Abstract: The heat transfer effect of nanofluid in electric heater was studied. Fe3O4⁃water nanofluid was prepared by two⁃step method. The effect of Fe3O4⁃water nanofluid with various nanoparticle concentrations (mass fraction of 0.1%~2.0%) on heating efficiency of the electric heater with or without magnetic field was studied. Mechanism of enhanced heat transfer by Fe3O4⁃water nanofluids under a magnetic field was also discussed. Results show that the Fe3O4⁃water nanofluid with a mass fraction of 1.0% obtains 18.2% enhancement of heat transfer on environment temperature compares to without a magnetic field. The Fe3O4⁃water nanofluid with a mass fraction of 1.0% obtains 35.1% enhancement of heat transfer on environment temperature with an external magnetic field. This research provides an important reference for enhancements of natural convective heat transfer in nanofluid applications.

Key words: Electric heater, Nanofluid, Magnetic field, Natural convection, Heat transfer enhancement

摘要： 对电加热器中纳米流体的传热效果进行了实验研究，采用两步法制备Fe3O4⁃水纳米流体。此外，还研究了质量分数为0.1%~2.0%的Fe3O4⁃水纳米流体在有/无磁场作用下对电加热器换热效率的影响，探讨了磁场作用下纳米流体的强化换热机理。结果表明，与基液（去离子水）相比，无磁场时质量分数为1.0%的Fe3O4⁃水纳米流体可使环境温度提升18.2%；在外磁场作用下，质量分数为1.0%的Fe3O4⁃水纳米流体可使环境温度提升35.1%。研究结果可为纳米流体在电加热器中的强化传热研究提供重要参考。

关键词: 电加热器, 　纳米流体, 　磁场, 　自然对流, 　强化传热