A study on the particle deposition velocity according to surface roughness

Abstract

The mechanism for removing fine particles from an industrial field and the daily environment is very important. With the rapid development of the high-tech electronics industry leading the economy of South Korea, the importance of removing contamination from particles has increased, and as the national economic power has increased, the purchasing power of individuals has also increased. Individuals expectedly desire a good life in a clean environment beyond simply eating and drinking. However, their interest in breathing freely has also gradually increased as the right of an individual to breathe has become deprived by the impact of the increase in fine dust, which is a by-product of industrial development. Accordingly, research on methods for removing fine particles efficiently and economically is a task that the current generation must solve for the next one. Because there are many cases in which efficient and economic elimination of the cause or proactive prevention is difficult regardless of the cause, the present study examined a method for removing particles by depositing them and focused particularly on the mechanism of deposition. In this study, the degree of contamination deposited on the surface of the generated particles was evaluated using the index of particle deposition velocity. This is defined as the velocity ratio of the deposited particles for the number concentration of the particles generated. A high particle deposition velocity is associated with a high degree of contamination due to particle deposition. In contrast, a low deposition velocity implies that the degree of contamination due to the generated particles is low. If the degree of particle contamination can be measured accurately by understanding the particle deposition velocity at an industrial site, the productivity of the workplace will be increased and the health of workers there will be protected. In addition, it will provide significant assistance in promoting the respiratory health of people in terms of the living environment. In this study, a test on the amount of particle removal by an experimental method was conducted. To determine a wide range of degrees of particle deposition according to the change in surface roughness, the study focused on conducting research economically while reducing the experimental time. The objectives were to design a square deposition channel that can simulate the particles generated by the pollution generation mechanism in Korea at the laboratory scale and to sufficiently expose sandpaper to the particles. To this end, a design of a square deposition channel that produces an even flow and stable number of particles was proposed and built using ANSYS FLUENT Release 17.0, which is a commercial code for flow analysis. Selecting particles that fit the laboratory scale is important for quantitative evaluation, and an experiment was conducted with NaCl particles that generate particles with wide diameters. The surface roughness was relatively quantified, and the deposition surface was simulated by sandpaper, which is a material. Sandpaper was placed in three rows in the square deposition channel, and a horizontal flow containing NaCl particles was deposited on the sandpaper and allowed to leak. Particle deposition velocity was determined by measuring the number concentration of the particles on the front and rear sides of the sandpaper surface. The experiment confirmed that a change according to the degree of deposition of particulate matter is caused by the rough sandpaper. An experiment was conducted by simulating particles floating in air and varying surface roughness. The surface roughness was found to have an excellent effect on reducing the particles. In this study, NaCl particles were generated using an atomizer. Based on the results of the airflow analysis, a square deposition channel, which exposes NaCl particles to the sandpaper, was designed and fabricated, and the particle deposition characteristics were compared for different sandpaper particle sizes. A total of four types of sandpapers were used in the experiment. The particle deposition velocity values, which can reflect the degree of particle deposition per unit area, were in the order of 600, 320, 180, and 040, which represents the order of denseness of the sandpaper surface. These results are considered to be affected by the surface roughness or the geometric factors. Based on this study, the use of a surface that deposits particles well is expected to help reduce the concentration of flying particles generated by ash scattering.