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Kwang-Yong Kim is currently an Inha Harlim Professor in the Department of Mechanical Engineering and was a Dean of Engineering College of Inha University, Incheon, Korea. He was also an associate editor of ASME Journal of Fluids Engineering. He served as the co-editor-in-chief of the International Journal of Fluid Machinery and Systems, the editor-in-chief of the Transactions of Korean Society of Mechanical Engineers, the president of Korean Society for Fluid Machinery, and the chairman of the Asian Fluid Machinery Committee. He is a fellow of the Korean Academy of Science and Technology, a member of National Academy of Engineering of Korea, a fellow of the American Society of Mechanical Engineers (ASME), an associate fellow of the American Institute of Aeronautics and Astronautics (AIAA), and a recipient of order of science and technology merit, “Doyak Medal” from Republic of Korea.
The present work investigated the effects of bending the outlet nozzles of fluidic oscillators installed on the NACA0015 airfoil with a flap on the flow control performance and, thus, the aerodynamic performance of the airfoil. The effects of bending on fluidic oscillators have not been reported so far in previous works. The aerodynamic analysis was performed numerically using unsteady Reynolds-averaged Navier-Stokes equations. Three different cases were considered: Case 1 changes only the bending angle with a fixed pitch angle, Case 2 changes only the pitch angle without bending, and Case 3 changes both the bending and pitch angles. Although the bending of the oscillators was introduced inevitably due to a geometrical limitation in the installation, the results indicated that the bending rather improved the lift coefficient and lift-to-drag ratio of the airfoil by improving the characteristics of the fluidic oscillators, such as the jetting angle and peak velocity ratio.
Nam-Hun Kim; Kwang-Yong Kim. Effects of Bending of Fluidic Oscillators on Aerodynamic Performance of an Airfoil with a Flap. Processes 2021, 9, 1429 .
AMA StyleNam-Hun Kim, Kwang-Yong Kim. Effects of Bending of Fluidic Oscillators on Aerodynamic Performance of an Airfoil with a Flap. Processes. 2021; 9 (8):1429.
Chicago/Turabian StyleNam-Hun Kim; Kwang-Yong Kim. 2021. "Effects of Bending of Fluidic Oscillators on Aerodynamic Performance of an Airfoil with a Flap." Processes 9, no. 8: 1429.
A fluidic oscillator with a bent outlet nozzle was investigated to find the effects of the bending angle on the characteristics of the oscillator with and without external flow. Unsteady aerodynamic analyses were performed on the internal flow of the oscillator with two feedback channels and the interaction between oscillator jets and external flow on a NACA0015 airfoil. The analyses were performed using three-dimensional unsteady Reynolds-averaged Navier-Stokes equations with a shear stress transport turbulence model. The bending angle was tested in a range of 0–40°. The results suggest that the jet frequency increases with the bending angle for high mass flow rates, but at a bending angle of 40°, the oscillation of the jet disappears. The pressure drop through the oscillator increases with the bending angle for positive bending angles. The external flow generally suppresses the jet oscillation, and the effect of external flow on the frequency increases as the bending angle increases. The effect of external flow on the peak velocity ratio at the exit is dominant in the cases where the jet oscillation disappears.
Nam-Hun Kim; Kwang-Yong Kim. Effects of Bent Outlet on Characteristics of a Fluidic Oscillator with and without External Flow. Energies 2021, 14, 4342 .
AMA StyleNam-Hun Kim, Kwang-Yong Kim. Effects of Bent Outlet on Characteristics of a Fluidic Oscillator with and without External Flow. Energies. 2021; 14 (14):4342.
Chicago/Turabian StyleNam-Hun Kim; Kwang-Yong Kim. 2021. "Effects of Bent Outlet on Characteristics of a Fluidic Oscillator with and without External Flow." Energies 14, no. 14: 4342.
The paper presents a numerical investigation on the junction flow occurring at the intersection between a wall and a protruding circular cylinder. Simulations of flow for Reynolds number ( Re) in the range [125 - 20000] have been carried out using OpenFOAM, an open source CFD tool. Plots of stream tracers have been used to qualitatively characterize the flow topology as either attachment or separation based on the type of singular points, classified as nodes and saddle points. Quantitative variations of momentum flux have been applied to identify a key mechanism for the transition of topology using the relative momentum strength of the incoming and reverse flow. Effect of a thinner boundary layer has been assessed by (i) imposing a reduced wall shear stress, and (ii) increasing the Reynolds number. Features of a typical unsteady flow, in the transition regime, at Re = 20000 have been predicted using Large Eddy Simulation (LES) with a one-equation eddy viscosity sub-grid scale model. Description of the time evolution of the topology at Re = 20000 has been able to validate the one-equation model in OpenFoam as well as to further validate the key mechanism identified for topology transition.
R Abhilash; Kwang-Yong Kim; S Anil Lal. Topological investigation of junction flow between cylinder and flat plate. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 2021, 1 .
AMA StyleR Abhilash, Kwang-Yong Kim, S Anil Lal. Topological investigation of junction flow between cylinder and flat plate. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science. 2021; ():1.
Chicago/Turabian StyleR Abhilash; Kwang-Yong Kim; S Anil Lal. 2021. "Topological investigation of junction flow between cylinder and flat plate." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science , no. : 1.
The seasonal performance has become increasingly important for residential heat pumps which occupy a majority of household power consumption. Thus, the heat pump system and its components are requested to be re-designed with reflecting the part load characteristics. Furthermore, actuators should be optimally operated for each test condition to maximize system efficiency. Among them, indoor and outdoor fan speeds are the only variable that can be independently controlled and have the widest operation range. Therefore, in this study, a non-iterative heat pump simulation model is presented to precisely predict the optimum air flow rate for each part load condition by introducing the modified effectiveness. The non-dimensional correlation is developed for the modified effectiveness and semi-empirical efficiency models are utilized for estimating the compressor performance. Validating experiments identify that the model can predict the optimum air flow rate for various part load conditions within an error of 10%. Consequently, the optimum air flow rate can be instantly obtained for various operating conditions.
Minsu Park; Yong Hwan Eom; Min Soo Kim. Predictive optimization of the air flow rate for a residential heat pump in seasonal performance conditions. International Journal of Refrigeration 2021, 1 .
AMA StyleMinsu Park, Yong Hwan Eom, Min Soo Kim. Predictive optimization of the air flow rate for a residential heat pump in seasonal performance conditions. International Journal of Refrigeration. 2021; ():1.
Chicago/Turabian StyleMinsu Park; Yong Hwan Eom; Min Soo Kim. 2021. "Predictive optimization of the air flow rate for a residential heat pump in seasonal performance conditions." International Journal of Refrigeration , no. : 1.
An analytical model for predicting the performance of an organic Rankine cycle (ORC) system was reformulated. To do this, a constraint for operating temperature was newly proposed. Typically, based on the Carnot cycle, lots of performance equations for a power system have been derived. Besides, an adequate constraint for the operating temperature has been rarely considered in the previous studies. Those simplicities can increase the chance of error in predicting the performance properly. In this study, the analytical model is comprised of thermodynamic principles and several physical characteristics in the ORC system. Thereby, an analytical expression for the optimal condensation temperature was derived as a function of given parameters. The theoretical model was validated by comparing it with a numerical simulation. Results indicate that the predicted data from the theoretical model are in good agreement with the simulation data. The proposed theoretical model is applicable in the conceptual design of the ORC system or estimating the potential of thermal energy sources.
Hong Wone Choi; Min Soo Kim. A theoretical approach to predict the performance of organic Rankine cycle systems. Energy Conversion and Management 2021, 243, 114360 .
AMA StyleHong Wone Choi, Min Soo Kim. A theoretical approach to predict the performance of organic Rankine cycle systems. Energy Conversion and Management. 2021; 243 ():114360.
Chicago/Turabian StyleHong Wone Choi; Min Soo Kim. 2021. "A theoretical approach to predict the performance of organic Rankine cycle systems." Energy Conversion and Management 243, no. : 114360.
Membraneless microfluidic fuel cells (MMFCs) are being studied extensively as an alternative to batteries and conventional membrane fuel cells because of their simple functioning and lower manufacturing cost. MMFCs use the laminar flow of reactant species (fuel and oxidant) to eliminate the electrolyte membrane, which has conventionally been used to isolate anodic and cathodic half-cell reactions. This review article summarizes the MMFCs with six major categories of flow configurations that have been reported from 2002 to 2020. The discussion highlights the critical factors that affect and limit the performance of MMFCs. Since MMFCs are diffusion-limited, most of this review focuses on how different flow configurations act to reduce or modify diffusive mixing and depletion zones to enhance the power density output. Research opportunities are also pointed out, and the challenges in MMFCs are suggested to improve cell performance and make them practical in the near future.
Muhammad Tanveer; Kwang-Yong Kim. Flow Configurations of Membraneless Microfluidic Fuel Cells: A Review. Energies 2021, 14, 3381 .
AMA StyleMuhammad Tanveer, Kwang-Yong Kim. Flow Configurations of Membraneless Microfluidic Fuel Cells: A Review. Energies. 2021; 14 (12):3381.
Chicago/Turabian StyleMuhammad Tanveer; Kwang-Yong Kim. 2021. "Flow Configurations of Membraneless Microfluidic Fuel Cells: A Review." Energies 14, no. 12: 3381.
Jingkun Jiang; Maosheng Yao; Jungho Hwang; Can Wang. Bioaerosol: A Key Vessel between Environment and Health. Frontiers of Environmental Science & Engineering 2021, 15, 1 -1.
AMA StyleJingkun Jiang, Maosheng Yao, Jungho Hwang, Can Wang. Bioaerosol: A Key Vessel between Environment and Health. Frontiers of Environmental Science & Engineering. 2021; 15 (3):1-1.
Chicago/Turabian StyleJingkun Jiang; Maosheng Yao; Jungho Hwang; Can Wang. 2021. "Bioaerosol: A Key Vessel between Environment and Health." Frontiers of Environmental Science & Engineering 15, no. 3: 1-1.
During the last couple of decades, there have been rapid developments in analysis, design, and fabrication of micromixers
Kwang-Yong Kim. Editorial for the Special Issue on Analysis, Design and Fabrication of Micromixers. Micromachines 2021, 12, 533 .
AMA StyleKwang-Yong Kim. Editorial for the Special Issue on Analysis, Design and Fabrication of Micromixers. Micromachines. 2021; 12 (5):533.
Chicago/Turabian StyleKwang-Yong Kim. 2021. "Editorial for the Special Issue on Analysis, Design and Fabrication of Micromixers." Micromachines 12, no. 5: 533.
A casing treatment using inclined oblique slots (INOS) is proposed to improve the stability of the single-stage transonic axial compressor, NASA Stage 37, during operation. The slots are installed on the casing of the rotor blades. The aerodynamic performance was estimated using three-dimensional steady Reynolds-Averaged Navier-Stokes analysis. The results showed that the slots effectively increased the stall margin of the compressor with slight reductions in the pressure ratio and adiabatic efficiency. Three geometric parameters were tested in a parametric study. A single-objective optimization to maximize the stall margin was carried out using a Genetic Algorithm coupled with a surrogate model created by a radial basis neural network. The optimized design increased the stall margin by 37.1% compared to that of the smooth casing with little impacts on the efficiency and pressure ratio.
Tien-Dung Vuong; Kwang-Yong Kim. Stability Enhancement of a Single-Stage Transonic Axial Compressor Using Inclined Oblique Slots. Energies 2021, 14, 2346 .
AMA StyleTien-Dung Vuong, Kwang-Yong Kim. Stability Enhancement of a Single-Stage Transonic Axial Compressor Using Inclined Oblique Slots. Energies. 2021; 14 (9):2346.
Chicago/Turabian StyleTien-Dung Vuong; Kwang-Yong Kim. 2021. "Stability Enhancement of a Single-Stage Transonic Axial Compressor Using Inclined Oblique Slots." Energies 14, no. 9: 2346.
It is important to monitor the temperature and H2O concentration in a large combustion environment in order to improve combustion (and thermal) efficiency and reduce harmful combustion emissions. However, it is difficult to simultaneously measure both internal temperature and gas concentration in a large combustion system because of the harsh environment with rapid flow. In regard, tunable diode laser absorption spectroscopy, which has the advantages of non-intrusive, high-speed response, and in situ measurement, is highly attractive for measuring the concentration of a specific gas species in the combustion environment. In this study, two partially overlapped H2O absorption signals were used in the tunable diode laser absorption spectroscopy (TDLAS) to measure the temperature and H2O concentration in a premixed CH4/air flame due to the wide selection of wavelengths with high temperature sensitivity and advantages where high frequency modulation can be applied. The wavelength regions of the two partially overlapped H2O absorptions were 1.3492 and 1.34927 μm. The measured signals separated the multi-peak Voigt fitting. As a result, the temperature measured by TDLAS based on multi-peak Voigt fitting in the premixed CH4/air flame was the highest at 1385.80 K for an equivalence ratio of 1.00. It also showed a similarity to those tendencies to the temperature measured by the corrected R-type T/C. In addition, the H2O concentrations measured by TDLAS based on the total integrated absorbance area for various equivalent ratios were consistent with those calculated by the chemical equilibrium simulation. Additionally, the H2O concentration measured at an equivalence ratio of 1.15 was the highest at 18.92%.
Sunghyun So; Nakwon Jeong; Aran Song; Jungho Hwang; Daehae Kim; ChangYeop Lee. Measurement of Temperature and H2O Concentration in Premixed CH4/Air Flame Using Two Partially Overlapped H2O Absorption Signals in the Near Infrared Region. Applied Sciences 2021, 11, 3701 .
AMA StyleSunghyun So, Nakwon Jeong, Aran Song, Jungho Hwang, Daehae Kim, ChangYeop Lee. Measurement of Temperature and H2O Concentration in Premixed CH4/Air Flame Using Two Partially Overlapped H2O Absorption Signals in the Near Infrared Region. Applied Sciences. 2021; 11 (8):3701.
Chicago/Turabian StyleSunghyun So; Nakwon Jeong; Aran Song; Jungho Hwang; Daehae Kim; ChangYeop Lee. 2021. "Measurement of Temperature and H2O Concentration in Premixed CH4/Air Flame Using Two Partially Overlapped H2O Absorption Signals in the Near Infrared Region." Applied Sciences 11, no. 8: 3701.
The review article introduces the development in membraneless microfluidic fuel cells (MMFCs) focusing on the microchannel geometry and electrode architecture and arrangement. Lamination of fuel and oxidant streams in a microchannel lets an MMFC work without physical membrane. The lack of convective mixing across liquid–liquid interface of two streams forms a distinct diffusive mixing region, which acts as a pseudo membrane. The ions can transport across the channel through the mixing region to reach the other side of the channel and complete the ionic conduction. The advantage of MMFCs lies in the absence of the membrane, as the problems associated with the membrane are eliminated. The channel geometry and electrode architecture have been investigated extensively to eliminate the problems caused by the mixing and depletion regions, which affect the performance significantly, such as power and current densities. The absence of instabilities due to the convective mass transer along the channel allows streams containing different substances with different concentrations to flow side by side axially through a microchannel, whereas the reactant’s mass transfer across the channel in an MMFC is mainly diffusion-limited. This review article mostly focuses on how the channel and electrodes can be designed effectually to enhance the mass transfers by reducing mixing and depletion regions. Additionally, the current status of theoretical and computational modeling for MMFCs to improve the performance are discussed. Moreover, the key issues and main challenges for prospective development of MMFCs are presented.
Muhammad Tanveer; Eun Su Lim; Kwang-Yong Kim. Effects of channel geometry and electrode architecture on reactant transportation in membraneless microfluidic fuel cells: A review. Fuel 2021, 298, 120818 .
AMA StyleMuhammad Tanveer, Eun Su Lim, Kwang-Yong Kim. Effects of channel geometry and electrode architecture on reactant transportation in membraneless microfluidic fuel cells: A review. Fuel. 2021; 298 ():120818.
Chicago/Turabian StyleMuhammad Tanveer; Eun Su Lim; Kwang-Yong Kim. 2021. "Effects of channel geometry and electrode architecture on reactant transportation in membraneless microfluidic fuel cells: A review." Fuel 298, no. : 120818.
In the development process of a fuel cell, understanding the local current distribution is essentially required to achieve better performance and durability. Therefore, many developers apply a segmented fuel cell to observe current distribution under various operating conditions. With the application, experimental data is collected. This study suggests a utilization method for this collected data to develop a local current prediction model. The details of this neural network-based prediction model are introduced, including the pretreatment of the data. In the pretreatment process, current residual values are used for better prediction performance. As a result, the model predicted local current values with a 2.98% error. With the model, the effects of pressure, temperature, cathode relative humidity, and cathode flow rate on local current distribution trends are analyzed. Since the non-uniform current distribution of a fuel cell often leads to low performances or fast local degradation, the optimal operating condition to achieve current uniformity is acquired with an additional model. This model is developed by switching inputs and outputs of the local current prediction model. With the model application, the uniform current distribution is achieved with a standard deviation of 0.039 A/cm2 under the current load at 1 Acm−2.
Jin Young Park; Yeong Ho Lee; In Seop Lim; Young Sang Kim; Min Soo Kim. Prediction of local current distribution in polymer electrolyte membrane fuel cell with artificial neural network. International Journal of Hydrogen Energy 2021, 1 .
AMA StyleJin Young Park, Yeong Ho Lee, In Seop Lim, Young Sang Kim, Min Soo Kim. Prediction of local current distribution in polymer electrolyte membrane fuel cell with artificial neural network. International Journal of Hydrogen Energy. 2021; ():1.
Chicago/Turabian StyleJin Young Park; Yeong Ho Lee; In Seop Lim; Young Sang Kim; Min Soo Kim. 2021. "Prediction of local current distribution in polymer electrolyte membrane fuel cell with artificial neural network." International Journal of Hydrogen Energy , no. : 1.
This research is aimed at studying the stability and tribology properties of the polyol ester oil- (POE-) based biolubricant mixed with various filler loadings from microparticle of TEMPO-oxidized bacterial cellulose (NDCt) as an additive and sorbitan monostearate (Span 60) as a surfactant. Morphology, rheology, and tribology tests were conducted. The addition of NDCt and Span 60 to pure POE as a base fluid showed elevated viscosity, lower value of coefficient friction (COF), and a remarkable decrease in the wear rate (WR). The presence of 0.6 wt% NDCt and 1.8 wt% Span 60 in POE (N2S4) decreased the COF value by 79% in comparison to POE. At room temperature, this N2S4 biolubricant sample showed a higher thermal conductivity by 4% and lower WR value by 49% compared to POE. This study introduced the preparation of the ecofriendly biolubricant filled with NDCt improving the tribology properties remarkably.
Dieter Rahmadiawan; Hairul Abral; N. Nasruddin; Zahrul Fuadi. Stability, Viscosity, and Tribology Properties of Polyol Ester Oil-Based Biolubricant Filled with TEMPO-Oxidized Bacterial Cellulose Nanofiber. International Journal of Polymer Science 2021, 2021, 1 -9.
AMA StyleDieter Rahmadiawan, Hairul Abral, N. Nasruddin, Zahrul Fuadi. Stability, Viscosity, and Tribology Properties of Polyol Ester Oil-Based Biolubricant Filled with TEMPO-Oxidized Bacterial Cellulose Nanofiber. International Journal of Polymer Science. 2021; 2021 ():1-9.
Chicago/Turabian StyleDieter Rahmadiawan; Hairul Abral; N. Nasruddin; Zahrul Fuadi. 2021. "Stability, Viscosity, and Tribology Properties of Polyol Ester Oil-Based Biolubricant Filled with TEMPO-Oxidized Bacterial Cellulose Nanofiber." International Journal of Polymer Science 2021, no. : 1-9.
Since frost on an outdoor heat exchanger in winter reduces the performance of an air source heat pump (ASHP), a defrosting process is necessary to restore the degraded performance. Therefore, frosting and defrosting are crucial challenges. For a more efficient defrosting process, many researchers have conducted studies on demand-based defrosting control so far. Recently, various researches on frost growth prediction using neural networks have been conducted. Here, we propose a novel method to quantitatively predict changes in the performance (heating capacity, power consumption, and COP) of ASHPs due to frost growth using a single model based on deep learning. Based on prediction results, this method can be utilized to optimize the defrosting start control strategy. With multiple outputs regression models, we can predict three performance parameters simultaneously. They are models trained with only the initially installed sensors without additional sensors. Besides, we compared the prediction accuracy differences depending on three deep learning structures, such as a fully-connected deep neural network (FCDNN), convolutional neural network (CNN), and long short-term memory (LSTM). Summarizing the results, the optimal FCDNN-based model achieved a root-mean-square (RMS) error of 2.8% for the prediction of heating capacity, 2.4% for power consumption, and 3.4% for COP of ASHPs.
Yong Hwan Eom; Yoong Chung; Min Su Park; Sung Bin Hong; Min Soo Kim. Deep learning-based prediction method on performance change of air source heat pump system under frosting conditions. Energy 2021, 228, 120542 .
AMA StyleYong Hwan Eom, Yoong Chung, Min Su Park, Sung Bin Hong, Min Soo Kim. Deep learning-based prediction method on performance change of air source heat pump system under frosting conditions. Energy. 2021; 228 ():120542.
Chicago/Turabian StyleYong Hwan Eom; Yoong Chung; Min Su Park; Sung Bin Hong; Min Soo Kim. 2021. "Deep learning-based prediction method on performance change of air source heat pump system under frosting conditions." Energy 228, no. : 120542.
A battery-electric-vehicle (BEV) relies on the state of charge (SoC) of the built-in battery system because it exclusively uses electric energy stored in rechargeable battery packs. The EV's mileage would be reduced due to the electricity consumption when the mobile heat pump system (MHP) is operated. In the case of the the winter season, the heat pump system operates not only for heating the cabin to achieve thermal comfort but also for defogging to maintain driving safety. To ensure the EV’s driving range, the energy consumption of MHP should be minimized as much as possible by recovering waste heat and applying a dehumidifier. For these purposes, the desiccant coated heat exchanger (DCHE) is introduced into the system, which is able to simultaneously transfer heat and mass (water vapor). In this study, the MHP and cabin thermal load models were made, and the DCHE model was validated by experiments using the unit DCHE. Based on the models, the energy consumption of the EV MHP with the DCHE was conducted, and compared to the conventional system, the proposed system required less energy.
Sun-Ik Na; Yoong Chung; Min Soo Kim. Performance analysis of an electric vehicle heat pump system with a desiccant dehumidifier. Energy Conversion and Management 2021, 236, 114083 .
AMA StyleSun-Ik Na, Yoong Chung, Min Soo Kim. Performance analysis of an electric vehicle heat pump system with a desiccant dehumidifier. Energy Conversion and Management. 2021; 236 ():114083.
Chicago/Turabian StyleSun-Ik Na; Yoong Chung; Min Soo Kim. 2021. "Performance analysis of an electric vehicle heat pump system with a desiccant dehumidifier." Energy Conversion and Management 236, no. : 114083.
In this work, a comparative investigation of chaotic flow behavior inside multi-layer crossing channels was numerically carried out to select suitable micromixers. New micromixers were proposed and compared with an efficient passive mixer called a Two-Layer Crossing Channel Micromixer (TLCCM), which was investigated recently. The computational evaluation was a concern to the mixing enhancement and kinematic measurements, such as vorticity, deformation, stretching, and folding rates for various low Reynolds number regimes. The 3D continuity, momentum, and species transport equations were solved by a Fluent ANSYS CFD code. For various cases of fluid regimes (0.1 to 25 values of Reynolds number), the new configuration displayed a mixing enhancement of 40%–60% relative to that obtained in the older TLCCM in terms of kinematic measurement, which was studied recently. The results revealed that all proposed micromixers have a strong secondary flow, which significantly enhances the fluid kinematic performances at low Reynolds numbers. The visualization of mass fraction and path-lines presents that the TLCCM configuration is inefficient at low Reynolds numbers, while the new designs exhibit rapid mixing with lower pressure losses. Thus, it can be used to enhance the homogenization in several microfluidic systems.
Toufik Naas; Shakhawat Hossain; Muhammad Aslam; Arifur Rahman; A. Hoque; Kwang-Yong Kim; S. Islam. Kinematic Measurements of Novel Chaotic Micromixers to Enhance Mixing Performances at Low Reynolds Numbers: Comparative Study. Micromachines 2021, 12, 364 .
AMA StyleToufik Naas, Shakhawat Hossain, Muhammad Aslam, Arifur Rahman, A. Hoque, Kwang-Yong Kim, S. Islam. Kinematic Measurements of Novel Chaotic Micromixers to Enhance Mixing Performances at Low Reynolds Numbers: Comparative Study. Micromachines. 2021; 12 (4):364.
Chicago/Turabian StyleToufik Naas; Shakhawat Hossain; Muhammad Aslam; Arifur Rahman; A. Hoque; Kwang-Yong Kim; S. Islam. 2021. "Kinematic Measurements of Novel Chaotic Micromixers to Enhance Mixing Performances at Low Reynolds Numbers: Comparative Study." Micromachines 12, no. 4: 364.
This study aims to enhance polymer electrolyte membrane fuel cell (PEMFC) performance in low humidity conditions without degrading the performance in high humidity conditions. The reference gas diffusion layer (GDL) is modified by deposition of HfO2 on the microporous layer (MPL) using atomic layer deposition (ALD), which was rarely used in GDL modification. Four HfO2 deposited GDLs with different numbers of deposition cycles (Hf_25, 50, 100, 200 shown in Table 1) are additionally prepared. The energy dispersive spectroscopy (EDS) image, contact angle, electrical resistance, vapor permeation rate, and liquid water saturation of the GDLs are evaluated and compared. Electrochemical performance experiments are conducted in three different humidity conditions. The results show that Hf_25 has 7% higher peak power than reference GDL due to better water management from its larger vapor permeation rate and smaller liquid water saturation. The electrochemical impedance spectroscopy (EIS) and equivalent circuit analysis demonstrate that Hf_25 has smaller charge transfer resistance and mass transport resistance in low and high humidity conditions. Hf_50, Hf_100, and Hf_200 display lower performance than Hf_25 due to increased electrical resistance and mass transport resistance, demonstrated by EIS and equivalent circuit analysis. Especially, Hf_200 shows a noticeable performance decrement than others.
In Seop Lim; Byeonghyun Kang; Jin Young Park; Min Soo Kim. Performance improvement of polymer electrolyte membrane fuel cell by gas diffusion layer with atomic-layer-deposited HfO2 on microporous layer. Energy Conversion and Management 2021, 236, 114070 .
AMA StyleIn Seop Lim, Byeonghyun Kang, Jin Young Park, Min Soo Kim. Performance improvement of polymer electrolyte membrane fuel cell by gas diffusion layer with atomic-layer-deposited HfO2 on microporous layer. Energy Conversion and Management. 2021; 236 ():114070.
Chicago/Turabian StyleIn Seop Lim; Byeonghyun Kang; Jin Young Park; Min Soo Kim. 2021. "Performance improvement of polymer electrolyte membrane fuel cell by gas diffusion layer with atomic-layer-deposited HfO2 on microporous layer." Energy Conversion and Management 236, no. : 114070.
In this study, a spiral ring cavity (SRC) is proposed to improve the operational stability of a centrifugal compressor. Aerodynamic performance of the compressor was analyzed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. To prove the superiority of the proposed cavity, adiabatic efficiency and stall margin of an SRC were compared with those of the smooth casing and conventional cavities, i.e., ring cavity and discrete ring cavities. To find the optimum shape of the cavity, a parametric study was performed for the SRC using three geometric parameters, i.e., the axial location, width of the cavity port, and circumferential location of the SRC. The operation stability was sensitive to the width of cavity port and circumferential location. The SRC improved the stall margin considerably compared to other cavities.
Min-Su Roh; Sang-Bum Ma; Kwang-Yong Kim. Spiral ring cavity to improve the stability of a centrifugal compressor. Journal of Mechanical Science and Technology 2021, 35, 1055 -1063.
AMA StyleMin-Su Roh, Sang-Bum Ma, Kwang-Yong Kim. Spiral ring cavity to improve the stability of a centrifugal compressor. Journal of Mechanical Science and Technology. 2021; 35 (3):1055-1063.
Chicago/Turabian StyleMin-Su Roh; Sang-Bum Ma; Kwang-Yong Kim. 2021. "Spiral ring cavity to improve the stability of a centrifugal compressor." Journal of Mechanical Science and Technology 35, no. 3: 1055-1063.
Optimum configuration of a micromixer with two-layer crossing microstructure was performed using mixing analysis, surrogate modeling, along with an optimization algorithm. Mixing performance was used to determine the optimum designs at Reynolds number 40. A surrogate modeling method based on a radial basis neural network (RBNN) was used to approximate the value of the objective function. The optimization study was carried out with three design variables; viz., the ratio of the main channel thickness to the pitch length (H/PI), the ratio of the thickness of the diagonal channel to the pitch length (W/PI), and the ratio of the depth of the channel to the pitch length (d/PI). Through a primary parametric study, the design space was constrained. The design points surrounded by the design constraints were chosen using a well-known technique called Latin hypercube sampling (LHS). The optimal design confirmed a 32.0% enhancement of the mixing index as compared to the reference design.
Shakhawat Hossain; Nass Tayeb; Farzana Islam; Mosab Kaseem; P.D.H. Bui; M.M.K. Bhuiya; Muhammad Aslam; Kwang-Yong Kim. Enhancement of Mixing Performance of Two-Layer Crossing Micromixer through Surrogate-Based Optimization. Micromachines 2021, 12, 211 .
AMA StyleShakhawat Hossain, Nass Tayeb, Farzana Islam, Mosab Kaseem, P.D.H. Bui, M.M.K. Bhuiya, Muhammad Aslam, Kwang-Yong Kim. Enhancement of Mixing Performance of Two-Layer Crossing Micromixer through Surrogate-Based Optimization. Micromachines. 2021; 12 (2):211.
Chicago/Turabian StyleShakhawat Hossain; Nass Tayeb; Farzana Islam; Mosab Kaseem; P.D.H. Bui; M.M.K. Bhuiya; Muhammad Aslam; Kwang-Yong Kim. 2021. "Enhancement of Mixing Performance of Two-Layer Crossing Micromixer through Surrogate-Based Optimization." Micromachines 12, no. 2: 211.
In this study, a wavy microchannel heat sink with grooves using water as the working fluid is proposed for application to cooling microprocessors. The geometry of the heat sink was optimized to improve heat transfer and pressure loss simultaneously. To achieve optimization goals, the average friction factor and thermal resistance were used as the objective functions. Three dimensionless parameters were selected as design variables: the distance between staggered grooves, groove width, and groove depth. A modified Latin hypercube sampling (LHS) method that combines the advantages of conventional LHS and a three-level full factorial method is also proposed. Response surface approximation was used to construct surrogate models, and Pareto-optimal solutions were obtained with a multi-objective genetic algorithm. The modified LHS was proven to have better performance than the conventional LHS and full factorial methods in the present optimization problem. A representative optimal design showed that both the thermal resistance and friction factor improved by 1.55% and 3.00%, compared to a reference design, respectively.
Min-Cheol Park; Sang-Bum Ma; Kwang-Yong Kim. Optimization of a Wavy Microchannel Heat Sink with Grooves. Processes 2021, 9, 373 .
AMA StyleMin-Cheol Park, Sang-Bum Ma, Kwang-Yong Kim. Optimization of a Wavy Microchannel Heat Sink with Grooves. Processes. 2021; 9 (2):373.
Chicago/Turabian StyleMin-Cheol Park; Sang-Bum Ma; Kwang-Yong Kim. 2021. "Optimization of a Wavy Microchannel Heat Sink with Grooves." Processes 9, no. 2: 373.