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建立磁性纳米流体Fe3O4-H2O对流换热特性实验系统,研究有无外磁场、磁场强度、磁场方向,纳米粒子质量分数、轴向比等因素对磁性纳米流体对流换热系数的影响。实验结果表明:对流换热系数随磁场强度的增加而增大;当磁场方向与流体运动方向一致时,外磁场强化了对流换热过程;外磁场对低流速流体的对流换热过程影响比对高流速更为显著;外磁场作用于流体入口段时对流换热系数得到明显提高;质量分数范围α=0.6%~0.8%的Fe3O4-H2O纳米流体可有效强化其对流换热性能。
The experimental system of convective heat transfer of magnetic nanofluid Fe3O4-H2O was established, and the influence of external magnetic field, magnetic field strength, magnetic field direction, nanoparticle mass fraction and axial ratio on the convective heat transfer coefficient of magnetic nanofluids was investigated. The experimental results show that the convection heat transfer coefficient increases with the increase of the magnetic field strength. When the direction of the magnetic field is consistent with the direction of the fluid, the external magnetic field strengthens the convective heat transfer. The effect of the external magnetic field on the convective heat transfer of the low-velocity fluid The high flow rate is more significant. The convective heat transfer coefficient increases obviously when the external magnetic field acts on the fluid inlet section. Fe3O4-H2O nanofluid with the mass fraction of α = 0.6% -0.8% can effectively enhance the convective heat transfer performance.