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조서현(Seohyun Cho),심창휘(Chang-Hwi Sim),김성진(Seong Jin Kim),정석(Seok Chung),문명운(Myoung-Woon Moon) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
Adhesion skimmer is widely used in diverse environmental and industrial fields, such as oil spill clean-up and primary treatment of industrial oily wastewater. The adhesion skimmer works by allowing oils to adhere to the oleophilic surface of a rotating drum, belt, or disk on the water surface. However, the adhesion-based mechanism is ineffective for collecting highly viscous oils, such as low-sulfur fuel oil (LSFO) that is increasingly being used under the IMO 2020 regulation, because they tend to slide off the skimmer surface by forming thick heavy clumps rather than an oil film. In the present work, we provide a hydrophilic ratchet skimmer that collects oil by scooping it rather than relying on the previous adhesion mechanism. The scooped oil then can be completely detached from the hydrophilic ratchet, without using an additional scraper, by inducing a capillary impulse on the ratchet tip, which prevents an oil fouling on the skimmer surface. The hydrophilic ratchet skimmer is found to produce a higher oil recovery rate than the traditional adhesion-type skimmer regardless of oil viscosity.
희박 유기증기의 박막 진공 증착률 예측 방법에 관한 수치적 연구
차중원(Jungwon Cha),김동원(Dong-Won Kim),조서현(Seohyun Cho),이영종(Youngjong Lee),김형민(Hyung Min Kim) 대한기계학회 2018 大韓機械學會論文集B Vol.42 No.11
OLED 생산 공정 중 가장 핵심은, 증착에 사용될 유기물질을 가열하고 진공에 가까운 상태의 증착기 내부로 분사하여 유기물을 승화시켜 기판에 10~100 Å 두께로 증착시키는 공정이다. 승화된 유기물은 매우 낮은 압력을 유지하고 있어 매우 희박한 상태이며, 따라서 증착량은 유기물의 유동에 많은 영향을 받게 된다. 본 연구에서는 매우 낮은 압력을 유지하고 있는 진공증착기 안에서 희박한 압축성 유동 상태인 유기물의 유동해석을 통해서 증착률을 예측하고자, 크누센수의 2차 차수를 갖는 Karniadakis 미끄럼모델을 적용한 해석방법을 제안하였다. 유기물의 Karniadakis 미끄럼모델의 계수는 DSMC해석과 Navier-Stokes 방정식 해석결과 비교를 통해서 결정하였으며, 공개코드 OpenFoam의 buoyantSimpleFoam에 Karniadakis 미끄럼모델이 적용된 유동해석을 통해서 크누센와 증착기판의 위치변화에 따른 증착률 변화를 예측하였다. The most important process for producing organic light-emitting diode (OLED) panels is to deposit the heated organic materials on the substrate at a 10–100-Å thickness in a vacuum chamber. The sublimed organic material in the chamber, which maintains a very low pressure, is in a very rarefied state, so the rate of deposition thickness on the substrate is greatly influenced by the flow patterns of organic materials. The Karniadakis slip model with the second order of Knudsen number is proposed to predict the deposition rate by analyzing the rarefied organic material flow in the low-pressure vacuum chamber. The coefficients of the Karniadakis slip model of organic materials were determined by comparing the DSMC and Navier-Stokes equation flow analysis. In this research, the slip model is applied to BuoyantSimpleFoam of OpenFoam to predict the change of the deposition rate with the change of the position and Knudsen number.