地下煤火具有持续时间长，储热量大，分布广泛等特点。通过相变传热移取地下煤火热能是具有开发和推广的潜在技术之一，而热虹吸器是热能移取的关键部件，通过热虹吸器内部工质的两相流动相变传热可提取煤自燃释放的热量，破坏煤体的蓄热条件，是实现“生态灭火，绿色用火”和推进绿色用能的有效途径。

为了探索改善工质物性及通过新型井身结构对热虹吸器移热效率的影响，本文通过搭建地下煤火热能移取实验平台，测试分散剂对纳米工质稳定性的影响，设计基于弯曲井身的“L型”热虹吸器，利用标准正交法设计改变纳米流体工质种类（Al₂O₃、CuO、SiO₂）、工质浓度（1%、2%、3%）、充液率（30%、40%、50%）、弯曲井身角度（0°、30°、45°）的9根热虹吸器，研究了不同热虹吸器关键参数及不同煤堆温度（100、200℃）下的煤堆温度场变化规律，计算不同工况下热虹吸器的移热性能指标参数（降温幅度、降温率、移热量），采用极差法分析不同参数对移热性能指标的敏感性。通过Pearson相关性分析确定出以移热量为热虹吸器移热性能的指标，并确定了不同温度场下性能最优热虹吸器。基于热虹吸器不同水平层的核心影响半径，建立热虹吸器移热模型，通过FLUENT模拟不同间距下的移热效果，模型得出场地尺度下热虹吸器的最佳布置间距。主要研究结果如下：

（1）在充分研究现有热虹吸器强化传热研究的基础上，设计了不同弯曲角度的“L型”热虹吸器以及配套灌液系统，增加实验的可操作性，实现了在实验室内制作热虹吸器的目标。

（2）通过研究不同浓度的分散剂对纳米工质稳定性的影响后得出，大部分纳米工质添加分散剂后稳定性效果显著增强。其中在纳米SiO₂和纳米Al₂O₃中，阿拉伯树脂（AG）分散效果更佳，十二烷基苯磺酸钠（SDS）对于纳米CuO的分散效果更佳明显。

（3）热虹吸器的移热效率与煤样距离热虹吸器距离呈现出负相关，煤堆温度为100 ℃时，“L型”热虹吸器对煤堆温度场扩散过程的抑制效果优于竖直型井身结构。当煤堆温度为200 ℃时，大部分“L型”热虹吸器的移热量优于竖直型热虹吸器，其中移热量最大的热虹吸器为5^#（井身结构：30°、充液率：30%、工质浓度：2%、工质种类：CuO），其移热量为45.19 MJ。

（4）对比不同温度场，热虹吸器的移热量发现，随着煤堆的温度增加，竖直型井身结构的移热量呈现减小的趋势，“L型”热虹吸器的移热量均增加，其中30°弯曲井身热虹吸器的移热量增加的幅度更大。

（5）通过选取两根移热量最佳的热虹吸器，设置不同间距下的5^#和6^#热虹吸器（井身结构：0°、充液率：40%、工质浓度：3%、工质种类：CuO）进行模拟，发现以2倍中下层核心影响半径（60 cm）作为场地尺度下的布置距离更为合理。

Underground coal fires have the characteristics of long duration, large heat storage and wide distribution. The removal of thermal energy from underground coal through phase change heat transfer is one of the potential technologies with development and promotion. The thermosyphon is the key component of thermal energy transfer. The heat released by the spontaneous combustion of coal can be extracted through the two-phase flow phase change heat transfer of the working fluid inside the thermosyphon, and the heat storage conditions of the coal body can be destroyed. It is an effective way to achieve "ecological fire extinguishing, green fire" and promote green energy use.

In order to explore the effect of improving the physical properties of the working medium and the heat transfer efficiency of the thermosyphon through a new well structure. In this paper, by building an experimental platform for thermal energy transfer from underground coal, and testing the effect of dispersants on the stability of nano-working fluids. The design is based on an "L-shaped" thermosyphon with a curved wellbore. Using the standard orthogonal design to change the type of nanofluid working fluid (Al₂O₃、CuO、SiO₂), working fluid concentration (1%、2%、3%), liquid filling rate (30%、40%、50%), curved well 9 thermosyphons at body angles (0°、30°、45°). The experiment studied the variation law of coal pile temperature field under different key parameters of thermosyphon and different coal pile temperatures (100、200 ℃). And the range method is used to analyze the sensitivity of different parameters to the heat transfer performance index. The correlation between the indicators was determined by Pearson correlation analysis. The heat transfer is taken as the index of the heat transfer performance of the thermosyphon. And the optimal thermosyphon is determined respectively. Based on the core influence radii of different horizontal layers of the thermosyphon. The thermosyphon heat transfer model is established, and the heat transfer effect under different spacings is simulated by FLUENT. The model obtains the optimal arrangement spacing of the thermosyphon at the site scale. The main findings are as follows:

（1）On the basis of the existing research on strengthening the heat transfer of the thermosyphon, the thermosyphon with different bending angles and the supporting liquid filling system are designed to increase the operability of the experiment. The goal of making a thermosyphon in the laboratory was achieved.

（2）After studying the effects of different concentrations of dispersants on the stability of nano-working fluids, it was concluded that the stability effect of most nano-working fluids was significantly enhanced after adding dispersants. Among them, in nano-SiO₂ and nano-Al₂O₃, gum arabic (AG) has better dispersion effect, and sodium dodecyl benzene sulfonate (SDS) has better dispersion effect on nano-CuO.

（3）The heat transfer efficiency of the thermosyphon is negatively correlated with the distance from the coal sample to the thermosyphon. When the temperature of the coal sample is 100 ℃, the "L-type" thermosyphon has better inhibition effect on the temperature field diffusion process of the coal pile than the vertical well structure. When the coal sample temperature is 200 °C, most of the "L-shaped" thermosyphons have better heat transfer than vertical thermosyphons. Among them, the thermosyphon with the largest heat transfer is 5^# (bending angle: 30°, filling rate: 30%, working fluid concentration: 2%, working fluid type: CuO). Its total heat transfer energy is 45.19 MJ.

（4）Compared with different temperature fields, the heat transfer of thermosyphon is found: As the temperature of the coal pile increases, the heat transfer of the vertical shaft structure shows a decreasing trend, and the heat transfer of the "L-shaped" thermosyphon increases. Among them, the heat transfer rate of the 30° curved wellbore thermosyphon increases more greatly.

（5）By selecting the two thermosyphons with the best heat transfer, To set 5^# and 6^# thermosyphons with different spacings (bending angle: 0°, liquid filling rate: 40%, working fluid concentration: 3%, working fluid type: CuO) for simulation. It is found that it is more reasonable to use twice the influence radius of the middle and lower layers (60 cm) as the layout distance at the site scale.

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