A scroll compressor refrigeration system with improved energy efficiency at low temperatures and stable operation under low load

Abstract

This invention provides a scroll compressor refrigeration system for low-temperature energy efficiency improvement and stable operation under low load, relating to the field of low-temperature refrigeration technology. In the scroll compressor refrigeration system provided by this invention, the condensed liquid refrigerant enters a gas-liquid separator with a regenerative function, completing the first subcooling. This improves system energy efficiency and also increases system superheat, significantly reducing the risk of liquid return. Furthermore, the increased superheat of the return gas facilitates the return of refrigeration oil accumulated in the gas-liquid separator to the compressor oil sump for lubrication via the system return gas pipe, thereby improving the reliability of lubrication in the low-temperature system. Simultaneously, the combined use of a balance bypass expansion valve and a one-way valve allows for rapid balancing of the high and low pressures of the refrigeration system, preventing the compressor from starting under pressure.

Description

Technical Field

[0001] This invention relates to the field of cryogenic refrigeration technology, and more particularly to a scroll compressor refrigeration system that improves energy efficiency at low temperatures and allows for stable operation under low load. Background Technology

[0002] Currently, cryogenic refrigeration technology has a wide range of applications, and in recent years, the government has introduced relevant policies to encourage enterprises to manufacture high-efficiency refrigeration products to achieve energy conservation and emission reduction. To actively respond to these environmental policies, this refrigeration system performs two subcooling heat exchanges on the condensed refrigerant liquid, significantly increasing the system's subcooling degree and achieving enthalpy increase, thereby improving the energy efficiency of the cryogenic system. Through expansion valve throttling, the refrigerant enters the evaporator to absorb heat, fulfilling the refrigeration and cooling process requirements. The compressor's suction pressure is controlled by a low-pressure sensor to meet the cryogenic refrigeration process requirements of the application scenario. Currently, cryogenic refrigeration is widely used in food, pharmaceutical, chemical, military, aerospace, semiconductor, and scientific research fields.

[0003] When existing cryogenic refrigeration systems start up under high pressure ratio conditions in summer, the compressor starting torque is closely related to the suction and discharge pressures. The starting torque increases with the increase of the compression ratio. The higher the discharge pressure, the greater the torque required by the motor. After a short shutdown, there is a torque required to overcome the pressure difference, especially in single-phase refrigeration systems, which greatly increases the instantaneous load torque at startup. This refrigeration system can quickly balance the high and low pressures by using a combination of a balancing bypass expansion valve and a check valve, thereby reducing the starting current, improving the starting performance of the cryogenic scroll compressor, and enhancing the operational reliability of the refrigeration system.

[0004] Existing cryogenic refrigeration systems, when operating under large load spans and low load conditions, cannot maintain low-load operation for extended periods, failing to meet certain refrigeration process requirements. This refrigeration system, through the combined use of a balanced bypass expansion valve and a low-pressure sensor, can achieve the goal of maintaining low-load, non-negative pressure operation even with large load spans. The low-pressure sensor in the refrigeration system is set with a low-pressure shutdown value. When the load decreases, to ensure the compressor maintains low-load, non-negative pressure operation, a control logic is set. When the difference between the low-pressure operating pressure and the low-pressure shutdown value is less than the set difference, the balanced bypass expansion valve opens. The balanced bypass expansion valve is an electronic expansion valve that can be fully closed. This balanced bypass expansion valve can control the number of opening steps through a program to control the low-pressure operating pressure, thereby achieving the goal of maintaining stable low-load operation and meeting special refrigeration process requirements.

[0005] In view of the problems existing in the above-mentioned existing technologies, it is necessary to study and design a scroll compressor refrigeration system for low temperature applications that improves energy efficiency and enables stable operation under low load, thereby overcoming the problems existing in the existing technologies. Summary of the Invention

[0006] To address the aforementioned technical problems of existing cryogenic refrigeration systems, such as difficulty in starting under high-pressure conditions, poor stability under low-load operation with large load spans, and difficulty in maintaining stable operation under non-negative pressure, this invention provides a cryogenic energy-efficient scroll compressor refrigeration system that enables stable operation under low loads. In this system, the condensed liquid refrigerant undergoes two subcooling processes: a gas-liquid separator with heat recovery function and an economizer. After these two subcooling heat exchanges, the high-pressure refrigerant liquid significantly increases the system's subcooling degree, thereby increasing the enthalpy of the refrigeration system and ultimately improving its energy efficiency.

[0007] The technical means employed in this invention are as follows:

[0008] A scroll compressor refrigeration system for low-temperature energy efficiency improvement and stable operation under low load includes a compressor, a balanced bypass expansion valve, a one-way valve, a gas-liquid separator with heat recovery function, an economizer, and a low-pressure sensor. The compressor's discharge end is connected in sequence via pipelines to the one-way valve, oil separator, condenser, liquid receiver, dryer filter, gas-liquid separator with heat recovery function, economizer, liquid line solenoid valve, expansion valve, and evaporator. The compressor's return end is connected in sequence via pipelines to the suction filter and the gas-liquid separator with heat recovery function. The economizer has a gas replenishment circuit, which includes a gas replenishment expansion valve and a gas replenishment solenoid valve connected in sequence and connected to the compressor's gas replenishment port. The high-pressure inlet of the balanced bypass expansion valve is connected between the compressor's discharge end and the one-way valve, and the low-pressure outlet is connected to the compressor's suction end. The low-pressure sensor is installed on the compressor's suction end pipeline. The system is configured to perform two subcoolings on the condensed liquid refrigerant through a gas-liquid separator with a regenerative function and the economizer, balance the high and low pressure difference before the compressor starts through the balanced bypass expansion valve, and adjust the opening degree according to the detection signal of the low pressure sensor to maintain the system operating at low pressure during low load operation.

[0009] Furthermore, the gas-liquid separator with heat recovery function is provided with a liquid inlet and a liquid outlet. The liquid refrigerant flowing through the dryer filter flows in through the liquid inlet, exchanges heat with the return gas in the gas-liquid separator with heat recovery function, and then flows out from the liquid outlet, realizing the first subcooling and increasing the superheat of the return gas.

[0010] Furthermore, the economizer is provided with a main liquid inlet, a main liquid outlet, a gas replenishment inlet, and a gas replenishment outlet. The liquid refrigerant, after being subcooled for the first time, flows in from the main liquid inlet and undergoes heat exchange within the economizer after being throttled by the gas replenishment expansion valve, achieving a second subcooling before flowing out from the main liquid outlet. The medium-pressure gas formed by the refrigerant absorbing heat and vaporizing after throttling flows out from the gas replenishment outlet and enters the gas replenishment port of the compressor via the gas replenishment solenoid valve.

[0011] Furthermore, the balance bypass expansion valve is connected to the low-pressure sensor signal; the system is set with a low-pressure shutdown pressure value. When the difference between the operating pressure detected by the low-pressure sensor and the low-pressure shutdown pressure value is less than a preset threshold, the balance bypass expansion valve opens and performs step adjustment to maintain the compressor's stable operation under low-load conditions without negative pressure.

[0012] Furthermore, the system also includes a high-pressure switch and a sight glass. The high-pressure switch is disposed on the exhaust end pipeline of the compressor, and the sight glass is disposed on the pipeline between the liquid line solenoid valve and the expansion valve.

[0013] Furthermore, the one-way valve is located between the high-pressure inlet of the balanced bypass expansion valve and the oil separator to prevent refrigerant from flowing back into the compressor during the pressure balancing process.

[0014] Furthermore, the refrigerant charged into the system is one or more selected from R404A, R448A, R449A, and R507A.

[0015] Compared with the prior art, the present invention has the following advantages: 1. The scroll compressor refrigeration system provided by the present invention provides that the condensed liquid refrigerant undergoes two subcooling processes through a gas-liquid separator with heat recovery function and an economizer. After the high-pressure refrigerant liquid undergoes two subcooling heat exchanges, the subcooling degree of the system is greatly improved, thereby increasing the enthalpy value of the refrigeration system and improving the energy efficiency of the low-temperature system.

[0016] 2. The scroll compressor refrigeration system provided by this invention allows the condensed liquid refrigerant to enter a gas-liquid separator with a regenerative function, completing the first subcooling. This improves system energy efficiency and also increases system superheat, thereby greatly reducing the risk of liquid return. Furthermore, the increased superheat of the return gas also facilitates the return of the refrigeration oil accumulated in the gas-liquid separator to the compressor oil sump through the system return gas pipe for lubrication, thus improving the reliability of lubrication in the low-temperature system.

[0017] 3. The scroll compressor refrigeration system provided by the present invention has a liquid refrigerant in the gas replenishment circuit that enters the economizer after being throttled by the gas replenishment expansion valve. After heat exchange, the medium-pressure gas enters the compressor for gas replenishment and compression. The energy efficiency of the refrigeration system is greatly improved, and the compressor discharge temperature can be significantly reduced, which is conducive to the stable operation of the system.

[0018] 4. The scroll compressor refrigeration system provided by the present invention uses a combination of a balance bypass expansion valve and a one-way valve; it can quickly balance the high and low pressures of the refrigeration system and avoid the compressor starting under pressure.

[0019] 5. The scroll compressor refrigeration system provided by this invention uses a combination of a balanced bypass expansion valve and a low-pressure sensor. The function of the balanced bypass expansion valve is to allow the high-pressure gaseous refrigerant on the exhaust side to flow to the low-pressure suction side after throttling and pressure reduction. When the compressor needs to start, the balanced bypass expansion valve opens to equalize the pressure. After the compressor starts, the balanced bypass expansion valve closes. When the unit needs to maintain low-load non-negative pressure operation, the balanced bypass expansion valve opens again. Through the above control logic, the low-temperature refrigeration process requirements are achieved. It can achieve the goal of maintaining low-load, non-negative-pressure operation with a large range of refrigeration loads, thus meeting the refrigeration process requirements of the refrigeration system. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the system of the present invention.

[0022] In the diagram: 1. Compressor; 2. Balanced bypass expansion valve; 2A. High-pressure inlet; 2B. Low-pressure outlet; 3. High-pressure switch; 4. Check valve; 5. Oil separator; 6. Condenser; 7. Liquid receiver; 8. Dryer filter; 9. Gas-liquid separator with regenerative function; 9C. Liquid inlet; 9D. Liquid outlet; 10. Economizer; 10E. Main line liquid inlet; 10F. Main line liquid outlet; 10G. Makeup gas line liquid inlet; 10H. Makeup gas line gas outlet; 11. Liquid line solenoid valve; 12. Sight glass; 13. Expansion valve; 14. Evaporator; 15. Suction filter; 16. Low-pressure sensor; 17. Makeup gas solenoid valve; 18. Makeup gas expansion valve. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0027] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0028] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0029] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0030] This invention provides a scroll compressor refrigeration system that improves energy efficiency at low temperatures and ensures stable operation under low loads, such as... Figure 1 As shown, the system includes a compressor 1, a balanced bypass expansion valve 2, a check valve 4, a gas-liquid separator 9 with heat recovery function, an economizer 10, and a low-pressure sensor 16. The discharge end of the compressor 1 is connected in sequence via pipelines to the check valve 4, oil separator 5, condenser 6, liquid receiver 7, dryer filter 8, gas-liquid separator 9 with heat recovery function, economizer 10, liquid line solenoid valve 11, expansion valve 13, and evaporator 14. The return end of the compressor 1 is connected in sequence via pipelines to the suction filter 15 and the gas-liquid separator 9 with heat recovery function. The economizer 10 has a gas replenishment circuit, which includes a gas replenishment expansion valve 18 and a gas replenishment solenoid valve 17 connected in sequence and connected to the gas replenishment port of the compressor 1. The high-pressure inlet 2A of the balanced bypass expansion valve 2 is connected between the discharge end of the compressor 1 and the check valve 4, and the low-pressure outlet 2B is connected to the suction end of the compressor 1. The low-pressure sensor 16 is located on the suction end pipeline of the compressor 1. The system is configured to perform two subcoolings on the condensed liquid refrigerant through a gas-liquid separator 9 with a regenerative function and an economizer 10, and to balance the high and low pressure difference before the compressor starts through a balancing bypass expansion valve 2, and to adjust the opening degree according to the detection signal of the low pressure sensor 16 to maintain the system's low-pressure operation during low-load operation.

[0031] The gas-liquid separator 9 with heat recovery function is provided with a liquid inlet 9C and a liquid outlet 9D. The liquid refrigerant flowing through the dryer filter 8 flows in through the liquid inlet 9C, exchanges heat with the return gas in the gas-liquid separator 9 with heat recovery function, and then flows out from the liquid outlet 9D, realizing the first subcooling and improving the superheat of the return gas.

[0032] Economizer 10 is provided with main line liquid inlet 10E, main line liquid outlet 10F, make-up gas line liquid inlet 10G, and make-up gas line outlet 10H. The liquid refrigerant that has been subcooled for the first time flows in from the main line liquid inlet 10E, and after being throttled by the make-up gas expansion valve 18, the refrigerant exchanges heat in the economizer 10 to achieve a second subcooling and then flows out from the main line liquid outlet 10F. The medium-pressure gas formed by the refrigerant absorbing heat and vaporizing after throttling flows out from the make-up gas line outlet 10H and enters the make-up gas port of compressor 1 through the make-up gas solenoid valve 17.

[0033] The balance bypass expansion valve 2 is connected to the low pressure sensor 16. The system is set with a low pressure shutdown pressure value. When the difference between the operating pressure detected by the low pressure sensor 16 and the low pressure shutdown pressure value is less than the preset threshold, the balance bypass expansion valve 2 opens and performs step adjustment to maintain the compressor's stable operation under non-negative pressure and low load conditions.

[0034] The system also includes a high-pressure switch 3 and a sight glass 12. The high-pressure switch 3 is installed on the exhaust pipe of the compressor 1, and the sight glass 12 is installed on the pipe between the liquid pipe solenoid valve 11 and the expansion valve 13.

[0035] One-way valve 4 is located between the high-pressure inlet 2A of the balance bypass expansion valve 2 and the oil separator 5 to prevent refrigerant from flowing back into the compressor during the pressure balancing process.

[0036] The refrigerant charged into the system is one or more selected from R404A, R448A, R449A, and R507A.

[0037] principle: After condensation, the liquid refrigerant in the refrigeration system enters the gas-liquid separator 9 with heat recovery function through the liquid inlet 9C and flows out through the liquid outlet 9D, completing the first liquid refrigerant subcooling. This not only improves the system's energy efficiency but also increases the system's superheat, thereby greatly reducing the risk of liquid return. Furthermore, the increased superheat of the return gas also helps to carry the refrigeration oil accumulated in the gas separator back to the compressor oil sump for lubrication through the system's return gas pipe, thus improving the reliability of lubrication in the low-temperature system.

[0038] After the first subcooling, the liquid refrigerant enters the economizer 10 through the main inlet port 10E and then flows out of the economizer 10 through the main outlet port 10F, completing the second subcooling of the liquid refrigerant and forming a secondary subcooling circuit for the liquid refrigerant. This significantly improves the subcooling degree of the system, achieves the purpose of increasing the enthalpy of the refrigeration system, and thus greatly improves the energy efficiency of the low-temperature system.

[0039] In the refrigeration system, the liquid refrigerant in the gas replenishment circuit is throttled by the gas replenishment expansion valve 18 and enters the economizer 10 through the liquid inlet port 10G of the gas replenishment circuit. After heat exchange, it flows out through the gas outlet port 10H of the gas replenishment circuit and enters the compressor 1 for gas replenishment and compression. The energy efficiency of the refrigeration system is greatly improved, and the compressor discharge temperature can be significantly reduced, which is conducive to the stable operation of the system.

[0040] In the refrigeration system, a combination of a balance bypass expansion valve 2 and a one-way valve 4 is used. The high-pressure inlet 2A of the balance bypass expansion valve 2 is connected to the high-pressure exhaust pipe of the compressor 1, and the low-pressure outlet 2B of the balance bypass expansion valve 2 is connected to the low-pressure suction pipe of the compressor 1. The high-pressure inlet 2A of the balance bypass expansion valve 2 is located between the compressor 1 and the exhaust one-way valve 4. This system can quickly balance the high and low pressures of the refrigeration system before restarting after a short-term shutdown in high-temperature summer conditions. At the same time, it can reduce the starting current and reduce the impact on the power grid, creating conditions for stable start-up operation. In particular, the application of this system can make the refrigeration system operate more stably in the scroll single-phase refrigeration system.

[0041] The combined use of the balanced bypass expansion valve 2 and the low-pressure sensor 16 in the refrigeration system can maintain low-load, non-negative pressure operation when the load span of the refrigeration system is large. The low-pressure sensor 16 in the refrigeration system is set with a low-pressure stop value. A control logic is set so that when the load decreases, when the difference between the low-pressure operating pressure and the low-pressure stop value is less than the set difference, the balanced bypass expansion valve 2 opens. The balanced bypass expansion valve 2 is an electronic expansion valve that can be fully closed. The number of opening steps of this balanced bypass expansion valve 2 can be controlled by the program to control the low-pressure operating pressure, thereby achieving the purpose of maintaining low-load, non-negative pressure operation. The application of this system can enable the refrigeration system to meet certain refrigeration process requirements.

[0042] In addition to its application in low-temperature cold storage, refrigeration systems can also be used in low-temperature environmental test chambers and other low-temperature applications.

[0043] In operation: The low-temperature scroll compressor refrigeration system operates by condensing high-temperature, high-pressure refrigerant in condenser 6. The high-pressure refrigerant liquid is then subcooled to increase enthalpy, allowing it to be depressurized and enter the evaporator 14 to absorb heat and achieve the required cooling process. When the operating environment temperature rises and the system needs to be restarted for cooling, the high and low pressures of the refrigeration system can be quickly balanced using the combination of the balancing bypass expansion valve 2 and the discharge check valve 4, reducing the starting current and ensuring stable operation of compressor 1.

[0044] In use: When the low-temperature scroll compressor refrigeration system is operating under conditions with a large range of refrigeration loads, it can be effectively regulated by using the combination of the balance bypass expansion valve 2 and the low-pressure sensor 16 in the system, thereby ensuring that the compressor 1 maintains a low-load, non-negative-pressure state for reliable operation.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A scroll compressor refrigeration system for improving energy efficiency at low temperatures and ensuring stable operation under low load, characterized in that, The compressor (1) includes a compressor (1), a balanced bypass expansion valve (2), a check valve (4), a gas-liquid separator with regenerative function (9), an economizer (10), and a low-pressure sensor (16). The discharge end of the compressor (1) is connected in sequence to the check valve (4), oil separator (5), condenser (6), liquid receiver (7), dryer filter (8), gas-liquid separator with regenerative function (9), economizer (10), liquid line solenoid valve (11), expansion valve (13), and evaporator (14) via pipelines. The return end of the compressor (1) is connected in sequence to the suction filter via pipelines. (15) and the gas-liquid separator (9) with heat recovery function; the economizer (10) is provided with a gas replenishment circuit, the gas replenishment circuit includes a gas replenishment expansion valve (18) and a gas replenishment solenoid valve (17) connected in sequence, and connected to the gas replenishment port of the compressor (1); the high pressure inlet (2A) of the balance bypass expansion valve (2) is connected between the exhaust end of the compressor (1) and the one-way valve (4), and the low pressure outlet (2B) is connected to the suction end of the compressor (1); the low pressure sensor (16) is set on the suction end pipeline of the compressor (1); The system is configured to perform two subcoolings on the condensed liquid refrigerant through the gas-liquid separator (9) with heat recovery function and the economizer (10), balance the high and low pressure difference before the compressor starts through the balance bypass expansion valve (2), and adjust the opening degree according to the detection signal of the low pressure sensor (16) to maintain the system operating at low pressure during low load operation.

2. The low-temperature energy-efficient and low-load stable operation scroll compressor refrigeration system according to claim 1, characterized in that, The gas-liquid separator (9) with heat recovery function is provided with a liquid inlet (9C) and a liquid outlet (9D). The liquid refrigerant flowing through the dryer filter (8) flows in through the liquid inlet (9C), exchanges heat with the return gas in the gas-liquid separator (9), and then flows out from the liquid outlet (9D), realizing the first subcooling and improving the superheat of the return gas.

3. The low-temperature energy-efficient and low-load stable operation scroll compressor refrigeration system according to claim 2, characterized in that, The economizer (10) is provided with a main liquid inlet (10E), a main liquid outlet (10F), a gas replenishment inlet (10G), and a gas replenishment outlet (10H). The liquid refrigerant, after being subcooled for the first time, flows in from the main liquid inlet (10E), and after being throttled by the gas replenishment expansion valve (18), the refrigerant exchanges heat in the economizer (10) to achieve a second subcooling and then flows out from the main liquid outlet (10F). The medium-pressure gas formed after the refrigerant absorbs heat and vaporizes after throttling flows out from the gas replenishment outlet (10H) and enters the gas replenishment port of the compressor (1) via the gas replenishment solenoid valve (17).

4. The low-temperature energy-efficient and low-load stable operation scroll compressor refrigeration system according to claim 1, characterized in that, The balance bypass expansion valve (2) is connected to the low pressure sensor (16) for signal connection. The system is set with a low pressure shutdown pressure value. When the difference between the operating pressure detected by the low pressure sensor (16) and the low pressure shutdown pressure value is less than a preset threshold, the balance bypass expansion valve (2) is opened and step adjustment is performed to maintain the compressor in stable operation under low load conditions without negative pressure.

5. The low-temperature energy-efficient and low-load stable operation scroll compressor refrigeration system according to claim 1, characterized in that, The system also includes a high-pressure switch (3) and a sight glass (12). The high-pressure switch (3) is located on the exhaust pipe of the compressor (1), and the sight glass (12) is located on the pipe between the liquid pipe solenoid valve (11) and the expansion valve (13).

6. The low-temperature energy-efficient and low-load stable operation scroll compressor refrigeration system according to claim 1, characterized in that, The one-way valve (4) is located between the high-pressure inlet (2A) of the balance bypass expansion valve (2) and the oil separator (5) to prevent refrigerant from flowing back into the compressor during the pressure balancing process.

7. The low-temperature energy-efficient and low-load stable operation scroll compressor refrigeration system according to claim 1, characterized in that, The refrigerant charged into the system is one or more selected from R404A, R448A, R449A, and R507A.

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