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1. The magnetic field at the center of the housing end face of a high-gradient magnetic filter developed for treating high-viscosity gear oil was tested under different temperatures. The results showed that the magnetic field strength at 70°C was only about 1/4 of that at 18°C. This test did not take into account the effect of insulation time, but it is sufficient to demonstrate that the magnetic field of the high-gradient magnetic filter is significantly affected by temperature. 2. By integrating cooling and purification functions through the relationship between the magnetic field strength of the high-gradient magnetic filter and temperature, permanent magnets can be placed in the cooling medium to keep them at low temperatures and maintain their high magnetic properties, thereby improving the efficiency of high-gradient magnetic purification. 3. A rough heat exchange surface improves the efficiency of heat transfer. The particles captured by magnetic purification are mostly iron-based wear debris; by placing magnets in the cooling water pipes, some of these particles get attracted to the outer surface of the pipes. These particles on the heat exchange surface act as a rough surface for heat transfer, preventing the formation of a boundary layer and thus helping to further enhance heat transfer efficiency. When the permanent magnets in the cooling pipes are removed, the particles lose their adhesive force, making it easy to clean the surfaces. 4. Development and performance testing of the shell-and-tube cooling purifier: By integrating porous media-enhanced heat transfer technology with high-gradient magnetic purification technology, a shell-and-tube cooling purifier was developed. The structural schematic is shown; the polymagnetic porous media consists of slender filaments made from amorphous soft magnetic alloys, with a thickness of 0.04 mm and a width of 0.5 mm. All other components are made of stainless steel to avoid affecting the magnetic field. Permanent magnets are placed within the water pipes and the central tube, with their identical pole faces facing each other, allowing the magnetic field lines to extend outward. This enables thorough magnetization of the ferromagnetic porous medium. Gaps in the tube walls allow cooling water to flow through, thus functioning as heat transfer tubes as well. At the same time, the permanent magnets are cooled as well. Filter performance tests show that under the same conditions, a conventional magnetic filter has a filtration efficiency of only 1.38 for particles larger than 1 μm, resulting in a filtration efficiency of 27%. In contrast, the newly developed shell-and-tube type cooling purifier achieves a filtration efficiency of 84% for particles larger than 1 μm; thus, its filtration efficiency is 2.1 times higher than that of the conventional magnetic filter. The convective heat transfer coefficients on the shell side of the newly developed cooling purifier are compared with those of existing products. This also shows a comparison of the performance of this cooling purifier with the SL307 oil cooler and the TSO306 oil cooler. At a Reynolds number of 2000, the shell-side convective heat transfer coefficient T of the cooling purifier is 19.7% higher than that of SL307, and 3% higher than that of TS306.