HEAT TRANSFER MECHANISM IN POROUS COPPER FOAM WICK HEAT PIPES USING NANOFLUIDS

Porous copper foam was combined with three nanofluids comprised of three types of nanoparticles, Al2O3, CuO, and SiO2 in order to develop a new type of heat pipe. The effects of factors, such as nanoparticles, filling ratio, and mass concentration, on the heat transfer performance of the heat pipe were investigated. Results showed that compared with water, the nanofluids improved the heat transfer performance of the heat pipe with varying degrees of success, and a low temperature difference was achieved. CuO nanofluids showed the best heat transfer enhancement, followed by Al2O3 and SiO2. This study mainly focused on Al2O3 nanofluids, considering stability and thermal conductivity. The thermal resistance of the heat pipe first decreased and then increased with the filling ratio; with a 50% filling ratio being considered optimal. The heat pipe performed well with a 50% filling ratio and a 0.5% mass concentration. Wick microstructures were also investigated with a scanning electron microscope to compare the heat transfer mechanism between the porous copper foam and the mesh wicks. Results indicated that adsorption of Al2O3 nanoparticles onto the copper surface increased the roughness of the heat transfer surface and increased the active nucleation site density.