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CN-122015396-A - Precooler of liquid nitrogen strengthening single-stage GM refrigerator and method

CN122015396ACN 122015396 ACN122015396 ACN 122015396ACN-122015396-A

Abstract

The application discloses a precooler of a liquid nitrogen reinforced single-stage GM refrigerator and a method thereof, and relates to the technical field of superconducting nuclear magnetic resonance, wherein the liquid nitrogen reinforced magnet precooler comprises a main refrigeration loop and a liquid nitrogen reinforced loop, and the main refrigeration loop comprises a circulating press, a main heat exchanger, a single-stage GM large cold head, a cold head heat exchanger and a low-temperature transmission line; the liquid nitrogen strengthening loop comprises a strengthening heat exchanger and a liquid nitrogen container, wherein the liquid nitrogen container is internally provided with the liquid nitrogen and a coil heat exchanger, and the magnet precooler of the liquid nitrogen strengthening and single-stage GM refrigerator and the method thereof carry out strengthening cooling on helium through liquid nitrogen, thereby effectively improving cooling power, reducing precooling time and reducing electricity consumption during cooling period, and further reducing energy consumption.

Inventors

  • BI YANFANG
  • Zhu Linju
  • SHI XIAODONG
  • ZHANG KAIKAI
  • DUAN XUNQI
  • ZHENG JIE
  • XU JIANYI

Assignees

  • 宁波健信超导科技股份有限公司

Dates

Publication Date
20260512
Application Date
20260410

Claims (10)

  1. 1. A pre-cooler for a liquid nitrogen-enhanced, single-stage GM refrigerator, comprising: the main refrigeration loop comprises a circulating press (1), a main heat exchanger (2), a cold head (3) and a cold head heat exchanger (4), wherein the input end of the circulating press (1) is communicated with the low-pressure side of the main heat exchanger (2), the output end of the circulating press (1) is communicated with the high-pressure side of the main heat exchanger (2), the cold head (3) and the cold head heat exchanger (4) are integrally arranged, the high-pressure side of the main heat exchanger (2) is communicated with the input end of the cold head heat exchanger (4), the input end of the cold head heat exchanger (4) is communicated with a magnet (100) through a supply pipeline (5), the magnet (100) is communicated with the low-pressure side of the main heat exchanger (2) through a return pipeline (6), and a first valve body (7) is arranged between the return pipeline (6) and the main heat exchanger (2); The liquid nitrogen strengthening pipeline comprises a strengthening heat exchanger (8) and a liquid nitrogen container (9), wherein liquid nitrogen is filled in the liquid nitrogen container (9), the strengthening heat exchanger (8) is positioned in the liquid nitrogen, a reflux branch is arranged between the reflux pipeline (6) and the first valve body (7), the reflux branch is communicated with the input end of the strengthening heat exchanger (8), the strengthening heat exchanger (8) is communicated with the low-pressure side of the main heat exchanger (2) through the strengthening branch, and the strengthening branch is provided with a second valve body (10).
  2. 2. The liquid nitrogen strengthening, single-stage GM refrigerator precooler of claim 1, wherein said liquid nitrogen strengthening pipeline is further provided with a precooling heat exchanger (11), said precooling heat exchanger (11) being located between said return branch and said strengthening heat exchanger (8), an input of said precooling heat exchanger (11) being in communication with said return branch, an output of said precooling heat exchanger (11) being in communication with said strengthening heat exchanger (8).
  3. 3. The liquid nitrogen-enhanced, single-stage GM refrigerator precooler of claim 2, further comprising a cold trap (14), said cold trap (14) being disposed between said enhanced heat exchanger (8) and said second valve body (10).
  4. 4. A pre-cooler for a liquid nitrogen-enhanced, single-stage GM refrigerator according to claim 3, further comprising a cold box (15), wherein the cold head (3), the cold head heat exchanger (4), the main heat exchanger (2), the pre-cooling heat exchanger (11), the enhanced heat exchanger (8), and the cold trap (14) are all disposed in the cold box (15).
  5. 5. The liquid nitrogen-enhanced single-stage GM refrigerator precooler according to claim 1, further comprising a control module, wherein a temperature sensor is provided at the return line (6), and wherein the temperature sensor is electrically connected to the control module, and wherein the control module is electrically connected to the first valve body (7) and the second valve body (10).
  6. 6. The liquid nitrogen-enhanced, single-stage GM refrigerator precooler of claim 1 wherein said enhanced heat exchanger (8) is a corrugated coil heat exchanger.
  7. 7. Pre-cooler of a liquid nitrogen-enriched, single-stage GM refrigerator according to claim 1, characterized in that the circulation press (1) and the main heat exchanger (2) can be replaced by a cryogenic fan.
  8. 8. A method for precooling a large superconducting device, applied to the precooler of the liquid nitrogen-enriched single-stage GM refrigerator of any one of claims 1-7, comprising the steps of: The first step, checking the circuit, closing the first valve body (7), and opening the second valve body (10); secondly, cooling the magnet (100), introducing low-temperature helium flow into the magnet (100), absorbing heat and then refluxing; thirdly, cooling helium flow, wherein the helium flow enters a liquid nitrogen strengthening pipeline and is cooled through a precooling heat exchanger (11), a liquid nitrogen container (9), a main heat exchanger (2) and a cold head heat exchanger (4); fourth, the cooled medium is input into the magnet (100) again, and the second step to the fourth step are repeated until the magnet (100) is precooled to 80K.
  9. 9. The method of precooling a large-scale superconducting apparatus according to claim 8, wherein when the medium temperature of the reflux in the second step is lower than a preset threshold value, the first valve body (7) is opened, the second valve body (10) is closed, and the medium continues to be cooled only by the main heat exchanger (2) until the target temperature is reached.
  10. 10. A method of pre-cooling a large superconducting apparatus according to claim 8, wherein the first step is preceded by heating the cold trap (14) to 105 ℃ and evacuating the magnet (100) and cold trap (14) to effect regeneration of the cold trap (14).

Description

Precooler of liquid nitrogen strengthening single-stage GM refrigerator and method Technical Field The application relates to the technical field of nuclear magnetic resonance, in particular to a precooler of a liquid nitrogen reinforced single-stage GM refrigerator and a method thereof. Background Large superconducting devices such as superconducting magnets, superconducting motors, etc. must be pre-cooled from room temperature to about 20K (K is kelvin) or less before formally injecting liquid helium into the device. The traditional industrial scheme mainly adopts a liquid nitrogen soaking superconducting material mode to finish 300-80K precooling, and then uses a GM refrigerator or liquid helium filling to finish 80-20K deep cooling. However, direct contact of the magnet with liquid nitrogen may cause excessive thermal stress to the coil epoxy impregnation layer, and nitrogen remains inside the superconducting device after pre-cooling, complicating the high purity helium substitution operation and increasing the helium consumption cost. In recent years, a precooling scheme of 'single-stage GM refrigerator plus forced helium flow circulation' appears in the industry, namely, high-flow circulating helium is used as a secondary refrigerant, and a single-stage GM cold head provides refrigeration capacity at 80-20K. However, this structure still lacks sufficient refrigeration capacity at the higher temperatures of 300-80K. For superconducting devices with a cold mass of about 2 tons, such existing precoolers still take about 6-7 days to cool from room temperature to about 20-25K, and the total energy efficiency is low. Disclosure of Invention The application aims to provide a liquid nitrogen strengthening single-stage GM refrigerator and a method, which can improve refrigeration energy efficiency. In order to achieve the aim, the application provides a precooler of a liquid nitrogen strengthening and single-stage GM refrigerator, which comprises a main refrigeration loop and a liquid nitrogen strengthening loop; The main refrigeration loop comprises a circulating press, a main heat exchanger, a cold head and a cold head heat exchanger, wherein the input end of the circulating press is communicated with the low-pressure side of the main heat exchanger, the output end of the circulating press is communicated with the high-pressure side of the main heat exchanger, the cold head and the cold head heat exchanger are integrally arranged, the high-pressure side of the main heat exchanger is communicated with the input end of the cold head heat exchanger, the input end of the cold head heat exchanger is communicated with a magnet through a flow supply pipeline, the magnet is communicated with the low-pressure side of the main heat exchanger through a return pipeline, and a first valve body is arranged between the return pipeline and the main heat exchanger; The liquid nitrogen strengthening loop comprises a strengthening heat exchanger and a liquid nitrogen container, wherein liquid nitrogen is filled in the liquid nitrogen container, the strengthening heat exchanger is positioned in the liquid nitrogen, a reflux branch is arranged between a reflux pipeline and a first valve body, the reflux branch is communicated with the input end of the strengthening heat exchanger, the strengthening heat exchanger is communicated with the low-pressure side of the main heat exchanger through the strengthening branch, and a second valve body is arranged on the strengthening branch. In an embodiment, the liquid nitrogen strengthening pipeline is further provided with a pre-cooling heat exchanger for recovering part of cold energy of the evaporated nitrogen, the pre-cooling heat exchanger is located between the backflow branch and the strengthening heat exchanger, the input end of the pre-cooling heat exchanger is communicated with the backflow branch, and the output end of the pre-cooling heat exchanger is communicated with the strengthening heat exchanger. In the embodiment, a cold trap is further arranged to adsorb impurity gas and ensure the efficiency of each heat exchanger, and the cold trap is arranged between the reinforced heat exchanger and the second valve body. In an embodiment, a cold box is further provided, and the cold head, the cold head heat exchanger, the main heat exchanger, the pre-cooling heat exchanger, the strengthening heat exchanger and the cold trap are all arranged in the cold box. In some embodiments, a control module is further provided, a temperature sensor is provided at the backflow line, the temperature sensor is electrically connected with the control module, and the control module is electrically connected with the first valve body and the second valve body. In an embodiment, the enhanced heat exchanger is a corrugated coil heat exchanger. In an embodiment, the recycle press and the main heat exchanger can be replaced with a cryogenic fan. The precooling method of the large superconducting equipmen