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Effect of droplet size on the droplet behavior on the heterogeneous surface
최호연,손성완,박용갑,하만영 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.6
The characteristics of a three-dimensional hemispherical droplet on a heterogeneous surface were studied using the Lattice Boltzmannmethod (LBM). The hydrophilic surface has a hydrophobic part at the center. The hemispherical droplets are located at the center of theheterogeneous surface. According to the contact angles of hydrophilic and hydrophobic bottom surfaces, the droplet either separates orreaches a new equilibrium state. The separation time varies according to the change in droplet size, and it affects the status of dropletseparation. The droplet separation behavior was investigated by analyzing the velocity vector around the phase boundary line. The shapeand separation time of a droplet are determined by the contact angle of each surface. The speed of droplet separation increases as thedifference in contact angle increases between the hydrophobic surface and hydrophilic surface. The separation status and the separationtime of a droplet are also determined by the change of the droplet size. As the size of the droplet decreases, the effect of surface tensiondecreases, and the separation time of the droplet also decreases. On the other hand, as the droplet becomes larger, the effect of surfacetension increases and the time required for the droplet to separate also increases.
Numerical study on the effect of staggered wire electrodes in an electrostatic precipitator
최호연,박용갑,하만영 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8
In this paper, a numerical model is developed to describe the wire-plate electrostatic precipitator used in industrial application for air cleaning. The complex interactions between fluid dynamics, electric fields and particle dynamics are considered. Therefore, the combined Eulerian and Lagrangian approach is used in this study. In order to describe corona phenomena around high voltage electrode, electric field and ion current density field in electrostatic precipitator are numerically calculated using the iterative method for corona discharge model suggested by Kim [1]. The charging model suggested by Lawless [2] is used for the charging phenomena of particles by corona discharge because it was designed to predict combination effect of diffusion charge and field charge. The numerical model in this study is implemented by UDF in commercial software FLUENT and validated with experimental and numerical results from literatures. The effects of wire arrangement on electrostatic precipitator characteristics are investigated. Both inline and staggered arrangements of wire electrode have been considered for fixed value of gas velocity equal to 2 m/s. Applied voltage on wire electrode is varied in the range of 6 to 13 kV and particle diameter is 4 µm. For low voltage condition, staggered arrangement of wire electrode caused the turbulent effect so that the collection efficiency increases more than inline arrangement. However, the collection efficiency decreases in high voltage condition because electric force applied on particles passing between the wire electrodes is canceled out by both side wire electrodes.
최호연,이상민,이구연,Choi, Ho-Yeon,Lee, Sang-Min,Lee, Goo-Yeon 강원대학교 산업기술연구소 2011 産業技術硏究 Vol.31 No.2
Recently, smartphones have been widely used in wireless communications which caused severe data overload in cellular networks. Cellular companies consider increasing wireless data capacity in overloaded areas. Determining overloaded areas is mainly made from user reports which are currently collected by calling or simple apps by some active users experiencing overloads. Since the current reporting method is inconvenient and does not contain detail information about the overload conditions, and therefore is used by only some active users, the overloaded areas determined from the reports are not likely to be accurate. Therefore, we need a new reporting method which is convenient enough for even inactive users to willingly report the overload condition and which delivers detail information about the overloads. In this paper, we design and implement a measurement function of smartphone's WCDMA communication quality including overload condition and management system of mobile wireless communication networks about smartphones' communication quality.
최호연,Jae Hyun Oh,박만수,Sai Kee Oh,박용갑,하만영 대한기계학회 2021 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.35 No.4
A numerical simulation was carried out to investigate the cooling performance and thermal comfort of a 4-way cassette air conditioner when its vanes are positioned at constant angles of 30°, 40°, 50° and 60° and swinging with a constant angular velocity. The indoor airflow characteristics and thermal comfort were evaluated. The average room temperature variation with respect to time have a good agreement with the measured data with a maximum relative error of 2 %. The average room air temperature variation according to time shows that the case of swinging vane is increased by 5.9 %, compared to the case of fixed vane angle of 60°, due to the enhancement of heat transfer by the swinging motion of discharged airflow. Moreover, the flapping discharged airflow resulting from the swinging motion makes occupants feel thermally more comfortable, based on thermal comfort indices.
수산 발효 식품 제조에 관한 연구 : 1. 어육 발효조의 설계 1. A Model Design of Fermentor
崔浩然,李康鎬,崔雄 釜山水産大學校 1971 釜山水産大學 硏究報告 Vol.11 No.1
In Korea, fermented fish has been playing an important role as a preserved and flavor rich food. It is said that the digestion of fish protein is due to both action of intrinsic(autolytic enzymes) and bacterial enzymes in fish. The mass production of fermented fish has been impeded since traditional method of fermentation requires a long duration for a complete digestion. A high concentration of salt and unsanitary condition are also considered disadvantages of the old method. To improve the quality of the product and to develop mechanized process of fermentation, fermentors which have such control device as temperature, pH and agitation control system have been urgently needed, In this study, a model design of a fermentor is studied. The calculation was based on the optimum conditions for enzymatic hydrolysis of fish protein which involve temperature, pH, viscosity and other factors.
최호연(Hoyeon Choi),김성혁(Sunghyuk Kim),윤정수(Jungsoo yoon),윤영빈(Yungbin Yoon) 한국추진공학회 2009 한국추진공학회 학술대회논문집 Vol.2009 No.11
본 연구는 케로신-LOX를 연료와 산화제로 하는 액체로켓엔진의 가스발생기용 스월 동축형 인젝터의 리세스 길이에 따른 분무특성 파악을 목표로 하였다. 리세스 길이에 따른 두 추진제의 혼합 형태가 내부 혼합, 팁 혼합, 외부 혼합 등으로 분류되고, 인젝터 외부의 분무안정성에 영향을 미치므로 분무특성과 큰 연관성을 가진다. This paper presents experimental results of Recess Characteristic of Swirl Coaxial Injector of fuel-rich gas generators. It was revealed that the internal impinging phenomenon played an important role in the spray characteristics, such as spray angle and breakup length.