• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.171-178
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• 2014

From now on, in order to meet more stringer diesel emission standard, diesel vehicle should be equipped with emission after-treatment devices as NOx reduction catalyst and particulate filters. Urea-SCR is being developed as the most efficient method of reducing NOx emissions in the after-treatment devices of diesel engines, and recent studies have begun to mount the urea-SCR device for diesel passenger cars and light duty vehicles. That is because their operational characteristics are quite different from heavy duty vehicles, urea solution injection should be changed with other conditions. Therefore, the number and diameter of the nozzle, injection directions, mounting positions in front of the catalytic converter are important design factors. In this study, major design parameters concerning urea solution injection in front of SCR are optimized by using a CFD analysis and Taguchi method. The computational prediction of internal flow and spray characteristics in front of SCR was carried out by using STAR-CCM+7.06 code that used to evaluate $NH_3$ uniformity index($NH_3$ UI). The design parameters are optimized by using the $L_{16}$ orthogonal array and small-the-better characteristics of the Taguchi method. As a result, the optimal values are confirmed to be valid in 95% confidence and 5% significance level through analysis of variance(ANOVA). The compared maximize $NH_3$ UI and activation time($NH_3$ UI 0.82) are numerically confirmed that the optimal model provides better conversion efficiency of $NH_3$. In addition, we propose a method to minimize wall-wetting around the urea injector in order to prevent injector blocks caused by solid urea loading. Consequently, the thickness reduction of fluid film in front of mixer is numerically confirmed through the mounting mixer and correcting injection direction by using the trial and error method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2285-2290
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• 2012

This study is about atherosclerosis which occupies the highest rate in many diseases people have and we have studied about atherosclerosis for abdominal aorta. Atherosclerosis is the phenomenon which blood vessel gets narrower, harder and thicker due to the stenosis of colesterol in blood vessel. If it becomes worse, arteries will be hard and blood can't flow smoothly, and even it can reach to death. In this study, the geometric models of the considered stenotic blood flow are two different types of constriction of cross-sectional area of blood vessel; 20 and 45% of constriction in each elastic wall and rigid wall. We have modeled by using finite element method to observe the changes of velocity and pressure. In case of the diameter of blood vessel decreased 45% in elastic wall model, the values of velocity and pressure were higher than the case of 20% and in case of the diameter of blood vessel decreased 45% in rigid wall model, the values of velocity and pressure were higher than the case of 20%. In cases of elastic wall models of the diameters of blood vessels decreased each of 20% and 45%, recirculation zones appeared. This results show understanding of hemodynamic properties depending on stenosed blood vessels.

• Journal of Biomedical Engineering Research
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• v.25 no.6
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• pp.489-496
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• 2004

Insertion of cannulae into vessels may disturb the blood flow doing non-physiological load and stress on blood cells such that ADP may increase and result in hemolysis. Authors used the computational method to simulate the 3-dimensional blood flow inside of the cannula using numerical method. We limited the research to within the drainage cannulae with side holes inserted through the human vein. In this paper, 9 different cannulae with side holes categorized by the number of side holes of 4, 12, and 20, and also categorized by the array type of side holes of staggered array, in-line array, and alternative in-line array were studied and compared to the cannula with no side holes by using CFD analysis. We evaluated the flow rate, the wall shear stress, and the shear rate and compared them with one another to estimate the effect of the side holes. The flow rate is not proportional to the number of the side holes. However, larger number of side holes can reduce the mean shear rate. Both the number and the array type of side holes play an important role on the fluid dynamics of the blood flow in cannulae.

• Journal of the Microelectronics and Packaging Society
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• v.30 no.4
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• pp.44-49
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• 2023

In the global pursuit of carbon neutrality, the rapid increase in the adoption of electric vehicles (EVs) has led to a corresponding surge in the demand for batteries. To achieve high efficiency in electric vehicles, considerations of weight reduction and battery safety have become crucial factors. Copper and aluminum, both recognized as lightweight materials, can be effectively joined through laser welding. However, due to the distinct physical characteristics of these two materials, the process of joining them poses technical challenges. This study focuses on conducting simulations to identify the optimal laser parameters for welding copper and aluminum, with the aim of streamlining the welding process. Additionally, a Graphic User Interface (GUI) program has been developed using the Python language to visually present the results. Using machine learning image data, this program is anticipated to predict joint success and serve as a guide for safe and efficient laser welding. It is expected to contribute to the safety and efficiency of the electric vehicle battery assembly process.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.3
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• pp.223-229
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• 2015

In this study, the effects of the leakage flow between the baffle and tube bundles on the performance of a shell and tube heat exchanger (STHE) were examined using the commercial software ANSYS FLUENT v.14. A computational fluid dynamics model was developed for a small STHE with five different cases for the ratio of the leakage cross-sectional area to the baffle cross-sectional area, ranging from 0 to 40%, in order to determine the optimum leakage flow corresponding to the maximum outlet temperature. Using fixed tube wall and inlet temperatures for the shell side of the STHE, the flow and temperature fields were calculated by increasing the Reynolds number from 4952 to 14858. The present results showed that the outlet temperature, pressure drop, and heat transfer coefficient were strongly affected by the leakage flow, as well as the Reynolds number. In contrast with a previous researcher's finding that the leakage flow led to simultaneous decreases in the pressure drop and heat transfer rate, the present study found that the pertinent leakage flow provided momentum in the recirculation zone near the baffle plate and thus led to the maximum outlet temperature, a small pressure drop, and the highest heat transfer rate. The optimum leakage flow was shown in the case with a ratio of 20% among the five different cases.

• Journal of Biosystems Engineering
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• v.37 no.2
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• pp.75-81
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• 2012

Oyster mushroom farm which could not meet optimum temperature range yields non-uniform sized, low quality products. Thus, this study, utilizing STAR CCM+, one of the computational fluid dynamics (CFD) programs, analyzed the impact of air circulation and temperature distribution. Methods: After we visited numerous mushroom farms, we measured the temperature at the discharge ports of heaters, fan capacity, and the locations of the air circulators in the farms. According to the data, most mushroom growers installed the heaters near the entrance and discharge ports of the heaters at the third growing bed on the same height as the heaters in the entrance. The temperature at the discharge port of heater was $1,26^{\circ}C$, and the fan capacity was 4,500 $m^3$/hr. The air circulator was placed in the center of the mushroom farm 50cm above the ground, and its capacity of inlet port was 1,100 $m^3$/hr and discharge port 1,600 $m^3$/hr. The mushroom farm was insulated. Results: According to the analysis of the temperature distribution in the vertical plane of the entrance side, no air circulation causes the high temperature zone of 296~299K at the discharge port of the heater to take up 34% of area while the operation of air circulators causes it to occupy only 9%. This means that not using air circulators leads to a concentration of high temperature at the discharge port near the entrance. In addition, with the results of the analysis of the temperature distribution in the vertical planes of the center, no air circulation causes the temperature zone of 295~298K at the discharge port of the heater to take up 48% of area while the operation of air circulators causes it to occupy 80%. This shows that the high outlet port temperature disseminated to the center. Conclusions: After ninety minute operation of both heater and air circulator, the interior temperature became stabilized in the mushroom farm. Air circulation made the high temperature at the discharge port disseminate to the center and exit in the farm and equalize the temperature distribution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.310-316
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• 2019

In automotive application, customers are demanding high efficiency and various functions for convenience. The demand for these automotive applications is steadily increasing. In this study, it has been studied the analysis of heat flow to improve the PCB(printed circuit board) heating performance of WPC (wireless power charger) recently developed for convenience. The charging performance of the wireless charger has been reduced due to power dissipation and thermal resistance of PCB. Therefore, it has been proposed optimal PCB design, layout and position of electronic parts through the simulation of heat flow analysis and PCB design was analyzed and decided at each design stage. Then, the experimental test is performed to verify the consistency of the analysis results under actual environmental conditions. In this paper, The PCB modeling and heat flow simulation in transient response were performed using HyperLynx Thermal and FloTHERM. In addition, the measurement was performed using infrared thermal imaging camera and used to verify the analysis results. In the final comparison, the error between analysis and experiment was found to be less than 10 % and the heating performance of PCB was also improved.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1106-1115
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• 2021

In this study, a fin that controls ship stern flow was attached on stern hull of a 80k bulk carrier to improve resistance performance. The rectangular cross-sectional fin was attached at several locations on the hull, and angle to streamline was changed with constant length, breadth, and thickness. The resistance performance and wake on propeller plane of the hull with and without the fin were analyzed using model-scale computational fluid dynamics simulation. The analysis results were extrapolated to full-scale to compare the performance and wake of the full-scale ship. First, the fin changed path of bilge vortex that flowed into the propeller along the stern hull without the fin to transom stern. This change increased pressure of the stern hull and upper region of the propeller, so pressure resistance and total resistance of the hull were reduced - the nearer the fin location to after perpendicular (AP) and base line of the hull, the larger the reduction of the resistances. Second, nominal wake fraction of the hull with the fin was lower than that without the fin. This dif erence was in proportion to the angle of the fin, but the total resistance reduction was in proportion until a certain angle at which the reduction was maximum. The largest total resistance reduction was approximately 2.1% at 12.5% of length between perpendiculars from the AP, 10% of draft from the base line, and 14° with respect to the streamline.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.77-82
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• 2010

Our study aims to understand the flow of liquid in an open-top rectangular microchannel that can be used in micro total analysis systems ($\mu$-TAS) because it has advantages in terms of light transmission and energy efficiency. We measured the liquid velocity using particle tracking technique and conducted a simulation with computational fluid dynamics by altering the area of channel cross section and channel length for the capillary-driven flow in the open-top rectangular microchannel. When liquid water drops to an entrance of the fabricated microchannel with a height of 20 μm and a width of 20 ${\mu}m$, it flows along the microchannel by only capillary force. In the wetting behavior of the liquid, important parameters of this flow are channel size, contact angle and liquid properties such as surface tension and viscosity, which are used to control the flow of liquid in the microchannel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.3
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• pp.10-16
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• 2020

Computational simulations of adsorption columns were carried out to investigate the removal characteristics of VOCs from a laundry shop. n-Decane was selected as the representative component among the VOCs emitted, and the activity of the adsorbents, such as activated carbon, was evaluated using commercial CFD code. The mathematical framework was composed of continuity and Navier-stokes equations, and the simulation was performed using the Matlab program. The adsorption isotherms of LDF, Freundlich, and Langmuir were evaluated, and the adsorption amount of the adsorption isotherms with the adsorption parameter was compared. The simulation was carried out using a particle porosity, dispersion coefficient, particle density, bed diameter, and bed length of 0.79, 42.4 ㎠/min, 485 g/L, 2.0 cm, and 2.5 cm, respectively. The effect of the gas velocity, dispersion coefficient, and voidage on the adsorption amount was compared in the Langmuir adsorption isotherm. The simulation was carried out in the velocity range of 50 to 200 cm/min, dispersion coefficient range of 100 to 400 ㎠/min, and particle porosity range of 0.66 to 0.79. The simulation results of activated carbon with benzene coincided with the Langmuir isotherm. Three types of adsorption isotherm were compared under similar conditions, and the simulation results showed the efficient adsorption condition for hydrocarbons.