of the refrigerant: Ca) a freezing temperature expansion device fluidly connected to the liquid outlet of the receiver; Cb) a freezing temperature evaporator; Cc) a freezing temperature compressor unit comprising at least one freezing temperature compressor; and Cd) a freezing temperature flowpath valve unit configured for fluidly connecting the outlet of the freezing temperature compressor unit selectively either to the inlet of the high pressure compressor unit or to the ejector inlet valve wherein a desuperheater is arranged between the freezing temperature compressor unit and the freezing temperature flowpath valve unit.

2. The refrigeration system of claim 1, wherein the high pressure compressor unit comprises an economizer compressor and at least one standard compressor.

3. The refrigeration system of claim 2, further comprising an economizer valve, the economizer valve and the normal cooling temperature flowpath valve unit being configured for fluidly connecting the gas outlet of the receiver selectively to the inlet(s) of the economizer compressor or to the inlet(s) of the at least one standard compressor.

4. The refrigeration system of claim 1, wherein the normal cooling temperature flowpath valve unit comprises: an outlet fluidly connected to the inlet side of the high pressure compressor unit; a first inlet fluidly connected to the gas outlet of the receiver; and a second inlet fluidly connected to an outlet of the normal cooling temperature evaporator; and allows to fluidly connect the outlet selectively with the first inlet or the second inlet.

5. The refrigeration system of claim 1, wherein the freezing temperature flowpath valve unit comprises: an inlet fluidly connected to an outlet side of the freezing temperature compressor unit; a first outlet fluidly connected to the inlet side of the high pressure compressor unit; and a second outlet fluidly connected to the ejector secondary inlet line; and allows to fluidly connect the inlet selectively with the first outlet or the second outlet.

6. The refrigeration system of claim 1, wherein at least one of the freezing temperature flowpath valve unit and the normal cooling temperature flowpath valve unit comprises a three-way-valve or a combination of at least two valves, wherein at least one of the valves is in particular an adjustable valve.

7. The refrigeration system of claim 1, comprising a suction line heat exchanger providing heat exchange between refrigerant flowing from the gas outlet of the receiver to the high pressure compressor unit and refrigerant flowing from the heat rejecting heat exchanger/gas cooler to the ejector.

8. The refrigeration system of claim 1, further comprising at least one of an ambient temperature sensor, which is configured for measuring the ambient temperature, a pressure sensor, which is configured for measuring the pressure of the refrigerant at the inlet side of the high pressure compressor unit, and a pressure sensor, which is configured for measuring the pressure of the refrigerant at the outlet of the normal cooling temperature evaporator.

9. The refrigeration system of claim 1, further comprising an oil separator for separating oil from the refrigerant, in particular from refrigerant flowing within the normal temperature flowpath.

10. The refrigeration system of claim 9, wherein the oil separator is configured to deliver the oil, which has been separated from the refrigerant leaving the normal cooling temperature evaporator to the inlet of the freezing temperature compressor unit.

11. A method of operating a refrigeration system of claim 1 in a standard mode, the method comprising: circulating a first flow of refrigerant from the high pressure compressor unit via the heat rejecting heat exchanger/gas cooler; the ejector and the receiver to the inlet side of the high pressure compressor unit; directing a second flow of refrigerant from the receiver via the normal cooling temperature expansion device and the normal cooling temperature evaporator to the inlet side of the high pressure compressor unit; and directing a third flow of refrigerant from the receiver via the freezing temperature expansion device, the freezing temperature evaporator and the freezing temperature compressor unit to the inlet side of the high pressure compressor unit.

12. A method of operating a refrigeration system of claim 7 in a first ejector mode, the method comprising: circulating a first flow of refrigerant from the high pressure compressor unit via the heat rejecting heat exchanger/gas cooler; the ejector and the receiver back to the inlet side of the high pressure compressor unit; directing a second flow of refrigerant from the receiver via the normal cooling temperature expansion device, the normal cooling temperature evaporator and the ejector inlet valve to the secondary inlet of the ejector; and directing a third flow of refrigerant from the receiver via the freezing temperature expansion device, the freezing temperature evaporator and the freezing temperature compressor unit to the inlet side of the high pressure compressor unit.

13. A method of operating a refrigeration system of claim 1 in a second ejector mode, the method comprising: circulating a first flow of refrigerant from the high pressure compressor unit via the heat rejecting heat exchanger/gas cooler; the ejector and the receiver to the inlet side of the high pressure compressor unit; directing a second flow of refrigerant from the receiver via the normal cooling temperature expansion device, the normal cooling temperature evaporator and the ejector inlet valve to the secondary inlet of the ejector; and directing a third flow of refrigerant from the receiver via the freezing temperature expansion device, the freezing temperature evaporator, the freezing temperature compressor unit and the ejector inlet valve to the secondary inlet of the ejector.

14. A method of operating a refrigeration system according to claim 1 in an economizer mode, wherein the method comprises directing refrigerant from the gas outlet of the receiver to the economizer compressor of the high pressure compressor unit.

Description

SHORT DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a refrigeration system according to an exemplary embodiment of the invention operating in a first mode of operation.

(2) FIG. 2 shows refrigeration system according to an exemplary embodiment of the invention operating in a second mode of operation.

(3) FIG. 3 shows refrigeration system according to an exemplary embodiment of the invention operating in a third mode of operation.

(4) FIG. 4 shows refrigeration system according to an exemplary embodiment of the invention operating in a fourth mode of operation.

DETAILED DESCRIPTION OF THE FIGURES

(5) The embodiment of a refrigeration system 1 shown in the figures comprises an ejector circuit 3, a normal cooling temperature flowpath 5, and a freezing temperature flowpath 7 respectively circulating a refrigerant.

(6) In the figures, the flow of the refrigerant in the ejector circuit 3 is indicated by dashed lines, the flow of refrigerant in the normal cooling temperature flowpath 5 is indicated by dotted lines, and the flow of refrigerant in the freezing temperature flowpath 7 is indicated by dash-dotted lines.

(7) FIG. 1 shows a refrigeration system 1 according to an exemplary embodiment of the invention operating in a first mode of operation.

(8) The ejector circuit 3 comprises in the direction of the flow F of the circulating refrigerant a high pressure compressor unit 2 including a plurality of compressors 2a-2d connected in parallel. The compressors 2a-2d in particular include an economizer compressor 2a and a plurality of standard compressors 2b, 2c and 2d.

(9) The high pressure side outlets of the compressors 2a-2d are fluidly connected to an outlet manifold 40, which collects the refrigerant from the compressors 2a-2d and delivers it via a heat rejection heat exchanger/gas cooler inlet line 42 to the inlet 4a of a heat rejecting heat exchanger/gas cooler 4. The heat rejecting heat exchanger/gas cooler 4 is configured for transferring heat from the refrigerant to the environment reducing the temperature of the refrigerant. In the embodiment shown in the figures, the heat rejecting heat exchanger/gas cooler 4 comprises two fans 38 which may be operated for blowing air through the heat rejecting heat exchanger/gas cooler 4 in order to enhance the transfer of heat from the refrigerant to the environment.

(10) The cooled refrigerant leaving the heat rejecting heat exchanger/gas cooler 4 through its outlet 4b is delivered via a heat rejecting heat exchanger/gas cooler outlet line 44 and a successive ejector primary inlet line 46 to a primary inlet 6a of an ejector 6, which is configured for expanding the refrigerant to a reduced pressure. The expanded refrigerant leaves the ejector 6 via an ejector outlet 6c and is delivered by means of an ejector outlet line 48 to an inlet 8a of a receiver 8. Within the receiver 8, the refrigerant is separated by gravity into a liquid portion collecting at the bottom of the receiver 8 and a gas phase portion collecting in an upper portion of the receiver 8.

(11) The gas phase portion of the refrigerant leaves the receiver 8 through a receiver gas outlet 8b, which is arranged in the upper portion of the receiver 8, and is delivered via a receiver gas outlet line 50, 52 to the inlet side of the high pressure compressor unit 2 completing the refrigerant cycle of the ejector circuit 3.

(12) Optionally, a suction line heat exchanger 36 may be arranged in the receiver gas outlet line 50, 52 for allowing a transfer of heat between the refrigerant leaving the heat rejecting heat exchanger/gas cooler 4 and the gaseous refrigerant leaving the receiver 8 through the gas outlet 8b. Such a heat exchange has been found to enhance the efficiency of the refrigeration system 1.

(13) In the first mode of operation (standard operation mode), which is illustrated by FIG. 1, gas phase refrigerant from the receiver 8 is delivered via an open economizer valve 24 and a second inlet line 58 downstream of the economizer valve 24 to a normal cooling temperature flowpath valve unit 22, which (in said first mode of operation) delivers the gas phase refrigerant via a high pressure compressor unit inlet line 60 and a high pressure compressor unit inlet manifold 62 to the inlets of the standard compressors 2b, 2c, 2d.

(14) Refrigerant from the liquid phase portion of the refrigerant collecting at the bottom of the receiver 8 exits from the receiver 8 via its liquid outlet 8c and is delivered through a receiver liquid outlet line 64 to a first expansion device 10 (normal cooling temperature expansion device) and a second expansion device 14 (freezing temperature expansion device).

(15) After having passed the normal cooling temperature expansion device 10, where it has been expanded further, the refrigerant enters through an inlet 12a into a first evaporator 12 (normal cooling temperature evaporator), which is configured for operating at normal cooling temperatures, in particular in a temperature range of 0 C. to 15 C. for providing normal temperature refrigeration.

(16) In said first mode of operation (standard operation mode), the refrigerant, after having left the normal cooling temperature evaporator 12 via its outlet 12b, flows through a normal cooling temperature evaporator outlet line 66 into the second inlet line 58 of the normal cooling temperature flowpath valve unit 22 from where it is delivered to the inlet side of the high pressure compressor unit 2 together with the gas portion of the refrigerant supplied by the receiver 8.

(17) An ejector secondary inlet line 68 branches from the normal cooling temperature evaporator outlet line 66 downstream of the normal cooling temperature evaporator 12 and fluidly connects the normal cooling temperature evaporator outlet line 66 to an inlet side of an ejector inlet valve 26. An outlet side of said ejector inlet valve 26 is fluidly connected to a secondary (suction) inlet 6b of the ejector 6. The ejector inlet valve 26, however, is closed in the standard operation mode, which is illustrated in FIG. 1, and in consequence no refrigerant is delivered from the outlet 12b of the normal cooling temperature evaporator 12 via the ejector secondary inlet line 68 into the ejector 6.

(18) The portion of the liquid refrigerant, which has been expanded by the second (freezing temperature) expansion device 14 enters through an inlet 16a into a second (freezing temperature) evaporator 16, which is configured for operating at freezing temperatures below 0 C., in particular at temperatures in the range of 15 C. to 5 C. for providing freezing temperature refrigeration. The refrigerant leaves the freezing temperature evaporator 16 through its outlet 16b and is delivered via a freezing temperature evaporator outlet line 70 to the inlet side of a freezing temperature compressor unit 18, which comprises one or more freezing temperature compressors 18a, 18b.

(19) In operation, the freezing temperature compressor unit 18 compresses the refrigerant supplied by the freezing temperature evaporator outlet line 70 to medium pressure. After said compression, the refrigerant is delivered via a freezing temperature compressor unit outlet line 72 and an optional desuperheater 34 to a freezing temperature flowpath valve unit 20. Said freezing temperature flowpath valve unit 20 is configured for selectively directing the refrigerant supplied by the freezing temperature compressor unit 18 either via a first outlet line 74 into the high pressure compressor unit inlet line 60, which is done in the first mode of operation illustrated in FIG. 1, or via a second outlet line 76 into the second inlet line 58 of the normal cooling temperature flowpath valve unit 22 when the refrigeration system 1 is operated in an alternative mode of operation, which will be discussed further below.

(20) In an embodiment, an oil separator 32 is provided within the ejector secondary inlet line 68. The oil separator 32 is configured for separating oil comprised in the refrigerant circulating within the normal cooling temperature flowpath 5 from said refrigerant and feeding said separated oil into the freezing temperature evaporator outlet line 70 in order to avoid that the oil collects within the normal cooling temperature flowpath 5 and in consequence the compressors 18a, 18b, 2b, 2c, 2d run out of oil. Said oil separation is in particular important when the refrigeration system 1 is operated in the third or fourth mode of operation, which will be discussed below, as in said modes of operation the refrigerant from the normal cooling temperature evaporator 12 is not fed back into the high pressure compressor unit 2. When the refrigeration system 1 is operated in one of said modes of operation, oil separation is necessary for transferring oil from the normal cooling temperature flowpath 5 back to the compressors 18a, 18b, 2b, 2c, 2d.

(21) Pressure and/or temperature sensors 28, 30 are provided at the normal cooling temperature evaporator outlet line 66 and at the receiver gas outlet line 52, respectively, for measuring the pressure and/or the temperature of the refrigerant flowing in said lines 66, 52. Alternatively or additionally an ambient temperature sensor 78 is provided, which is configured for measuring the ambient temperature.

(22) The sensors 28, 30, 78 deliver their outputs to a control unit 80, which is configured for controlling the operation of the compressor units 2, 18 and the valve units 20, 22 based on the outputs of at least some of the sensors 28, 30, 78 in order to operate the refrigeration system with optimal efficiency.

(23) For transferring the data and the control signals, the control unit 80 may be connected with the sensors 28, 30, 78, the compressor units 2, 18 and the valve units 20, 22 by means of electrical and/or hydraulic control lines, which are not shown in the figures, or by means of a wireless connection.

(24) The control unit 80 in particular is configured for switching the operation of the refrigeration system between different modes of operation by driving the valve units 20, 22 accordingly. Said switching in particular may be controlled and triggered based on the pressure and/or temperature data provided by the sensors 28, 30, 78.

(25) The first mode of operation (standard operation mode), which has been described before with reference to FIG. 1, is typically employed at relatively low ambient temperatures, e.g. at ambient temperatures below 10-15 C.

(26) At higher ambient temperatures, e.g. in the range of 10-15 C. to 18-20 C., which are detected either directly by means of the ambient temperature sensor 78 or indirectly by a change of the refrigerant pressure measured by at least one of the sensors 28, 30, the control unit 80 switches the refrigeration system 1 into a second mode of operation (economized mode), which is illustrated in FIG. 2.

(27) In said second mode of operation the economizer valve 24 is shut in order to deliver the gas phase refrigerant supplied by the receiver 8 to the economizer compressor 2a instead of delivering it to the standard compressors 2b, 2c, 2d as it is done in the first mode of operation.

(28) Thus, when the system is operated in the second mode of operation (economized mode), the refrigerant circulating within the ejector circuit 3 is driven and compressed only by means of the economizer compressor 2a, whereas the refrigerant supplied by the evaporators 12, 16 is still compressed by the standard compressors 2b, 2c, 2d. As the economizer compressor 2a is optimized for this kind of operation, this work sharing enhances the efficiency of the system when operated in the medium range of ambient temperatures mentioned before.

(29) At even higher ambient temperatures, e.g. in the range of 18-20 C. to 30-35 C., the system is switched into a third mode of operation called first ejector mode, which is illustrated in FIG. 3.

(30) In said third mode of operation the economizer valve 24 remains closed as in the second mode of operation (FIG. 2), but the normal cooling temperature flowpath valve unit 22 is switched for fluidly connecting its first inlet line 56, which is fluidly connected to the evaporator's 8 gas outlet line 52, to the high pressure compressor unit inlet line 60. In consequence, the gas phase refrigerant supplied by the receiver 8 is compressed by a combination of all compressors 2a-2d of the high pressure compressor unit 2, in particular including the economizer compressor 2a and the standard compressors 2b, 2c, 2d.

(31) Further, in said third mode the normal cooling temperature flowpath valve unit 22 is switched to close the fluid connection between its second inlet line 58 fluidly connected to the outlet 12b of the normal cooling temperature evaporator 12 and the high pressure compressor unit line 60, and the ejector inlet valve 26 is opened. As a result, the refrigerant from the normal cooling temperature evaporator 12 is sucked by the ejector 6 via the ejector secondary inlet line 68 and the ejector inlet valve 26 into the secondary (suction) inlet 6b of the ejector 6.

(32) Thus, when the refrigeration system 1 is operated in the third mode of operation (first ejector mode), which is illustrated in FIG. 3, the refrigerant of the normal cooling temperature flowpath 5 is not delivered to the compressors 2a-2d of the high pressure compressor unit 2 anymore, but it is driven only by means of the ejector 6. In contrast, the refrigerant of the freezing temperature flowpath 7 is still compressed by the freezing temperature compressor unit 18 and the successive high pressure compressor unit 2, as the freezing temperature flowpath valve unit 20 has not been switched with respect to the first and second modes of operation.

(33) Finally, in case the ambient temperature increases even further to very high temperatures above 30-35 C., the refrigeration system 1 is switched into a fourth mode of operation, which is called second ejector mode and illustrated in FIG. 4.

(34) For switching the refrigeration system from the third mode of operation (first ejector mode), which has been described before with reference to FIG. 3, into the fourth mode of operation (second ejector mode) the freezing temperature flowpath valve unit 20 is switched to deliver the refrigerant supplied by the freezing temperature compressor unit 18 via its second outlet line 76 into the second inlet line 58 of the normal cooling temperature flowpath valve unit 22 instead of delivering the refrigerant into the high pressure compressor unit inlet line 60.

(35) When the refrigeration system 2 is operated in said fourth mode of operation (second ejector mode), the position of the normal cooling temperature flowpath valve unit 22 remains the same as in the third mode of operation (first ejector mode), i.e. the connection between the second inlet line 58 of the normal cooling temperature flowpath valve unit 22 and the high pressure compressor unit inlet line 60 remains closed. In consequence, the refrigerant supplied by the freezing temperature compressor unit 18 is delivered via the second inlet line 58 of the normal cooling temperature flowpath valve unit 22 together with the refrigerant supplied by the normal cooling temperature evaporator 12 into the ejector secondary inlet line 68 from where it is sucked through the open ejector inlet valve 26 into the secondary (suction) inlet 8b of the ejector 6.

(36) Thus, when the refrigeration system 2 is operated in said fourth mode of operation (second ejector mode), the refrigerant flow of the normal cooling temperature flowpath 5 as well as the refrigerant flow of the freezing temperature flowpath 7 are both driven only by means of the ejector 6, and the compressors 2a-2d of the high pressure compressor unit 2 are operated only for driving the refrigerant circulating within the ejector circuit 3 driving the ejector 6.

(37) A refrigeration system, as it has been described before, may be operated with high efficiency over a wide range of ambient temperatures, in particular from ambient temperatures below 10 C. to ambient temperatures above 35 C.

Further Embodiments

(38) In an embodiment the high pressure compressor unit comprises an economizer compressor and at least one standard compressor in order to allow an economical compression of the refrigerant by means of the economizer compressor.

(39) In an embodiment the refrigeration system further comprises an economizer valve which is configured for fluidly connecting the gas outlet of the receiver selectively to the inlet(s) of the economizer compressor or to the inlet(s) of the at least one standard compressor. This allows to selectively compress the refrigerant by means of the economizer compressor and/or by means of the standard compressor(s) in order to select the most efficient compression, which may depend on the actual environmental conditions, in particular including the ambient temperature, and/or the pressure of the refrigerant.

(40) In an embodiment the normal cooling temperature flowpath valve unit comprises: an outlet fluidly connected to the inlet side of the high pressure compressor unit, a first inlet fluidly connected to the gas outlet of the receiver, and a second inlet fluidly connected to an outlet of the normal cooling temperature evaporator. Such a configuration allows to select efficiently between different modes of operation by switching the normal cooling temperature flowpath valve unit.

(41) In an embodiment the freezing temperature flowpath valve unit comprises: an inlet fluidly connected to an outlet side of the freezing temperature compressor unit, a first outlet fluidly connected to the inlet side of the high pressure compressor unit, and a second outlet fluidly connected to the ejector secondary inlet line. Such a configuration allows to select efficiently between different modes of operation by switching the freezing temperature flowpath valve unit.

(42) In an embodiment at least one of the freezing temperature flowpath valve unit and the normal cooling temperature flowpath valve unit comprises a three-way-valve. A three-way-valve provides a compact and cheap valve unit providing the desired functionality. Alternatively, the valve unit(s) may be provided by an appropriate combination of at least two simple two-way-valves.

(43) At least one of the valves may be an adjustable valve, in particular a continuously adjustable valve, for allowing to switch gradually, in particular continuously between the different modes of operation.

(44) In an embodiment a desuperheater is arranged between the freezing temperature compressor unit and the freezing temperature flowpath valve unit, which allows to enhance the efficiency of the freezing temperature flowpath even further.

(45) In an embodiment the refrigeration system further comprises a suction line heat exchanger which is configured for providing heat exchange between refrigerant flowing from the gas outlet of the receiver to the high pressure compressor unit and refrigerant flowing from the heat rejecting heat exchanger/gas cooler to the ejector in order to enhance the efficiency of the ejector circuit.

(46) In an embodiment the refrigeration system further comprises at least one pressure and/or temperature sensor which is configured for measuring the pressure/temperature of the refrigerant circulating within the refrigeration system.

(47) Such a sensor in particular may be provided at the inlet side of the high pressure compressor unit and/or at the outlet of the normal cooling temperature evaporator.

(48) Providing such sensors allows to switch between the different modes of operation based on the pressure and/or temperature of the refrigerant measured by the sensors. Alternatively or additionally an ambient temperature sensor may be provided allowing to switch between different modes of operation based on the measured ambient temperature.

(49) In an embodiment the refrigeration system further comprises an oil separator for separating oil from the refrigerant, in particular from the refrigerant flowing within the normal temperature flowpath in order to avoid that the compressors run out of oil.

(50) In an embodiment the oil separator is in particular configured to deliver the oil, which has been separated from the refrigerant, to the inlet of the freezing temperature compressor unit in order to ensure a sufficient supply of oil to the compressors of the freezing temperature compressor unit.

(51) While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalence may be substitute for elements thereof without departing from the scope of the invention. In particular, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention is not limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the pending claims.

REFERENCE NUMERALS

(52) 1 refrigeration system 2 high pressure compressor unit 2a economizer compressor 2b, 2c, 2d standard compressors 3 ejector circuit 4 heat rejecting heat exchanger/gas cooler 4a inlet of the heat rejecting heat exchanger/gas cooler 4b outlet of the heat rejecting heat exchanger/gas cooler 5 normal cooling temperature flowpath 6 ejector 6a primary inlet of the ejector 6b secondary inlet of the ejector 6c outlet of the ejector 7 freezing temperature flowpath 8 receiver 8a inlet of the receiver 8b gas outlet of the receiver 8c liquid outlet of the receiver 10 normal cooling temperature expansion device 12 normal cooling temperature evaporator 12a inlet of the normal cooling temperature evaporator 12b outlet of the normal cooling temperature evaporator 14 freezing temperature expansion device 16 freezing temperature evaporator 16a inlet of the freezing temperature evaporator 16b outlet of the normal cooling temperature evaporator 18 freezing temperature compressor unit 18a, 18b freezing temperature compressors 20 freezing temperature flowpath valve unit 22 normal cooling temperature flowpath valve unit 24 economizer valve 26 ejector inlet valve 28, 30 pressure sensors 32 oil separator 34 desuperheater 36 suction line heat exchanger 38 fan 40 manifold of the high pressure compressor unit 42 heat rejecting heat exchanger/gas cooler inlet line 44 heat rejecting heat exchanger/gas cooler outlet line 46 ejector primary inlet line 48 ejector outlet line 50, 52 receiver gas outlet line 54 economizer compressor inlet line 56 first inlet line of the normal cooling temperature flowpath valve unit 58 second inlet line of the normal cooling temperature flowpath valve unit 60 high pressure compressor unit inlet line 62 high pressure compressor unit inlet manifold 64 receiver liquid outlet line 66 normal cooling temperature evaporator outlet line 68 ejector secondary inlet line 70 freezing temperature evaporator outlet line 72 freezing temperature compressor unit outlet line 74 first outlet line of the freezing temperature flowpath valve unit 76 second outlet line of the freezing temperature flowpath valve unit 78 ambient temperature sensor 80 control unit