煤自燃灾害防治是安全领域重要研究课题之一。双碳战略下，纳米流体热管移热技术通过相变在冷凝段移热干扰煤氧化蓄热自燃，同时实现煤自燃废热提取利用，具有重要研究价值。前期研究发现含铜的金属氧化物纳米流体可有效提高热管移热效率，但高稳定性，高移热效率铜基氧化物复合纳米流体可控制备难以实现，纳米流体的物性参数影响因素不明，煤自燃过程中纳米流体与热管之间的相互影响尚不清楚，需要进一步展开研究。本文制备了新型具有高稳定性传热性能好的CuO/MgO/Al₂O₃复合纳米流体，对其导热系数等物性参数进行探讨，并将其作为热管工质开展煤堆自燃移热效能实验研究，为煤火灾害防治提供新思路。本文的研究内容主要包括：

（1）采用前驱体焙烧法制备得到铜基金属氧化物纳米颗粒，通过超声分散-表面改性耦合技术制备出不同质量分数（0.1%、0.5%、0.8%、1.0%和1.5%），不同基液（水、乙二醇）的CuO/MgO/Al₂O₃复合纳米流体。通过沉降实验与Zeta电位分析等实验测试手段，定性定量研究纳米流体的悬浮稳定性，结果表明：纳米流体具有良好的悬浮稳定性。制备的CuO/MgO/Al₂O₃纳米流体在静置5天后无明显沉降现象；Zeta电位测试值均＞30 mV。

（2）采用导热系数测试、粘度测试、表面张力测试等实验手段对纳米流体的物性参数开展研究，结合Merit数筛选并确定最优性能的纳米流体。结果表明：基液（水，乙二醇）的导热系数最大分别增加了15.1%和24.0%；在T为20 ℃和100 ℃时，基液（水，乙二醇）的粘度分别降低了47.3%和56.7%，水基纳米流体的表面张力最大下降了21.0%，乙二醇基纳米流体的表面张力最大下降了24.6%。此外，纳米流体的接触角随质量分数增大有所增加，随分散剂的添加有所减小。

（3）实验研究了纳米流体工质不同充液率及热管布置倾角对煤堆效能的影响。实验表明，当工质充液率为30%、热管布置倾角为60°时，1.5%CuO/MgO/Al₂O₃-H₂O纳米流体煤堆移热效能最好，其与纯水热管相比，煤堆上部、中部与下部降温值提升了6.2%、42.8%和7.9%。与市面常见的CuO纳米流体相比，煤堆内部降温值分别提高了9.8%、9.7%和8.3%。表明CuO/MgO/Al₂O₃-H₂O纳米流体移热效能显著。

The prevention and control of coal spontaneous combustion disasters is one of the important research topics in the field of safety. Under the dual carbon strategy, the heat transfer technology of nanofluid heat pipes interferes with coal oxidation, thermal storage, and spontaneous combustion through phase change in the condensation section, while achieving the extraction and utilization of waste heat from coal spontaneous combustion, which has important research value. Previous studies have found that metal oxide nanofluids containing copper can effectively improve the heat transfer efficiency of heat pipes, but high stability and high heat transfer efficiency make it difficult to control the preparation of copper based oxide composite nanofluids. The factors affecting the physical properties of nanofluids are unclear, and the mutual influence between nanofluids and heat pipes during coal spontaneous combustion is still unclear. Further research is needed. This article prepares a new type of CuO/MgO/Al₂O₃ composite nanofluid with high stability and good heat transfer performance, explores its thermal conductivity and other physical properties parameters, and uses it as a heat pipe working fluid to conduct experimental research on the heat transfer efficiency of coal pile spontaneous combustion, providing new ideas for coal fire disaster prevention and control. The research content of this article mainly includes:

(1) Copper based metal oxide nanoparticles were prepared by precursor calcination method, and CuO/MgO/Al₂O₃ composite nanofluids with different mass fractions (0.1%, 0.5%, 0.8%, 1.0%, and 1.5%) and different base liquids (water, ethylene glycol) were prepared by ultrasonic dispersion surface modification coupling technology. Through sedimentation experiments and Zeta potential analysis, the suspension stability of nanofluids was qualitatively and quantitatively studied. The results showed that nanofluids have good suspension stability. The prepared CuO/MgO/Al₂O₃ nanofluid showed no significant sedimentation after 5 days of standing; The Zeta potential test values are all greater than 30 mV.

(2) Experimental methods such as thermal conductivity testing, viscosity testing, and surface tension testing were used to study the physical properties of nanofluids, and the Merit number was used to screen and determine the optimal performance of nanofluids. The results showed that the thermal conductivity of the base solution (water, ethylene glycol) increased by 15.1% and 24.0%, respectively; At temperatures of 20 ℃ and 100 ℃, the viscosity of the base solution (water, ethylene glycol) decreased by 47.3% and 56.7%, respectively. The surface tension of water-based nanofluids decreased by a maximum of 21.0%, while the surface tension of ethylene glycol based nanofluids decreased by a maximum of 24.6%. In addition, the contact angle of the nanofluid increases with the increase of mass fraction and decreases with the addition of dispersant.

(3) The experimental study investigated the effects of different filling rates of nanofluid working fluids and the inclination angle of heat pipe arrangement on the efficiency of coal piles. Experiments have shown that when the filling rate of the working fluid is 30% and the inclination angle of the heat pipe arrangement is 60 °, the heat transfer efficiency of the 1.5% CuO/MgO/Al₂O₃-H₂O nanofluid coal stack is the best. Compared with pure water heat pipes, the cooling values of the upper, middle, and lower parts of the coal stack have increased by 6.2%, 42.8%, and 7.9%. Compared with the common CuO nanofluids on the market, the internal cooling value of coal piles has increased by 9.8%, 9.7%, and 8.3%, respectively. The surface CuO/MgO/Al₂O₃-H₂O nanofluid exhibits significant heat transfer efficiency.

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