# A Study on the Improvement of Filter Performance to Remove Indoor Air Pollution
## 3 Conclusions  
A shape study was conducted on a physical over the range (OTR) filter used in general kitchens. A shape was proposed to improve the efficiency of the filter through simulation; physically proposed filters have the advantage of reducing pressure loss, and electrically  
Figure 18: Efficiency comparison of I-Filter (**a**) and S-Filter (**b**).  
proposed filters have the advantage of collecting ultrafine dust. The conclusions drawn from the experimental results can be summarized as follows.  
1. A simple baffle-type filter was selected as the basic filter by removing protrusions that cause high pressure loss from the previously studied chevron-type filter. The Coanda effect was applied to the basic baffle-type filter to adjust the flow rate and allow dust particles to flow on the wall surface of the dust collection filter. As a result, when the Coanda effect was applied, the efficiency increased by 7 to 15%. However, it is very inefficient to use in a typical kitchen.
2. In order to further increase the effect of the existing filter, a sub-filter was installed at the lower part of the main filter to serve as a turbulence generator. After simulating three types of filters, circular type, conical type, and droplet type, the circular-type sub-filter worked the best. The dust-collection efficiency is not much different, but it is increased by about 25%. These results show that sub-filters have a greater effect on efficiency than filters with the Coanda effect.
3. The simulation should ensure reliability throughout experiments. A wind tunnel test device suitable for the standard test method of the Korea Air Purifier Association was designed and manufactured. A filter used in the test was manufactured using a 3D printer, and particles were sprayed using di-Octyl-Phthalate. As a result, the filter to which the Coanda effect was applied achieved an error rate of about 10% compared to the simulation, and the filter to which the sub-filter was applied showed an error rate of about 2-7%. This demonstrates that the results of the simulation are somewhat reliable.
4. An electrostatic dust-collection filter was proposed to remove ultrafine dust that is difficult to remove with a physical filter. It was confirmed that ultrafine dust below PM2.5 can be removed. In addition, since there is no difference in the dust-collection efficiency according to the shape of the dust-collection filter, structural simplification is also possible. In the future, it is expected that a more realistic result will be obtained if the simulation is conducted so that it can be charged in real time according to the movement of the particles. In addition, we intend to secure the reliability of the simulations by manufacturing an actual electrostatic dust collection filter. The experimental device is also equipped with a sealed chamber for testing the purifying capacity system based on the test standards of the Korea Air Purifier Association, and thus it is judged that the reliability of the experiment can also be increased.  
Conceptualization, H.-G.K., S.-C.K. and L.-K.K.; methodology, L.-K.K., S.-C.K. and H.-G.K.; validation, Y.-S.K. and S.-C.K.; software, Y.-S.K.; formal analysis, S.-C.K.; investigation, Y.-S.K.; resources, Y.-S.K. and S.-C.K.; data curation, Y.-S.K.; writing--original draft preparation, Y.-S.K.; writing--review and editing, Y.-S.K. and S.-C.K.; visualization, Y.-S.K.; supervision, S.-C.K.; project administration, H.-G.K.; funding acquisition L.-K.K. and H.-G.K. All authors have read and agreed to the published version of the manuscript. This research was also supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. 2016 RIA6A1A03012069). This work was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2017R1D1A1B03036070). Not applicable. Not applicable. Not applicable. Not applicable. Not applicable. Not applicable. Conflicts of Interest: The authors declare no conflict of interest.