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纳米改性变压器油在导热性和介电强度上较普通变压器油均有显著提高，具有广泛的应用前景。针对纳米改性变压器油强化传热机理，采用粒子图像测试技术(particle image velocimetry，PIV)测试了纳米改性变压器油在直流电场下的流场分布，并与普通变压器油流场进行了对比分析。试品放在有机玻璃杯内，电极为相距1cm 的两圆形平面电极以产生均匀电场，示踪粒子为直径为10μm的中空玻璃球；流场测试平面为电极的中心面，分别施加10，15，20kV的直流高压。结果表明：纳米改性变压油在电场下的流场比普通变压器油流场更有规律性，流速场由正极板到负极板逐渐减慢，比普通变压器油在电场下平均流速更快，说明纳米颗粒的添加使得整个变压油的流动性质发生了变化，使得变压器油的散热效果更好，这也是纳米改性变压器油导热性增强的原因之一，并间接证明了双电层结构假设的正确性。“,”The transformer oil-based nanofluids has significant improvements in their thermal conductivity and dielectric strength than traditional transformer oil, so they have a wide prospect of application. In order to explore the mechanism of the thermal conductivity enhancement of transformer oil-based nanofluids, the flow field distribution of them under the DC voltage was measured by particle image velocimetry (PIV), and the results were compared with that of the traditional transformer oil. The test samples were placed in an organic glass and two circular planar electrodes for 1cm apart were placed in the center of the glass in order to produce a uniform electric field. The tracer particles were hollow glass spheres of 10 μm diameters. The flow field measurement profile was the center of the electrode plate and the test samples were applied DC 10kV, 15kV and 20kV, respectively. The results show that the flow field distribution of transformer oil-based nanofluids is more regular and the flow velocity is faster than those of the traditional transformer oil, and its flow velocity is gradually slowed down from the positive plate to the negative plate. It is concluded that the flow field property of the transformer oil-based nanofluids is changed due to the addition of nanoparticles, whichexplains why the heat dissipation effect of transformer oil-based nanofluids is enhanced. The assumption of the electric double layer structure is reasonable. The investigation provides a new idea for exploring the reasons for the enhancement of the thermal conductivity of transformer oil-based nanofluids.