Flow study in magnetic micro-channel heat pipe

Since the magnetic field can provide an alternative driving force to help the condensed liquid traveling to the evaporating side of heat pipe, we can take advantage of this to enhance the performance of heat pipe. In order to enhance the performance of our next generation magnetic ferro-fluid heat pipe and further investigate the fluid motion in micro channels, experiments of a magnetic drop through a narrow passage are carried under various control parameters. The magnetic ferro-fluids we used are commercial light mineral oil-based ferro-fluids (EMG905) produced by Ferrotec Corp. The experiments have shown the process of a ferro-fluid drop passing through narrow passages with different sizes (diameters =0.3mm, 0.5 mm and 0.8mm) under various applied magnetic field strengths. The common characteristics are recorded in details, such as drop deformation, necking down, pinch-off, separation, and the formation of a satellite drop. Although the capillary driving force drops as the size of micro-channel increases, it is easier and faster for magnetic fluid to pass through larger size of micro-channel. Therefore, an optimized size or maybe several mixed-size micro-channels of magnetic heat pipe should be adopted for better performance. In addition, initial location of the magnetic field source (a coil of electromagnet) is also an important factor to be considered when a magnetic micro-channel heat pipe is designed. Last but not least, applying magnetic field to enhance the performance of heat pipe is now possible and practical. The magnetic flow motion is interesting and should be further studied with various thermal conditions. More theoretical analysis and simulations of the new idea is currently under development and some preliminary results with experimental data will be presented.