Gas thermal switch, refrigerator using same and use method of thermal switch

Abstract

The invention discloses a gas thermal switch, a refrigerator using the same and a using method of the thermal switch, the gas thermal switch comprises a first-stage cold head heat conduction plate and a second-stage cold head cold conduction plate, the first-stage cold head heat conduction plate and the second-stage cold head cold conduction plate are respectively fixed on a first-stage cold head and a second-stage cold head, and the first-stage cold head heat conduction plate and the second-stage cold head heat conduction plate are fixed on a second-stage cold head. The cylinder wall is hermetically connected with a high-temperature end, an evacuation helium filling port and a low-temperature end by adopting a welding process, a gap is formed between the high-temperature end and the low-temperature end, and the evacuation helium filling port spans the vacuum layer to be connected with a molecular pump set and a gas supply source and is used for evacuating and supplying gas to the gap so as to switch a thermal disconnection state and a thermal connection state of the gas thermal switch. According to the cooling device, the cooling capacity of the first-stage cold head is transmitted to the high-temperature end through the first-stage cold head heat conduction plate, the gap is filled with helium, and the cooling capacity is transmitted to the low-temperature end from the high-temperature end through the heat conduction effect of the helium and then is transmitted to cooled equipment through the second-stage cold head heat conduction plate, so that the cooled equipment can be rapidly cooled, and the cooling capacity utilization rate and the refrigeration efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of cryogenic engineering technology, and in particular to a gas thermal switch, a refrigerator in which it is applied, and a method of using the thermal switch. Background Technology

[0002] In cryogenic engineering applications, two-stage cryogenic systems are commonly used refrigeration equipment. Due to the large cooling capacity of the first-stage cold head and the low limiting temperature of the second-stage cold head, they are widely used in various devices requiring deep cryogenic environments, such as superconducting equipment and cryogenic detectors. The first-stage cold head of a two-stage cryogenic system has the advantage of large cooling capacity, but its limiting temperature is relatively high, typically around 30K; the second-stage cold head has a relatively smaller cooling capacity, but its limiting temperature is lower, reaching 3K-4K. In actual equipment cooling processes, the equipment to be cooled is usually connected to the second-stage cold head to achieve deep cooling.

[0003] However, during the cooling process, most of the cooling capacity of the primary cooling head is used only for cooling the cooling screen, resulting in a significant waste of cooling capacity in the 300K-30K temperature range. This leads to a longer cooling time for the equipment and reduces the overall cooling efficiency. Summary of the Invention

[0004] This invention provides a gas thermal switch, a refrigerator using it, and a method for using the thermal switch, which can solve the problems of long cooling time and low overall cooling efficiency in existing technologies.

[0005] A gas thermal switch is applicable to a refrigeration machine, the refrigeration machine including a refrigeration machine body, the refrigeration machine body being provided with a primary cold head and a secondary cold head, the gas thermal switch including: a primary cold head heat-conducting plate and a secondary cold head cold-conducting plate, the primary cold head heat-conducting plate and the secondary cold head cold-conducting plate being respectively fixed to the primary cold head and the secondary cold head; It also includes: a cylinder wall with adjustable length, wherein the cylinder wall is sealed and connected by welding process to a high-temperature end, a vacuum filling port and a low-temperature end, and a gap is provided between the high-temperature end and the low-temperature end; The evacuation and helium filling port spans the vacuum layer and is connected to the molecular pump assembly and the gas supply source. It is used to evacuate and supply gas to the gap in order to switch the thermal disconnection and thermal connection states of the gas thermal switch.

[0006] Preferably, the primary cold head heat conduction plate, the secondary cold head cold conduction plate, the high-temperature end, and the low-temperature end are all made of TU0 oxygen-free copper.

[0007] Preferably, the cylinder wall is made of Ti 15-3-3-3 material.

[0008] Preferably, the evacuation and helium filling port and its connected pipes are both made of 316L material.

[0009] Preferably, when the gas thermal switch is in the gas-filled state, the gap is a confined space with natural convection heat transfer, exhibiting gas thermal conduction.

[0010] Preferably, the length of the cylinder wall can be selected based on the model of the refrigeration unit.

[0011] A refrigeration unit includes: a refrigeration unit body, wherein the refrigeration unit body is provided with a primary cold head and a secondary cold head, and both the primary cold head and the secondary cold head are connected to a gas thermal switch.

[0012] A method of using a gas thermal switch includes: S1. First, evacuate the gap through the evacuation port and then fill it with helium to replace it. Repeat this operation until the impurities in the gap are fully removed. S2. Introduce high-purity helium into the gap and control the inflation pressure. After inflation is complete, close the external valve. S3. Start the refrigeration unit from room temperature to allow it to run normally and cool the equipment being cooled. S4. Set a cooling temperature value, continuously monitor the temperature of the equipment being cooled until the temperature of the equipment being cooled reaches the preset cooling temperature value, then reopen the external valve and evacuate the gas in the gap again through the evacuation port. S5. Preset a vacuum range. When the vacuum level in the gap reaches the preset vacuum range, stop evacuating and close the external valve to complete the entire thermal switch operation process.

[0013] Preferably, in S4, the preset cooling temperature value is 30K.

[0014] Preferably, in step S5, the preset vacuum level range is 10. -3 Pa.

[0015] The beneficial effects of this invention are: (1) In this invention, after the refrigerator body is started, the first-stage cold head and the second-stage cold head gradually cool down. The cold energy of the first-stage cold head is transferred to the high-temperature end through the heat-conducting plate of the first-stage cold head. At this time, the gap is filled with helium. The cold energy is transferred from the high-temperature end to the low-temperature end through the heat conduction effect of the helium, and then transferred to the cooled equipment through the heat-conducting plate of the second-stage cold head, so as to realize the cooling of the cooled equipment. The cold energy of the first-stage cold head is conducted to the second-stage cold head, which can quickly cool down the cooled equipment, improve the utilization rate of cold energy, save cooling time, and improve the refrigeration efficiency.

[0016] (2) In this invention, the evacuation and helium replacement adsorption through the evacuation and helium filling port realizes thermal connection and thermal disconnection. It has the advantages of low thermal conductivity, simple structure and high versatility when thermally disconnected. The elimination of the adsorption module and the elimination of the need for a heater can make the entire gas thermal switch and its application refrigerator simpler in structure and reduce the difficulty of operation in terms of usage.

[0017] (3) In this invention, by selecting different lengths of cylinder wall, it can be adapted to different models of refrigeration machines without making large-scale modifications to the overall structure of the gas thermal switch, effectively reducing the adaptation cost of the equipment and improving the applicability of the gas thermal switch. Attached Figure Description

[0018] Figure 1 A schematic diagram of a gas thermal switch and its application in a refrigeration unit provided by the present invention; Figure 2 This is a flowchart illustrating a method of using a gas thermal switch provided by the present invention.

[0019] Explanation of reference numerals in the attached figures: 1. Refrigeration unit body; 2. Primary cold head heat conduction plate; 3. High temperature end; 4. Cylinder wall; 5. Evacuation and helium filling port; 6. Low temperature end; 7. Secondary cold head heat conduction plate; 8. Gap. Detailed Implementation

[0020] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0021] Two-stage refrigerators are commonly used refrigeration equipment in cryogenic engineering applications. In practical applications, traditional two-stage refrigerators suffer from a waste of cooling capacity due to the large cooling capacity of the first-stage cold head.

[0022] To solve this problem, such as Figure 1 As shown in the figure, an embodiment of the present invention provides a gas thermal switch applicable to a refrigeration machine. The refrigeration machine includes a refrigeration machine body 1, which is provided with a primary cold head and a secondary cold head. The gas thermal switch includes a primary cold head heat-conducting plate 2 and a secondary cold head cold-conducting plate 7, which are respectively fixed to the primary cold head and the secondary cold head.

[0023] The primary cold head heat-conducting plate 2 is connected to the primary cold head of the refrigerator body 1 by bolt pressing. Similarly, the secondary cold head cold-conducting plate 7 is also fixed to the secondary cold head by bolt pressing. This connection method ensures good contact between the two, thereby achieving efficient transfer of cold energy. At the same time, bolt pressing facilitates subsequent installation, disassembly, and maintenance, reducing the difficulty of equipment assembly and repair.

[0024] It also includes: a cylinder wall 4, which is connected to a high-temperature end 3, a evacuation and helium filling port 5, and a low-temperature end 6. A gap 8 is provided between the high-temperature end 3 and the low-temperature end 6. The cylinder wall 4 is sealed to the high-temperature end 3, the evacuation and helium filling port 5, and the low-temperature end 6 using welding technology. The welded seal can effectively ensure the airtightness of the entire thermal switch, prevent the entry of external gases or the leakage of internal gases, and ensure that a stable vacuum environment or helium atmosphere can be formed within the gap 8, providing the necessary conditions for the normal operation of the thermal switch.

[0025] The selection of welding processes has undergone rigorous screening and verification to ensure that the welded joints have good strength and low-temperature adaptability, enabling them to work stably for a long time in low-temperature environments and avoid thermal switch failure due to welding quality issues.

[0026] It should be noted that the high-temperature end 3 and the first-stage cold head heat-conducting plate 2 are fixed by bolts, which can ensure the smooth transfer of cold energy from the first-stage cold head heat-conducting plate 2 to the high-temperature end 3 and avoid cold energy loss due to loose connection.

[0027] Furthermore, the evacuation and helium filling port 5 spans the vacuum layer and connects to an external molecular pump assembly and gas supply source. Its main function is to evacuate and supply gas to gap 8. By connecting to the external molecular pump assembly, the gas within gap 8 can be extracted, creating a high-vacuum environment and placing the thermal switch in a thermally disconnected state. The evacuation and helium filling port 5, connected to the gas supply source, can fill gap 8 with high-purity helium at a specific pressure, placing the thermal switch in a thermally connected state. By controlling the gas within gap 8, the operating state of the gas-filled thermal switch can be flexibly switched.

[0028] In addition, the low-temperature end 6 and the secondary cold head cooling plate 7 are also fixed together by bolts. This connection method facilitates the transfer of cold energy from the low-temperature end 6 to the secondary cold head cooling plate 7, and then to the cooled equipment connected to the secondary cold head cooling plate 7, thereby achieving equipment cooling. The gap 8 is located between the high-temperature end 3 and the low-temperature end 6. The gas state in the gap 8, whether it is vacuum or filled with helium, directly determines the thermal conductivity of the thermal switch and is the core area for achieving thermal connection and thermal disconnection.

[0029] To further improve the performance of this gas thermal switch, the materials of each component were selected and improved. Specifically, the primary cold head heat-conducting plate 2, the secondary cold head cold-conducting plate 7, the high-temperature end 3, and the low-temperature end 6 are all made of TU0 oxygen-free copper. TU0 oxygen-free copper, due to its high purity and low oxygen content, possesses excellent thermal conductivity, enabling efficient transfer of cold energy at low temperatures, reducing cold energy loss during transfer, and ensuring that the cold energy from the primary cold head can be quickly and effectively transferred to the secondary cold head.

[0030] The cylinder wall 4 is made of Ti 15-3-3-3 material. Through experimental research and performance testing, the inventors discovered that within the temperature range of 50K-4K, the heat leakage performance of this material is significantly better than that of traditional 316L stainless steel, with heat leakage approximately one-fifth that of 316L stainless steel. This characteristic effectively reduces the loss of cold energy when passing through the cylinder wall 4, significantly improving the insulation effect and cold energy utilization efficiency of the gas thermal switch. This is of great significance for maintaining the stability of the low-temperature environment and reducing the energy consumption of the refrigeration system.

[0031] The evacuation and helium filling port 5 and its connected piping are both made of 316L stainless steel. 316L stainless steel is a commonly used corrosion-resistant stainless steel with excellent corrosion resistance, high-temperature resistance, and low-temperature adaptability. In cryogenic engineering applications, the environment in which the equipment is located is prone to various corrosive media, and the temperature variation range is large. 316L material can maintain stable performance in harsh environments, avoiding pipe leaks caused by material corrosion or cryogenic brittleness, ensuring the normal operation of the evacuation and helium filling port 5 and the piping, and guaranteeing the reliability and stability of the gas thermal switch's operating state switching.

[0032] In this invention, experiments revealed that the gas thermal switch exhibits excellent performance parameters under different operating conditions. When the primary cold head temperature is 50K, the secondary cold head temperature is 4K, and the gas thermal switch is in an uncharged state, its heat leakage is only 0.016W. This extremely low heat leakage effectively reduces unnecessary loss of cooling capacity, ensuring that heat transfer between the primary and secondary cold heads is blocked to the greatest extent possible in the thermal disconnect state, thereby maintaining the low-temperature environment on the secondary cold head side.

[0033] When the thermal switch is in the gas-filled state (the gas pressure is accurately controlled at 30 kPa), the heat transfer within gap 8 is a confined space with natural convection. Thermal calculations show a Grashof number of 63, less than 2860. According to thermal theory, the heat transfer within gap 8 at this time is gas conduction. Further calculations show that the heat transfer capacity of the gas thermal switch in this state is 86.3 W, and the on / off ratio (the ratio of heat transfer in the thermally connected state to heat loss in the thermally disconnected state) reaches 5394. This high on / off ratio significantly improves the thermal conductivity of the thermal switch, enabling rapid and efficient transfer of cooling energy from the primary cold head to the secondary cold head when thermal connection is required, significantly shortening the cooling time of the cooled equipment and improving refrigeration efficiency. The above calculation results can be obtained through conventional calculation methods by those skilled in the art, and therefore will not be elaborated upon here.

[0034] Currently, the commonly used refrigeration unit models on the market are 410 / 412 / 415 / 418, all of which have the same length dimensions for both the primary and secondary cold heads. The thermal switch of this invention also has high versatility, suitable for various models of two-stage cold head refrigeration units. For some less commonly used refrigeration unit models, differences in structural dimensions, specifically the spacing between the primary and secondary cold heads, lead to variations in the distance between the primary cold head heat-conducting plate 2 and the secondary cold head cold-conducting plate 7. This invention, by selecting different lengths of the cylinder wall 4, can achieve compatibility with different models of two-stage cold head refrigeration units without requiring large-scale modifications to the overall structure of the gas thermal switch. This effectively reduces the adaptation cost of the equipment, expands the applicability of the gas thermal switch, and gives it broader application prospects in the field of cryogenic engineering.

[0035] like Figure 1 As shown, this embodiment of the invention also provides a refrigeration machine, including: a refrigeration machine body 1, the refrigeration machine body 1 is provided with a primary cold head and a secondary cold head, both of which are connected to a gas thermal switch.

[0036] like Figure 2 As shown, in one embodiment, based on the above-mentioned gas thermal switch and refrigerator, the present invention also provides a method for using the gas thermal switch, specifically including the following steps: S1. Before starting the primary and secondary cold heads of the refrigeration unit 1, the gap 8 needs to be pre-treated to ensure that the subsequent thermal switch can work normally.

[0037] The pretreatment method involves evacuating the gas in gap 8 through the evacuation port 5, followed by helium purging and replacement. This process is repeated at least twice. The purpose of repeated evacuation and helium purging is to ensure that air, moisture, and other impurities in gap 8 are fully removed, preventing condensation of these impurities at low temperatures or adverse effects on the thermal conductivity of the gas thermal switch. During the evacuation and replacement process, it is crucial to ensure a tight connection between the evacuation port 5 and the external molecular pump assembly to prevent leakage and ensure effective evacuation.

[0038] It is important to note that after each vacuuming process, pressure must be maintained for a certain period of time. The change in vacuum level within gap 8 should be monitored using a vacuum level measuring instrument to check whether the vacuum level meets the requirements. If the vacuum level is abnormal during the pressure maintenance process (such as the vacuum level dropping too quickly), the sealing condition needs to be checked, the leak point eliminated, and the vacuuming operation repeated.

[0039] S2. After completing the vacuum purging operation, high-purity helium gas (99.999% purity) is introduced into gap 8. High-purity helium has excellent thermal conductivity and is chemically stable at low temperatures, preventing chemical reactions with other components of the gas thermal switch. Furthermore, its extremely low liquefaction temperature ensures it remains gaseous within the operating temperature range of the thermal switch, thus achieving stable heat conduction.

[0040] During inflation, the gas inlet rate needs to be controlled to prevent excessive pressure fluctuations within gap 8 due to an excessively fast inlet rate, which could affect the subsequent heat transfer performance of the thermal switch. Simultaneously, a pressure sensor monitors the inflation pressure in real time to ensure accurate control at 30 kPa. When the pressure reaches the set value, the external valve is promptly closed to complete the inflation operation.

[0041] S3. Start the refrigerator body 1 from room temperature (generally 300K) to ensure normal operation and enter the refrigeration working state. After the refrigerator body 1 starts, the primary and secondary cold heads begin to gradually cool down. The cooling capacity of the primary cold head is transferred to the high-temperature end 3 through the primary cold head heat conduction plate 2. At this time, the gap 8 is filled with high-purity helium. The cooling capacity is transferred from the high-temperature end 3 to the low-temperature end 6 through the thermal conductivity of the helium, and then transferred to the equipment being cooled through the secondary cold head cold conduction plate 7, thus achieving the cooling of the equipment. The cooling capacity of the primary cold head is conducted to the secondary cold head, which can quickly cool the equipment, improve the utilization rate of cooling capacity, save cooling time, and improve refrigeration efficiency.

[0042] During the operation of the refrigeration unit 1, temperature sensors are needed to monitor the temperature changes of the primary cold head, the secondary cold head, and the cooled equipment in real time to keep track of the progress of the cooling process.

[0043] S4. A preset cooling temperature value is set. In this embodiment, the preset cooling temperature value is 30K. As the refrigerator body 1 continues to run, the temperature of the cooled equipment continues to decrease. The temperature of the cooled equipment is continuously monitored until the temperature of the cooled equipment reaches 30K. The external valve is then reopened, and the gas in the gap 8 is evacuated again through the evacuation port 5.

[0044] S5. Preset a vacuum range; the preset vacuum range is less than 10. -3 Pa. When the vacuum level within gap 8 reaches 10 Pa. -3 When the pressure drops below Pa, stop vacuuming and close the external valve to complete the entire thermal switch operation process.

[0045] The inventors discovered that, in order to solve the problem of wasted cooling capacity in the primary cooling head of existing refrigerators, those skilled in the art have developed various thermal switch structures to achieve thermal connection and disconnection control between the primary and secondary cooling heads. These developed thermal switch structures generally use an adsorbent to adsorb helium to achieve a thermal disconnection state. When a thermal connection state is required, a heater is used to heat the adsorbent, causing it to desorb and release helium.

[0046] This approach requires the addition of an adsorption unit, significantly increasing the complexity of the entire thermal switch structure. This not only increases manufacturing difficulty and cost but also reduces the reliability of equipment operation. Furthermore, due to the presence of the adsorption unit and the influence of the heating and desorption process, it is difficult to guarantee the vacuum level of the entire system. A poor vacuum level will affect the thermal insulation effect of the thermal switch, thereby reducing the efficiency of cold energy transfer.

[0047] This invention employs a vacuum pump for direct evacuation, resulting in better vacuum and stronger insulation during thermal disconnection. Thermal connection is achieved by filling with helium. Thermal connection and disconnection are accomplished through evacuation and helium replenishment via the evacuation and helium filling port 5, replacing adsorption. This method offers advantages such as low thermal conductivity during thermal disconnection, simple structure, and high versatility. It effectively utilizes the cooling capacity of the first-stage cold head of the refrigerator, saving cooling time. Eliminating the adsorption module and the need for a heater simplifies the structure of the entire gas thermal switch and the refrigerator it applies to, reducing operational complexity.

[0048] This application achieves efficient transfer and control of cold energy between the primary and secondary cold heads through innovative structural design and working method, providing strong support for the optimized operation of cryogenic engineering equipment.

[0049] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A gas thermal switch, applicable to a refrigeration machine, the refrigeration machine comprising a refrigeration machine body (1), the refrigeration machine body (1) being provided with a primary cold head and a secondary cold head, characterized in that, The gas thermal switch includes: a primary cold head heat-conducting plate (2) and a secondary cold head cold-conducting plate (7), wherein the primary cold head heat-conducting plate (2) and the secondary cold head cold-conducting plate (7) are respectively fixed to the primary cold head and the secondary cold head; It also includes: a cylinder wall (4) with adjustable length, wherein the cylinder wall (4) is sealed with a high-temperature end (3), a vacuum filling port (5) and a low-temperature end (6) by welding process, and a gap (8) is provided between the high-temperature end (3) and the low-temperature end (6). The evacuation and helium filling port (5) is connected to the molecular pump group and the gas supply source across the vacuum layer, and is used to evacuate and supply gas to the gap (8) to switch the thermal disconnection state and thermal connection state of the gas thermal switch.

2. A gas thermal switch as described in claim 1, characterized in that, The primary cold head heat conduction plate (2), the secondary cold head cold conduction plate (7), the high temperature end (3) and the low temperature end (6) are all made of TU0 oxygen-free copper.

3. A gas thermal switch as described in claim 1, characterized in that, The cylinder wall (4) is made of Ti 15-3-3-3 material.

4. A gas thermal switch as described in claim 3, characterized in that, The evacuation and helium filling port (5) and its connected pipes are both made of 316L material.

5. A gas thermal switch as described in claim 2, characterized in that, When the gas thermal switch is in the gas-filled state, the gap (8) is a limited space with natural convection heat transfer, exhibiting gas heat conduction.

6. A gas thermal switch as described in claim 5, characterized in that, The length of the cylinder wall (4) can be selected based on the model of the refrigeration unit.

7. A refrigeration machine, characterized in that, include: The refrigerator body (1) is provided with a primary cold head and a secondary cold head, and both the primary cold head and the secondary cold head are connected to a gas thermal switch as described in any one of claims 1-6.

8. A method of using a gas thermal switch as described in any one of claims 1-6, characterized in that, include: S1. First, evacuate the gap (8) through the evacuation port (5), then fill it with helium to replace it. Repeat this operation until the impurities in the gap (8) are fully discharged. S2. Introduce high-purity helium into the gap (8) and control the filling pressure. After filling is completed, close the external valve. S3. Start the refrigeration machine from room temperature to allow the refrigeration machine body (1) to run normally and cool the equipment being cooled. S4. Set a cooling temperature value, continuously monitor the temperature of the cooled equipment until the temperature of the cooled equipment reaches the set cooling temperature value, reopen the external valve, and evacuate the gas in the gap (8) again through the evacuation port (5). S5. Preset a vacuum range. When the vacuum level in the gap (8) reaches the preset vacuum range, stop evacuating and close the external valve to complete the entire thermal switch usage process.

9. The method as described in claim 8, characterized in that, In S4, the preset cooling temperature value is 30K.

10. The method as described in claim 8, characterized in that, In step S5, the preset vacuum level range is 10. -3 Pa.

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