An experimental system for liquid nitrogen soaking and real-time temperature measurement was designed and implemented to investigate the characteristics of temperature field changes in coal under liquid nitrogen soaking. Then, the heat conduction law of the coal in the process of liquid nitrogen soaking and room temperature recovery for dry and water-saturated coal were examined. The microstructure characteristics of the coal before and after liquid nitrogen soaking were analyzed with nuclear magnetic resonance (NMR) technology. The results showed that, during the liquid nitrogen cold soaking process, the heat transfer law of the dry and water-saturated coal samples exhibited a notable three-stage distribution. For the room temperature recovery process, the dry and water-saturated coal samples exhibited rapid heating characteristics, and the cooling rate gradually decreased to zero. NMR test results indicated that the liquid nitrogen soaking increased the number of micro and small pores in the coal. Thermal stress analysis revealed that the thermal stress generated by the dry coal was larger than that produced by the saturated coal, and the damage was primarily caused by thermal stress. However, the permeability of the saturated coal was better than that of the dry coal. The damage on the saturated coal was caused by the volume expansion of pores and fissures caused by water-ice phase transition.

中文翻译：

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液氮浸泡下煤的导热系数和孔结构的演变。

设计并实现了液氮均热和实时温度测量的实验系统，以研究液氮均热条件下煤的温度场变化特征。然后，研究了煤在液氮浸泡过程中的热传导规律以及干燥和水饱和煤的室温回收率。利用核磁共振（NMR）技术分析了液氮浸泡前后煤的微观结构特征。结果表明，在液氮冷浸过程中，干，水饱和煤样品的传热规律呈现出明显的三阶段分布。在室温恢复过程中，干煤和水饱和煤样品表现出快速加热特性，冷却速度逐渐降低至零。NMR测试结果表明，液氮浸泡增加了煤中微孔和小孔的数量。热应力分析表明，干煤产生的热应力大于饱和煤产生的热应力，其破坏主要是由热应力引起的。但是，饱和煤的渗透率比干煤好。对饱和煤的破坏是由于水冰相变引起的孔隙和裂缝的体积膨胀所致。热应力分析表明，干煤产生的热应力大于饱和煤产生的热应力，其破坏主要是由热应力引起的。但是，饱和煤的渗透率比干煤好。对饱和煤的破坏是由于水冰相变引起的孔隙和裂缝的体积膨胀所致。热应力分析表明，干煤产生的热应力大于饱和煤产生的热应力，其破坏主要是由热应力引起的。但是，饱和煤的渗透率比干煤好。对饱和煤的破坏是由于水冰相变引起的孔隙和裂缝的体积膨胀所致。