Journal of the Korean Society for Precision Engineering

A Numerical Investigation on Heat Transfer Enhancement of a Dual-impeller Heat Exchanger for Electro-optical Tracking System Cooling via System Structural Modification: Sungbin Lee, Manyul Jeon, Hyungpil Park, Donghyeok Park, Hoonhyuk Park, Jongin Bae, Heesung Park; J. Korean Soc. Precis. Eng. 2025;42(10):871-877.
Published online October 1, 2025; DOI: https://doi.org/10.7736/JKSPE.025.071

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This study presents a dual-impeller air-cooled heat exchanger aimed at improving thermal management in electro-optical tracking systems operating under high power density. Two geometric modifications were introduced to enhance flow characteristics and heat transfer performance: the curvature of the center plate and the integration of a pin-fin structure at the outlet. Through numerical simulation, the improved model demonstrated more efficient internal flow compared to the original model, achieved through enhanced inflow characteristics and reduced flow separation. The pin-fin structures induced localized turbulence and recirculation zones, contributing to an increased thermal exchange surface area and longer effective heat transfer time. Consequently, the outlet temperature of the internal system decreased by an average of 1.4°C across various rotational speeds, resulting in a 5.9% increase in heat exchanger efficiency compared to the original model. Overall, this study shows that structural enhancements in heat exchanger design can significantly improve the cooling performance of high-power electronic systems, suggesting practical applicability for advanced thermal management solutions.

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Optimal Design Technique for the Shape of Induction Heating Electric Range Coil Using Response Surface Method: Soonjae Hwang, Changyeon Lee, Seokmoo Hong; J. Korean Soc. Precis. Eng. 2024;41(5):407-413.
Published online May 1, 2024; DOI: https://doi.org/10.7736/JKSPE.024.023

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Induction heating is a technology that uses heat generated by resistance when a high-frequency current is applied to a coil. An electric range using this is called an Induction Heating (IH) electric range. IH electric ranges are being widely applied in commercial products recently because they have higher thermal efficiency performances than other methods. The performance of a heating coil of an IH electric range greatly varies depending on the shape and number of coils. Thus, research on optimal coil shape and number according to product shape is required. Therefore, this study aimed to design an optimal heating coil at the set temperature of an electric range product. Target temperature was set to the temperature that a commercial stainless-steel container could withstand. The thickness of the coil copper wire, the number of windings, the applied voltage, and the frequency were set as design variables. A sensitivity analysis was performed to check the influence of each design variable on coil temperature. Based on this, optimal design was performed using the response surface method. Electromagnetic field-thermal analysis was performed with the designed coil and a very approximate result was obtained with a 0.07% error from the set target temperature.

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Study on PCM Cooling of Wireless Charger Using Electromagnetic Field-thermal-fluid-structure Coupled Analysis: Soonjae Hwang, Sarang Yi, Seakmoo Hong; J. Korean Soc. Precis. Eng. 2024;41(4):305-312.
Published online April 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.150

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With the increasing use of portable devices, the safety and efficiency of wireless chargers have become significant concerns. Wireless chargers can cause battery damage, deformation, and failure of the charging module due to the high temperatures generated during the charging process. Thus, the importance of thermal management has been increasingly emphasized. In this study, we experimentally confirmed that cooling performance was improved by applying phase change material (PCM) to the heat-generating parts of the wireless charger. The cooling performance of the PCM was analyzed using Ansys Fluent, the component temperature was measured with an infrared camera, and 3D thermal deformation was measured with a DIC measurement device. Electromagnetic field, thermal, fluid, and structural coupled analyses were performed to investigate the impact of thermal deformation caused by wireless charging. The results showed that the temperature and deformation error was within 3% of the coupled analysis results, and the proposed electromagneticthermal-fluid-structural coupled analysis enabled more accurate simulation prediction of the physical coupling process inside the wireless charger.

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CFD Analysis of the Mechanical Power and the Wake of a Scaled Wind Turbine and Its Experimental Validation: Yechan Hwang, Insu Paek; J. Korean Soc. Precis. Eng. 2021;38(3):223-233.
Published online March 1, 2021; DOI: https://doi.org/10.7736/JKSPE.020.113

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In this study, both mechanical power and the wind speed distribution in the wake of a wind turbine scaled model were analyzed using a commercial CFD program (Ansys CFX) along with experimental validation. For the simulation, two different turbulence models including the SST model and the k-ε model were used. The scaled model was originally designed and manufactured by the researchers at the Technical University of Munich and was slightly modified for this research. To experimentally verify the CFD results, tests were performed with the scaled model under the turbulent wind in a wind tunnel. From the experimental validation, it was found that the k-ε turbulence model gives a better prediction than the SST model in the wake results. However, the SST turbulence model showed better prediction than the k-ε turbulence model in the power prediction. The discrepancy between the CFD results and the experimental validation is partially due to the fact that the blades are deformed at all times and control of pitch in the rated power region but these aspects are not considered in the simulation. If a transient analysis is performed using LES models, it will more accurately predict the change of wake with high turbulence intensity.

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Design and Performance Analysis for 3 MW Waste Pressure Steam Turbine Using 2D and 3D Numerical Simulation
Hwabhin Kwon, Jong Yun Jung, Joon Seob Kim, Ye Lim Jung, Heesung Park
Journal of the Korean Society for Precision Engineering.2021; 38(6): 455. CrossRef

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Performance Test of 3D Printed Blades for a Scaled Wind Turbine in a Wind Tunnel: Dongmyoung Kim, Insu Paek, Byeongcheol Won, Taesu Jeon; J. Korean Soc. Precis. Eng. 2020;37(9):707-715.
Published online September 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.057

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In this study, blades manufactured by 3D printing technology were experimentally tested to be used for a scaled wind turbine in a wind tunnel. The scaled model was originally designed and manufactured by researchers at the Technical University of Munich. The model has been slightly modified to adopt the 3D printed blades for this study. Also, control algorithms for the power maximization in the low wind speed regions were constructed and applied to a commercial programmable logic controller for wind tunnel tests of the scaled model. For comparison, the scaled model was also modeled in MATLAB/Simulink and dynamic simulations were performed with the measured wind speed as an input. The simulation results seemed to overpredict the experimental results initially, but by considering the unexpected extra generator torque due to friction of the shaft, the errors were reduced to be less than 5%. Based on this study, the application of 3D printed blades to the wind turbine scaled models of a similar rotor diameter was found to be an efficient and effective way of blade manufacturing and scaled model testing.

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Performance Validation of Control Algorithm Considering Independent Generator Torque Control in PCS
Dongmyoung Kim, Min-Woo Ham, Insu Paek, Wirachai Roynarin, Amphol Aphathanakorn
Applied Sciences.2024; 14(24): 11598. CrossRef
The Suitability of Substructures of the Offshore Wind Power Complex
Dae Kyung Kim, Dong Soon Kang, Jong Hak Lim, Young Il Byun, Chul Ki Song
Journal of the Korean Society for Precision Engineering.2022; 39(4): 299. CrossRef
CFD Analysis of the Mechanical Power and the Wake of a Scaled Wind Turbine and Its Experimental Validation
Yechan Hwang, Insu Paek
Journal of the Korean Society for Precision Engineering.2021; 38(3): 223. CrossRef
Design and Validation of Demanded Power Point Tracking Control Algorithm for MIMO Controllers in Wind Turbines
Taesu Jeon, Dongmyoung Kim, Yuan Song, Insu Paek
Energies.2021; 14(18): 5818. CrossRef

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Rapid Fabrication of Magnesium Hydroxide Layer on Magnesium Alloy to Improve Corrosion Resistance: JuHan Kim, Byungrak Park, Woonbong Hwang; J. Korean Soc. Precis. Eng. 2019;36(5):493-496.
Published online May 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.5.493

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A simple and rapid method of fabricating Mg(OH)2 layer by chemical immersion was developed to improve the corrosion resistance of the magnesium alloy AZ31. The fabricated surface was superhydrophobic with a self-assembled monolayer coating of silane. The surface characteristics were evaluated by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS). The average water contact angle and sliding angle were determined to be 160° and 7° respectively as a result of wettability test. Potentiodynamic polarization indicated that both Mg(OH)2 layer and the thin layer of air were effective in improving anti-corrosion. This method which is efficient with regard to time and cost would be useful for magnesium industries and its application

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The mechanisms and advances in magnesium-based materials protection against corrosion by the superhydrophobic coatings
Ludmila B. Boinovich, Kirill A. Emelyanenko, Alexandre M. Emelyanenko
Surface and Coatings Technology.2024; 481: 130607. CrossRef

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Study on Mobility of Planetary Rovers and the Development of a Lunar Rover Prototype with Minimized Redundancy of Actuators: Mingyo Seo, Woosub Lee; J. Korean Soc. Precis. Eng. 2019;36(4):339-348.
Published online April 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.4.339

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This paper reviews design elements and presents a mobile platform that has full access of wheel actuation for explicit steering with a minimized number of actuators. For the purpose of exploring lunar surfaces, there are two main design perspectives to be considered. First, the mobile system should guarantee traversability on rough terrain in microgravity condition. Secondly, the system should be sustainable in the extreme environment of the lunar surface including cosmic rays and excessive temperature changes. One of the potential solutions to improve the reliability of the rover system is to reduce the chance of failure by minimizing the number of electronic components including actuators and their following components and installing them in the rover’s warm-box. We approached the design of the mobile system in the aspect of its kinematics with assumptions of pure-rolling and non-lateral slip. We found a relation that a pair of front and rear wheels on the same side is coupled so that their alignment and rotational speed can be coupled by a mechanism. This allows advantages of explicit steering, minimizing redundancy of actuators and isolating all the electronic components from the effects of external environments. To demonstrate the feasibility of the system, we developed a rover testbed and presented its mobility of explicit steering by experiments of open-loop trajectory traveling.

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Deep Reinforcement Learning-Based Failure-Safe Motion Planning for a 4-Wheeled 2-Steering Lunar Rover
Beom-Joon Park, Hyun-Joon Chung
Aerospace.2023; 10(3): 219. CrossRef
Trends in Development of Micro Rovers for Planetary Exploration
Keon-Woo Koo, Hae-Dong Kim
Journal of Space Technology and Applications.2023; 3(3): 213. CrossRef

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The Study on the Mine Protective Structural Design of Wheeled Armored Vehicle Body: Chan Young Park, Kyoung Hoon Lee; J. Korean Soc. Precis. Eng. 2019;36(3):255-261.
Published online March 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.3.255

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In this study, to develop mine protective design technology for wheeled armored vehicles, designing and simulating of test specimens based on the 8×8 military combat vehicle, were executed and mine protection effectiveness was proven, by testing under the two work steps such as 1st step for conceptual model and 2nd step for vehicle segment. Experiments for both test models of each step were performed according to test conditions of NATO standard, STANAG 4569 Level, and simulations were performed by the commercial code, LS-DYNA. On the 1st step, a conceptual model was designed, and its protection effectiveness was verified by simulation before testing and then it was proven by testing. On the 2nd step, the vehicle segment with protection design technology from the 1st step was designed better, to consider dynamic vertical deformation, injury values of a human dummy, and effects of installed components on the bottom of the model. Finally, satisfaction for protection effectiveness and IARVs (Injury Assessment Reference values) of a human dummy were verified by testing, and also the possibility of application for wheeled armored vehicles were confirmed.

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Construction of Programmable Drug Delivery System with Additive Manufacturing: Noehyun Myung, Hyun-Wook Kang; J. Korean Soc. Precis. Eng. 2018;35(9):835-840.
Published online September 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.9.835

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A programmable drug delivery system can control the release rate of a drug. It can minimize side effects while maximizing therapeutic effects. In this research, we investigated the feasibility of producing a programmable drug delivery system using 3D printing technology. A capsule with a micro-orifice and a drug-laden hydrogel was designed. The designed system was then fabricated by the printing process using polycaprolactone and hydrogel. The printed drug delivery system was immersed in PBS at 37°C and the number of molecules released was measured thorough colorimetric analysis. The effect of diameter and length of the micro-orifice and concentration of the hydrogel on drug release characteristics was then determined. The initial burst release rate was found to be increased with increasing orifice size. Increasing the length of the orifice linearly delayed the start time of drug release. At length of 600 μm and 1,200 μm, drug release was initiated after 36 h and 72 h for, respectively. When the concentration of hydrogel was increased, drug release rate tended to decrease. These results successfully confirmed that a drug delivery system with controlled release rate and initiation time could be manufactured using 3D printing technology.

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Evaluation of the Manufacturing and Viral Killing Efficacy of Chitosan Microbeads Loaded with Disinfectants
Bong Su Kang, Sung Hak Choi, Moon Kyu Kwak, Ho-Sup Jung
Journal of the Korean Society for Precision Engineering.2024; 41(7): 507. CrossRef
User-designed device with programmable release profile for localized treatment
Noehyun Myung, Seokha Jin, Hyung Joon Cho, Hyun-Wook Kang
Journal of Controlled Release.2022; 352: 685. CrossRef

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A Study of Droplet Transmissivity Change by Characteristic of Mesh: Jinyoung Park, Woonbong Hwang; J. Korean Soc. Precis. Eng. 2018;35(6):629-633.
Published online June 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.6.629

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Super-wettability surface has various applications and actively studied in many fields. However water droplet transmissivity on super-wettability mesh was not be studied. This work is about water droplet transmissivity of an aluminum mesh with super-wettability on its surface. The mesh which fabricated surface structures with semi-permanent and non-etching process has super-wettability without strength drop of mesh structure. With this process, water droplet transmissivity was measured along various mesh pore per inch and dropping angle. Also water droplet transmissivity along dropping height was measure with super-hydrophobic mesh. As a result, super-hydrophilic mesh shows similar transmissivity behavior with bare mesh which has hydrophilic surface at high pore per inch and high dropping angle, super-hydrophobic 120 mesh shows lowest water droplet transmissivity in various situation.

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Fabrication of Superoleophobic Surface on Zinc Substrate Using Anodization and Self-Assembled Monolayer Coating: Wonshik Kwak, Woonbong Hwang; J. Korean Soc. Precis. Eng. 2018;35(5):561-565.
Published online May 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.5.561

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In this study, we developed a convenient method to achieve superoleophobic surfaces on zinc substrates by using anodization and self-assembled monolayer coating, and to facilitate the fabrication of superoleophobic surfaces having reentrant structures, even for lower surface tension liquids than 30 mN/m- including hexadecane (γ = 27.5 mN/m). The liquid repellency of the structured surface was validated through observable experimental results; contact angle measurement. The optimal anodizing condition was determined as a critical parameter in building the superoleophobicity. The re-entrant had nanowire/microball structures formed by anodization with a high voltage. Under an optimized morphology by re-entrant structures with fluorination treatment, the contact angle over 150o is achieved, even for hexadecane.

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Thermal-Fluid Coupled Analysis of the Nozzle Part for the FDM 3D Printers Considering Flow Characteristics of Cooling Fan: Chang-Whan Lee, Hyun-Woo Kim, Jea-Hyeong Yu, Keun Park; J. Korean Soc. Precis. Eng. 2018;35(5):479-484.
Published online May 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.5.479

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For 3D printing of high-strength polymers, such as PC (Polycarbonate) and PEI (Polyetheimide), the temperature of the nozzle should exceed the melting temperature of the high-strength materials. At the same time, the temperature of the transfer part, composed of the shaft extruder and the Teflon hose, should be cooled below the glass transition temperature and below the limit temperature of the transfer part. In this study, we analyzed the effect of the flow rate of the cooling fan when the extruder nozzle is heated to 300oC. We compare the natural convection environment, in which the cooling fan is not operated, and the forced convection condition, in which the cooling fan is operated, and analyze the effect on the cooling fan flow rate. The simulation considered the heat transfer in the air and the nozzle, as well as the flow characteristics of the air.

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A Study on the Improving Extrusion Defects in FDM 3D Printers
Jun-Seok Do
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(4): 80. CrossRef
Analysis of Correlation between FDM Additive and Finishing Process Conditions in FDM Additive-Finishing Integrated Process for the Improved Surface Quality of FDM Prints
Ji Won Yu, Hyung Jin Jeong, Jae Hyung Park, Dong Hun Lee
Journal of the Korean Society for Precision Engineering.2022; 39(2): 159. CrossRef
Analysis on the Warm Bending Process of Magnesium Alloy Sheet Using Additively Manufactured Polymer Die-Set
Hyung-Won Youn, Jun-Hyun Kyeong, Keun Park, Chang-Whan Lee
Journal of the Korean Society for Precision Engineering.2021; 38(10): 775. CrossRef
Indirect Temperature Measurement in High Frequency Heating Systems
Alexander Oskolkov, Igor Bezukladnikov, Dmitriy Trushnikov
Sensors.2021; 21(7): 2561. CrossRef

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Development of Bending Lifetime Tester for Flexible OLEDs: Ji-Yeon Han, Jae-Hyun Lee; J. Korean Soc. Precis. Eng. 2018;35(4):451-456.
Published online April 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.4.451

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The applicability of flexible OLED devices has been expanding to rollable or foldable displays and lighting. At this time, a system to measure the durability of flexible OLEDs needs to be developed to successfully launch flexible OLEDs in future electronic devices. In this paper, we develop a bending lifetime tester to measure the performance of flexible OLEDs by measuring the luminance of the device in real-time during the bending test. A fixed distance between the bent OLEDs and detector during the bending test improves the accuracy of the measured brightness in real time. This bending tester can measure the lifetime of flexible OLEDs with a mean deviation of less than 0.23% over a temperature range of -30 to 80℃. This performance is sufficient to measure the accelerated lifetime test of flexible OLEDs for reliability engineering.

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Thermal-Structural Coupled Numerical Analysis for Design of High-Temperature Extruder of FDM 3D Printers: Da-Yeon Shin, Hyun-Joong Lee, Chang-Whan Lee, Keun Park; J. Korean Soc. Precis. Eng. 2018;35(3):341-347.
Published online March 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.3.341

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This study aims at developing a high temperature extruder for an FDM (Fused Deposition Modeling) type 3D printer that uses engineering thermoplastic filaments. An extruder is a key part of an FDM type printer, in which a filament moves to a heating block and is extruded through a nozzle with a specific diameter. For an appropriate extrusion, the filament should be heated above its softening temperature. Specifically, the filament should not be melted nor softened before it reaches the heating block for appropriate delivery. Hence, the extruder temperature should be carefully controlled to ensure its heating capability as well as its proper delivery. To meet these requirements, thermal-structural finite element (FE) analyses were performed for the prediction of the distributions of temperature and thermal stress. Various extruder designs were then considered to maximize the temperature difference between the nozzle and delivery parts, as well as to ensure structural safety.

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A Study on the Improving Extrusion Defects in FDM 3D Printers
Jun-Seok Do
Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(4): 80. CrossRef
Optimization Design of Student KSAE BAJA Knuckle Using SLM 3D Printer
Young Woo Im, Geon Taek Kim, Hyeon Sang Shin, Kang Min Kim, Bu Hyun Shin, Jong Won Lee, Jinsung Rho
Journal of the Korean Society for Precision Engineering.2023; 40(9): 719. CrossRef
Thermal-Fluid Coupled Analysis of the Nozzle Part for the FDM 3D Printers Considering Flow Characteristics of Cooling Fan
Chang-Whan Lee, Hyun-Woo Kim, Jea-Hyeong Yu, Keun Park
Journal of the Korean Society for Precision Engineering.2018; 35(5): 479. CrossRef

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Fabrication of Superhydrophobic Surface on Various Metals Using Abrasive Blasting and Self-Assembled Monolayer Coating: Byungrak Park, Woonbong Hwang; J. Korean Soc. Precis. Eng. 2018;35(2):197-201.
Published online February 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.2.197

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A study about superhydrophobic surface started from the analysis of lotus leaf, and superhydrophobic surface fabrication methods have been researched. These methods cannot be used on various metals because the fabrication methods have complex and material-selective processes. In this work, we report a simple fabrication method using abrasive blasting and a self-assembled monolayer coating to produce a superhydrophobic surface. Abrasive blasting was used to create microstructures on metal surfaces. Random peak and valley microstructures were created after abrasive blasting, and a surface profile was measured to analyze the relationship between blasting pressure and a roughness parameter. A hydrophobic material coating was performed by a self-assembled monolayer method. Six kinds of metal surfaces displayed superhydrophobic properties. This utilitarian method could be applied to diverse applications.

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