中文摘要：

进行了提高磁场中含四氧化三铁（Fe3O4）纳米磁性颗粒机油（磁性纳米流体）热导率的研究。在有或无超声波辅助的条件下,采用共沉淀法合成了不同粒度的Fe3O4磁性纳米颗粒,采用一种热常数分析仪对该磁性纳米流体的热导率进行了测定,探讨了纳米磁性颗粒粒度、体积分数以及背景磁场对磁性纳米流体导热性能的影响。实验结果表明,在外磁场中,磁性纳米流体所含Fe3O4纳米颗粒的体积分数越大,磁性颗粒粒度越小,磁性纳米流体的热导率越高;当磁场方向平行于温度梯度时更有利于提高磁性纳米流体的热导率。

英文摘要：

This paper investigated the enhancement of thermal conductivity of engine oil based magnetite（Fe3O4） nanofluids,which were prepared via a co-precipitation method with and without ultrasound assistance in the presence of external magnetic field.The thermal conductivity was determined using a thermal constants analyzer.Effects of particle size,particle volume fraction and magnetic field on the thermal conductivity ratio of the magnetic nanofluids were analyzed.The results show that the thermal conductivity can be enhanced with the finer magnetite particles used in the nanofluid at a greater particle volume fraction.In addition,the thermal conductivity enhancement was found to be related to magnetic field parallel to temperature gradient.