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The effects of coolant channels on Large-scale Polymer Electrolyte Fuel Cells (PEFCs)
Hyunchul Ju,Chao-Yang Wang,Wenbin Gu 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
Fully coupled simulations of two-phase transport in PEFC and heat transfer in coolant channels is performed, in order to investigate the effects of cooling channel configuration on the distributions of temperature and water within PEFCs. When the practical coolant flow rate is applied to large-scale cells for automotive applications, significant coolant temperature rise is expected from the coolant inlet to outlet, particularly under the high current density operation, creating the significant cell temperature gradient along the flow direction as well. Consequently, two-phase water profile resulting from evaporation¬condensation processes inside PEFCs is also strongly influenced by cell temperature gradient from the hot coolant inlet toward cold coolant outlet regions, demonstrating that both temperature and liquid saturation strongly depend on the thermal gradient along the coolant flow path.
고분자전해질형연료전지내 유로채널 최적화를 위한 수치적 연구
주현철(Hyunchul Ju) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
The performance and durability of Polymer Electrolyte Fuel Cells (PEFCs) are strongly influenced by the uniformity of current density, temperature, species distributions inside a cell In order to obtain uniform distributions in them, the optimal design of flowfield must be a key factor. In this paper, the numerical study of land/channel flowfield optimizations is performed, using a multi-dimensional, multi-phase, non-isothermal PEFC model. The simulation results indicate the effects of contact resistance variation along the in-plane direction and oxygen depletion near the land region considerably alter the uniformity of current density and oxygen distributions.
고분자전해질형연료전지의 가스 채널 최적화를 위한 수치적 연구 (Ⅱ)
주현철(Hyunchul Ju),남진무(Jinmoo Nam) 대한기계학회 2009 大韓機械學會論文集B Vol.33 No.9
Using the multi-dimensional, multi-phase, nonisothermal Polymer Electrolyte Fuel Cell (PEFC) model presented in Part I, the effects of land/channel flow-field on temperature and liquid saturation distributions inside PEFCs are investigated in Part II. The focus is placed on exploring the coupled water transport and heat transfer phenomena within the nonisothermal and two-phase zone existing in the diffusion media (DM) of PEFCs. Numerical simulations are performed varying the land and channel widths and simulation results reveal that the water profile and temperature rise inside PEFCs are considerably altered by changing the land and channel widths, which indicates that oxygen supply and heat removal from the channel to the land regions and liquid water removal from the land toward the gas channels are key factors in determining the water and temperature distributions inside PEFCs. In addition, the adverse liquid saturation gradient along the thru-plane direction is predicted near the land regions by the numerical model, which is due to the vapor-phase diffusion driven by the temperature gradient in the nonisothermal two-phase DM where water evaporates at the hotter catalyst layer, diffuses as a vapor form and then condenses on the cooler land region. Therefore, the vapor phase diffusion exacerbates DM flooding near the land region, while it alleviates DM flooding near the gas channel.
Kim Hyunchul,Byeon Sun-ju,Kim Cheol Hong,Bae Young-A,Lee Heesung,Kim Hyun Soo 대한진단검사의학회 2021 Annals of Laboratory Medicine Vol.41 No.1
Dear Editor, Rhodotorula species, belonging to the family Sporidiobolaceae, are yeasts that are present in the environment and can cause opportunistic infections in immunocompromised patients [1, 2]. Among Rhodotorula species, only R. mucilaginosa, R. glutinis, and R. minuta have been reported to cause human infections [1, 2]. Rhodotorula sp. are mostly isolated from the blood of immunocompromised patients, where they cause fungemia or catheter-related infections. Only one case of pneumonia caused by R. mucilaginosa has been reported to date in an immunocompromised patient [3]. We report the first case of fungal pneumonia caused by R. mucilaginosa in an immunocompetent patient. The infection was confirmed by fungal ribosomal RNA (rRNA) sequencing using wedge-resected lung tissue.
Three-Dimensional Swimming Tadpole Mini-Robot using Three-Axis Helmholtz Coils
Choi, Hyunchul,Jeong, Semi,Lee, Cheong,Park, Bang Ju,Ko, Seong Young,Park, Jong-Oh,Park, Sukho 제어로봇시스템학회 2014 Transaction on control, automation and systems eng Vol. No.
Electromagnetic-actuated robotic systems have been studied recently for special purposes. Because these systems use external magnetic fields to control their robots, the robots can have simple structures and move with much freedom. In particular, these electromagnetic actuation (EMA) systems are being widely adopted for the actuation of biomedical mini-robots and microrobots for minimally invasive surgery (MIS) and diagnosis. We previously reported, as a feasible biomedical robot, the biomimetic swimming tadpole mini-robot, which can only swim above water. Indeed, the two-dimensional (D) plane swimming tadpole mini-robot is limited in its use because of its motility in the 2D plane. Therefore, this paper proposes a 3D swimming tadpole mini-robot that can move freely in water. First, in the proposed 3D swimming tadpole mini-robot, the buoyancy force was regulated for subaqueous swimming, and the permanent magnet was rearranged for precise movement. Second, to attain a 3D swimming motion, the actuation mechanism of the robot was developed using an EMA system. Finally, various experiments verified that the proposed 3D swimming tadpole mini-robot can swim freely in a 3D water environment.