A high efficiency regenerative refrigerator system employing cold end direct current

Abstract

The application discloses a high-efficiency regenerative refrigerator system with cold-end direct current, which comprises a regenerative refrigeration module and a direct current loop module; the regenerative refrigeration module comprises a refrigerator compression device, a rotary valve and a cold finger which are connected in sequence, the refrigerator compression device is provided with a high-pressure exhaust port, a gas supplement port and a low-pressure gas inlet port; one side of the rotary valve is connected with the high-pressure exhaust port, the other side is connected with the low-pressure gas inlet port, and the center hole of the rotary valve is connected with the cold finger; the direct current loop module comprises a throttling cold-end heat exchanger, a copper clamping sleeve heat exchanger and a direct current control assembly; the direct current is led out from the regenerator cold-end heat exchanger of the cold finger, throttled and heat-exchanged in the throttling cold-end heat exchanger, and then enters the direct current pipeline; the direct current pipeline is in contact with the copper clamping sleeve heat exchanger fixed on the cold finger; the cold finger is cooled by the direct current cold energy; the flow is controlled through the direct current control assembly; finally, the direct current is pressurized and returned to the gas supplement port to complete the external circulation. The intermediate refrigeration power of the regenerator is fully utilized, and the system performance is further improved.

Description

Technical Field

[0001] This invention relates to the field of refrigeration technology, and in particular to a high-efficiency regenerative refrigeration system employing cold-end direct current. Background Technology

[0002] Regenerative cryogenic refrigerators, such as pulse tube refrigerators and GM refrigerators, have advantages such as simple structure, high reliability, and small size, and are widely used in cryogenic technologies such as small-scale hydrogen and helium liquefaction and low-temperature superconductivity.

[0003] In regenerative cryogenic refrigerator systems, the efficiency of the regenerator has a significant impact on the overall performance of the system. Traditional regenerative cryogenic refrigerators, such as pulse tube refrigerators, do not have direct current (DC) flow during operation. With the introduction of a bidirectional air intake structure, the regenerator and pulse tube form a closed loop, inducing DC flow. Further research into work and heat transfer in the regenerator under actual conditions has shown that DC flow can significantly affect the efficiency of the regenerator.

[0004] In practice, especially for refrigeration temperatures below 20K, the actual gas effect is significant, and enthalpy is related not only to temperature but also to pressure. In this case, the gaseous working fluid in the regenerator will generate enthalpy flow due to pressure changes, causing the regenerator itself to generate thermal enthalpy flow to maintain energy balance, resulting in inherent heat loss. By setting a direct current (DC) with a specific magnitude and direction, not only is the performance of the refrigeration unit unaffected, but it can also serve as a heat input or heat output for the regenerator to balance the pressure-enthalpy changes within the regenerator, minimizing thermal enthalpy flow and even improving refrigeration performance.

[0005] For example, Chinese patent document CN112097422A discloses a high-efficiency liquefaction system using a DC regenerative refrigeration unit, comprising a regenerative refrigeration module and a liquefaction module. The regenerative refrigeration module includes a regenerative refrigeration unit and a DC external circulation unit; the regenerative refrigeration unit includes a compression device, a regenerator hot-end heat exchanger, a regenerator, a regenerator cold-end heat exchanger, an expansion mechanism cold-end heat exchanger, an expansion mechanism, and an expansion mechanism hot-end heat exchanger, connected in sequence; the DC external circulation unit is led out from the regenerator cold-end heat exchanger and enters a counter-current heat exchanger, using DC to pre-cool the gas to be liquefied, while the performance of the refrigeration unit itself remains unchanged.

[0006] However, existing regenerative cryogenic refrigeration systems using a direct current (DC) structure still have shortcomings. These shortcomings include: repeated flow in the DC pipeline, which affects the performance of the refrigeration unit itself; less of the cooling capacity drawn from the DC is used to improve the refrigeration unit's performance; and there is room for improvement in the utilization rate of the cooling capacity by enhancing the heat exchange process. Summary of the Invention

[0007] This invention provides a high-efficiency regenerative refrigeration system using a cold-end DC current. Based on regenerative refrigeration, a DC current is drawn from the cold end to balance the pressure and enthalpy changes in the regenerator. Without affecting or improving the original performance of the refrigeration unit, the intermediate refrigeration power of the regenerator is fully utilized through cold-end throttling heat exchange, recooling of the cold end, and gas replenishment to the refrigeration unit, thereby further improving the performance of the system.

[0008] A high-efficiency regenerative refrigeration system employing cold-end DC transmission includes a regenerative refrigeration module and a DC circuit module;

[0009] The regenerative refrigeration module includes a refrigeration compressor, a rotary valve, and a cold finger connected in sequence. The refrigeration compressor is provided with a high-pressure exhaust port, a gas inlet port, and a low-pressure inlet port. One side of the rotary valve is connected to the high-pressure exhaust port through a high-pressure pipeline, and the other side is connected to the low-pressure inlet port through a low-pressure pipeline. The central hole of the rotary valve is connected to the cold finger through a transmission pipeline.

[0010] The DC loop module includes a throttling cold-end heat exchanger, a copper ferrule heat exchanger, and a DC control component. DC power is drawn from the cold-end heat exchanger of the cold finger's regenerator, undergoes throttling and heat exchange in the throttling cold-end heat exchanger, and then enters the DC pipeline. The DC pipeline partially contacts the copper ferrule heat exchanger fixed to the cold finger, utilizing the cooling capacity of the DC power to recool the cold finger. The flow rate is controlled by the DC control component. Finally, the DC power is pressurized in the gas injection compression device and returns to the gas injection port of the refrigeration compressor to complete the external circulation.

[0011] Furthermore, the copper ferrule heat exchanger is fixed to the outer wall of the cold finger, including a primary copper ferrule heat exchanger and a secondary copper ferrule heat exchanger, with at least one in each stage.

[0012] Furthermore, the copper ferrule heat exchanger is formed by bolting together two flat, semi-circular copper blocks of the same shape, with the direct current pipeline section wrapped around the outside of the copper ferrule heat exchanger.

[0013] Furthermore, the DC control assembly includes a pressure sensor, a pressure reducing valve, a first needle valve, a second needle valve, and a butterfly valve connected in sequence.

[0014] Alternatively, the regenerative refrigeration module may be one of the following: GM refrigerator, GM type pulse tube refrigerator, Stirling refrigerator, Stirling type pulse tube refrigerator, or VM refrigerator.

[0015] Optionally, the regenerative refrigeration module has a coaxial, U-shaped, or linear structure, and its refrigeration stages are single-stage, two-stage, or multi-stage, with a thermal coupling or gas coupling structure.

[0016] Alternatively, the internal throttling structure of the throttling cold-end heat exchanger may be a capillary tube or a throttling orifice, and the number of such orifices may be one or more.

[0017] Furthermore, the compressor unit of the refrigeration unit is also equipped with a high-pressure exhaust pressure gauge, a low-pressure intake pressure gauge, a compressor unit display screen, and a compressor unit control panel.

[0018] The present invention also provides a refrigeration method using the above-mentioned high-efficiency regenerative refrigeration system, the specific process of which is as follows:

[0019] Introduce the working gas into the regenerative refrigeration module, adjust the frequency of the compressor, and start the compressor to begin cooling.

[0020] Once the temperature of the cold end heat exchanger of the regenerator stops decreasing, the pressure reducing valve, needle valve No. 1, needle valve No. 2, butterfly valve, and gas injection compression device in the DC control assembly are opened in sequence to start the DC cycle. When the temperature of the cold end heat exchanger of the regenerator and the throttling cold end heat exchanger stabilizes, the corresponding cooling temperature and cooling capacity are obtained at the cold end heat exchanger of the regenerator and the throttling cold end heat exchanger.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. Compared with the inherent heat loss of the actual gas in traditional regenerative refrigeration systems, this invention connects the cold end of the regenerator and the gas injection port of the compressor through pipelines to form a stable DC circulation. The use of DC reduces the actual gas loss of the regenerator, which is beneficial to improving the performance of the refrigeration machine.

[0023] 2. This invention increases the cooling capacity of the cold end of the refrigerator by throttling the drawn DC current at the cold end of the regenerator, while maintaining or enhancing the original performance of the refrigerator.

[0024] 3. In this invention, the cold end DC is fed back to the regenerator through the heat exchange component on the outer wall of the cylinder and then fed into the compressor. The heat exchange area is increased by the copper sleeve heat exchanger to enhance heat exchange. The total heat loss of the regenerator is reduced by the use of DC cooling capacity, which further improves the performance of the refrigeration machine.

[0025] 4. Compared with existing regenerative refrigeration systems that use direct current at the cold end, this invention avoids repeated flow in the direct current pipeline from affecting the performance of the refrigeration unit by adding a throttling structure at the cold end. Attached Figure Description

[0026] Figure 1 This diagram illustrates the energy flow for DC with and without a cold end.

[0027] Figure 2 The curve showing the ratio of heat enthalpy flow to sound power caused by irreversible heat exchange in the regenerator of a pulse tube refrigerator as a function of DC flow rate;

[0028] Figure 3 The curve shows the change in acoustic power at the cold end with DC flow rate.

[0029] Figure 4 The curves showing the change of cooling capacity with DC flow rate at different cold junction temperatures;

[0030] Figure 5 A schematic diagram of a three-stage Stirling pulse tube refrigerator with a closed-circuit DC structure and the results of DC experiments are shown.

[0031] Figure 6 This is a schematic diagram of the structure of a high-efficiency regenerative refrigeration system using cold-end direct current, as an embodiment of the present invention.

[0032] Figure 7 This is a schematic diagram of the copper ferrule heat exchanger in an embodiment of the present invention;

[0033] Figure 8 This is a schematic diagram of the internal structure of the throttling cold-end heat exchanger in an embodiment of the present invention.

[0034] In the diagram: 1. Refrigeration unit compression device; 2. High-pressure exhaust port; 3. Injection port; 4. High-pressure pipeline; 5. High-pressure exhaust pressure gauge; 6. Low-pressure intake pressure gauge; 7. Low-pressure intake port; 8. Compression device display screen; 9. Compression device control panel; 10. Low-pressure pipeline; 11. Rotary valve; 12. Transmission pipeline; 13. Cold finger; 14. Primary copper ferrule heat exchanger; 15. Secondary copper ferrule heat exchanger; 16. Regenerator cold end heat exchanger; 17. Throttling cold end heat exchanger; 18. DC pipeline; 19. Pressure sensor; 20. Pressure reducing valve; 21. Needle valve No. 1; 22. Needle valve No. 2; 23. Butterfly valve; 24. Injection compression device. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be noted that the embodiments described below are intended to facilitate the understanding of the present invention and do not constitute any limitation thereof.

[0036] For a regenerative refrigerator, according to the first law of thermodynamics, the energy flow within the regenerator in steady state can be expressed as:

[0037]

[0038] in, This is a pressure-enthalpy flow caused by the real gas effect. The enthalpy flow is caused by irreversible heat exchange. This refers to the heat conduction term of the regenerator.

[0039] like Figure 1 As shown in (a), neglecting shuttle losses and heat conduction losses from cylinder walls, exhaust pipe walls, etc., the cooling capacity at the cold end can be expressed as:

[0040]

[0041] in, This represents the acoustic power at the cold end.

[0042] For a regenerative refrigerator using direct current, according to the first law of thermodynamics, the energy flow within the regenerator in steady state can be expressed as:

[0043]

[0044] in, This is the enthalpy flow caused by direct current.

[0045] like Figure 1 As shown in (b), neglecting shuttle losses and heat conduction losses from cylinder walls, exhaust pipe walls, etc., the cooling capacity at the cold end can be expressed as:

[0046]

[0047] Compared to the absence of direct current (DC), the presence of DC within the regenerator alters its internal energy flow due to the increased enthalpy flow induced by the DC. To maintain energy balance, the pressure-enthalpy flow inside the regenerator... Enthalpy flow caused by irreversible heat exchange Decrease, while the total energy flow The changes were minor.

[0048] Figure 2 The curves showing the ratio of heat enthalpy flow to sound power caused by irreversible heat exchange in the regenerator of a pulse tube refrigerator as a function of DC flow rate are presented. As can be seen from the figure, when a certain amount of DC is introduced, the proportion of heat enthalpy flow caused by irreversible heat exchange in the regenerator to sound power gradually decreases.

[0049] Figure 3 The curves showing the change of acoustic power at the cold end with DC flow rate are presented. As can be seen from the figure, an appropriate DC flow rate will increase the acoustic power at the cold end.

[0050] Therefore, appropriate DC can increase reduce And make and The impact is relatively small. At this point, the cooling capacity of the cold end when the DC structure is added is... It must be greater than the cooling capacity without a DC structure.

[0051] Figure 4The curves showing the variation of cooling capacity with DC flow rate at different cold end temperatures are presented. It can be concluded that introducing appropriate DC flow into the regenerative refrigerator can effectively utilize the actual gas enthalpy flow effect, improve the refrigerator performance, and increase the cooling capacity at the cold end without changing the geometry and packing of the regenerator.

[0052] Furthermore, the use of a closed-loop DC structure also has a positive impact on the cold end temperature. Figure 5 An experimental setup and results for a three-stage Stirling pulse tube refrigerator demonstrating the effect of a closed-loop direct current (DC) structure on the minimum cold-end temperature are presented. The flow originates from the 300K end of the regenerator and flows into the 90K and 20K temperature zones of the regenerator. It exits at the 20K thermal bridge, flows through a capillary tube to the outside of the refrigerator's vacuum chamber, and is then regulated by a set of parallel Swagelok needle valves before returning to the room-temperature end of the regenerator, forming a closed loop. The curves in the figure show that when the DC valve opening is 0%, the cold-end temperature is 7.42K. As the opening increases, the cold-end temperature gradually decreases, reaching a minimum of 7.16K at an opening of 50 divisions. Therefore, introducing an appropriate DC flow into the regenerative refrigerator can, to some extent, reduce the minimum cold-end temperature of the refrigerator.

[0053] However, existing regenerative cryogenic refrigeration systems using a direct current (DC) structure still have shortcomings. These shortcomings include: repeated flow in the DC pipeline, which affects the performance of the refrigeration unit itself; less of the cooling capacity drawn from the DC is used to improve the refrigeration unit's performance; and there is room for improvement in the utilization rate of the cooling capacity by enhancing the heat exchange process.

[0054] This invention collects intermediate refrigeration power by drawing out direct current, thereby obtaining refrigeration capacity at lower temperatures and enhancing the performance of the regenerative refrigeration unit itself, rather than using it for liquefied gas. Similarly, the direct current drawn out by this invention can be directly supplied to the compression unit without the need for high-pressure gas, resulting in a closed-loop system. Furthermore, this invention enhances heat exchange by incorporating a throttling cold-end heat exchanger and a copper-ferrule heat exchanger, increasing the refrigeration capacity at the cold-end temperature, further improving the overall performance of the refrigeration unit, and avoiding recirculation.

[0055] Specifically, such as Figure 6 As shown, a high-efficiency regenerative refrigeration system employing cold-end DC transmission includes a regenerative refrigeration module and a DC circuit module.

[0056] The regenerative refrigeration module includes a refrigeration compressor unit 1, a high-pressure exhaust port 2, an air inlet 3, a high-pressure pipeline 4, a high-pressure exhaust pressure gauge 5, a low-pressure intake pressure gauge 6, a low-pressure intake port 7, a compressor unit display screen 8, a compressor unit control panel 9, a low-pressure pipeline 10, a rotary valve 11, a transmission pipeline 12, a cold finger 13, and a regenerator cold end heat exchanger 16.

[0057] The DC circuit module includes a primary copper fitting heat exchanger 14, a secondary copper fitting heat exchanger 15, a throttling cold end heat exchanger 17, a DC pipeline 18, a pressure sensor 19, a pressure reducing valve 20, a first needle valve 21, a second needle valve 22, a butterfly valve 23, and a gas replenishment and compression device 24.

[0058] The high-pressure exhaust port 2 of the refrigeration compressor unit 1 is connected to one side of the rotary valve 11 via the high-pressure pipeline 4. The low-pressure inlet port 7 of the refrigeration compressor unit 1 is connected to the other side of the rotary valve 11 via the low-pressure pipeline 10. The center hole of the rotary valve 11 is connected to the cold finger 13 via the transmission pipeline 12. A primary copper ferrule heat exchanger 14 and a secondary copper ferrule heat exchanger 15 are fixed on the cold finger 13. The regenerator cold end heat exchanger 16 of the cold finger 13 is connected to and energized with the throttling cold end heat exchanger 17, and then connected to the direct current pipeline 18. The direct current pipeline 18 is wound around and contacts the secondary copper ferrule heat exchanger 15 and the primary copper ferrule heat exchanger 14 fixed on the cold finger 13, and then connected to the pressure sensor 19, pressure reducing valve 20, needle valve 21, needle valve 22, butterfly valve 23, and gas replenishment compression device 24 in sequence. The gas replenishment compression device 24 is connected to the gas replenishment port 3 of the refrigeration compressor unit 1 via a pipeline.

[0059] like Figure 7 As shown, the copper ferrule heat exchanger is fixed by two flat, semi-circular copper blocks of the same shape with bolts and screw holes, and a direct current pipeline is wound around its exterior.

[0060] like Figure 8 As shown, a throttling cold-end heat exchanger is a heat exchanger with a throttling structure arranged inside, such as a capillary tube or a throttling orifice, with the two ends of the pipeline connected to the cold-end heat exchanger of the regenerator and the direct current pipeline, respectively.

[0061] The working process of this embodiment is as follows:

[0062] The system should be installed according to the procedures and requirements described above. After installation, the system components and piping should be evacuated to 10°C. -1 Then, fill with a gaseous working fluid, maintain for about 5 minutes, and then evacuate to 10 Pa. -1Approximately Pa. After repeating this process 3-4 times, the working pressure of the gaseous working fluid is finally introduced into the regenerative refrigeration unit to ensure the purity of the working fluid in the system. The refrigeration unit is driven by a compressor motor, and its rotary valve and discharge device operate at a certain frequency. During startup, first adjust the compressor frequency through the compressor control panel 9, then turn on the power to the refrigeration unit compressor 1, and the refrigeration unit begins to cool down. When the temperature of the cold end heat exchanger 16 of the regenerator at the refrigeration unit 13 stops decreasing, sequentially open the pressure reducing valve 20, needle valve 21, needle valve 22, butterfly valve 23, and gas injection compression device 24 to start the DC circulation and allow the system to operate normally until the temperature of the cold end heat exchanger 16 and the throttling cold end heat exchanger 17 stabilizes. At this point, the corresponding cooling temperature and cooling capacity can be obtained at the cold end heat exchanger 16 and the throttling cold end heat exchanger 17.

[0063] Taking a 1.5W@4.2K two-stage GM refrigerator with a frequency of 1Hz as an example, its compressor has a mass flow rate of 4g / s and a frequency of 50Hz. Assuming the refrigerator's charging pressure is 16bar, a DC current with a pressure of 16bar and a temperature of 4.2K is drawn from the cold end of the refrigerator. The DC current flow rate is taken as 1% of the compressor's mass flow rate, which is 40mg / s. At this time, the cold end cooling capacity of adding the DC current structure will be greater than or equal to the original cooling capacity. The increase in cold end cooling capacity due to cold end throttling can then be calculated.

[0064] The specific enthalpy of an ideal helium working fluid at a temperature of 4.2 K and a pressure of 16 bar is 6.8557 kJ / kg. After adiabatic throttling to atmospheric pressure of 1 bar, its temperature changes to 4.21 K. Based on the enthalpy at the saturated state point, the dryness fraction at the throttling state point can be calculated to be 0.33275, the corresponding saturated liquid helium flow rate to be 26.69 mg / s, and the corresponding latent heat of vaporization to be 0.556 W. Therefore, using a direct current supply from the cold end improves the refrigeration performance of this GM refrigerator, increasing the cooling capacity from 1.5 W to 2.056 W. Assuming the power consumption of the refrigerator's compressor is 6.9 kW, and the power consumption of the supplementary gas compressor is negligible, the coefficient of performance (COP) increases from 2.17E-4 to 2.98E-4, and the thermodynamic perfection improves from 0.0153 to 0.0210.

[0065] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-efficiency regenerative refrigeration system employing cold-end direct current, characterized in that, Including regenerative cooling modules and DC loop modules; The regenerative refrigeration module includes a refrigeration compressor (1), a rotary valve (11), and a cold finger (13) connected in sequence. The refrigeration compressor (1) is provided with a high-pressure exhaust port (2), a gas inlet (3), and a low-pressure inlet (7). One side of the rotary valve (11) is connected to the high-pressure exhaust port (2) through a high-pressure pipeline (4), and the other side is connected to the low-pressure inlet (7) through a low-pressure pipeline (10). The center hole of the rotary valve (11) is connected to the cold finger (13) through a transmission pipeline (12). The DC loop module includes a throttling cold end heat exchanger (17), a copper sleeve heat exchanger, and a DC control component. After the DC is drawn from the cold end heat exchanger (16) of the cold finger (13), it is throttled and heat exchanged in the throttling cold end heat exchanger (17) and enters the DC pipeline (18). The DC pipeline (18) partially contacts the copper sleeve heat exchanger fixed on the cold finger (13). The cold energy of the DC is used to cool the cold finger (13). The flow rate is controlled by the DC control component. Finally, the DC is pressurized in the gas injection compression device (24) and returns to the gas injection port (3) of the refrigeration compressor device (1) to complete the external circulation.

2. The high-efficiency regenerative refrigeration system using cold-end direct current as described in claim 1, characterized in that, The copper ferrule heat exchanger is fixed on the outer wall of the cold finger (13) and includes a primary copper ferrule heat exchanger (14) and a secondary copper ferrule heat exchanger (15), with at least one in each stage.

3. The high-efficiency regenerative refrigeration system using cold-end direct current as described in claim 1, characterized in that, The copper ferrule heat exchanger is formed by bolting together two flat semi-circular copper blocks of the same shape, and the DC pipeline (18) is partially wrapped around the outside of the copper ferrule heat exchanger.

4. The high-efficiency regenerative refrigeration system using cold-end direct current as described in claim 1, characterized in that, The DC control assembly includes a pressure sensor (19), a pressure reducing valve (20), a first needle valve (21), a second needle valve (22), and a butterfly valve (23) connected in sequence.

5. The high-efficiency regenerative refrigeration system using cold-end direct current as described in claim 1, characterized in that, The regenerative refrigeration module is one of the following: GM refrigerator, GM type pulse tube refrigerator, Stirling refrigerator, Stirling type pulse tube refrigerator, and VM refrigerator.

6. The high-efficiency regenerative refrigeration system employing cold-end direct current as described in claim 5, characterized in that, The regenerative refrigeration module has a coaxial, U-shaped, or linear structure, and its refrigeration stages are single-stage, two-stage, or multi-stage. Its coupling structure is thermal coupling or gas coupling.

7. The high-efficiency regenerative refrigeration system employing cold-end direct current as described in claim 1, characterized in that, The internal throttling structure of the throttling cold end heat exchanger (17) is a capillary tube or a throttling orifice, and the number of such orifices is one or more.

8. The high-efficiency regenerative refrigeration system using cold-end direct current as described in claim 1, characterized in that, The compressor unit (1) of the refrigeration machine is also equipped with a high pressure exhaust pressure gauge (5), a low pressure intake pressure gauge (6), a compressor unit display screen (8), and a compressor unit control panel (9).

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