Liquid hydrogen temperature zone temperature calibration system with low-temperature thermal switch assembly

Abstract

The invention discloses a liquid hydrogen temperature zone temperature calibration system with a low-temperature thermal switch assembly, and the system comprises a GM refrigerating machine, a vacuum cavity, a low-temperature thermal switch assembly, and a thermometer carrier. A first-stage cold head and a second-stage cold head of the GM refrigerating machine penetrate through mounting holes in the flange connecting disc and extend downwards into the vacuum cavity, and the second-stage cold head is connected with the thermometer carrier through a low-temperature thermal switch assembly. The temperature fluctuation at the temperature measuring point of the thermometer can be reduced by using the low-temperature thermal switch, and the cooling time of the calibration device can be shortened, so that the requirements of high precision and high efficiency of temperature calibration are met.

Description

Technical Field

[0001] The invention relates to a low-temperature thermometer calibration system, in particular to a liquid hydrogen temperature zone temperature calibration system with a low-temperature thermal switch component. Background Art

[0002] In large-scale cryogenic engineering systems or deep cryogenic experimental projects in the fields of aerospace engineering, liquefied natural gas industry, etc., temperature measurement is always one of the most basic and important operations. The accuracy of temperature measurement is related to the reliability and usefulness of experimental data and the quality of completion of the experimental purpose. The accuracy of temperature measurement is not only related to the experimental system and environmental conditions, but also depends on the measurement accuracy of the temperature sensor itself. The temperature measurement accuracy of the thermometer is mainly reflected in two aspects: sensitivity and accuracy. The temperature sensor needs to be calibrated before use.

[0003] The research on the calibration of low-temperature thermometers started early both at home and abroad. In the early days, most of them were low-temperature thermostat calibration systems, that is, cryogenic fluids were used as the cold source of the system. In recent years, there has been a gradual emergence of research on the calibration system of low-temperature refrigerator thermometers, but the research results are still relatively small, and in terms of temperature fluctuation control of isothermal carriers, a system cannot guarantee the accuracy of temperature fluctuations in multiple temperature zones. In order to achieve higher calibration accuracy, more mature calibration systems all use a steady-state calibration method, which requires steady-state temperature control for each graduation point. The calibration of each graduation point takes at least ten minutes and at most several hours, so the entire calibration process requires a lot of time cost. In the current application process, the temperature calibration process of low-temperature temperature sensors is complicated and the accuracy is difficult to guarantee.

[0004] Accurate temperature measurement has always been an important part of the cryogenic field. With the development of aerospace and cryogenic physics, the demand for cryogenic temperature measurement will also increase, which also puts higher requirements on the thermometer calibration system. The development of low-cost, high-precision, and high-efficiency cryogenic thermometer calibration system is of great significance to improving the level of cryogenic measurement and is conducive to promoting the development of industry and research in the cryogenic field.

[0005] Most low-temperature thermometer calibration systems use oxygen-free copper as the isothermal carrier to ensure that it has good temperature uniformity. However, when the temperature required for calibration is changed, the temperature of the isothermal carrier will fluctuate slightly with the temperature fluctuation of the cold source. For the calibration system using a two-stage GM refrigerator as the cold source, the temperature fluctuation of the two-stage cold head can reach ±100mK. Such a large fluctuation amplitude is difficult to meet the accuracy requirements required for thermometer calibration. In order to ensure that the temperature fluctuation of the isothermal carrier in the higher temperature zone meets the requirements, it is necessary to increase the heat transfer resistance to expand the controllable temperature zone, but the increase in thermal resistance will greatly reduce the cooling speed of the system and prolong the cooling time. Simply increasing the thermal resistance between the cold head and the isothermal carrier to improve the calibration accuracy of the system will inevitably be accompanied by a decrease in calibration efficiency. Therefore, for the low-temperature thermometer calibration system using a low-temperature refrigerator as the cold source, a special temperature control calibration scheme is required to ensure that the fluctuation of the temperature control point is within the required range, and to make the temperature control point cover as much of the entire calibration temperature zone as possible under the premise of safety and reliability. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in order to overcome the deficiencies in the prior art, a liquid hydrogen temperature zone temperature calibration system with a low-temperature thermal switch component is provided.

[0007] The technical solution adopted by the present invention is: a liquid hydrogen temperature zone temperature calibration system with a low-temperature thermal switch assembly, the system includes a GM refrigerator, a vacuum cavity, a low-temperature thermal switch assembly, and a thermometer carrier, the GM refrigerator is installed on a flange connection plate at the top of the vacuum cavity, the first-stage cold head and the second-stage cold head of the GM refrigerator extend downward into the vacuum cavity through the mounting holes on the flange connection plate, and the second-stage cold head is connected to the thermometer carrier through the low-temperature thermal switch assembly;

[0008] The low-temperature thermal switch assembly includes two vertical insulation brackets on the left and right, the upper end of the insulation bracket is connected to the secondary cold head by installing a cold end copper block, and the lower end of the insulation bracket is connected to the thermometer carrier by installing a hot end copper block;

[0009] A guide rod group is arranged between the left and right vertical insulation brackets, and a sliding copper block is slidably connected to the guide rod group. Electromagnets are installed on the inner side walls of the two insulation brackets, and permanent magnets corresponding to the positions of the electromagnets are also arranged on the left and right side walls of the sliding copper block.

[0010] By adopting the above technical solution, the sliding copper block can slide left and right on the guide rod, and the permanent magnet is fixed on the sliding copper block. When the thermometer carrier needs to be cooled, the electromagnet is energized in the forward direction to attract the permanent magnet, drive the sliding copper block to move to close the thermal switch, and use the cooling capacity of the secondary cold head of the GM refrigerator to quickly cool the thermometer carrier; when the temperature is cooled to the temperature required for calibration, in order to maintain the temperature stability during the calibration process, the electromagnet is energized in the reverse direction, the sliding copper block moves in the reverse direction to disconnect the thermal switch, the heat transfer thermal resistance between the thermometer carrier and the secondary cold head increases, and the influence of the temperature fluctuation of the secondary cold head on the temperature of the thermometer carrier is reduced.

[0011] Furthermore, a copper cooling screen is installed on the first-stage cold head of the present invention, and the copper cooling screen covers the second-stage cold head, the low-temperature thermal switch assembly and the thermometer carrier;

[0012] By adopting the above technical solution, installing a copper cooling screen can reduce the impact of environmental radiation on the temperature stability of the thermometer carrier, and the above device is placed in a vacuum cavity, using high vacuum insulation to reduce heat leakage to the device from the outside.

[0013] Furthermore, the guide rod group described in the present invention includes two guide rods arranged in parallel up and down.

[0014] Furthermore, the installation position of the electromagnet described in the present invention is located between the upper and lower guide rods.

[0015] Furthermore, a heat-conducting column is provided between the hot-end copper block and the thermometer carrier of the present invention, and an electric heating rod is installed in the heat-conducting column, which cooperates with the GM refrigerator to change the temperature of the thermometer carrier, thereby calibrating the temperature sensor installed on the thermometer carrier.

[0016] Compared with the prior art, the present invention has the following advantages: the present invention utilizes a low-temperature heat switch assembly to be added between the secondary cold head of the refrigerator and the thermometer carrier. When the system cools down, the heat switch is closed to ensure that the thermometer carrier is cooled to the lower limit of the calibration temperature zone in a relatively short time, thereby improving the calibration efficiency; when performing steady-state temperature control, the heat switch is disconnected, and the thermal resistance between the secondary cold head and the isothermal carrier will be very large, and the steady-state temperature control temperature zone will be expanded, and the temperature can even be controlled to near room temperature, thereby greatly improving the calibration accuracy. The use of a low-temperature heat switch can reduce the temperature fluctuation at the temperature measuring point of the thermometer, and at the same time shorten the cooling time of the calibration device, thereby achieving the requirements of high precision and high efficiency of temperature calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the structure of the present invention;

[0018] Figure 2 It is a schematic diagram of the internal structure of the vacuum chamber in the present invention;

[0019] Figure 3 This is a schematic diagram of the internal structure of the copper cooling screen in the present invention;

[0020] Figure 4 It is a structural schematic diagram of the low-temperature thermal switch assembly of the present invention.

[0021] Numbers in the figure: 1. GM refrigerator, 2. vacuum chamber, 3. low-temperature thermal switch assembly, 4. thermometer carrier, 5. flange connection plate, 6. primary cold head, 7. secondary cold head, 8. insulation bracket, 9. cold end copper block, 10. hot end copper block, 11. guide rod group, 12. sliding copper block, 13. electromagnet, 14. permanent magnet, 15. copper cooling screen, 16. thermal conductive column, 17. electric heating rod. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below. The embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0023] like Figure 1 to Figure 4 An embodiment of a liquid hydrogen temperature zone temperature calibration system with a low-temperature thermal switch assembly is shown, the system comprises a GM refrigerator 1, a vacuum chamber 2, a low-temperature thermal switch assembly 3, and a thermometer carrier 4, the GM refrigerator 1 is mounted on a flange connection plate 5 at the top of the vacuum chamber 2, a primary cold head 6 and a secondary cold head 7 of the GM refrigerator 1 extend downward into the vacuum chamber 2 through the mounting holes on the flange connection plate 5, and the secondary cold head 7 is connected to the thermometer carrier 4 through the low-temperature thermal switch assembly 3;

[0024] The low temperature thermal switch assembly 3 comprises two vertical insulation brackets 8 on the left and right, the upper end of the insulation bracket 8 is connected to the secondary cold head 7 by installing a cold end copper block 9, and the lower end of the insulation bracket 8 is connected to the thermometer carrier 4 by installing a hot end copper block 10;

[0025] A guide rod group 11 is arranged between the two vertical insulation brackets 8 on the left and right, and a sliding copper block 12 is slidably connected to the guide rod group 11. Electromagnets 13 are installed on the inner side walls of the two insulation brackets 8, and permanent magnets 14 corresponding to the positions of the electromagnets 13 are also arranged on the left and right side walls of the sliding copper block 12.

[0026] Among them, a copper refrigeration screen 15 is installed on the first-level cold head 6, and the copper refrigeration screen 15 covers the second-level cold head 7, the low-temperature thermal switch assembly 3 and the thermometer carrier 4; installing the copper refrigeration screen can reduce the influence of environmental radiation on the temperature stability of the thermometer carrier, and the above-mentioned device is placed in a vacuum cavity, and a high vacuum insulation method is adopted to reduce the heat leakage of the device from the outside.

[0027] The guide rod group 11 includes two guide rods arranged in parallel up and down. The installation position of the electromagnet 13 is located between the two guide rods. A heat-conducting column 16 is arranged between the hot end copper block 10 and the thermometer carrier 4, and an electric heating rod 17 is installed in the heat-conducting column 16.

[0028] Working principle:

[0029] The present invention uses a GM refrigerator as a cold source, in combination with electric heating, to change the temperature of a thermometer carrier installed on the secondary cold head of the GM refrigerator, and then calibrate the temperature sensor installed on the thermometer carrier. The copper cooling screen installed on the primary cold head of the GM refrigerator can reduce the influence of environmental radiation on the temperature stability of the thermometer carrier. The GM refrigerator, the copper cooling screen, the low-temperature thermal switch, and the thermometer carrier are all installed in a vacuum cavity to reduce the heat leakage from the outside to the device.

[0030] During the thermometer calibration process, it is required to perform steady-state temperature control on each graduation point until the steady state is reached before calibration of the next graduation point. When the thermometer carrier needs to be cooled down, the electromagnet is energized in the forward direction to attract the permanent magnet, which drives the sliding copper block to slide left and right on the guide rod, closing the low-temperature thermal switch. The cooling capacity of the secondary cold head of the GM refrigerator is used to quickly cool the thermometer carrier, ensuring that the thermometer carrier is cooled to the calibration temperature zone in a short time, thereby improving the calibration efficiency. When the temperature is cooled to the required calibration temperature, in order to maintain the temperature stability during the calibration process and reduce the adverse effects of temperature fluctuations, the electromagnet is energized in the reverse direction, and the sliding copper block moves in the reverse direction to disconnect the low-temperature thermal switch, thereby increasing the heat transfer resistance between the thermometer carrier and the secondary cold head, and reducing the influence of the temperature fluctuation of the secondary cold head on the temperature of the thermometer carrier, thereby improving the calibration accuracy.

Claims

1. A liquid hydrogen temperature zone temperature calibration system with a low temperature thermal switch assembly, characterized in that: The system comprises a GM refrigerator (1), a vacuum chamber (2), a low-temperature thermal switch assembly (3), and a thermometer carrier (4); the GM refrigerator (1) is mounted on a flange connection plate (5) at the top of the vacuum chamber (2); a primary cold head (6) and a secondary cold head (7) of the GM refrigerator (1) extend downward into the vacuum chamber (2) through a mounting hole on the flange connection plate (5); and the secondary cold head (7) is connected to the thermometer carrier (4) via the low-temperature thermal switch assembly (3); The low-temperature thermal switch assembly (3) comprises two left and right vertically placed insulating brackets (8), the upper end of the insulating bracket (8) being connected to the secondary cold head (7) by installing a cold-end copper block (9), and the lower end of the insulating bracket (8) being connected to the thermometer carrier (4) by installing a hot-end copper block (10); A guide rod group (11) is arranged between the two vertical insulation brackets (8) on the left and right, a sliding copper block (12) is slidably connected to the guide rod group (11), and an electromagnet (13) is installed on the inner side walls of each of the two insulation brackets (8), and permanent magnets (14) corresponding to the positions of the electromagnets (13) are also arranged on the left and right side walls of the sliding copper block (12).

2. A liquid hydrogen temperature zone temperature calibration system with a low temperature thermal switch assembly according to claim 1, characterized in that: A copper cooling screen (15) is installed on the first-stage cold head (6), and the copper cooling screen (15) covers the second-stage cold head (7), the low-temperature heat switch assembly (3) and the thermometer carrier (4).

3. A liquid hydrogen temperature zone temperature calibration system with a low temperature thermal switch assembly as claimed in claim 1, characterized in that: The guide rod group (11) comprises two guide rods which are arranged in parallel up and down.

4. A liquid hydrogen temperature zone temperature calibration system with a low temperature thermal switch assembly as claimed in claim 3, characterized in that: The installation position of the electromagnet (13) is located between the upper and lower guide rods.

5. A liquid hydrogen temperature zone temperature calibration system with a low temperature thermal switch assembly as claimed in claim 1, characterized in that: A heat-conducting column (16) is arranged between the hot-end copper block (10) and the thermometer carrier (4), and an electric heating rod (17) is installed in the heat-conducting column (16).

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