CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of CN Application No. 201811338236.0, filed on November 12, 2018, which is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

[0001] The present application belongs to the field of refrigeration, and in particular relates to a refrigeration system.

BACKGROUND OF THE INVENTION

[0002] In a refrigeration system, a refrigerant liquid pump is used to draw liquid refrigerant from a pipeline to remove excessive liquid supplied or to pressurize. For example, in a conventional or trans-critical refrigeration system, a refrigerant liquid pump is used to achieve a flooded evaporation operation. In an injector system, the refrigerant liquid pump can also be used to increase the pressure of liquid leaving a reservoir to avoid insufficient liquid supply to the evaporator, wherein the reservoir receives a high-pressure refrigerant and separates flash gas out. However, the refrigerant liquid pump is expensive and difficult to service.

SUMMARY OF THE INVENTION

[0003] The technical problem to be solved by the present application is to provide a refrigeration system to improve or replace the technical solutions of refrigeration system in the related art.

[0004] The refrigeration system according to the present application comprises: a compressor; a first gas-liquid separation device connected to an exhaust port of the compressor via a condenser branch, the condenser branch being provided with a condensation element via which refrigerant condenses, and the first gas-liquid separation device having a gas outlet and a liquid outlet, and the gas outlet is connected to a suction port of the compressor through a pipeline; a first evaporator through which the refrigerant passes to provide a refrigerating capacity, and the first evaporator being connected to the liquid outlet through a pipeline; an injector pump having a primary inlet, a secondary inlet and an outlet, wherein the primary inlet is configured to connect to the exhaust port of the compressor, at least a portion of the refrigerant exiting the liquid outlet enters the injector pump via the secondary inlet, and the outlet is connected to the first gas-liquid separation device via a pipeline.

[0005] The above refrigeration system further comprises a refrigerant recovery branch connected to the first gas-liquid separation device, the first evaporator is disposed on the refrigerant recovery branch, and the injector pump is connected to the refrigerant recovery branch.

[0006] In the above refrigeration system, the first evaporator is a flooded evaporator or semi-dry evaporator.

[0007] In the above refrigeration system, an outlet of the first evaporator is provided with a second gas -liquid separation device, wherein a gas outlet of the second gas -liquid separation device is connected to the suction port of the compressor through a pipeline, and a liquid outlet of the second gas-liquid separation device is connected to the secondary inlet of the injector pump.

[0008] In the above refrigeration system, the condenser branch further comprises a first throttling element, the condensation element is a condenser, and the condenser is connected to the first gas-liquid separation device via the first throttling element.

[0009] In the above refrigeration system, the first throttling element is a high-pressure valve or an expansion valve.

[0010] In the above refrigeration system, the refrigerant recovery branch is provided with a second throttling element connected to an inlet of the first evaporator, and the liquid outlet of the first gas-liquid separation device is connected to the second throttling element.

[0011] In the above refrigeration system, the second throttling element is an expansion valve.

[0012] The above refrigeration system further comprises a heat exchanger branch connected to the first gas -liquid separation device, and the heat exchanger branch is provided with a third throttling element and a heat exchanger through which the refrigerant exiting the gas outlet of the first gas-liquid separation device passes successively; wherein the refrigerant exiting the gas outlet of the first gas-liquid separation device exchanges heat with the refrigerant from the liquid outlet of the first gas-liquid separation device in the heat exchanger, and is then mixed with the refrigerant from the gas outlet of the second gas-liquid separation device before flowing toward the suction port of the compressor.

[0013] In the above refrigeration system, the first gas-liquid separation device is a flash tank. [0014] In the above refrigeration system, the secondary inlet of the injector pump is connected to the liquid outlet of the first gas-liquid separation device to receive all of the liquid refrigerant.

[0015] In the above refrigeration system, the refrigerant recovery branch is further provided with a second throttling element connected to the inlet of the first evaporator, and the outlet of the injector pump is connected to the second throttling element.

[0016] In the above refrigeration system, a pressurizing element is further disposed on the condenser branch, and the pressurizing element is connected between the condensation element and the first gas-liquid separation device.

[0017] In the above refrigeration system, the pressurizing element is a gas injector, a gas inlet of the gas injector is connected to an outlet of the first evaporator, a primary inlet of the gas injector is connected to the condenser, and an outlet of the gas injector is connected to the first gas-liquid separation device.

[0018] In the above refrigeration system, the outlet of the first evaporator is provided with a second gas-liquid separation device, a gas outlet of the second gas-liquid separation device is connected to the gas inlet of the gas injector through a pipeline, and a liquid outlet of the second gas-liquid separation device is connected to the secondary inlet of the injector pump.

[0019] In the above refrigeration system, the compressor comprises an intermediate- temperature compressor and a low-temperature compressor, and the refrigerant exiting the gas outlet of the first gas-liquid separation device flows toward a suction port of the intermediate- temperature compressor.

[0020] The above refrigeration system further comprises a second evaporator, and the refrigerant leaving the liquid outlet of the first gas -liquid separation device enters the first evaporator and the second evaporator respectively, wherein the second evaporator is connected to a suction port of the low-temperature compressor.

[0021] The injector pump of the present application can absorb the refrigerant discharged from the first gas-liquid separation device in the refrigerant recovery branch and circulate the refrigerant back to the first gas-liquid separation device. The refrigerant is divided into a gas refrigerant and a liquid refrigerant in the first gas-liquid separation device. In particular, the injector pump absorbs the liquid refrigerant and can replace the refrigerant liquid pump, thus having the advantage of cost reduction.

[0022] In addition, since the injector pump uses the high-pressure steam refrigerant stream discharged from the compressor as the driving fluid, this portion of the fluid has a higher energy, so that the mixed fluid leaving the injector pump can be more pressurized, and the efficiency of the injector pump is improved.

[0023] For the entire refrigeration system circuit, the increased pressurizing level of the injector pump increases the pressure level of the evaporator, which in turn increases the suction level and compressor efficiency of the compressor.

[0024] Other aspects and features of the present application will become apparent from the following detailed description with reference to the drawings. However, it should be understood that the drawings are intended for purposes of illustration only, rather than defining the scope of the present application since it should be determined with reference to the appended claims. It should also be understood that the drawings are merely intended to conceptually illustrate the structure and flowchart described herein, and it is not necessary to draw the figures to the scale, unless otherwise specified.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present application will be more fully understood from the following detailed description of specific embodiments with reference to the drawings. Identical elements are denoted by identical reference signs throughout the drawing, wherein:

[0026] FIG. 1 is a schematic view of a first embodiment of a refrigeration system according to the present application;

[0027] FIG. 2 is a schematic view of a second embodiment of a refrigeration system according to the present application; and

[0028] FIG. 3 is a schematic view of a third embodiment of a refrigeration system according to the present application.

DETAILED DESCRIPTION OF THE EMBODIMENT(S) OF THE INVENTION

[0029] To help those skilled in the art precisely understand the subject matter of the present application, specific embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0030] FIG. 1 is an embodiment of a refrigeration system according to the present application. Referring to FIG. 1, the refrigeration system comprises a first compressor 12 and a second compressor 14. A refrigerant undergoes a two-stage compression refrigeration cycle through the first and second compressors 12, 14. The first compressor 12 is provided as an intermediate-temperature compressor, the second compressor 14 is provided as a low- temperature compressor, and the compressed refrigerant leaving the second compressor 14 is drawn into the first compressor 12 for further compression. Due to the development of production, the requirements on refrigeration temperature are becoming higher and higher. In many refrigeration applications, a two-stage compression refrigeration cycle is employed. The two-stage compression refrigeration cycle may be set to correspond to different temperature levels to meet a variety of refrigeration requirements. Corresponding to the first and second compressors 12, 14, a first evaporator 41 and a second evaporator 42 are disposed in the system. The first evaporator 41 is provided as an intermediate-temperature evaporator, and the second evaporator 42 is provided as a low-temperature evaporator. The first and second evaporators

41, 42 are disposed separately on two branches. The refrigerant passing through the first evaporator 41 will eventually enter the first compressor 12. For the refrigeration system of the illustrated embodiment including the two-stage compressor, the refrigerant from the first evaporator 41 will merge with the refrigerant output from the second compressor 14 and then enter the first compressor 12. On the other hand, the refrigerant that absorbs heat in the second evaporator 42 and leaves the second evaporator 42 will eventually enter the second compressor 14.

[0031] Although the illustrated embodiment comprises a two-stage compressor, it should be understood that the pipeline connecting the second compressor 14 and the second evaporator 42 may be removed so that the system becomes a single-stage refrigeration cycle comprising only the first compressor 12 and the first evaporator 41. It should also be understood that other devices such as a heat exchanger or the like through which a refrigerant passes to provide a refrigeration capacity may be further connected in parallel with the first evaporator 41 and the second evaporator 42. It should also be understood that on the basis of the illustrated embodiment, a valve is provided between the second compressor 14 and the second evaporator

42, i.e., in front of a suction port of the second compressor 14. By controlling the opening of the valve, temperature and/or velocity of the refrigerant entering the second compressor 14 is adjusted so that the entire refrigeration system becomes a possible compression refrigeration cycle having more stages (e.g., three stages).

[0032] The refrigerant may be commonly used R410A, R404A, R134A, etc., and the refrigeration system using the above refrigerant operates in a subcritical mode. The refrigerant may also be carbon dioxide, and the refrigeration system using such a refrigerant operates in a trans-critical refrigeration mode.

[0033] The refrigerant compressed by the first compressor 12 leaves the first compressor 12 in the form of compressed steam and is divided into two parts, one part of which enters a condenser branch provided with a condenser 21. The refrigerant is cooled in the condenser 21 (or gas cooler) and is phase-transformed into a condensed liquid stream. The condensed liquid stream then enters a first throttling element 22, such as an expansion valve as shown or a high-pressure valve. After throttling, the condensed liquid stream further enters a first gas-liquid separation device 3 for a first gas-liquid separation. The separation device is a low-pressure device, so that the high-pressure refrigerant is flashed in the low-pressure first gas-liquid separation device 3 such as a flash tank to produce a gas refrigerant and a liquid refrigerant. The gas refrigerant exits a gas outlet 31 of the flash tank and will flow toward the suction port of the first compressor 12. The liquid refrigerant is stored in the flash tank, or enters the first evaporator 41 from the flash tank and is vaporized therein to provide a refrigeration capacity.

[0034] A portion of the liquid refrigerant leaving the liquid outlet 32 of the flash tank may be recovered and recycled back to the flash tank. In FIG. 1, the liquid refrigerant first passes through a heat exchanger 62. After being cooled, a portion of the liquid refrigerant enters a second throttling element 43 for a second throttling expansion, and then the expanded liquid stream enters the first evaporator 41 for evaporation, wherein the second throttling element 43 is an expansion valve. Similarly, the other portion of the liquid refrigerant passing through the heat exchanger 62 enters the pipeline in which the second evaporator 42 is located, wherein it firstly undergoes a second throttling expansion through a throttling element 44 (i.e., an expansion valve 44) similar to the second throttling element, and then it enters the second evaporator 42 and is evaporated. In the illustrated embodiment, the refrigerant is subjected to a flooded or semi-dry evaporation operation in the first evaporator 41. In order to increase the operating efficiency of the evaporator, the dryness of the outlet of the first evaporator 41 can be controlled, so that the refrigerant entrains a portion of the liquid after evaporation. This portion of the liquid can be recycled back to the flash tank, while the remaining portion of the refrigerant, i.e., the gas portion, may be used for suction of the compressor. Referring to FIG. 1, a second gas-liquid separation device 45, such as a general separator, is disposed at the outlet of the first evaporator 41. The liquid-containing refrigerant gas stream enters the separator and is separated into a gas stream and a liquid stream. The separated gas stream exits the top of the separator and flows to the first compressor 41 as a portion of the suction gas. The liquid stream will return to the flash tank, as will be described below with respect to the refrigerant liquid stream leaving the second gas-liquid separation device 45.

[0035] The gas refrigerant exiting the flash tank is a saturated gas stream that will act as another portion of the suction gas of the first compressor 12. After exiting the flash tank, the saturated gas stream first passes through a third throttling element 64, such as a throttling valve, and then enters the heat exchanger 62 for heat exchange with the saturated liquid refrigerant exiting the flash tank. The pressure of the saturated gas stream discharged from the first gas- liquid separation device 3 is greater than the pressure of the refrigerant gas stream supplied from the second gas-liquid separation device 45, i.e., the separator. After the throttling, the saturated gas stream will contain a liquid phase which, after heat exchange in the heat exchanger 62, will be re-converted into steam. The gas refrigerant finally leaving the heat exchanger 62 is mixed with the steam stream discharged from the separator and supplied to the first compressor 12.

[0036] In the system illustrated in FIG. 1 , a refrigerant recovery branch is provided to circulate liquid refrigerant exiting the flash tank back into the flash tank. The liquid refrigerant exits the flash tank and then passes through the heat exchanger 62, the second throttling element 43 (the expansion valve), the first evaporator 41, and the separator 45 in sequence. An injector pump 5 is connected to the refrigerant recovery branch. The injector pump 5 comprises a primary inlet 51, a secondary inlet 52, and an outlet 53. The refrigerant output from the first compressor 12 is branched, a portion thereof condenses in the condenser 21 as described above, and the remaining portion is introduced into the injector pump 5 as a mainstream fluid via the primary inlet 51. The refrigerant exiting the liquid outlet of the separator 45 enters the injector pump 5 via the secondary inlet 52. A nozzle is disposed in the injector pump 5 for converting the pressure energy of the refrigerant from the first compressor 12 into velocity energy, and is capable of suctioning a branch fluid (i.e., the refrigerant from the separator) coming from the secondary inlet 52. The injector pump 5 is further provided with a pressurizing portion, which can convert the mixed refrigerant from the velocity energy to the pressure energy again and eject it through the outlet 53. The ejected gas is a high-pressure refrigerant which returns to the flash tank through a pipeline. A commercially available injector may be used for the injector pump 5. Excessive liquid refrigerant generated in the first evaporator 41 due to overheating may be recovered by the injector pump 5 after being separated by the separator 45. The injector pump 5 has the advantages of low cost and easy maintenance as compared with a solution in which a liquid pump is used in a general system to recover this portion of the liquid. Further, the refrigerant output from the first compressor 12 is used for the mainstream fluid of the injector pump 5. In most refrigeration systems, the primary inlet of the injector is connected to the condenser, and although the refrigerant stream pressure at the outlet of the first compressor 12 is the same as the refrigerant stream pressure at the outlet of the condenser, it has greater energy. The refrigerant discharged from the first compressor 12 is introduced to the primary inlet 51 of the injector pump 5 , and after the refrigerant stream is expanded by the nozzle inside the injector pump 5, the energy is converted into kinetic energy so that the liquid refrigerant on the secondary inlet side is induced and mix together to be pressurized. Therefore, by using the energy of the discharged refrigerant of the first compressor 12 to drive the injector pump 5, the pressurizing ability of the injector pump 5 can be improved. The pressurized mixed gas enters the flash tank, then the gas discharged from the flash tank flows back to the first compressor 12, and the discharged liquid enters the first evaporator 41 again or other devices to provide a refrigeration capacity. In the embodiment shown in FIG. 1, the outlet of the first evaporator 41 may be arranged without a separator, but is directly connected to a branch leading to the secondary inlet 52 of the injector pump 5. The refrigerant leaving the first evaporator 41 and containing both gas phase and liquid phase directly enters the injector pump 5 as a branch stream.

[0037] FIG. 2 shows another embodiment of the refrigeration system according to the present application, wherein elements identical to those in FIG. 1 are denoted by identical reference numerals. The saturated gas leaving the flash tank will flow directly back to the first compressor 12, that is, the suction gas of the first compressor 12 comprises only the gas refrigerant supplied by the flash tank and the compressed refrigerant supplied by the second compressor 14. In the illustrated embodiment, the injector pump 5 is directly connected to the liquid outlet of the flash tank. All the liquid refrigerant leaving the flash tank is suctioned in via the injector pump 5 and circulated back to the flash tank after passing through the first evaporator 41. The injector pump 5 is still driven by the high-energy refrigerant stream output by the first compressor 12. The refrigerant stream output by the first compressor 12 is divided into two parts, one part of which enters the condenser 21 (or gas cooler) to be cooled and phase- transformed into a condensed liquid stream, and the remaining part enters the injector pump 5 as a mainstream fluid via the primary inlet 51. The liquid refrigerant discharged from the flash tank is suctioned in via the secondary inlet 52 of the injector pump 5, and then the mixed stream branches flow toward the two branches of the first and second evaporators 41, 42. On each branch, the mixed streams enter the respective evaporators 41, 42 after being expanded by the expansion valves 43, 44. The steam stream discharged from the first evaporator 41 is pressurized via a gas injector 7 and circulated back to the flash tank. The gas injector 7 is disposed between the condenser 21 on the condenser branch and the flash tank, wherein a primary inlet 71 thereof is connected to the outlet pipeline of the condenser 21, and a secondary inlet 72, that is, a gas inlet, is connected to a pipeline through which the refrigerant stream discharged from the first evaporator 41 flows. In the illustrated embodiment, the secondary inlet is directly connected to the first evaporator 41. The mixed stream pressurized by the gas injector 7 flows into the flash tank. In the above process, the injector pump 5 pressurizes the liquid refrigerant discharged from the flash tank, thereby increasing the inlet pressure of the first evaporator 41, and further increasing the refrigeration efficiency of the entire refrigeration system circuit.

[0038] The above description regarding the refrigeration system circuit is not limited to the illustrated form. As shown in FIG. 3, the arrangement of the injector pump 5 is the same as that of FIG. 1, and the refrigerant leaving the flash tank directly enters the branches where the respective evaporators are located. The gas injector 7 is disposed in a pipeline between the condenser 21 and the flash tank to replace the expansion valve. The main stream fluid flowing in the primary inlet 71 of the gas injector 7 is the refrigerant stream discharged from the condenser 21, and the branch stream fluid suction in the secondary inlet 72 of the gas injector 7 is the separated refrigerant gas stream from the separator. The pressurized mixed refrigerant stream ejected from the gas injector 7 via the outlet 73 is remixed with the pressurized mixed refrigerant stream ejected from the injector pump 5 and then introduced into the flash tank. Such a system can have multiple modes of operation; that is, the gas injector 7 and the injector pump 5 can operate independently or cooperatively, thus solving the problem of limited operating temperature range of the gas injector 7. For example, when the ambient temperature is low, the gas injector 7 may not function properly, and in this case the injector pump 5 may be activated to assist the gas injector 7, or the injector pump 5 may operate separately to recover the refrigerant and recycle it back to the flash tank.

[0039] Principles of the present application are described in connection with the specific embodiments of the present application that have been shown and described in detail, but it should be understood that the present application can be implemented in other ways without departing from the principles.