氧化铜-碳纳米管/水混合纳米流体的光热性能屈健,张若梅,田敏

摘要

采用微波加热法制备了氧化铜(CuO)/水纳米流体,并在质量分数0~0.25%的CuO/水纳米流体中添加不同质量分数的多壁碳纳米管(MWCNT)得到 CuO-MWCNT/水混合纳米流体.借助分光光度计测试比较了不同浓度的CuO/水纳米流体和混合纳米流体的透射率随波长变化的情况,并通过闷晒实验对比研究了上述纳米流体的光热转换性能.结果发现,CuO/水纳米流体的透射率随着CuO质量分数的提高而下降,添加MWCNT可显著降低CuO/水纳米流体的透射率,混合纳米流体具有更好的光谱吸收特性.CuO/水纳米流体的光热转换性能随着CuO质量分数的提高而增强,与水相比光照45min后0.25%的CuO/水纳米流体温升提高了9.2℃.混合纳米流体的光热转化效果优于单一成分的CuO/水或MWCNT/水纳米流体,且与浓度大小密切相关:两种纳米材料浓度较低时,相互混合利于光热转化性能的提高;而当浓度较高时,添加某种纳米材料虽可以提高其光热转换性能,但添加浓度存在最佳值.本实验中,当 CuO 质量分数为0.05%和0.1%时,添加 MWCNT 的质量分数不宜超过0.005%;而当CuO质量分数继续增大为0.25%时,添加MWCNT质量分数不宜超过0.0015%,且存在最佳浓度.%Water-based CuO nanofluids were prepared by microwave heating method,and then multi-walled carbon nanotubes(MWCNTs)were dispersed into the aqueous suspensions of CuO to obtain hybrid CuO-MWCNT/H2O nanofluids with the CuO concentration ranging from 0 to 0.25%. The transmittances of CuO/H2O and hybrid nanofluids at different wavelengths were measured and compared,and their photo-thermal conversion performance were experimentally investigated as well. The results showed that the transmittances of CuO/H2O nanofluids decreased with the increase of mass fraction,and a significant reduction of transmittance was achieved after the addition of MWCNTs, indicating better solar energy spectral absorption property of hybrid nanofluids as compared with single nanofluids. The photo-thermal conversion performance of CuO/H2O nanofluids was enhanced with the increase of CuO concentration. Compared with deionized(DI)water,the temperature of CuO/H2O nanofluids at a mass fraction of 0.25% was increased by 9.2℃ after a light irradiation time of 45min. Besides,the photo-thermal conversion performance of the hybrid nanofluids was superior to just CuO/H2O or MWCNT/H2O nanofluids and highly dependent on the nanomaterial concentration. In the present experiment,the mass fraction of added MWCNT should be less than 0.005% when the mass fraction of CuO was 0.05% or 0.1%,while the concentration of MWCNT should not exceed 0.0015% when the mass fraction of CuO was 0.25% and the optimal concentration of MWCNT with respect to best photo-thermal conversion performance was observed.