岩土力学 ›› 2022, Vol. 43 ›› Issue (9): 2624-2633.doi: 10.16285/j.rsm.2021.1909

• 数值分析 • 上一篇    下一篇

液氮冻结加固冻结管内换热机制及 对流换热系数研究

黄建华1, 2,严耿明1, 2,覃少杰1, 2   

  1. 1. 福建工程学院 土木工程学院,福建 福州 350118;2. 福建工程学院 地下工程福建省高校重点实验室,福建 福州350118
  • 收稿日期:2021-11-11 修回日期:2022-05-07 出版日期:2022-09-12 发布日期:2022-09-12
  • 通讯作者: 严耿明,男,1995年生,硕士,主要从事特殊土力学等方面的研究。E-mail: yangengming@163.com E-mail:huangjh@fjut.edu.cn
  • 作者简介:黄建华,男,1969年生,博士后,教授,主要从事特殊土力学、冻结围护结构与地下结构等方面的教学和研究。
  • 基金资助:
    国家自然科学基金(No.51678153)

Heat transfer mechanism and convective heat transfer coefficient in freezing pipes for freezing reinforcement using liquid nitrogen

HUANG Jian-hua1, 2, YAN Geng-ming1, 2, QIN Shao-jie1, 2   

  1. 1. College of Civil Engineering, Fujian University of Technology, Fuzhou, Fujian 350118, China; 2. Key Laboratory of Underground Engineering of Fujian Province University, Fujian University of Technology, Fuzhou, Fujian 350118, China
  • Received:2021-11-11 Revised:2022-05-07 Online:2022-09-12 Published:2022-09-12
  • Supported by:
    This work was supported by the National Natural Science Foundation of China(51678153).

摘要: 液氮冻结加固是通过液氮在冻结管内沸腾吸热和对流换热来降低环境土层温度,快速冻结土层中水分形成具有支护效果的冻结帷幕。但相较于传统的盐水冻结技术,液氮冻结温度极低,温度场分布不均匀,影响冻结效果的因素更多,对液氮冻结过程热交换的研究较少。依据对流换热理论,分析了管内冻结能量交换过程,计算了液氮吸热的对流换热系数,模拟了液氮冻结温度场特征,并结合现场实测数据对液氮对流换热系数进行反传热分析,降低了对流换热系数计算误差。研究结果表明:液氮吸收热量的方式主要是液氮沸腾吸热以及低温氮气对流换热;以对流换热理论及其换热系数为基础的液氮冻结温度场模拟需要考虑换热系数随冻结时间和冻结深度变化,常量换热系数无法精确反映对流换热全过程,将导致积极冻结期与维护冻结期内温度下降趋势与实测情况、模拟温度与实测温度均产生差异,计算的温度场整体温度偏低;将冻结时间划分为 16个时间段,冻结空间划分为 4个区域,对换热系数进行非均匀性修正,使换热系数成为随冻结时间与空间变化的变量,不仅符合实际而且减小了误差,更契合工程实测数据。研究成果可为类似液氮冻结工程提供理论依据和技术参考。

关键词: 液氮冻结, 冻结管, 温度场, 对流换热, 反传热分析

Abstract:

Liquid nitrogen freezing reduces the temperature of environmental soil layer by boiling heat absorption and convection heat transfer of liquid nitrogen in the freezing pipe, and quickly freezes the water in the soil to form a freezing curtain with supporting effect. Compared with the traditional brine freezing technology, the freezing temperature of liquid nitrogen is extremely low, the temperature field is not uniformly distributed, and there are more factors affecting the freezing effect, while the heat exchange of liquid nitrogen freezing process lacks of study. Based on the theory of convective heat transfer, the freezing energy exchange process in the pipe is analyzed, the convection heat transfer coefficient of liquid nitrogen heat absorption is calculated, and the characteristics of the freezing temperature field of liquid nitrogen is simulated. Combined with the field measured data, the reverse heat transfer analysis of the liquid nitrogen convective heat transfer coefficient is carried out, which reduces the calculation error of the convective heat transfer coefficient. The study results show that the liquid nitrogen absorbs heat mainly by boiling heat absorption of liquid nitrogen and convective heat transfer of low-temperature nitrogen. The simulation of the freezing temperature field of liquid nitrogen based on convective heat transfer theory and its heat transfer coefficient needs to consider the change of heat transfer coefficient with freezing time and freezing depth, and a constant heat transfer coefficient cannot accurately reflect the whole process of convective heat transfer, which will lead to the difference between the temperature decline trend and actual measurement during the active freezing period and maintenance freezing period, and between the simulated temperature and actual temperature, the temperature obtained by calculation is relatively low. The freezing time is divided into 16 time periods and the freezing space is divided into 4 areas. The non-uniformity correction of the heat transfer coefficient is carried out to make the heat transfer coefficient a variable that changes with the freezing time and space, which not only conforms to the reality but also reduces the error, and it is more consistent with the practical engineering measured data. The research results can provide theoretical basis and technical reference for similar liquid nitrogen freezing projects.

Key words: liquid nitrogen freezing, freezing pipe, temperature field, convective heat transfer, inverse heat transfer analysis

中图分类号: 

  • TU411
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