ZrO_2-水纳米流体管内层流的传热特性

制备了粒径为50 nm的ZrO2-水纳米流体,并通过添加分散剂NH4PAA改善纳米流体的稳定性。测量了4种不同质量分数(0.2%,0.4%,0.8%,1.2%)的ZrO2-水纳米流体在层流状态下的对流换热系数。实验结果表明:在相同雷诺数下,纳米流体的换热系数要比纯水的有所提高,并随着ZrO2纳米颗粒质量分数的增加而增大。当纳米流体的质量分数为0.2%,0.4%,0.8%,1.2%时,其平均换热系数比纯水分别提高了1.9%,2.4%,5.2%和8.8%。实验管道内的不同位置也影响纳米流体换热系数的提高,入口段的换热系数要比充分发展段提高得更明显,其主要原因是纳米颗粒对流体边界层的干扰。

Heat transfer characteristics of ZrO2-water nanofluid with laminar flow in tube

Making the ZrO2-water nanofluid with particle size of 50 nm,and improving the stability of nanofluid by adding the dispersant-NH4PAA.The convective heat transfer coefficients with four different mass fractions(0.2%,0.4%,0.8%,1.2%) of ZrO2-water nanofluids were measured under laminar flow conditions.The experimental results show that the heat transfer coefficient of nanofluids becomes higher than that of pure water at the same Reynolds number,and increases with the increasing of the mass fraction of ZrO2 nanoparticles.When the mass fractions of nanofluid are 0.2%,0.4%,0.8%,1.2%,the average convection heat transfer coefficient of which is increased by 1.9%,2.4%,5.2% and 8.8% respectively compared with that of pure water.The enhancements of convective heat transfer coefficients are different in the different positions of experimental pipeline.The nanofluid heat transfer coefficient of entrance section is increasing more obviously than that of the fully developed section,and the main reason is due to the nanoparticles′ disturbance to the fluid boundary layer.