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液氮冻结温度场是具有相变、水分迁移的瞬态热传导问题。基于水热耦合理论建立了液氮冻结的温度场数学模型,获得了液氮冻结帷幕厚度和平均温度随时间发展均呈对数规律分布;冻结管组内连接方式对冻结效果有较大影响:三管串联形成的冻结帷幕厚度最不均匀、平均温度也最高,单管供回液连接方式冻结效果最好;但从经济效益和冻结效果综合因素考虑,双管串联冻结方式宜优先采用。研究成果完善了盾构进洞液氮冻结温度场理论和工艺。
The liquid nitrogen freezing temperature field is a transient heat conduction problem with phase transition and moisture migration. Based on the theory of hydrothermal coupling, a mathematical model of the temperature field of liquid nitrogen freezing was established, and the logarithmic regular distribution of the thickness and average temperature of liquid nitrogen freezing curtain was obtained. The connection modes in the freezing tube group had a significant effect on the freezing effect: The thickness of the frozen curtain formed by the three pipes in series is the most inhomogeneous and the average temperature is also the highest. The freezing effect of the single-pipe feed-back connection is the best. However, considering the combination of economic benefits and freezing effects, the double-tube series freezing method should be prioritized. The research results have perfected the theory and technology of temperature field of liquid nitrogen freezing in shield tunnel.