冻土层竖埋供水立管传热特性研究

发布时间：2018-06-13 23:56

本文选题：冻土 + 供水立管　；参考：《北京交通大学》2016年硕士论文

【摘要】：我国冻土区面积广阔,生活在冻土区人口众多,由于部分冻土区自然条件恶劣等多种原因,全国有9.65%人口受到了水管冻裂冻胀,供水困难的影响。供水工程中,穿过冻土层的供水立管工作条件与主管不同,供水立管处于间歇性工作状态,尤其在夜间经常处于静止状态,或流量较小,极易发生冻结。因此研究冻土层供水立管的传热问题,对于指导生产,保证管道的安全运行具有重要意义,研究这个问题的关键之一是分析管道周围土壤温度场和计算管道内介质的温度分布。本文将我国季节性冻土层分为浅层冻土区和深层冻土区。给出了冻土深度估算的两种方法,并据此估算了西藏地区浪卡子、聂荣两地的季节性冻土深度。通过选取这两个地方作为典型浅层冻土区与深层冻土区进行了真实冻土环境下的供水立管换热实验,获得了不同工况下的水管壁面、保温层外壁面温度分布以及冻土温度场。探究了冻土深度、伴热功率、伴热形式、初始水温等对管道传热的影响。针对现场实验条件开展了数值研究,计算了裸露在空气外的地上管段对流换热系数,以及实际地表温度变化情况,并以此为边界条件建立了穿过冻土层的供水立管数值分析模型,较准确地反映了供水支管真实工作条件下的换热情况。与多组实验测得数据进行了对比,验证了模型的可靠性。同时探究了伴热功率、风速、风温、管内流量对水管换热的影响。搭建了室内人工冻土模型冻融实验台,并通过不同工况下的土壤冻融实验,探究了含水率、热流密度对土壤冻融的影响。同时建立了饱和冻土水热耦合数学模型,进行了不同条件下饱和冻土融化数值模拟并与实验数据进行了对比,获得了土壤融化过程中的温度场、流场以及冻土融化界面。探究了孔隙率、土壤粒径对土壤温度场、融化率、水分迁移的影响,为冻融条件下埋地管道传热分析提供了参考。
[Abstract]:The area of frozen soil region in China is vast and the population living in frozen soil region is large. Due to the bad natural conditions in some frozen soil regions, 9.65% of the population in China is affected by the frost heaving of water pipes and the difficulty of water supply. In water supply engineering, the working condition of water supply riser through frozen soil is different from that of supervisor. The water supply riser is in intermittent working state, especially in the static state at night, or the discharge is small, so it is easy to freeze. Therefore, it is of great significance to study the heat transfer of water supply risers in frozen soil, which is of great significance for guiding production and ensuring the safe operation of pipelines. One of the key points in this study is to analyze the soil temperature field around pipelines and to calculate the temperature distribution of the medium in the pipes. In this paper, the seasonal frozen soil layer in China is divided into shallow permafrost region and deep permafrost region. Two methods for estimating the depth of permafrost are given and the seasonal depth of frozen soil in Longkazi and Nie Rong in Tibet is estimated. By selecting these two places as typical shallow frozen soil region and deep frozen soil region, the heat transfer experiment of water supply riser in real frozen soil environment is carried out, and the temperature distribution of water pipe wall, insulation layer outside wall and frozen soil temperature field under different working conditions are obtained. The influences of permafrost depth, heat tracing power, heat tracing form and initial water temperature on pipe heat transfer are investigated. A numerical study was carried out on the field experimental conditions, and the convection heat transfer coefficient of the above ground tube section exposed to the air and the actual surface temperature variation were calculated. The numerical analysis model of water supply riser through permafrost is established under the boundary condition, which accurately reflects the heat transfer of the water supply branch pipe under the actual working condition. The reliability of the model is verified by comparison with many groups of experimental data. At the same time, the effects of heat tracing power, wind speed, wind temperature and flow rate on the heat transfer of water pipes are investigated. The experiment bench of artificial frozen soil model was set up, and the effects of moisture content and heat flux on soil freezing and thawing were investigated through the experiment of soil freezing and thawing under different working conditions. At the same time, the coupled mathematical model of saturated permafrost was established, and the numerical simulation of saturated frozen soil thawing under different conditions was carried out and compared with experimental data. The temperature field, flow field and thawing interface during soil thawing were obtained. The effects of porosity, soil particle size on soil temperature field, melting rate and water migration are discussed, which provides a reference for the analysis of heat transfer in buried pipeline under freezing and thawing conditions.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU991.36;TK124

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