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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A Study on Numerical Analysis for Determination of Glass Molding Process Conditions for Glass Lenses: Jaehun Choi, Sajan Tamang, Heesung Park; J. Korean Soc. Precis. Eng. 2024;41(3):207-214.
Published online March 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.136

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The Glass Molding Process (GMP) produces large quantities of glass optical parts and provides the advantages of high molding accuracy, short production cycle, low cost, and little pollution. Developments in different sectors, such as cameras and telescopes, are prompting studies on the design of aspherical optical components. Modeling heat transfer and deformation at high temperatures are crucial aspects of studying glass because its properties are significantly influenced by temperature-induced phase changes. In this study, temperature changes and geometric deviations of lenses were studied with respect to heating, pressing, and cooling times and the heat capacity of the heater used. A 3D model was designed for the heating, pressing, and cooling steps, and heat transfer was subjected to numerical analysis considering the specific heat of glass and the temperature dependence of thermal conductivity. Lens molding temperature conditions were then analyzed with the heat capacity of the lens molding heating system. Lens molding conditions were derived by analyzing lens temperatures with respect to heating and cooling capacities at each process step.

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Precision glass aspherical lens manufacturing by compression molding: a review
Xiaohua Liu, Jian Zhou, Bo Tao, Yang Shu, Zexin Feng, Shih-Chi Chen, Yingying Zhang, Allen Y. Yi
Light: Advanced Manufacturing.2026; 7: 1. CrossRef
A Study on Temperature and Stress Distribution in a Lens under Multi-Stage Cooling Conditions in Progressive Glass Molding Processes
Ji Hyun Hong, Jeong Taek Hong, Dong Yean Jung, Young Bok Kim, Keun Park, Chang Yong Park
Journal of the Korean Society for Precision Engineering.2025; 42(2): 157. CrossRef

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Implementation and Verification of Fresnel Zone Plate Patterns Designed by Optimization of Surface Phase: Huy Vu, Joohyung Lee; J. Korean Soc. Precis. Eng. 2024;41(1):79-84.
Published online January 1, 2024; DOI: https://doi.org/10.7736/JKSPE.023.124

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In this study, we present a numerical simulation approach for designing Fresnel zone plate (FZP) patterns. By optimizing surface phase parameters using desired merit functions in ray-tracing software, the obtained surface phase was converted into an FZP pattern through a 5-step procedure. A comparison between our numerical simulation approach and the traditional analytical method showed a negligible zone size difference of 0.606 nm and nearly absolute agreement of 17.549 μm in focal spot size. The FZP pattern was experimentally verified by an expected focal spot size of 18.55 μm. Our approach demonstrated design flexibility and has potential applications in simulating various functionalities in FZP patterns and refractive-diffractive hybrid lenses to address specific optical challenges. The surface phase can be freely modified based on optimization objectives that cannot be achieved using the analytical approach, ensuring high-precision design for accurate extraction.

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Mechanistic evaluations of radial fiber tip for circumferential laser ablation
Minh Duc Ta, Jiho Lee, Seonho Jung, Van Gia Truong, Hyun Wook Kang
Optics & Laser Technology.2025; 192: 113660. CrossRef
Quantitative investigations on light emission profiles for interstitial laser treatment
Minh Duc Ta, Yeongeun Kim, Hwarang Shin, Van Gia Truong, Hyun Wook Kang
Biomedical Optics Express.2024; 15(12): 6877. CrossRef

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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; J. Korean Soc. Precis. Eng. 2021;38(6):455-460.
Published online June 1, 2021; DOI: https://doi.org/10.7736/JKSPE.020.115

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In this study, the design of an axial steam turbine that is installed for a using waste pressure. Airfoils and flow fields are designed based on 1D and 2D meridional plane design techniques. The 3D geometry of the steam turbine is designed considering the 1D and 2D design parameters. The turbine is designed with an average radius of 287 mm and rotates at 8,300 re v/min. The inlet boundary condition of the steam turbine was applied in consideration of the installation condition of the waste pressure turbine. When analyzing the results of the numerical simulation, the performance of the steam turbine is predicted with an output of 3.5 MW and isentropic efficiency of 88.4%. The choked flow in the nozzle throat and the flow separation in the suction side on the blades are predicted numerically, and it is expected to be a study to determine the cause of the reduction in efficiency of the steam turbine.

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Numerical Investigation on the Cooling Performance of Energy Storage System according to Type of HVAC: Hwabhin Kwon, Heesung Park; J. Korean Soc. Precis. Eng. 2020;37(9):685-690.
Published online September 1, 2020; DOI: https://doi.org/10.7736/JKSPE.020.027

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In this paper, we analyze the cooling performance according to the HVAC types installed in the energy storage system (ESS). Batteries in ESS have the disadvantages of decomposition and catching fire at high temperatures, so it is important to control the temperature. For the purpose of cooling the batteries in ESS, we designed the cooling systems with stand and ceiling type HVAC. Both the cooling systems for ESS are analyzed numerically for the comparison of cooling performance. The heat dissipation of the battery is 1979.3 W/m3 on 1 C-Rate discharge, and the cooling flow rate and temperature are 6.375 kg/s and 17℃, respectively. The maximum temperature of batteries with stand and ceiling type cooling systems are calculated to be 65.85 and 60.5℃, respectively. In conclusion, cooling systems with ceiling type HVAC are more efficient than cooling systems with stand type HVAC.

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A Numerical Study on the Cooling Efficiency of the Gas Turbine Vane with the Film Cooling Hole Shape: Jaehun Choi, Hwabhin Kwon, Heesung Park; J. Korean Soc. Precis. Eng. 2020;37(2):107-113.
Published online February 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.094

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Research on advanced cooling system design is significant in achieving a high turbine inlet temperature in the gas turbine industry. The higher turbine inlet temperature of the gas turbine increases thermal efficiency. However, it also aggravates the gas turbine deterioration, lifespan, and efficiency. In this study, a numerical model is developed for simulating the cooling performance of the gas turbine vane with the turbine inlet temperature of 1528 K. The impact of the coolant air flow rate and hole-shape were investigated. The expanded hole shape had better cooling performance than the general cylindrical shape, and showed higher cooling efficiency. We suggest that there is a relationship between the shape of the film cooling holes and the cooling air flow rate that achieves the desired cooling effectiveness.

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Integrated Analytical Approach for the Definition and the Control of the Radial-Axial Ring Rolling Process: Do yeon Kim, Luca Quagliato; J. Korean Soc. Precis. Eng. 2019;36(9):821-835.
Published online September 1, 2019; DOI: https://doi.org/10.7736/KSPE.2019.36.9.821

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This research aims to provide a useful algorithm for the prediction of the geometrical expansion of flat rings in the radialaxial ring rolling process in case of multiple variations of the mandrel feeding speed during the process. The proposed algorithm was subjected to a 2-phases validation process, where results were compared with those of laboratory experiments, conducted at 150℃ on rings made of AA-1070 and AA-6061 aluminum alloys, and with numerical simulations, considering 7 different rings with outer diameter ranging from 800 to 2000 ㎜ and made of 42CrMo4 steel alloy, Ti6Al4V titanium alloy and AA-6061 aluminum alloys. In the first and second validation phases, the maximum deviation in the estimation of the outer diameter of the ring has been calculated in 1.7% and 6.82%, respectively. According to the results of the validation, the proposed algorithm is able to properly predict the geometrical expansion of the ring for multiple variations of the mandrel feeding speed during the process and has good accordance with both relatively small and large rings.