Refrigeration system with multiple heat absorption heat exchangers

Abstract

A refrigeration system includes a compression device, a heat rejection heat exchanger, an ejector, a first expansion device with a corresponding first heat absorption heat exchanger, and a second expansion device with a corresponding second heat absorption heat exchanger. The ejector has a high-pressure inlet, a low-pressure inlet, and an outlet, and the ejector is arranged to receive a refrigerant fluid from the heat rejection heat exchanger at the high-pressure inlet. A fluid pathway extends from the outlet of the ejector into a branched flow path so as to provide a separate refrigerant flow from the outlet of the ejector to the first expansion device and the second expansion device. The first heat absorption heat exchanger is used to provide cooling at a first temperature via a refrigerant fluid, and the refrigerant fluid from the outlet of the first heat absorption heat exchanger is directed to the low-pressure inlet of the ejector. The second heat absorption heat exchanger is used to provide cooling at a second temperature lower than the first temperature via a refrigerant fluid, and the refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device.

Description

Technical Field

[0001] The present invention relates to a refrigeration system having a plurality of heat absorption heat exchangers, and a corresponding method for providing refrigeration via a plurality of heat absorption heat exchangers. Background Art

[0002] As is well known, cooling or heating can be provided by a refrigeration system that uses a refrigeration cycle in which a refrigerant fluid is compressed, cooled, expanded, and then heated. In a common use in which such a refrigeration system is used to meet a cooling load, cooling of the refrigerant fluid is performed via a heat rejection heat exchanger that rejects heat to the atmosphere, and heating of the refrigerant fluid is performed via a heat absorption heat exchanger that absorbs heat from an object to be cooled (such as a refrigerated space for cryogenic storage) or the interior of a building to be occupied by people. In this way, the refrigeration system can transfer heat from inside a building to the outside of the building even when the interior is cooler than the atmosphere. A complete or partial phase change of the refrigerant fluid can be used to increase the possible temperature difference between the heat rejection phase and the heat absorption phase. Summary of the invention

[0003] From a first aspect, the present invention provides a refrigeration system, the refrigeration system comprising: a compression device having an inlet for receiving a refrigerant fluid at a suction pressure and an outlet for providing a compressed refrigerant fluid at a discharge pressure; a heat rejection heat exchanger arranged to receive the compressed refrigerant fluid from the outlet of the compression device; an ejector having a high-pressure inlet, a low-pressure inlet and an outlet, the ejector being arranged to receive the refrigerant fluid from the heat rejection heat exchanger at the high-pressure inlet of the ejector; a fluid path extending from the outlet of the ejector and branching into a branched flow path so as to provide the refrigerant from the outlet of the ejector to a first expansion device and a second expansion device; a first heat absorption heat exchanger arranged to receive a refrigerant fluid from the first expansion device; and a second heat absorption heat exchanger arranged to receive a refrigerant fluid from the second expansion device; wherein the first heat absorption heat exchanger is used to provide cooling via a refrigerant fluid at a first temperature, and the refrigerant fluid from the outlet of the first heat absorption heat exchanger is directed to a low-pressure inlet of the ejector; wherein the second heat absorption heat exchanger is used to provide cooling via a refrigerant fluid at a second temperature, and the refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device; and wherein the second temperature is lower than the first temperature.

[0004] With this arrangement, it is possible to provide cooling at two different temperatures while using only a single compression device and a single ejector. The connection of the first heat absorption heat exchanger between the outlet of the ejector and the low-pressure inlet of the ejector allows it to provide a sub-circuit about the first heat absorption heat exchanger, while the second heat absorption heat exchanger is placed on the main circuit, wherein the outlet of the second heat absorption heat exchanger directs the refrigerant towards the suction inlet of the compression device. The second heat absorption heat exchanger can be operated at the suction pressure of the compression device (i.e., the lowest pressure within the circuit), while the first heat absorption heat exchanger can be operated at a higher pressure such as provided by the suction pressure at the low-pressure inlet of the ejector.

[0005] Advantageously, the first heat absorption heat exchanger may be used for air conditioning and may therefore be operated with a refrigerant fluid temperature in the range of 0°C to 25°C and / or may be arranged for an air side temperature in the range of 15°C to 30°C, such as for cooling air by 5°C, for example, from 25°C to 20°C, while the second heat absorption heat exchanger may be used for medium temperature applications (such as for refrigeration cabinets) and may therefore be operated with a refrigerant fluid temperature in the range of -35°C to 0°C and / or may be arranged for an air side temperature in the range of -25°C to 8°C, such as for cooling the cabinet to an internal temperature in the range of 0°C to 8°C for refrigerated storage or -25°C to -10°C for frozen storage. Other possible medium temperature applications include chilled water, in which case the first heat absorption heat exchanger is a plate or shell / tube heat exchanger for cooling water. Thus, the refrigeration system can conveniently provide cooling for facilities requiring a combination of such heat exchangers, such as buildings requiring both air conditioning and refrigerated storage with relatively low capacities involved. This often occurs with small retail establishments, such as gas stations or small stores requiring air conditioning as well as refrigeration for refrigerated merchandise and / or perishable goods.

[0006] The first expansion device and the second expansion device may provide different degrees of expansion in order to provide a required difference in refrigerant temperature at the first heat absorption heat exchanger and the second heat absorption heat exchanger. The first expansion device and / or the second expansion device may, for example, be an electronic expansion device with a controllable degree of expansion. This allows control of the expansion device(s) in order to vary the cooling provided by the first heat absorption heat exchanger and / or the second heat absorption heat exchanger.

[0007] The ejector is used to allow an additional circuit including a first heat absorption heat exchanger, and the ejector provides two suction pressures via a high pressure inlet and a low pressure inlet, wherein the combined flow leaves at the outlet. The ejector advantageously receives all the refrigerant fluid flowing through the heat rejection heat exchanger via the high pressure inlet, and receives some or all of the refrigerant fluid that has subsequently passed through the first heat absorption heat exchanger. The ejector may be, for example, a low entrainment / high lift modulating ejector. Such an ejector may be arranged to modulate the Kv value on the motive nozzle throat diameter (or motive nozzle throat diameter) by means of an adjustment device (e.g., an axially adjustable needle or a similar method of adjustable orifice flow area), and the ejector may be made to perform with a total motive (high side) mass flow rate, but only aspirate a portion of the mass flow rate at the low pressure suction inlet, which is typically referred to as a low entrainment / high lift method. The ejector may be arranged to provide an ejector lift force between 0 bar and 15 bar depending on the application and conditions. The refrigeration system may comprise only a single ejector device, i.e. there may be only one ejector stage as specified above with inlet connections to the heat rejection heat exchanger and the first heat absorption heat exchanger and an outlet connection for transferring fluid towards the branched flow path. Thus, the refrigeration system advantageously does not comprise any additional ejector devices located elsewhere within the refrigerant circuit. However, in some embodiments, the single ejector device may comprise a multi-bank ejector.

[0008] The refrigeration system may include a receiver having an inlet for receiving a refrigerant fluid from an outlet of an ejector and a liquid outlet for providing the refrigerant fluid to a branched flow path. Thus, a first expansion device and a second expansion device may be provided with a refrigerant fluid from the liquid outlet of the receiver. This is beneficial because ejector outlets typically have a two-phase flow, with the result that expansion is difficult to control. The receiver enables the expansion device to be provided with a single-phase liquid refrigerant fluid, thereby allowing the expansion to be more consistent and / or more easily controlled. The gas outlet of the receiver may be connected to the inlet of a compression device. For example, as discussed below, this may be done via an expansion valve, or the compression device may include a medium pressure inlet.

[0009] The compression device may be any suitable form of compressor. Optionally, the compression device may provide two compression stages, for example, wherein the outlet of the second heat absorption heat exchanger provides refrigerant fluid to the suction inlet of the first compression stage; and the discharge outlet of the second compression stage provides compressed refrigerant fluid to the heat rejection heat exchanger. The compression device may use an arrangement of multiple compressor elements to provide two-stage compression with a medium pressure inlet (and optional medium pressure outlet) as discussed above. For example, there may be multiple compressor elements driven by the same compressor motor. The refrigeration system may include a single compression device, such as a two-stage device as discussed herein. Optionally, the refrigeration system does not use parallel compressors. The refrigeration system may not have any additional compression devices located between the heat rejection heat exchanger and the ejector and / or there may not be any additional compression devices located between the ejector and the heat absorption heat exchanger. Therefore, the proposed system may not rely on multiple compression devices to achieve multiple different heat rejection pressures, but only utilizes ejectors to allow different heat rejection pressures.

[0010] The compression device may include a medium pressure inlet. In one arrangement, as mentioned above, the medium pressure inlet may be connected to the gas outlet of the receiver. Alternatively or additionally, the medium pressure inlet may be used for an intercooler. In this case, the compression device may have a medium pressure outlet for directing the refrigerant fluid to the intercooler, and the refrigerant fluid from the outlet of the intercooler may be directed to the medium pressure inlet, optionally in combination with the refrigerant fluid flowing from the gas outlet of the receiver. The intercooler may include an intercooler heat rejection heat exchanger, which is combined with a heat rejection heat exchanger that receives compressed refrigerant from the outlet of the compression device.

[0011] The heat rejection heat exchanger may be a condenser for at least partially condensing a compressed refrigerant fluid from a compression device, such that the refrigerant fluid is a liquid at the outlet of the heat rejection heat exchanger. The condenser and intercooler as discussed above may be combined so that heat is rejected to air in an air flow path, sequentially passing through the intercooler and then through the condenser. The intercooler and / or the condenser may be provided with suitable heat transfer elements on their exteriors, such as fins and the like. The heat rejection heat exchanger may be a gas cooler unit, for example, a gas cooler for a carbon dioxide refrigerant. Thus, the refrigeration system may use carbon dioxide as a refrigerant fluid. Alternatively, in addition to carbon dioxide, the refrigeration system may also use a high pressure refrigerant such as, for example, R410A.

[0012] In a simple construction of the refrigeration system, the outlet of the first heat absorption heat exchanger is directly connected to the low pressure inlet of the ejector without any intervening components. However, it has been found that the operating range of the system can be increased if additional features are provided to allow improved control of the flow of refrigerant fluid to the ejector. In one possible arrangement, a check valve is provided between the outlet of the first heat absorption heat exchanger and the low pressure inlet of the ejector to prevent flow reversal of the fluid flowing away from the ejector under certain operating conditions. Additionally or alternatively, a bypass line may be provided to allow refrigerant fluid flow from the outlet of the first heat absorption heat exchanger to the inlet of the compression device. The bypass line may include a bypass valve for controlling the flow of the refrigerant fluid along the bypass line and / or for controlling the pressure at the outlet of the first heat absorption heat exchanger. In the presence of a bypass line, the refrigeration system can be arranged for a first operating mode and a second operating mode, in which the bypass valve is closed and all refrigerant fluid from the first heat absorption heat exchanger flows to the ejector low pressure inlet, and in which the bypass valve is open or partially open and at least some of the refrigerant fluid from the first heat absorption heat exchanger flows through the bypass line.

[0013] Optionally, the refrigeration system comprises one or more internal heat exchangers for heat transfer between refrigerant fluids at different temperatures within the refrigeration system.Thus, there may be at least one internal heat exchanger for heat transfer from a first point in the system to a second point in the system.

[0014] For example, the first point may be located after the ejector outlet and before the expansion device, optionally before the branched flow path, wherein the second point is located after the second heat absorption heat exchanger and before the inlet of the compression device. In this case, the first point may also be located after the receiver, wherein the receiver is connected as above, i.e. the first point may be located after the liquid outlet of the receiver. Thus, the internal heat exchanger may transfer heat between the liquid refrigerant located after the receiver and the gaseous (or two-phase) refrigerant located after the second heat absorption heat exchanger.

[0015] Alternatively or additionally, the first point may be located after the outlet of the heat rejection heat exchanger and before the high pressure inlet of the ejector, wherein the second point is located between the gas outlet of the receiver and the inlet to the compression device, such as between the gas outlet of the receiver and the medium pressure inlet of the compression device discussed above. Thus, the internal heat exchanger may transfer heat between the refrigerant fluid located after the heat rejection heat exchanger and the gaseous refrigerant located after the gas outlet of the receiver.

[0016] Both of the internal heat exchangers discussed above may be present together with the receiver so that there is a first internal heat exchanger that transfers heat from the refrigerant liquid located after the liquid outlet of the receiver to the refrigerant fluid located after the second heat absorption heat exchanger, and a second internal heat exchanger that transfers heat from the refrigerant fluid located after the heat rejection heat exchanger to the refrigerant gas located after the gas outlet of the receiver.

[0017] The internal heat exchanger may be a plate type heat exchanger, such as a brazed plate type heat exchanger, with counter-flow or cross-flow of the refrigerant fluid from the first point to the second point.

[0018] Optionally, the refrigeration system may include a heat recovery device located after the compression device and before the heat rejection heat exchanger. Thus, there may be a suitable valve arrangement (such as a three-way valve) for allowing some or all of the compressed refrigerant to pass through the coil for heat recovery before the heat rejection heat exchanger.

[0019] The first heat absorption heat exchanger and / or the second heat absorption heat exchanger with the refrigerant fluid at the respective first and second temperatures may optionally be provided in parallel with another heat absorption heat exchanger with the refrigerant fluid at the respective first or second temperature. Thus, the refrigeration system may be arranged for absorbing heat via the refrigerant fluid at the first temperature using two or more heat absorption heat exchangers in parallel, preferably with corresponding multiple expansion valves (such as multiple air conditioning evaporators in the exemplary embodiment). Alternatively or additionally, the refrigeration system may be arranged for absorbing heat via the refrigerant fluid at the second temperature using two or more heat absorption heat exchangers in parallel, preferably with corresponding multiple expansion valves (such as multiple medium-temperature evaporators in the exemplary embodiment).

[0020] The refrigeration system may include a controller for controlling one or more elements of the system (such as for controlling some or all of the compression device, the first expansion device, and the second expansion device). In the case of optional features such as a bypass line and / or a heat recovery device, the controller may be used to control the corresponding valves to control the operation of the bypass and / or heat recovery.

[0021] The refrigeration system may be a rack type refrigeration system, and thus may include a rack mounted compression device. Alternatively, the refrigeration system may be a cooling distribution unit (CDU) type refrigeration system. As noted above, the refrigeration system may use a carbon dioxide refrigerant fluid, and this may be done in the context of a rack system or a CDU system.

[0022] The refrigeration system may be provided as part of a facility for providing a combination of air conditioning and medium temperature cooling, and the invention thus extends to a facility for providing air conditioning and medium temperature cooling comprising a refrigeration system as discussed above. The facility may be a facility for a small retail establishment such as a petrol station or small shop as discussed above.

[0023] Viewed from a further aspect, the present invention provides a method for refrigeration with cooling at two temperatures, the method comprising providing a refrigeration system as set out above, such as, in the first aspect and optionally including the further features as discussed above; using a first heat absorption heat exchanger to provide a first refrigeration temperature; and using a second heat absorption heat exchanger to provide a second refrigeration temperature.

[0024] The method may include using a first heat absorption heat exchanger to cool air for air conditioning and / or using a second heat absorption heat exchanger to cool air for refrigeration or freezing of stored goods. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Certain exemplary embodiments of the present invention will now be described, by way of example only, and with reference to the accompanying drawings, in which:

[0026] Figure 1 A refrigeration system having two heat absorption heat exchangers is shown;

[0027] Figure 2 Another refrigeration system using two heat absorption heat exchangers is shown; and

[0028] Figure 3 Another refrigeration system using multiple heat absorption heat exchangers in conjunction with an internal heat exchanger is shown. DETAILED DESCRIPTION

[0029] exist Figure 1 A simple refrigeration system is schematically shown in order to illustrate the basic principle of using an ejector to provide a multi-temperature arrangement. The refrigeration system includes a compression device 12, a heat rejection heat exchanger 14, an ejector 20, a first expansion device 18, a first heat absorption heat exchanger 16, a second expansion device 22, and a second heat absorption heat exchanger 24. The refrigeration system may use carbon dioxide refrigerant. The refrigeration system contains a refrigerant fluid, and the circulation of the refrigerant fluid through the compression device 12 enables the refrigeration system to utilize a refrigeration cycle to meet two types of cooling loads via two different temperatures at the first heat absorption heat exchanger 16 and the second heat absorption heat exchanger 24.

[0030] The first heat absorption heat exchanger 16 may, for example, be used for air conditioning, and may therefore operate with a refrigerant fluid temperature in the range 0°C to 25°C. The second heat absorption heat exchanger 24 provides cooling for lower temperatures (such as for refrigerated or frozen storage of goods), and may therefore operate with a refrigerant fluid temperature in the range -35°C to 0°C. The higher pressure inlet of the ejector 20 receives the refrigerant fluid from the outlet of the heat rejection heat exchanger 14, and the lower pressure inlet of the ejector 20 receives the refrigerant fluid from the outlet of the first heat absorption heat exchanger 16. It will be appreciated that the arrangement of the ejector 20 allows for two different temperatures at the two heat absorption heat exchangers 16, 24, because the pressure at the lower pressure inlet of the ejector 20 may be different from the suction pressure for the compression device 12.

[0031] In broad terms, the operation of the various parts of the refrigeration system is as follows. The compression device 12 has an inlet for receiving a refrigerant fluid at a suction pressure and an outlet for providing a compressed refrigerant fluid at a discharge pressure. The heat rejection heat exchanger 14 is arranged to receive the compressed refrigerant fluid from the outlet of the compression device 12, and the outlet of the heat rejection heat exchanger 14 is connected to the high-pressure inlet of the ejector 20. The ejector also has: a low-pressure inlet, as noted elsewhere herein, which receives fluid from the first heat absorption heat exchanger 16; and an outlet, from which the refrigerant fluid is directed toward the expansion devices 18, 22. The refrigerant fluid arrives at the expansion device via a fluid pathway extending from the outlet of the ejector 20 and branching into a branched flow path so as to provide refrigerant from the outlet of the ejector 20, wherein the separated streams are directed to the first expansion device 18 and the second expansion device 22.

[0032] The first heat absorption heat exchanger 16 is arranged to receive refrigerant fluid from a first expansion device 18, and the second heat absorption heat exchanger 24 is arranged to receive refrigerant fluid from a second expansion device 22. The expansion devices 18, 22 are capable of providing different degrees of expansion so that the first heat absorption heat exchanger 16 will provide cooling via the refrigerant fluid at a first temperature, and the second heat absorption heat exchanger 24 will provide cooling at a second, lower temperature. After absorbing heat at the first heat absorption heat exchanger 16, thereby providing cooling (such as for air conditioning), the refrigerant fluid from the outlet of the first heat absorption heat exchanger 16 is directed to the low pressure inlet of the ejector 20. The refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device after the other refrigerant fluid flows through the second heat absorption heat exchanger 24, thereby providing cooling at a lower temperature (such as for refrigerated or frozen storage of goods).

[0033] By way of example, the heat rejection heat exchanger 14 may be a gas cooler unit for cooling a compressed carbon dioxide refrigerant. The heat rejection heat exchanger 14 may be a condenser for at least partially condensing a refrigerant fluid. The first expansion device 18 and the second expansion device 22 are electronic expansion valves 18, 22 for expanding the refrigerant fluid with a controllable degree of expansion, and the first heat absorption heat exchanger 16 and the second heat absorption heat exchanger 24 are evaporators for at least partially evaporating the refrigerant fluid. The refrigeration system may be arranged so that the refrigerant fluid is completely condensed at the condenser 14 and completely evaporated at the evaporators 16, 24. The compression device 12 is used for compression of the refrigerant fluid and for circulation of the refrigerant fluid around the refrigeration system.

[0034] The refrigeration circuit is controlled by a controller 26, which can, for example, control the expansion devices 18, 22 and the compressor 12. The control of the refrigeration circuit can be performed with reference to various inputs to the controller 26, such as user inputs and external temperature and / or temperature measurements and / or pressure measurements related to the refrigeration circuit, etc. The controller 26 in this example is capable of controlling the expansion devices 18, 22 so as to match the refrigeration system to the varying cooling loads at the first evaporator 16 and the second evaporator 24.

[0035] Figure 2 Shown with Figure 1 The arrangement is similar to that of a refrigeration system utilizing an ejector 20, with the addition of a receiver 28, and also an intercooler 30, together with the use of a compression device 12 with an intermediate pressure inlet, such as a suitable two-stage compression device 12. Figure 1 The system of φ(R) serves well to explain the basic principle of the proposed arrangement, but is difficult to control in practice when two-phase flow is present at the expansion devices 18, 22. Figure 2 The additional optional features allow for easier control of the system, which therefore carries with it the ability to achieve high levels of efficiency. Figure 1 Improvements in control of the system may alternatively be provided by other optional features while still retaining a single-stage compressor, such as by adding Figure 2 A receiver similar to the receiver of FIG. 2 (wherein the gas outlet of the receiver is connected to the suction inlet of the single-stage compressor via a suitable valve) is provided. Those skilled in the art will appreciate that other variations are possible.

[0036] exist Figure 2In the case of the arrangement, the inlet of the receiver 28 receives the refrigerant fluid from the outlet of the ejector 20, which refrigerant fluid may be a two-phase mixture. The receiver separates the refrigerant fluid into liquid and gaseous refrigerant. The liquid outlet of the receiver 28 provides the refrigerant fluid (liquid) to the branched fluid path, and therefore, the expansion devices 18, 22 will receive liquid refrigerant. The heat absorption performed by the first heat absorption heat exchanger 16 and the second heat absorption heat exchanger 24 then continues as above. The gas outlet of the receiver 28 is connected to the intercooler circuit together with the intercooler 30, and the refrigerant fluid from the gas outlet of the receiver 28 is directed to the medium-pressure inlet of the two-stage compression device 12. The two-stage compression device 12 includes a high-pressure stage 12a, which takes the refrigerant fluid from the medium-pressure inlet and compresses the refrigerant fluid to a discharge pressure ready to be directed toward the heat rejection heat exchanger 14. There is also a low pressure stage 12b which receives the refrigerant fluid at suction pressure from the second heat absorption heat exchanger and compresses the refrigerant fluid to an intermediate pressure. The intermediate pressure refrigerant fluid passes from the outlet of the low pressure stage 12b through an intercooler 30 and combines with the refrigerant fluid from the gas outlet of the receiver 28 before being directed to the inlet of the high pressure stage 12a.

[0037] This arrangement allows for better handling of the two-phase refrigerant from the outlet of the ejector 20 and also adds further cooling of the refrigerant via the intercooler 30. The intercooler 30 can advantageously be used in series with the heat rejection heat exchanger 14, which may be a gas cooler unit such as a carbon dioxide gas cooler for use with carbon dioxide refrigerant fluid. Figure 2 Other features not mentioned in detail may be similar to those described above for Figure 1 And those characteristics discussed.

[0038] exist Figure 3 The refrigeration system of FIG. 1 shows possible additional features of more complex multi-temperature arrangements. Figure 3 The refrigeration system includes additional elements that can allow for an increased operating range for the system and a greater degree of control when varying cooling capacities between a first temperature and a second temperature are required. Figure 3 The arrangement has added features regarding the handling of the refrigerant fluid from the outlet of the first heat absorption heat exchanger, in particular, a check valve 32 is provided between the outlet of the first heat absorption heat exchanger 16 and the low pressure inlet of the ejector 20 to prevent flow reversal in the event that the fluid flows away from the ejector 20. In addition, a bypass line 34 may be provided for allowing refrigerant fluid flow from the outlet of the first heat absorption heat exchanger 16 to the suction inlet of the compression device 12. The bypass line 34 may include a bypass valve 36 for controlling the flow of the refrigerant fluid along the bypass line 34 and thus for controlling the pressure at the first heat absorption heat exchanger 16.

[0039] Figure 3 The refrigeration system of the invention further comprises one or more internal heat exchangers 38, 40 for heat transfer between refrigerant fluids at different temperatures within the refrigeration system. These internal heat exchangers 38, 40 may be brazed plate heat exchangers.

[0040] The first internal heat exchanger 38 provides for heat transfer from the first flow path after the receiver 28 to the second flow path in the system after the second heat absorbing heat exchanger 24. Figure 3 As seen in FIG. 1 , the first flow path of the first internal heat exchanger 38 is located between the receiver 28 and the branching point of the flow path to the expansion device 18, 22. The second flow path of the first internal heat exchanger 38 is located after the second heat absorption heat exchanger 24 and before the inlet of the compression device 12. The first internal heat exchanger thus transfers heat between the liquid refrigerant located after the receiver 28 and the gaseous (or two-phase) refrigerant located after the second heat absorption heat exchanger 24.

[0041] The second internal heat exchanger 40 provides for heat transfer from a first flow path located after the outlet of the heat rejection heat exchanger 14 and before the high pressure inlet of the ejector 20 and a second flow path located between the gas outlet of the receiver 28 and the medium pressure inlet to the compression device 12. The second internal heat exchanger 40 thus transfers heat between the refrigerant fluid located after the heat rejection heat exchanger 14 and the refrigerant located after the gas outlet of the receiver 28.

[0042] like Figure 3 As shown by the dashed features in , there may also be additional optional features. For example, the refrigeration system can include a heat recovery device located after the compression device 12 and before the heat rejection heat exchanger 14. Thus, there may be a three-way valve 42 for allowing some or all of the compressed refrigerant to pass through the coil 44 before the heat rejection heat exchanger 14 for heat recovery. A third internal heat exchanger 46 can be included in the heat recovery system for exchanging heat between the cold line and the hot line to the coil 44. Alternatively or additionally, the first heat absorption heat exchanger 16 and / or the second heat absorption heat exchanger 24 can be connected in parallel with additional heat absorption heat exchangers 16', 24', and the additional heat absorption heat exchangers 16', 24' therefore also handle the refrigerant fluid at the corresponding first temperature or second temperature. Thus, the refrigeration system can be arranged for heat absorption via a refrigerant fluid at a first temperature using two or more heat absorption heat exchangers 16, 16' in parallel with corresponding multiple expansion valves 18, 18'. For example, there may be multiple air conditioning evaporators. Similarly, the refrigeration system can include two or more heat absorbing heat exchangers 24, 24' in parallel with a refrigerant at a second lower temperature, such as multiple medium temperature evaporators for refrigeration or freezing of stored goods. Again, this can be achieved using a corresponding multiple expansion valves 22, 22'.

[0043] Figure 3 The refrigeration system can include: a controller (not shown) for control of the two-stage compressor 12 in a manner similar to that described above; expansion devices 18, 22, and additional expansion devices 18', 22' (when present); and various valves (when present), such as a bypass valve 36 and / or a three-way valve 42.

[0044] When in use, the various refrigeration systems described above each use the ejector 20 in a similar manner to allow two different pressures for the heat absorption heat exchangers 16, 24 and therefore two different cooling temperatures.

Claims

1. A refrigeration system, comprising: a single compression device having an inlet for receiving refrigerant fluid at a suction pressure and an outlet for providing compressed refrigerant fluid at a discharge pressure; a heat rejection heat exchanger arranged to receive compressed refrigerant fluid from said outlet of said compression device; an ejector having a high pressure inlet, a low pressure inlet, and an outlet, the ejector being arranged to receive refrigerant fluid from the heat rejection heat exchanger at the high pressure inlet of the ejector; a fluid pathway extending from the outlet of the ejector and branching into branched flow paths to provide refrigerant from the outlet of the ejector to a first expansion device and a second expansion device; a first heat absorption heat exchanger arranged to receive refrigerant fluid from the first expansion device; a second heat absorption heat exchanger arranged to receive refrigerant fluid from the second expansion device; a receiver having an inlet for receiving refrigerant fluid from the outlet of the ejector and a liquid outlet for providing refrigerant fluid to the branched flow path; and a first internal heat exchanger providing for heat transfer from a first flow path after the receiver to a second flow path after the second heat absorbing heat exchanger; wherein the first heat absorption heat exchanger is for providing cooling via a refrigerant fluid at a first temperature, and the refrigerant fluid from the outlet of the first heat absorption heat exchanger is directed to the low pressure inlet of the ejector; wherein the second heat absorption heat exchanger is used to provide cooling via a refrigerant fluid at a second temperature, and the refrigerant fluid from the outlet of the second heat absorption heat exchanger is directed to the inlet of the compression device; and Wherein, the second temperature is lower than the first temperature.

2. The refrigeration system according to claim 1, wherein: The first heat absorption heat exchanger is used for air conditioning and is used to operate with an air side temperature in the range of 15°C to 30°C, while the second heat absorption heat exchanger is used for medium temperature applications and is used to operate with an air side temperature in the range of -25°C to 8°C.

3. The refrigeration system according to claim 1 or 2, wherein: The first expansion device and the second expansion device are arranged to provide different degrees of expansion.

4. The refrigeration system according to claim 1 or 2, wherein: The ejector high pressure inlet receives all of the refrigerant fluid flowing through the heat rejection heat exchanger.

5. The refrigeration system according to claim 1, wherein: The gas outlet of the receiver is in communication with the medium-pressure inlet of the compression device.

6. The refrigeration system according to claim 1 or 2, wherein: The compression device has two compression stages, wherein the outlet of the second heat absorption heat exchanger provides refrigerant fluid to the suction inlet of the first compression stage, and the discharge outlet of the second compression stage provides the compressed refrigerant fluid to the heat rejection heat exchanger.

7. The refrigeration system according to claim 6, comprising an intercooler, wherein: The compression device comprises an intermediate pressure outlet for directing refrigerant fluid to the intercooler, and the refrigerant fluid from the outlet of the intercooler is directed to the intermediate pressure inlet of the compression device.

8. The refrigeration system according to claim 1 or 2, wherein the refrigeration system is without any additional compression device located between the heat rejection heat exchanger and the ejector and / or without any additional compression device located between the ejector and the heat absorption heat exchanger.

9. The refrigeration system according to claim 1 or 2, wherein: The heat rejection heat exchanger is a gas cooler unit.

10. The refrigeration system according to claim 1 or 2, wherein: The refrigeration system is configured for use with a carbon dioxide refrigerant.

11. A refrigeration system according to claim 1 or 2, comprising a check valve between the outlet of the first heat absorption heat exchanger and the low pressure inlet of the ejector to prevent flow reversal if fluid flows away from the ejector.

12. The refrigeration system according to claim 1 or 2, comprising a bypass line for allowing refrigerant fluid to flow from the outlet of the first heat absorption heat exchanger to the inlet of the compression device, wherein The bypass line comprises a bypass valve for controlling the flow of refrigerant fluid along the bypass line and / or for controlling the pressure at the outlet of the first heat absorption heat exchanger.

13. A refrigeration system according to claim 1 or 2, comprising one or more internal heat exchangers for transferring heat between refrigerant fluids at different temperatures within the refrigeration system.

14. A method for refrigeration with cooling at two temperatures, the method comprising: Providing a refrigeration system according to any one of the preceding claims; using the first heat absorption heat exchanger to provide a first refrigeration temperature; and using the second heat absorption heat exchanger to provide a second refrigeration temperature.

Images