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采用“两步法”制备出不同浓度的TiO_2-H_2O纳米流体,选用紫外分光光度法对纳米流体的分散稳定性进行了评价,使用差示扫描量热仪对纳米流体以及基液去离子水的固液相变过程进行了测试。实验结果表明:纳米流体的分散稳定性随着TiO2粒子质量浓度的增大先增强后减弱;添加纳米颗粒可以促进去离子水的异质成核,减小其固液相变过冷度;随着纳米流体质量浓度的增大,过冷度先减小后增大、固液相变时间和相变潜热则先增加后减少。分析得出:纳米流体的分散稳定性越好,其发生固液相变所需的过冷度越小,相变时间越长,释放的相变潜热越多。
Different concentrations of TiO_2-H_2O nanofluids were prepared by the two-step method. The dispersion stability of the nanofluids was evaluated by ultraviolet spectrophotometry. The nanofluid and base liquid deionized by differential scanning calorimeter Water solid-liquid phase change process was tested. The experimental results show that the dispersion stability of nanofluids first increases and then decreases with the increase of the mass concentration of TiO2 particles. Adding nano-particles can promote the heterogeneous nucleation of deionized water and reduce the degree of undercooling of the solid-liquid phase. With the increase of nanofluid concentration, the degree of undercooling decreases first and then increases, while the solid-liquid phase transition time and latent heat increase first and then decrease. The analysis shows that the better dispersion stability of nanofluids, the lower the degree of undercooling required for the solid-liquid phase transition, the longer the phase transition time, the more latent heat of phase transition.