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표면플라즈몬공명 가시화 장치를 이용한 증발하는 이종혼합물 액적의 실시간 농도 가시화 기법 개발
정찬호,이형주,최창경,이형순,이성혁,Jeong, Chan Ho,Lee, Hyung Ju,Choi, Chang Kyoung,Lee, Hyoungsoon,Lee, Seong Hyuk 한국분무공학회 2021 한국액체미립화학회지 Vol.26 No.4
The present study aims to develop the Surface Plasmon Resonance (SPR) imaging system facilitating the real-time measurement of the concentration of evaporating binary mixture droplet (BMD). We introduce the theoretical background of the SPR imaging technique and its methodology for concentration measurement. The SPR imaging system established in the present study consists of a LED light source, a polarizer, a lens, and a band pass filter for the collimated light of a 589 nm wavelength, and a CCD camera. Based on the Fresnel multiple-layer reflection theory, SPR imaging can capture the change of refractive index of evaporating BMD. For example, the present study exhibits the visualization process of ethylene glycol (EG)-water (W) BMD and measures real-time concentration change. Since the water component is more volatile than the ethylene glycol component, the refractive index of EG-W BMD varies with its mixture composition during BMD evaporation. We successfully measured the ethylene glycol concentration within the evaporating BMD by using SPR imaging.
CO<SUB>2</SUB> 하이드레이트를 이용한 냉방 시스템의 냉방 성능에 관한 실험적 연구
최성(Sung Choi),김솔(Shol Kim),최창경(Chang Kyoung Choi),강용태(Yong Tae Kang) 대한설비공학회 2017 대한설비공학회 학술발표대회논문집 Vol.2017 No.6
COS capture using the CO2 hydrate formation is considered as a promising method of Carbon Capture, Utilization and Storage (CCUS) technology. CO2 hydrate can be used as a secondary refrigerant of district cooling system with several advantages. By adding tetrahydrofuran (THF), equilibrium condition of CO2 hydrate can be changed into suitable condition for CO2 hydrate cooling system. Since CO2+THF hydrate is found to be suitable for secondary refrigerant of the cooling system, the dissociation enthalpy of CO2+THF hydrate with THF concentration of 1.5 mol% is measured, which is about 440.8 kJ/kg. As a result of lab-scale CO2 hydrate cooling experiment, the system is operated for 10 mins until blockage occurs, and the maximum coefficient of performance (COP) is estimated 4.17.
구리 표면의 젖음성에 따른 착상 특성에 관한 실험 연구
정찬호(Chan Ho Jeong),최창경(Chang Kyoung Choi),이정호(Jung Ho Lee),이성혁(Seong Hyuk Lee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
The main aim of this study is to investigate the heat transfer characteristics and frosting phenomenon affected by the surface wettability on the low temperature surface. Two different copper surfaces – bare and polymer coated nano structured - were prepared for the experiments. Their static contact angles were 74˚ and 154˚, respectively. The temperature of the copper substrate was measured by using RTD, embedded inside small holes drilled at 1 ㎜ underneath the surface. During the phase change, the temperature of copper sample was remained in the -7.8±0.6 ℃ and the ambient temperature was set as 24±0.5 with the relative humidity 65±1%. Film condensation takes place because of high wettability of the bare copper surface. Frost crystals are immediately generated on the frozen condensate and grow in the vertical direction. On the other hand, dropwise condensates formed on the nano-structured copper surface remain as the supercooled liquid phase. After droplet freezes, frosting is triggered and propagates until covering the whole surface. The frosting is delayed on the superhydrophobic copper surface due to the lower surface free energy. Moreover, it was found that the heat flux from hydrophobic surface was higher than the case of hydrophilic surface in the same working conditions.
다중 액적의 인접 거리에 따른 내부 유동 및 접촉선 거동 특성
이형주(Hyung Ju Lee),최창경(Chang Kyoung Choi),이성혁(Seong Hyuk Lee) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6
Control of the particle deposition patterns using droplet evaporation is important in inkjet printing technology to enhance the resolution of the printed electronics. Internal flow and contact line motion of the droplets significantly affect the particle deposition patterns. Thus, this study aims to analyze the internal flow and contact line motion of multiple droplets considering adjacency of the droplets. Micro-particle image velocimetry(μ-PIV) and shadowgraph method are used to visualize the internal flow and side view of the droplets. Droplet adjacency affects the droplet evaporation time, causing suppressed evaporation rate compared to the single droplet due to the vapor shielding effect. The center droplet shows a longer evaporation time than the side droplets. The side droplets break the pinning near the center droplet due to the non-uniform evaporation flux causing the temperature differences along the liquid-air interface. Also, the internal flows of the droplets move to the higher evaporation flux region for the side and the center droplets.
다중 액적의 인접 거리에 따른 내부 유동 및 접촉선 거동 특성
이형주(Hyung Ju Lee),최창경(Chang Kyoung Choi),이성혁(Seong Hyuk Lee) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6
Control of the particle deposition patterns using droplet evaporation is important in inkjet printing technology to enhance the resolution of the printed electronics. Internal flow and contact line motion of the droplets significantly affect the particle deposition patterns. Thus, this study aims to analyze the internal flow and contact line motion of multiple droplets considering adjacency of the droplets. Micro-particle image velocimetry(μ-PIV) and shadowgraph method are used to visualize the internal flow and side view of the droplets. Droplet adjacency affects the droplet evaporation time, causing suppressed evaporation rate compared to the single droplet due to the vapor shielding effect. The center droplet shows a longer evaporation time than the side droplets. The side droplets break the pinning near the center droplet due to the non-uniform evaporation flux causing the temperature differences along the liquid-air interface. Also, the internal flows of the droplets move to the higher evaporation flux region for the side and the center droplets.