초음파 진동을 이용한 빙축열 시스템의 아이스 슬러리 생성 연구

변성광(Byon, Sung-Kwang),공춘수(Gong, Chun-Su),김남웅(Kim, Nam-Woong) 한국산학기술학회 2013 한국산학기술학회논문지 Vol.14 No.2

아이스 슬러리는 유동성이 좋고 증발잠열이 커서 빙축열 시스템의 전열 유체로 선호되고 있다. 일반적으로 아이스 슬러리는 과냉각된 유체로부터 생성되는데, 동결이 과할 경우 배관을 막히게 하는 단점이 있다. 더욱이 아이 스 슬러리 생성을 쉽게 하기 위해 과냉각온도를 낮출 경우 빙축열 시스템의 효율을 떨어뜨리기도 한다. 따라서 아이 스 슬러리 생성을 효율적으로 제어할 수 있는 방법이 요구되고 있다. 본 논문에서는 초음파 진동에 의해 과냉각수에 캐비테이션 충격을 가하여 아이스 슬러리를 생성하는 새로운 방식의 빙축열 시스템에 관한 실험연구를 수행하여, 초 음파 진동과 아이스 슬러리 생성과의 상관관계를 규명하고, 초음파 진동이 아이스 슬러리 생성을 성공적으로 촉진할 수 있음을 확인하였다. Ice slurry that is a mixture of fine ice crystals and liquid water is a widely used working fluid in the ice thermal energy storage system due to its flowability and large latent heat of fusion. Generally ice slurry is made from supercooled water. But the excessive supercooling causes the water to freeze even worse to block the pipe. Additionally large degree of supercooling of water degrades the efficiency of the ice thermal energy storage system. Therefore the effective method to control the phase change from supercooled water to ice slurry is needed. In this paper we experimentally studied a novel method to generate the ice slurry from the supercooled water using the ultrasonic vibration. It was found that the cavitation impact of supercooled water by ultrasonic vibration can help the generation of ice slurry.

근사 최적화 방법을 이용한 사출금형 설계에 관한 연구

변성광(Sung-Kwang Byon),최하영(Ha-Young Choi) 한국기계가공학회 2020 한국기계가공학회지 Vol.19 No.6

The injection molding technique is a processing method widely used for the production of plastic parts. In this study, the gate position, gate size, packing time, and melt temperature were optimized to minimize both the stress and deformation that occur during the injection molding process of medical suction device components. We used a central composite design and Latin hypercube sampling to acquire the data and adopted the response surface method as an approximation method. The efficiency of the optimization of the injection molding problem was determined by comparing the results of a genetic algorithm, sequential quadratic programming, and a non-dominant classification genetic algorithm.

듀얼 레일 형상에 적합한 철도차량의 차륜 형상 설계

변성광(Sung-Kwang Byon),이동형(Dong-Hyeong Lee),최하영(Ha-Young Choi) 한국기계가공학회 2017 한국기계가공학회지 Vol.16 No.3

When a wheel profile of a train-tram is designed, both train and tram tracks should be considered. This study designed a wheel profile that enables high-speed driving(200km/h) on the train track and low speed driving on the tram track with multiple sharp curves. The study used the approximation optimization method to reduce cost and time, used the sequential quadratic programming method as the optimized algorithm, and the central composite design and response surface method as an approximate model. The optimized wheel shape based on this approximation optimization method reduced wear of the initial wheel showed a better performance in terms of derailment and lateral force.

압입축의 파손 저감을 위한 설계 방법에 대한 연구

변성광(Sung-Kwang Byon),최하영(Ha-Young Choi),이동형(Dong-Hyung Lee) 한국기계가공학회 2021 한국기계가공학회지 Vol.20 No.5

A press-fitted shaft is an essential part used in industrial machines, and it is generally used to transmit large quantities of power. Very high contact pressure occurs at the end parts of the contact between the shaft and boss, which are press-fitted shaft components. Such contact pressure not only damages the contact surface of a press-fitted shaft but also reduces its fatigue strength. To improve a press-fitted shaft’s fatigue strength, the contact pressure on the contact surface, which directly affects the fatigue strength, should be minimized. Thus, in this study, the design configuration optimization of the end part of the boss was based on the approximate optimization method and was aimed at minimizing the contact pressure at the end of a press-fitted shaft. Comparison of the contact pressure and the contact stress of a conventional press-fitted shaft with those of the optimized press-fitted shaft showed that the boss design of the optimized press-fitted shaft effectively improved the fatigue life.

의료용 베드 헤드 콘솔의 강도조건을 고려한 최적 설계

변성광(Sung-Kwang Byon),최하영(Ha-Young Choi),이봉구(Bong-Gu Lee) 한국기계가공학회 2016 한국기계가공학회지 Vol.15 No.3

Medical bed head consoles (BHC) are generally used to increase the efficiency of medical equipment and speed the medical treatment response time. The BHC design has been consistently improved including a movable shelf unit that is embedded to mount stably medical instruments on the lower part of the main console. The cost of a BHC can be reduced through design optimization to limit the overall weight. However, as the size of a head console might decrease due to design optimization, the BHC deflection could be increased. In this study, multi-objective optimal design was adopted to consider this BHC design problem. In order to reduce the cost of optimization planning, an approximate model was applied for the design optimization. In the context of approximate optimization, we used the response surface method and non-dominant sorting genetic algorithm developed from various fields. Multi-objective optimal solutions were also compared with a single objective optimal design.

모델재료를 이용한 범용 플랜지의 레이디얼 압출 공정설계

이상돈(Sang-Don Lee),변성광(Sung-Kwang Byon) 한국생산제조학회 2008 한국생산제조학회지 Vol.17 No.2

This study is to compare and analyze the material flow, deformation characteristics, and forming load of flange by means of similitude experimental method of model material using plasticine. In order to find optimal forming conditions, prototype experiments were designed to investigate forming characteristics of general-purpose flange under various working conditions. As a result of prototype experiments, billet thickness and gap-height ratio was found to be the most influential experimental parameter in flange forming. Forming loads from prototype experiments were compared to the results of finite element analysis after conducting estimation of forming loads of real material. Results of prototype experiments based on model material techniques are expected to be used as a basic data of die design for the development of products and process.

목분-폴리프로필렌 복합체의 상분리 및 기계적 특성에 관한 연구

이경희 ( Kyoung Hee Lee ),변성광 ( Sung Kwang Byon ) 한국고무학회 2013 엘라스토머 및 콤포지트 Vol.48 No.3

본 연구에서는 목분-고분자 복합체(Wood Flour-Polymer Composite, WPC)의 상분리 특성을 조사하고 이를 토대로 목분함량에 따른 WPC의 기계적 물성 변화에 관한 원인을 규명하였다. 이를 위해 고분자 매트릭스로 폴리프로필렌을 사용하여 서로 다른 함량의 목분을 갖는 시편을 제조하였다. 서로 다른 목분 함량을 갖는 시편들의 DSC thermogram으로부터 목분 함량에 따른 고분자 PP의 결정화 경향과 Tm 경향을 분석하였다. 목분 함량이 증가함에 따라 고분자 PP의 결정량 및 Tm값 모두 감소하다 다시 증가하는 결과를 나타내었다. 이로부터 낮은 목분 함량에서는 목분이 매트릭스인고분자 내에 분산되어 있으나 일정 목분 함량이상에서는 WPC의 매트릭스인 PP와 목분사이에 상분리가 일어남을 확인할수 있었다. 한편, WPC 시편의 인장강도는 목분 함량이 증가할수록 감소하는 결과를 나타내었다. 낮은 목분 햠량에서는 고분자에 분산된 목분과 고분자 사이에서의 낮은 계면 결합력과 시편내에서 강도를 높이는 역할을 하는 결정량의 감소가, 높은 목분 함량에서는 PP와 목분사이에서의 상분리로 인한 계면 결함이 WPC 시편의 인장강도를 목분함량 증가에 따라 지속적으로 감소시키는 원인이 되는 것으로 파악되었다. WPC 시편의 충격강도는 목분 함량이 증가함에 따라 증가하다가 목분 함량이 20%인 경우 최고값을 나타내며, 그 이후 다시 감소하는 경향을 나타내었는데, 낮은 목분 함량에서는 목분함량이 증가할수록 시편의 결정량이 감소하므로 시편의 취성 감소에 의해 충격강도가 향상되나, 높은 목분 함량에서는 고분자 매트릭스와 목분 사이의 상분리로 인해 다시 충격강도가 저하되기 때문인 것으로 판단된다. The phase separation in Wood Flour-Polymer Composite (WPC) was investigated and the reasons for change in mechanical properties with the content of wood flour were explored. The wood flour-polypropylene composite samples with different wood flour contents were prepared. From differential scanning calorimetry (DSC) thermograms of WPC samples, the trend of crystallinity and melting temperature (Tm) were analyzed. The crystallinity and melting temperature increased and then decreased as the content of wood flour increased. From these results, it was confirmed that at the low wood flour content the wood flours were dispersed into the polypropylene matrix but at the high wood flour content, the phase separation between polymer and wood flour phases appeared. The tensile strength of WPC samples was continuously decreased with the increase of wood flour content. At a low wood flour content, the low interfacial bonding and the decrease in crystallinity were the main reasons for the decrease in tensile strength with the increase of wood flour content. At a high wood flour content, the decrease in tensile strength resulted from the interfacial defects between the polymer and wood flour phases. The impact strength of the WPC sample showed the maximum behavior with the content of wood flour. At a low wood flour content, the impact strength was enhanced owing to the decrease in brittleness, which results from the decrease in crystallinity. At a high wood flour content, however, the impact strength decreased due to phase separation.

유한요소법을 이용한 수소충전용 압력용기의 균열에 관한 연구

조승현(Seunghyun Cho),최하영(Ha Young Choi),변성광(Sung Kwang Byon),김상현(Yun Tae Kim) 한국가스학회 2023 한국가스학회 학술대회논문집 Vol.2023 No.5

유한요소법을 이용한 수소충전용 압력용기의 균열진전 거동에 관한 연구

최하영(Ha Young Choi),조승현(Seunghyun Cho),변성광(Sung Kwang Byon),김윤태(Yun Tae Kim) 한국가스학회 2022 한국가스학회 학술대회논문집 Vol.2022 No.11

도넛형 축열시스템의 열전달 해석 연구

김명수(Myoung-Soo Kim),박성근(Sung-Geun Park),최형권(Hyoung Gwon Choi),용호택(Ho-Taek Yong),변성광(Sung-Kwang Byon) 한국유체기계학회 2006 유체기계 연구개발 발표회 논문집 Vol.- No.-

In this paper, the heat and fluid flow analysis of an ice thermal storage system has been performed for various ice-ball configurations in order to investigate the efficiency of the ice thermal storage system. It has been shown that the donut with bar type ice ball has a higher heat exchange rate than others. Furthermore, the effect of ice packing ratio and the inlet velocity of brine on the heat exchange rate is to be discussed.