A three-stage cascade refrigeration system

Abstract

The application relates to the technical field of refrigeration equipment, in particular to a three-stage cascade refrigeration system which comprises a carrier refrigerant system and a three-stage compression refrigeration system; the three-stage compression refrigeration system comprises a first compressor, a second compressor and a third compressor; the carrier refrigerant system comprises a liquid storage tank, a circulating pump and a first evaporator, a second evaporator and a third evaporator which are arranged in series; the liquid storage tank is connected with a first carrier refrigerant passage inlet of the first evaporator through a pipeline and the circulating pump; the liquid storage tank is connected with a second carrier refrigerant passage inlet of the second evaporator through a pipeline and the circulating pump; the liquid storage tank is connected with a third carrier refrigerant passage inlet of the third evaporator through a pipeline and the circulating pump; a first carrier refrigerant passage outlet of the first evaporator, a second carrier refrigerant passage outlet of the second evaporator and a third carrier refrigerant passage outlet of the third evaporator all return to the liquid storage tank through pipelines; the application can reduce the cost of refrigeration in different temperature ranges.

Description

Technical Field

[0001] This application relates to the field of refrigeration equipment technology, and in particular to a three-stage cascade refrigeration system. Background Technology

[0002] In the fields of chemical engineering and pharmaceuticals, many chemical reactions need to be carried out in specific low-temperature or ultra-low-temperature environments, which places extremely high demands on the temperature range and stability of the cold source. For example, some reactions need to be carried out at around -40°C, some at below -80°C, and some special reactions require temperatures as low as -120°C. At the same time, a normal temperature environment of around 25°C may be required during the preparation or completion of the reaction.

[0003] In existing technologies, to meet the aforementioned different temperature requirements, multiple independent cryogenic devices are typically used to cover different temperature zones: such as separate -120℃ to -80℃ cryogenic devices, -80℃ to -40℃ cryogenic devices, and -40℃ to 25℃ ambient temperature devices. In practical applications, it is necessary to frequently change equipment or switch cold sources according to the required reaction temperature, which has the following significant drawbacks: the purchase, installation, and maintenance costs of multiple devices increase significantly, and the equipment idle rate is high; the cold source temperature needs to be readjusted during equipment switching, resulting in large temperature fluctuations, affecting reaction stability, and the switching time is long, reducing production efficiency; a single device can only cover a limited temperature zone, and even under low load demand, the equipment still needs to operate at full load, resulting in low energy utilization. Utility Model Content

[0004] To reduce the cost of refrigeration in different temperature ranges, this application provides a three-stage cascade refrigeration system.

[0005] This application provides a three-stage cascade refrigeration system, which adopts the following technical solution: it includes a refrigerant system and a three-stage compression refrigeration system; the three-stage compression refrigeration system includes a first compressor, a second compressor, and a third compressor;

[0006] The refrigerant system includes a storage tank, a circulation pump, and a first evaporator, a second evaporator, and a third evaporator connected in series. The storage tank is connected to the inlet of the first refrigerant channel of the first evaporator via a pipeline and the circulation pump. The storage tank is also connected to the inlet of the second refrigerant channel of the second evaporator via a pipeline and the circulation pump. The outlets of the first, second, and third refrigerant channels of the first, second, and third evaporators are all returned to the storage tank via pipelines.

[0007] The refrigerant circuit of the first compressor is connected to the first evaporator or the second condenser-evaporator, the refrigerant circuit of the second compressor is connected to the second evaporator or the third condenser-evaporator, and the refrigerant circuit of the third compressor is connected to the third evaporator, forming a structure in which the system can operate in single compressor mode, dual compressor cooperative mode, and triple compressor cooperative mode.

[0008] Optionally, the refrigerant circuit of the first compressor includes a first oil separator, a condenser, a liquid receiver, and a first dryer filter connected in sequence. The first dryer filter is connected to a first expansion valve through a first solenoid valve. The first expansion valve is connected to the inlet of the first refrigerant passage of the first evaporator. The outlet of the first refrigerant passage of the first evaporator is connected back to the first compressor via a gas-liquid separator.

[0009] Optionally, in the refrigerant circuit of the first compressor, the first dryer filter is also connected to the second expansion valve via a second solenoid valve. The second expansion valve is connected to the refrigerant passage inlet of the second condenser-evaporator, and the refrigerant passage outlet of the second condenser-evaporator is connected back to the first compressor via a gas-liquid separator. The refrigerant circuit of the second compressor includes a second oil separator, a second condenser-evaporator, and a second dryer filter connected in sequence. The second dryer filter is connected to the third expansion valve via a third solenoid valve. The third expansion valve is connected to the second refrigerant passage inlet of the second evaporator, and the second refrigerant passage outlet of the second evaporator is connected back to the second compressor.

[0010] Optionally, the outlet of the second oil separator is divided into two paths: one path is connected to the second condenser-evaporator, and the other path is connected to the first expansion container through the first unloading valve. The outlet of the first expansion container is then connected back to the second compressor.

[0011] Optionally, in the refrigerant circuit of the second compressor, the second dryer filter is also connected to the fourth expansion valve via the fourth solenoid valve. The fourth expansion valve is connected to the inlet of the third refrigerant passage of the third condenser-evaporator, and the outlet of the third refrigerant passage of the third condenser-evaporator is connected back to the second compressor. The refrigerant circuit of the third compressor includes a third oil separator, a third condenser-evaporator, and a third dryer filter connected in sequence. The third dryer filter is connected to a capillary tube, which is connected to the inlet of the third refrigerant passage of the third evaporator. The outlet of the third refrigerant passage of the third evaporator is connected back to the third compressor.

[0012] Optionally, the outlet of the third oil separator is divided into two paths: one path is connected to the third condenser-evaporator, and the other path is connected to the second expansion container through the second unloading valve. The outlet of the second expansion container is then connected back to the third compressor.

[0013] Optionally, in the refrigerant system, the refrigerant channels of the first evaporator, the second evaporator, and the third evaporator are connected in series to form a circulation path through which the refrigerant flows sequentially through each evaporator.

[0014] Optionally, the gas-liquid separator is located between the outlet of the first refrigerant channel of the first evaporator and the inlet of the first compressor.

[0015] Optionally, the condenser outlet is connected to a liquid receiver for temporarily storing the refrigerant liquid after condensation by the condenser.

[0016] In summary, this application includes the following beneficial technical effects:

[0017] 1. By using a three-stage compression refrigeration system in conjunction with a series-connected refrigerant evaporator, it can cover the entire temperature range of -120 to 25℃. The corresponding number of compressors can be selectively started according to the required temperature range of the refrigerant: single compressor operation covers -39.9 to 25℃, dual compressor operation covers -80 to -40℃, and three compressor operation covers -120 to -80.1℃, avoiding energy waste from a single device operating at full load;

[0018] 2. In the refrigerant system, the refrigerant channels of the first evaporator, the second evaporator, and the third evaporator are connected in series, so that the refrigerant can be gradually cooled during the flow process and exchange heat with the refrigerants driven by different compressors in a stepped manner, which improves the heat exchange efficiency and temperature control accuracy, and ensures that the refrigerant temperature is stable within the target range.

[0019] 3. The first compressor is connected to the first evaporator or the second condenser-evaporator by switching between the first solenoid valve and the second solenoid valve, and the second compressor is connected to the second evaporator or the third condenser-evaporator by switching between the third solenoid valve and the fourth solenoid valve, so that the system can quickly switch between single compressor, dual compressor and triple compressor modes.

[0020] 4. Both the second and third oil separators are equipped with unloading valves and expansion containers at their outlets. When the refrigerant pressure exceeds the safety set value, the unloading valve opens and the pressure is released and returned through the expansion container to prevent system overpressure damage. The dryer filters installed in each refrigerant circuit can effectively filter out moisture and impurities in the refrigerant. The gas-liquid separator can separate the liquid in the refrigerant to ensure safe system operation. Attached Figure Description

[0021] Figure 1 This is a structural diagram of a three-stage cascade refrigeration system according to this application.

[0022] Reference numerals: 1 First compressor, 2 First oil separator, 3 Condenser, 4 Liquid receiver, 5 First dryer filter, 6 First solenoid valve, 1st expansion valve, 8 First evaporator, 8.1 First refrigerant channel outlet, 8.2 First refrigerant channel inlet, 9 Second solenoid valve, 10 Second expansion valve, 11 Second condenser-evaporator, 11.3 Refrigerant channel inlet, 11.4 Refrigerant channel outlet, 12 Gas-liquid separator, 13 Second compressor, 14 Second oil separator, 15 First unloading valve, 16 First expansion container, 17 Second dryer filter, 18 Third solenoid valve, 1 9 Third expansion valve, 20 Second evaporator, 20.1 Second refrigerant channel outlet, 20.2 Second refrigerant channel inlet, 21 Fourth solenoid valve, 22 Fourth expansion valve, 23 Third condenser-evaporator, 23.1 Third refrigerant channel outlet, 23.2 Third refrigerant channel inlet, 24 Third compressor, 25 Third oil separator, 26 Second unloading valve, 27 Second expansion container, 28 Third dryer filter, 29 Capillary tube, 30 Third evaporator, 30.1 Third refrigerant channel outlet, 30.2 Third refrigerant channel inlet, 31 Liquid receiver, 32 Circulation pump. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1 This application will be described in further detail.

[0024] This application discloses a three-stage cascade cooling system. For example... Figure 1 As shown, it includes a refrigerant system and a three-stage compression refrigeration system; the three-stage compression refrigeration system includes a first compressor 1, a second compressor 13, and a third compressor 24; the refrigerant system includes a liquid storage tank 31, a circulation pump 32, and a first evaporator 8, a second evaporator 20, and a third evaporator 30 arranged in series. The liquid storage tank 31 is connected to the first refrigerant channel inlet 8.2 of the first evaporator 8 via a pipe and the circulation pump 32. The liquid storage tank 31 is connected to the second refrigerant channel inlet 20.2 of the second evaporator 20 via a pipe and the circulation pump 32. The liquid storage tank 31 is connected to the third refrigerant channel inlet 30 of the third evaporator 30 via a pipe and the circulation pump 32. 2. The first refrigerant channel outlet 8.1 of the first evaporator 8, the second refrigerant channel outlet 20.1 of the second evaporator 20, and the third refrigerant channel outlet 30.1 of the third evaporator 30 all return to the liquid storage tank 31 through pipes; the refrigerant circuit of the first compressor 1 is connected to the first evaporator 8 or the second condensing evaporator 11, the refrigerant circuit of the second compressor 13 is connected to the second evaporator 20 or the third condensing evaporator 23, and the refrigerant circuit of the third compressor 24 is connected to the third evaporator 30, forming a structure in which the system can operate in single compressor mode, dual compressor cooperative mode, and triple compressor cooperative mode.

[0025] The refrigerant circuit of the first compressor 1 includes a first oil separator 2, a condenser 3, a liquid receiver 4, and a first dryer filter 5 connected in sequence. The first dryer filter 5 is connected to a first expansion valve 7 via a first solenoid valve 6. The first expansion valve 7 is connected to the first refrigerant passage inlet 8.2 of the first evaporator 8. The first refrigerant passage outlet 8.1 of the first evaporator 8 is connected back to the first compressor 1 via a gas-liquid separator 12. The gas-liquid separator 12 is located between the first refrigerant passage outlet 8.1 of the first evaporator 8 and the inlet of the first compressor 1. The outlet of the condenser 3 is connected to a liquid receiver 4 for temporarily storing the refrigerant liquid condensed by the condenser 3.

[0026] In the refrigerant circuit of the first compressor 1, the first dryer filter 5 is also connected to the second expansion valve 10 via the second solenoid valve 9. The second expansion valve 10 is connected to the refrigerant passage inlet 11.3 of the second condenser-evaporator 11. The refrigerant passage outlet 11.4 of the second condenser-evaporator 11 is connected back to the first compressor 1 via the gas-liquid separator 12. The refrigerant circuit of the second compressor 13 includes the second oil separator 14, the second condenser-evaporator 11, and the second dryer filter 17 connected in sequence. The second dryer filter 17 is connected to the third expansion valve 19 via the third solenoid valve 18. The third expansion valve 19 is connected to the second refrigerant passage inlet 20.2 of the second evaporator 20. The second refrigerant passage outlet 20.1 of the second evaporator 20 is connected back to the second compressor 13. The outlet of the second oil separator 14 is divided into two paths: one path is connected to the second condenser-evaporator 11, and the other path is connected to the first expansion container 16 via the first unloading valve 15. The outlet of the first expansion container 16 is connected back to the second compressor 13.

[0027] In the refrigerant circuit of the second compressor 13, the second dryer filter 17 is also connected to the fourth expansion valve 22 via the fourth solenoid valve 21. The fourth expansion valve 22 is connected to the third refrigerant passage inlet 23.2 of the third condenser-evaporator 23. The third refrigerant passage outlet 23.1 of the third condenser-evaporator 23 is connected back to the second compressor 13. The refrigerant circuit of the third compressor 24 includes the third oil separator 25, the third condenser-evaporator 23, and the third dryer filter 28 connected in sequence. The third dryer filter 28 is connected to the capillary tube 29. The capillary tube 29 is connected to the third refrigerant passage inlet 30.2 of the third evaporator 30. The third refrigerant passage outlet 30.1 of the third evaporator 30 is connected back to the third compressor 24. The outlet of the third oil separator 25 is divided into two paths: one path is connected to the third condenser-evaporator 23, and the other path is connected to the second expansion container 27 via the second unloading valve 26. The outlet of the second expansion container 27 is connected back to the third compressor 24.

[0028] In the refrigerant system, the refrigerant channels of the first evaporator 8, the second evaporator 20, and the third evaporator 30 are connected in series to form a circulation path through which the refrigerant flows through each evaporator in sequence.

[0029] The implementation principle of a three-stage cascade cooling system according to an embodiment of this application is as follows:

[0030] The refrigerant system includes a liquid storage tank 31, a circulation pump 32, and a first evaporator 8, a second evaporator 20, and a third evaporator 30 arranged in series. The refrigerant in the liquid storage tank 31 is pumped into the refrigerant channel of each evaporator by the circulation pump 32, and after heat exchange, it flows back to the liquid storage tank 31 to form a circulation.

[0031] The three-stage compression refrigeration system includes a first compressor 1, a second compressor 13, a third compressor 24, and supporting components such as an oil separator, a condenser, a condenser-evaporator, a dryer filter, a solenoid valve, an expansion valve, and a gas-liquid separator. Each component is connected by pipes to form an independent refrigerant circuit, and heat transfer between circuits is achieved through the condenser-evaporator.

[0032] Usage process

[0033] 1. Single compressor operating mode: refrigerant temperature -39.9~25℃

[0034] When the required temperature of the refrigerant is -39.9 to 25°C, only the first compressor 1 operates, and the specific process is as follows:

[0035] The high-temperature and high-pressure refrigerant vapor discharged from the first compressor 1 enters the first oil separator 2, where it is separated from the lubricating oil and then enters the condenser 3, where it is condensed into a room-temperature and high-pressure refrigerant liquid.

[0036] After being temporarily stored in the liquid receiver 4, the refrigerant is filtered through the first dryer filter 5 and then enters the first expansion valve 7 through the first solenoid valve 6.

[0037] After being throttled by the first expansion valve 7, the refrigerant becomes a low-temperature, low-pressure liquid and enters the first refrigerant channel inlet 8.2 of the first evaporator 8. It exchanges heat with the refrigerant flowing through the first evaporator 8 in the refrigerant system and absorbs heat to become a low-temperature, low-pressure vapor.

[0038] Low-temperature, low-pressure steam is discharged from the outlet 8.1 of the first refrigerant channel of the first evaporator 8, and after the liquid is separated by the gas-liquid separator 12, it flows back to the first compressor 1 to complete the cycle.

[0039] The refrigerant is cooled to the target temperature after heat exchange in the first evaporator 8, meeting the usage requirements of -39.9 to 25℃.

[0040] 2. Dual compressor cooperative working mode, refrigerant temperature -80~-40℃

[0041] When the required temperature of the refrigerant is -80 to -40°C, the first compressor 1 and the second compressor 13 work together, and the specific process is as follows:

[0042] First compressor 1 circuit: The high-temperature and high-pressure refrigerant vapor discharged from the first compressor 1 passes through the first oil separator 2, condenser 3, liquid receiver 4, and first dryer filter 5, and then enters the second expansion valve 10 through the second solenoid valve 9; after throttling, it enters the refrigerant passage inlet 11.3 of the second condenser evaporator 11, and after exchanging heat with the refrigerant in the second compressor 13 circuit, it becomes low-temperature and low-pressure vapor, which is discharged from the refrigerant passage outlet 11.4 of the second condenser evaporator 11, and flows back to the first compressor 1 through the gas-liquid separator 12.

[0043] Second compressor 13 circuit: The high-temperature and high-pressure refrigerant vapor discharged from the second compressor 13 is separated from the lubricating oil by the second oil separator 14, and then enters the second condenser evaporator 11 to exchange heat with the refrigerant in the first compressor 1 circuit, condensing into a low-temperature and high-pressure liquid; after being filtered by the second dryer filter 17, it enters the third expansion valve 19 through the third solenoid valve 18; after being throttled, it enters the second refrigerant channel inlet 20.2 of the second evaporator 20, exchanges heat with the refrigerant flowing through the second evaporator 20 in the refrigerant system, absorbs heat and becomes a low-temperature and low-pressure vapor, and flows back to the second compressor 13 from the refrigerant channel outlet 20.1 of the second evaporator 20 to complete the cycle.

[0044] The refrigerant is cooled to the target temperature of -80 to -40℃ through a stepped heat exchange process via the first evaporator 8 and the second evaporator 20.

[0045] 3. Three-compressor collaborative working mode: refrigerant temperature -120~-80.1℃

[0046] When the required temperature of the refrigerant is -120 to -80.1℃, the first compressor 1, the second compressor 13, and the third compressor 24 work together, and the specific process is as follows:

[0047] The circuit of the first compressor 1 and the second compressor 13: The working process is the same as the dual compressor mode. The high temperature and high pressure refrigerant vapor discharged from the second compressor 13 passes through the second oil separator 14, enters the fourth expansion valve 22 through the fourth solenoid valve 21, and enters the third refrigerant channel inlet 23.2 of the third condenser evaporator 23 after throttling, and exchanges heat with the refrigerant in the circuit of the third compressor 24.

[0048] The third compressor 24 circuit: The high-temperature and high-pressure refrigerant vapor discharged from the third compressor 24 is separated from the lubricating oil by the third oil separator 25, and then enters the third condenser evaporator 23 to exchange heat with the refrigerant in the second compressor 13 circuit, condensing into a low-temperature and high-pressure liquid; after being filtered by the third dryer filter 28, it enters the third refrigerant channel inlet 30.2 of the third evaporator 30 through the capillary tube 29, where it exchanges heat with the refrigerant flowing through the third evaporator 30 in the refrigerant system, absorbs heat and becomes a low-temperature and low-pressure vapor, and flows back to the third compressor 24 from the third refrigerant channel outlet 30.1 of the third evaporator 30, completing the cycle.

[0049] The refrigerant is cooled in a stepped manner through the first evaporator 8, the second evaporator 20, and the third evaporator 30 to meet the ultra-low temperature requirements of -120 to -80.1℃.

[0050] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A three-stage cascade refrigeration system, characterized by, It includes a refrigerant system and a three-stage compression refrigeration system; the three-stage compression refrigeration system includes a first compressor (1), a second compressor (13), and a third compressor (24). The refrigerant system includes a storage tank (31), a circulation pump (32), and a first evaporator (8), a second evaporator (20), and a third evaporator (30) arranged in series. The storage tank (31) is connected to the first refrigerant channel inlet (8.2) of the first evaporator (8) via a pipe and the circulation pump (32). The storage tank (31) is connected to the second refrigerant channel inlet (20.2) of the second evaporator (20) via a pipe and the circulation pump (32). The storage tank (31) is connected to the third refrigerant channel inlet (30.2) of the third evaporator (30) via a pipe and the circulation pump (32). The first refrigerant channel outlet (8.1) of the first evaporator (8), the second refrigerant channel outlet (20.1) of the second evaporator (20), and the third refrigerant channel outlet (30.1) of the third evaporator (30) all return to the storage tank (31) via pipes. The refrigerant circuit of the first compressor (1) is connected to the first evaporator (8) or the second condenser-evaporator (11), the refrigerant circuit of the second compressor (13) is connected to the second evaporator (20) or the third condenser-evaporator (23), and the refrigerant circuit of the third compressor (24) is connected to the third evaporator (30).

2. A three-level cascade refrigeration system according to claim 1, characterized in that The refrigerant circuit of the first compressor (1) includes a first oil separator (2), a condenser (3), a liquid receiver (4), and a first dryer filter (5) connected in sequence. The first dryer filter (5) is connected to a first expansion valve (7) through a first solenoid valve (6). The first expansion valve (7) is connected to the inlet (8.2) of the first refrigerant passage of the first evaporator (8). The outlet (8.1) of the first refrigerant passage of the first evaporator (8) is connected back to the first compressor (1) through a gas-liquid separator (12).

3. A three-level cascade refrigeration system according to claim 1, characterized in that, In the refrigerant circuit of the first compressor (1), the first dryer filter (5) is also connected to the second expansion valve (10) through the second solenoid valve (9). The second expansion valve (10) is connected to the refrigerant passage inlet (11.3) of the second condenser evaporator (11). The refrigerant passage outlet (11.4) of the second condenser evaporator (11) is connected back to the first compressor (1) through the gas-liquid separator (12). The refrigerant circuit of the second compressor (13) includes a second oil separator (14), a second condenser-evaporator (11), and a second dryer filter (17) connected in sequence. The second dryer filter (17) is connected to a third expansion valve (19) through a third solenoid valve (18). The third expansion valve (19) is connected to the inlet (20.2) of the second refrigerant passage of the second evaporator (20). The outlet (20.1) of the second refrigerant passage of the second evaporator (20) is connected back to the second compressor (13).

4. A three-level cascade refrigeration system according to claim 3, characterized in that The outlet of the second oil separator (14) is divided into two paths. One path is connected to the second condenser evaporator (11), and the other path is connected to the first expansion container (16) through the first unloading valve (15). The outlet of the first expansion container (16) is connected back to the second compressor (13).

5. A three-level cascade refrigeration system according to claim 1, characterized in that, In the refrigerant circuit of the second compressor (13), the second dryer filter (17) is also connected to the fourth expansion valve (22) through the fourth solenoid valve (21). The fourth expansion valve (22) is connected to the third refrigerant passage inlet (23.2) of the third condenser evaporator (23). The third refrigerant passage outlet (23.1) of the third condenser evaporator (23) is connected back to the second compressor (13). The refrigerant circuit of the third compressor (24) includes a third oil separator (25), a third condenser-evaporator (23), and a third dryer filter (28) connected in sequence. The third dryer filter (28) is connected to a capillary tube (29). The capillary tube (29) is connected to the inlet (30.2) of the third refrigerant passage of the third evaporator (30). The outlet (30.1) of the third refrigerant passage of the third evaporator (30) is connected back to the third compressor (24).

6. A three-level cascade refrigeration system according to claim 5, characterized in that The outlet of the third oil separator (25) is divided into two paths. One path is connected to the third condenser evaporator (23), and the other path is connected to the second expansion container (27) through the second unloading valve (26). The outlet of the second expansion container (27) is connected back to the third compressor (24).

7. A three level cascade refrigeration system as claimed in claim 1 wherein, In the refrigerant system, the refrigerant channels of the first evaporator (8), the second evaporator (20), and the third evaporator (30) are connected in series to form a circulation path through which the refrigerant flows through each evaporator.

8. A three level cascade refrigeration system as claimed in claim 2 wherein, The gas-liquid separator (12) is located between the outlet (8.1) of the first refrigerant channel of the first evaporator (8) and the inlet of the first compressor (1).

9. A three level cascade refrigeration system as claimed in claim 2 wherein, The outlet of the condenser (3) is connected to a liquid receiver (4) for temporarily storing the refrigerant liquid after it has been condensed by the condenser (3).

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