| Summary: | 碩士 === 中原大學 === 機械工程研究所 === 102 === This thesis conducts an analysis of the flow and thermal fields and their corresponding characteristics of the magnetic nanofluids in a microtube. The main purpose is to investigate the influences of microtube length, particle volume fraction, and external magnetic field strength on the fluid velocity, temperature, pressure, pressure drop, flow drag, and heat transfer rate. First, we complete the preparation of water-based magnetite (Fe3O4) nanofluids and the determination of their material properties. Further, we apply mass, momentum, and energy conservation equations as well as the boundary conditions to establish the thermal-flow field mode, which can be verified by the comparison of the experimental data with theoretical results. Finally, the flow and thermal fields and the correspeonding characteristics of nanofluids in a microtube are numerically analyzed by using the marching implicit (MI) method.
The results reveal that when the tube length increases, the velocity, pressure and temperature fields tend to be fully developed. Also, the pressure drop tends to increase, but the flow drag tends to a fixed value. As the particle volume fraction increases, the average flow drag increases but the average heat transfer rate decreases. As the the external magnetic field increases, the average flow drag increases and the average heat transfer rate also increases in the general case.
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