• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.510-518
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• 2018

Recently, lots of interests have been concentrated on the scrubber system that abates waste gases produced from semiconductor manufacturing processes. An effective design of the thermal decomposition reactor inside a scrubber system is significantly important since it is directly related to the removal performance of pollutants and overall stabilities. In the present study, a computational fluid dynamics (CFD) analysis was conducted to figure out the thermal and flow characteristics inside the reactor of wet scrubber. In order to verify the numerical method, the temperature at several monitoring points was compared to that of experimental results. Average error rates of 1.27~2.27% between both the results were achieved, and numerical results of the temperature distribution were in good agreement with the experimental data. By using the validated numerical method, the effect of the reactor geometry on the heat transfer rate was also taken into consideration. From the result, it was observed that the flow and temperature uniformity were significantly improved. Overall, our current study could provide useful information to identify the fluid behavior and thermal performance for various scrubber systems.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.364-367
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• 2011

The development of the DCS thrust unit during the attitude control thruster of the launch vehicle and guided missile is introduced. The DCS thrust unit using solid propellants based on a two-axis control is designed and through the thermo-structural and flow analysis is designed in detail. The performance of the thrust unit based on the detail design is demonstrated through a combustion test.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.7-14
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• 1986

To predict the fuel clad temperature during the reflooding phase of a LOCA, one may need a knowledge of reflood heat tranfer mechanism in a rod bundle. For this purpose reflooding experiments have been carried out with an electrically heated 3*3 rod bundle. Using the method for the determination of local heat transfer coefficient from the measured wall temperature the parametric effects of coolant flow rate, initial wall temperature, coolant subcooling and heat generation rate on the propagation of rewetting front were investigated. Prediction of the wall temperature histories for these experiments was discussed using REFLUX code with modification of the rewetting temperature correlation. Through this modification, better agreement between experiment and prediction was obtained.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.5
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• pp.100-109
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• 2003

A performacne simulation model of the PT6A-62 turboprop engine using the $SIMULINK^R$ was proposed to predict transient and steady state behaviors. The $SIMULINK^R$ has several advantages such as user-friendliness due to the GUI(Graphic User Interfaces) and ease in the modification of the computer program. The $SIMULINK^R$ model consists of subsystems to represent engine gas path components such as flight initial subsystem, compressor subsystem, burner subsystem, compressor turbine subsystem, power turbine, exhaust nozzle subsystem and integrator subsystem. In addition to subsystems, there are search subsystems to find an appropriate operating point by scaling from the 2-D components look-up table, Gasprop Subsystem to calculate the gas property precisely. In case of steady state validation, performance results analyzed by the proposed $SIMULINK^R$ model were agreed well with the analysis results by the commercial GASTURB program. Moreover in validation of the transient model, it was found that performance simulation results by the proposed model were reasonable agreement with analysis results by the well-proved computer program using FORTRAN.

• Clean Technology
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• v.29 no.4
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• pp.305-312
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• 2023

Due to the strengthening of environmental requirements, aging denitrification facilities need to improve their performance. The present study aims to suggest the possibility of improving performance using computational analysis techniques. This involved modifying both the geometric design and the operating conditions, including the flow path shape of the equipment such as the inlet guide vane and the curved diffusing part, and the flow control of the ammonia injection nozzle. The conditions presented in this study were compared with existing operating conditions in terms of the flow uniformity, the NH₃/NO molar ratio of the mixed gas flowing into the catalyst layer, and the total pressure drop of the facility. The flow field applied in the computational analysis ranged from the outlet of the economizer in the combustion furnace to the inlet of the air preheater, the full domain of the denitrification facility. The performances were derived by solving the flow fields using ANSYS-Fluent and the injection amount of ammonia was adjusted for each nozzle using Design Xplorer. Compared to the denitrification performances of the equipment currently in operation, the conditions proposed in this study showed an improvement in the flow uniformity and NH₃/NO composition ratio by 45.1% and 8.7%, respectively, but the total pressure drop increased by 1.24%.

• Korean Journal of Poultry Science
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• v.30 no.4
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• pp.229-233
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• 2003

A study was conducted to investigate the effects of different BW control methods during rearing on laying performance of broiler breeder pullets. D-old 540 female breeder chicks (Arbor Acres) were assigned to three treatments consisted of standard BW (Control), 110% of standard BW at 12 wk of age (T1), and 90% of standard BW at 12 wk of age (T2), with three replicates of 60 birds per replicate (pen) for each treatment. At 20 wk of age, all birds from three treatments reached the BW reqired in the Arbor Acres Manual. There were no significant differences in egg production, egg weight and viability during laying period(p>0.05). However, total egg production rates were improved in T2 and T3. Average egg weight was the highest in T1 among all treatments. Fertility and hatchability were similar among treatments, but T2 tended to be higher than other treatments at 37 and 53 wk of age. No significant difference was found in hatchability among three treatments. The number of hatching egg of T2 reached 168 per year, showing higher number of eggs than did the other treatments. The number of hatched chicks in T2 was 131, which was also higher than the other treatments, but the difference was not significant. It appears that the laying performance of broiler breeder hens could be improved when their BW at 12 wk of age are kept at 90% of standard BW, and reach the standard BW at 20 week of age.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.2
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• pp.985-992
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• 2011

The 3D computational fluid dynamics (CFD) was performed in relation to the internal fluid characteristics and flow distribution for the development of the most optimal model in the complex post-disposal device. As it is expected that a channeling (drift) would be made by the semi-dry reactor due to the large difference in the flow distribution by the compartment in the bag filter, a structural improvement should be urgently made for more uniformed flow distribution in the bag filter. Three types of modifications such as i) changing the plenum shape, ii) orifice install in the exit part of cleaned gas, iii) increasing the plenum number were established. From the results of computational fluid dynamics, it was revealed that the changing of plenum shape and orifice install in the exit part of cleaned gas was more reasonable than the increasing the plenum number because of the difficulties of retrofit. The complex post-disposal device, modified and supplemented with this analysis, integrated the semi-dry reactor and the bag filter in a single body, so it follows that the improvement can make the device compact, save the installation area, save the operation fee, and management more convenient.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.545-550
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• 2017

When the systolic blood pressure is high, intermittent turbulence in blood flow appears in the aorta and carotid artery with stenosis during the systolic period. The turbulent blood flow is difficult to analyze using the Newtonian turbulence model due to the viscous characteristics of blood flow. As the shear rate is increased, the blood viscosity decreases by the viscoelastic properties of blood and a drag reduction phenomenon occurs in turbulent blood flow. Therefore, a new non-Newtonian turbulent model is required for viscoelastic fluid and hemodynamics. The main aims of this study were to develop a non-Newtonian turbulence model using the drag reduction phenomenon based on the standard $k-{\varepsilon}$ turbulent model for a general non-Newtonian fluid. This was validated with the experimental data and has a good tendency for non-Newtonian turbulent flow. In addition, the computation time and resources were lower than those of the low Reynolds number turbulent model. A modified turbulent model was used to analyze various turbulent blood flows.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.2
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• pp.115-120
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• 2014

To enhance the performance of an automobile turbocharger compressor, the circumferential inlet heights of the volute were modified and the flow field for the combined region of the diffuser and volute was numerically investigated using commercial software. Basically, a well-designed volute should have a high pressure recovery coefficient and a low loss coefficient for the total pressure. In this study, two circular volutes with the same cross sectional shape and tongue angle, but circumferentially different volute inlet heights, were selected. One volute had the middle inlet in the cross-section at the circumferential angle of $90^{\circ}$ but gradually lower inlet heights for the angles between $90^{\circ}$ to $360^{\circ}$ with respect to the cross sectional center of the volute, while maintaining the same height between the tangential line connecting the lowest positions of the cross section and the line connecting the volute inlets in the circumferential direction (case 1 volute). The other volute has an inlet height that is 2 mm lower than in case 1 volute such that the tongue section has a tangential inlet (case 2 volute). The results showed that the case 2 volute had a higher total pressure ratio because of its higher pressure recovery coefficient and higher isentropic efficiency, resulting from the lower loss coefficient along the circumferential position than the case 1 volute.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.142-148
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• 2002

Autonomous underwater vehicles (AUVs) are unmanned underwater vessels to investigate sea environments, oceanography and deep-sea resources autonomously. Docking systems are required to increase the capability of the AUVs to recharge the batteries and to transmit data in real time for specific underwater works, such as repeated jobs at sea bed. This paper presents a visual servo control system for an AUV to dock into an underwater station with a camera mounted at the nose center of the AUV. To make the visual servo control system, this paper derives an optical flow model of a camera, where the projected motions of the image plane are described with the rotational and translational velocities of the AUV. This paper combines the optical flow equation of the camera with the AUVs equation of motion, and derives a state equation for the visual servoing AUV. This paper proposes a discrete-time MIMO controller minimizing a cost function. The control inputs of the AUV are automatically generated with the projected target position on the CCD plane of the camera and with the AUVs motion. To demonstrate the effectiveness of the modeling and the control law of the visual servoing AUV, simulations on docking the AUV to a target station are performed with the 6-dof nonlinear equations of REMUS AUV and a CCD camera.