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<p>In response to the urgent demand for efficient and environmentally friendly refrigerants in the artificial freezing technology of ultra-low temperature strata, this study innovatively proposes to use transcritical CO<sub>2</sub> as a new type of refrigerant. Based on the self-developed double-pipe freezing physical model test system, by comparing the freezing processes of trancritical CO<sub>2</sub> and alcohol in homogeneous sand layers and combining with the COMSOL numerical simulation of heat transfer in porous media, the system reveals the evolution of the temperature field and the development laws of the frozen wall. The results show that the temperature difference between the inlet and outlet of the trancritical CO<sub>2</sub> reaches 25°C, which is significantly higher than that of alcohol at 3°C, highlighting its excellent heat exchange capacity. In the regions of the main surface (F5<sup>+</sup>~F5<sup>−</sup>), the interface (K<sup>+</sup>~K5<sup>−</sup>), and the axial plane (A0~U0), the temperature gradient formed by transcritical CO<sub>2</sub> is more than 35% higher than that of alcohol, accelerating the diffusion of coldness. The cross-cycle time of transcritical CO<sub>2</sub> at the boundary point (K0) is only 3.2h, which is 50% shorter than that of alcohol (6.4h). After freezing for 4 hours, the test values of the freezing curtain expansion radius of transcritical CO<sub>2</sub> on the main surface <i>R</i><sub><i>zzs</i></sub>, interface <i>R</i><sub><i>js</i></sub>, and axial plane <i>R</i><sub>0</sub> reached 60–80mm, 40–60mm, and 60–80mm respectively, while alcohol required 6 hours to achieve a similar effect. This study confirmed that transcritical CO<sub>2</sub> has high efficiency and engineering applicability in ultra-low temperature freezing at −60°C, providing an important basis for the freezing design of complex strata. This research not only verified the high efficiency and reliability of transcritical CO<sub>2</sub> in ultra-low temperature freezing at −60°C, but also provided key parameter support for the design optimization of freezing projects in complex strata, promoting the innovation of artificial freezing technology towards a green and low-carbon direction.</p>

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Study on the evolution law of transcritical CO2 double-pipe freezing temperature field in ultra-low temperature strata

  • 期刊论文

  • 发表日期：

    2025年9月13日

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  • Xiu-ling Liang,
  • Bin Wang,
  • Zi-hao Zhang,
  • Yan-hu Mu,
  • Ren-cai Jin

摘要

In response to the urgent demand for efficient and environmentally friendly refrigerants in the artificial freezing technology of ultra-low temperature strata, this study innovatively proposes to use transcritical CO2 as a new type of refrigerant. Based on the self-developed double-pipe freezing physical model test system, by comparing the freezing processes of trancritical CO2 and alcohol in homogeneous sand layers and combining with the COMSOL numerical simulation of heat transfer in porous media, the system reveals the evolution of the temperature field and the development laws of the frozen wall. The results show that the temperature difference between the inlet and outlet of the trancritical CO2 reaches 25°C, which is significantly higher than that of alcohol at 3°C, highlighting its excellent heat exchange capacity. In the regions of the main surface (F5+~F5−), the interface (K+~K5−), and the axial plane (A0~U0), the temperature gradient formed by transcritical CO2 is more than 35% higher than that of alcohol, accelerating the diffusion of coldness. The cross-cycle time of transcritical CO2 at the boundary point (K0) is only 3.2h, which is 50% shorter than that of alcohol (6.4h). After freezing for 4 hours, the test values of the freezing curtain expansion radius of transcritical CO2 on the main surface Rzzs, interface Rjs, and axial plane R0 reached 60–80mm, 40–60mm, and 60–80mm respectively, while alcohol required 6 hours to achieve a similar effect. This study confirmed that transcritical CO2 has high efficiency and engineering applicability in ultra-low temperature freezing at −60°C, providing an important basis for the freezing design of complex strata. This research not only verified the high efficiency and reliability of transcritical CO2 in ultra-low temperature freezing at −60°C, but also provided key parameter support for the design optimization of freezing projects in complex strata, promoting the innovation of artificial freezing technology towards a green and low-carbon direction.