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| Measurement of Thermal Conductivity of Magnetic Fluids under External Uniform Magnetic Field Using Transient Hot-wire Method |
| GU Bang-ming,WANG Zheng-liang,ZHANG Li-qiao,CHEN Shan-fei |
| Institute of Applied Physics Zhejiang Wanli University, Ningbo, Zhejiang 315101, China |
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Abstract Polymeric α-olefin based magnetic fluids sealed in two glass tubes were placed in external magnetic field. To eliminate the end effect and the natural convection induced by magnetic field force and gravity force, the transient hot-wire (THW) instrument was developed for accurate measurements of the thermal conductivity of magnetic fluids. The hot-wire apparatus was calibrated utilizing distilled water and anhydrous alcohol as reference fluids, which showed that the experimental system has a high accuracy. Effects of the direction of external magnetic field to the magnetic fluids with different volume fraction of suspended magnetic particles were measured. Results indicated that: when the direction of external magnetic field was parallel to the heat flow (the temperature gradient), the thermal conductivity of the magnetic fluid increased greatly. The conductivity increased almost linearly with the strength of the magnetic field, the higher the particle concentration, the more increment was. On the other hand, when the magnetic field was perpendicular to the heat flow, little change in the thermal conductivity was found.
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2011, Vol. 32 
