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将羧基基团引入多壁碳纳米管,改善了碳纳米管在水中的分散性及稳定性。同时研究了不同质量浓度纳米流体的导热系数、加热表面颗粒沉积、接触角变化对核沸腾传热性能的影响。结果表明;羧基化碳纳米流体可强化核沸腾传热。在测试浓度范围内,强化率在低热通时,随着热通量的增加急剧增大,高热通时,趋于稳定;当质量比ω为0.10%,功率为210.6 kW.m~(-2)时,强化率达到最大为138.3%;流体的导热系数随着质量浓度的增大而增大,0.15%浓度导热系数是纯水的1.18倍。分析认为纳米流体表面张力,纳米颗粒沉积,纳米颗粒扰动和导热系数的变化均是影响水基羧基化碳纳米流体沸腾的因素。结论由0.05%的纳米流体沸腾过程高速成像得到验证。
The introduction of carboxyl groups into multi-walled carbon nanotubes improves the dispersibility and stability of carbon nanotubes in water. At the same time, the effects of thermal conductivity, deposition of heated surface particles and contact angle on the nucleate boiling heat transfer performance of nanofluids with different mass concentrations were studied. The results show that the carboxylated carbon nanofluids can enhance nucleate boiling heat transfer. In the range of test concentration, the enhancement rate increases sharply with the increase of heat flux, and stabilizes with the increase of heat flux when the heat transfer is low. When the mass ratio ω is 0.10%, the power is 210.6 kW.m -2 ), The strengthening rate reached the maximum of 138.3%. The thermal conductivity of the fluid increased with the increase of mass concentration, and the thermal conductivity of 0.15% concentration was 1.18 times that of pure water. It is considered that the changes of surface tension, nanoparticle deposition, nanoparticle perturbation and thermal conductivity of nanofluids are all the factors affecting the boiling of water-based carboxylated carbon nanofluids. The conclusion is validated by the high-speed imaging of 0.05% nanofluid boiling process.