Study On Thermophoretic Motion Of Nano Particles In Narrow Channel

Power demand is extremely increasing with the developing industry of the modern society. Some small particles will be released in the electricity developing processes, such as the smokes being released from the fossil-fueled power plant and fossil-fueled cars, material processing and some accident of nuclear power station. The small particles are bad for the environment and humanity health, especially the nanoparticles can get into the human’s body easily for their some nanometer characteristics, which is a great threatening for both plants and human. However, it is difficult for the modern technology to remove the nanoparticles effectively. It is meaningful to investigate the thermophoresis mechanism and effective removal ways.The theory model and experiment were made to investigated the thermophoresis mechanism of nanoparticles in a narrow rectangular channel. It was found that the motion of nanoparticles is in the free molecule region and transient region, and the nanoparticles move with "the second flow" characteristic. According to changing the flowing medium, temperature gradient, diameter of nanoparticle or the type of nanoparticles, the thermophoresis forces in different flow conditions were calculated. Therefore, the thermophoresis some characteristics of nanoparticles in a narrow rectangular channel were obtained.Self-reliance computer code of thermophoresis deposition mechanism was assessed and improved with the analytical results and the experimental data. The developed code was used to analyze thermophoresis deposition characteristics. It was calculated that, the higher temperature gradient of velocity field, the larger thermophoresis forces of nanoparticles in the free molecule region and transient region, and obviously larger than the other forces on the nanoparticles. The thermophoresis force increase with the temperature of bulk flow. Especially, the facial thermophoresis force has nothing to do with the nanoparticles diameter. In different gas flow but hydrogen, the nanoparticles’thermophoresis deposition rate increase with the temperature gradient, decrease with the mass flow rate, and increase with the nanoparticles’diameter up to a certain value then decrease. The thermophoretic deposition rate of nanoparticles decreased with the particle’s dimension firstly then increased in a hydrogen-nanoparticle flow.The experiment system has been built to measuring the diameter and axial velocity of the nanoparticles. According to the second flow theory, thermophoretic theory, turbulent flow theory, a new thermophoretic deposition mechanism and the added thermophoretic force put forward. It was concluded that the nanoparticles keep moving in a circulation of suspension-collision-deposition-collision-suspension in the rectangular channel, the nanoparticles would evaporate when the fluid temperature high enough and varied the local temperature field. So that, there is an added thermophoretic force on the nanoparticles, and accelerate the nanoparticles’deposition.