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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A Numerical Investigation of Heat Transfer Characteristics with Varying Film Cooling Hole Shapes for Gas Turbine Blade Cooling: Chan Hyeok Park, Sajan Tamang, Hwabhin Kwon, Jaemun Choi, Heesung Park; J. Korean Soc. Precis. Eng. 2022;39(6):443-450.
Published online June 1, 2022; DOI: https://doi.org/10.7736/JKSPE.022.018

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Recently, film cooling has been continuously studied to increase the efficiency of gas turbines. A turbine inlet temperature increase occurs as a way to improve the efficiency. However, it is essential to improve the cooling performance of the blade surface because of the melting point of the part. In this paper, a side hole shape wherein a general cylinder hole and two auxiliary holes are combined, is proposed to improve the film cooling efficiency, and the blowing ratio was set to 0.4, 0.8, 1.2, and 2.0. When side hole was applied, the vortex interference at the hole entrance occurred less than that of the cylinder hole. That is, the flow rate of the coolant adsorbed to the surface increased to improve the cooling performance. In conclusion, compared to the cylinder hole, the cooling efficiency of the shape to which the side hole was applied was excellent, and in particular, the average area cooling efficiency with spanwisely designed side holes improved by 83%.

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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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Melt Pool Characterization of Selective Laser Melting of AlSi10Mg based on Numerical Model of Single-Track Scanning Process: Kang-Hyun Lee, Gyung Bae Bang, Hyung Giun Kim, Kyung Hwan Jung, Gun Jin Yun; J. Korean Soc. Precis. Eng. 2021;38(4):295-304.
Published online April 1, 2021; DOI: https://doi.org/10.7736/JKSPE.021.008

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In the selective laser melting (SLM) process, a three-dimensional part is manufactured based on the formation of numerous molten tracks. Consequently, the generated melt pool in the scanning process of each track exhibits close relation to the internal defect formation and the quality of the fabricated part. In this study, a numerical model of single-track scanning of the SLM process is presented to analyze the melt pool characteristics for various process conditions. The presented model considers the thermal behavior of the powder material including the phase change and densification during the SLM process. The temperature-dependent energy absorption and the increase in effective energy absorptivity due to the keyhole mode melting are also incorporated in the heat flux model to evaluate the process conditions in the presence of high energy density. Moreover, the single-track specimens were manufactured under various process conditions for validation of the proposed model. The predicted melt pool dimensions, as well as the melting modes (Conduction/Keyhole), demonstrated good agreement with the experimental measurements. Based on the analysis results, the process boundaries (Keyhole/Lack-of-Fusion) for the SLM process of AlSi10Mg are provided and the potential application of the proposed model for exploring the process window is discussed.

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Extreme gradient boosting-based multiscale heat source modeling for analysis of solid-state phase transformation in additive manufacturing of Ti-6Al-4V
Yeon Su Lee, Kang-Hyun Lee, Min Gyu Chung, Gun Jin Yun
Journal of Manufacturing Processes.2024; 113: 319. CrossRef

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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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Numerical Study on the Effects of the Manufacturing Parameters for Multi-Lumen Catheter Extrusion: Seung Gi Jo, Euntaek Lee; J. Korean Soc. Precis. Eng. 2020;37(1):17-24.
Published online January 1, 2020; DOI: https://doi.org/10.7736/JKSPE.019.129

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The multi-lumen catheter with complex and small cross section is widely used for interventional radiology and minimally invasive surgery. It is manufactured in the polymer extrusion process with many manufacturing parameters. The profile of the extrudate is difficult to predict because it depends on the die shape and many parameters. In this paper, the effects of the manufacturing parameters for multi-lumen catheter extrusion are studied. The commercial software ANSYS Polyflow is used to simulate the polymer flow and predict the profile of the extrudate. The optimized die shape is used to achieve the target profile of the extrudate. The extrudate profiles are investigated with respect to the puller speeds at the end of the extrudate and blowing air pressure of each lumen. Circularity and major diameter are compared for the different manufacturing parameters. The effects of the manufacturing parameters on the profile of the extrudate are examined. The target profile of the extrudate is obtained with optimized manufacturing parameters.

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Study on Improvement of Catheter Tip Forming Process according to Plating Characteristics in Mold
Han Chang Lee, Jinhyuk Jung, Gyu Ik Lee, Woojin Kim, Gyu Man Kim, Bong Gu Lee
Journal of the Korean Society for Precision Engineering.2022; 39(9): 711. CrossRef
Development of a Subpath Extrusion Tip and Die for Peripheral Inserted Central Catheter Shaft with Multi Lumen
Han Chang Lee, Jinhyuk Jeong, Seunggi Jo, Dong Yun Choi, Gyu Man Kim, Woojin Kim
Polymers.2021; 13(8): 1308. CrossRef
A Study on Die Design Optimization for Microcatheter Extrusion Processes
Seunggi Jo, Euntaek Lee
Journal of the Korean Society of Manufacturing Process Engineers.2021; 20(1): 34. CrossRef

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Analysis of Underfill Process on Micro-Pitch Flip-Chip by Epoxy Filling Rate: Ki Beom Ham, Jungo Son, Hyun-Ja Im, Yong-Jai Park; J. Korean Soc. Precis. Eng. 2018;35(6):641-647.
Published online June 1, 2018; DOI: https://doi.org/10.7736/KSPE.2018.35.6.641

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This study investigates epoxy filling rate in the capillary underfill process of flip-chip packaging when the air is not trapped. Various design features were considered, they include; the shape of soldering bump, inlet size, bump height and bump spacing. The geometric models were made by CATIA and the analysis was carried out using commercial CFD software (Moldex3D capillary underfill packaging). In order to improve the usability of the analysis, the spherical bump shape was authenticated by the means of believe as a rhombic shape, and the analysis results were verified. The inlet size did not in any way whatsoever affect the underfill process analysis. From the analysis, we concluded that the epoxy of center parts needs to fill 80% or more of the inside of the edge in order to keep away from the air trapping on the flip-chip. This result can be a guideline for the underfill process conditions that may not be a reason for the air trap in the flip-chip design and manufacturing.

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Numerical Analysis of Thermal Characteristics of a Milling Process of Titanium Alloy Using Nanofluid Minimum-Quantity Lubrication: Young Chang Kim, Jin Woo Kim, Jung Sub Kim, Sang Won Lee; J. Korean Soc. Precis. Eng. 2017;34(4):253-258.
Published online April 1, 2017; DOI: https://doi.org/10.7736/KSPE.2017.34.4.253

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This paper presents a numerical study on the thermal characteristics of a milling process of titanium alloy with nanofluid minimum-quantity lubrication (MQL). The computational fluid dynamics (CFD) approach is introduced for establishing the numerical model for the nanofluid MQL milling process, and estimated temperatures for pure MQL and for nanofluid MQL using both hexagonal boron nitride (hBN) and nanodiamond particles are compared with the temperatures measured by thermocouples in the titanium alloy workpiece. The estimated workpiece temperatures are similar to experimental ones, and the model is validated.