An experimental device was developed to measure the thermal conductivity of electrically conducting liquid based on the 3ω method.In this device，a line heater（Au）was patterned on the surface of a substrate（Pyrex glass），then a dielectric film（silicon nitride）was deposited to prevent the electrical leakage from the heater to the surrounding liquid.For the designed geometry，an analytic expression of the temperature oscillation of the heater was derived，and the effect of the dielectric film on the thermal-conductivity measurement was investigated.In the case that the thermal penetration depth was much larger than the heater widthFONT-SIZE: 10.5pt

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mso-fareast-theme-font: minor-fareast">ω法；绝缘层；多壁碳纳米管；纳米流体；热导率