• Journal of the Society of Naval Architects of Korea
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• v.51 no.4
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• pp.342-348
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• 2014

In general, the forming process of the curved hull plates consists of sub tasks, such as roll bending, line heating, and triangle heating. In order to complement the automated curved hull forming system, it is necessary to develop an algorithm to classify the curved hull plates of a ship into standard shapes with respect to the techniques of forming task, such as the roll bending, the line heating, and the triangle heating. In the previous research, the classification algorithm of curved hull plates was studied only about rectangle shaped plates, and other limitations were notified. In this paper, the classification algorithm is extended to classify not only rectangle shaped plates but also arbitrary polygon hull plates. The discrete curvature can be computed by using arbitrary polygon mesh which is represented by half-edge data structure and discrete differential geometry. The algorithm tests to verify the developed algorithm with sample plates of a real ship data have been performed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.28-34
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• 2019

Solar energy is one of the most abundant renewable energy sources on Earth but there are restrictions on the use of solar thermal energy due to the time-discrepancy between the solar-rich season and heating demand. In Europe and Canada, a seasonal solar thermal energy storage (SSTES), which stores the abundant solar heat in the summer and uses the heat for the winter heating load, is used. Recently, SSTES has been introduced in Korea and empirical studies are actively underway. In this study, a $2,000m^2$ flat plate type solar collector and $20,000m^2$ of borehole thermal energy storage (BTES) were studied for a greenhouse in Hwaseong City, which has a heating load of 2,164 GJ/year. To predict the dynamic performance of the system over time, it was simulated using the TRNSYS 18 program, and the solar fraction of the system with the control conditions was investigated. As a result, the solar BTES system proposed in this study showed an average solar fraction of approximately 60% for 5 years when differential temperature control was applied to both collecting solar thermal energy and discharging BTES. The proposed system simplified the configuration and control method of the solar BTES system and secured its performance.

• Design & Manufacturing
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• v.17 no.1
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• pp.1-5
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• 2023

In multi-material injection molding, since two or more materials with different process conditions are used, it is essential to maximize process efficiency by operating the cooling or heating system to a minimum. In this study, Liquid silicone rubber (LSR) that can be cured at a low temperature suitable for the multi-material injection molding was selected and the cure behavior according to the process conditions was analyzed through differential scanning calorimetry (DSC). Dynamic measurement results of DSC with different heating rate were obtained, and through this, the total heat of reaction when the LSR was completely cured was calculated. Isothermal measurement results of DSC were derived for 60 minutes at each temperature from 80 ℃ to 110 ℃ at 10 ℃ intervals, and the final degree of cure at each temperature was calculated based on the total heat of reaction identified from the Dynamic DSC measurement results. As the result, it was found that when the temperature is lowered, the curing start time and the time required for the curing reaction increase, but at a temperature of 90 ℃ or higher, LSR can secure a degree of cure of 80% or more. However, at 80 ℃., it was found that not only had a relatively low degree of curing of about 60%, but also significantly increased the curing start time. In addition, in the case of 110 ℃, the parameters were derived from experimental result using the Kamal kinetic model.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.215-220
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• 2006

Along with socioeconomic development and improving standard of living, the heat demand for heating and cooling in residential and commercial sectors is expected to expand rapidly, reaching over 43 million TOE by 2010 in Korea(about 80% increase compared with that in 1995). Since most of this heat demand is loop temperature below $60^{\circ}C$, the utilization of 'unused energy' is surely one of very effective measures to both environmental preservation and energy conservation. 'Unused energy' in this paper is implicated as 'temperature differential energy' available from treated sewage water, useful and abundant heat source for heat pump(cooler in summer and warmer in winter than outside air). An analysis was carried out to estimate the energy potential of treated sewage water for heat pump heat source. Some analysis were taken to study the characteristics of a heat pump system using the treated sewage water as heat source.

• Polymer(Korea)
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• v.24 no.1
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• pp.105-112
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• 2000

Using a commercial epoxy/carbon fiber composite prepreg (DMS 2224) as a model system, the cure kinetics of vitrifying thermoset system were analyzed by isothermal and dynamic-heating experiments. Focusing on the processing condition of high performance composite systems, a phenomenological kinetic model was developed by using differential scanning calorimetry (DSC) and reaction kinetics theories. The model system exhibited a limited degree of cure as a function of isothermal temperature seemingly due to the diffusion-controlled reaction rates. The diffusion-controlled cure reaction was incorporated in the development of the kinetic model, and the model parameters were determined from isothermal experiments. The first order reaction was confirmed from the characteristic shape of isothermal cure thermograms, and the activation energy wes 78.43 kJ/mol. Finally, the proposed model was used to predict a complex autoclave thermal condition, which was composed of several isothermal and dynamic-heating stages.

• The Journal of the Acoustical Society of Korea
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• v.3 no.1
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• pp.9-15
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• 1984

Thermoacoustic oscillation induced by a heater in a tube with air current is studied theoretically. Linearized perturbation equations are derived in dimensionless form under the assumption that the system is one dimensional. The equation to predict the acoustic power generation from a heating surface is derived and calculated by solving differential equations numerically. The effect of the mean velocity of the air current is illustrated. The energy conversion mechanism is shown by pressure-volume diagram like a heat engine.

• Nuclear Engineering and Technology
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• v.49 no.8
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• pp.1654-1659
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• 2017

The boundary layer of a two-dimensional forced convective flow along a persistent moving horizontal needle in an electrically conducting magnetohydrodynamic dissipative nanofluid was numerically investigated. The energy equation was constructed with Joule heating, viscous dissipation, uneven heat source/sink, and thermal radiation effects. We analyzed the boundary layer behavior of a continuously moving needle in Blasius (moving fluid) and Sakiadis (quiescent fluid) flows. We considered Cu nanoparticles embedded in methanol. The reduced system of governing Partial differential equations (PDEs) was solved by employing the Runge-Kutta-based shooting process. Computational outcomes of the rate of heat transfer and friction factors were tabulated and discussed. Velocity and temperature descriptions were examined with the assistance of graphical illustrations. Increasing the needle size did not have a significant influence on the Blasius flow. The heat transfer rate in the Sakiadis flow was high compared with that in the Blasius flow.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.11
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• pp.514-521
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• 2001

This paper uses the distributed heating thin metal moving at constant velocity which are modeled as distributed parameter systems, and applies the Paley order of Walsh functions to high order partial differential equations and matrix partial differential equations. This thesis presents a new algorithm which usefully exercises the optimal control in the distributed parameter systems. In this paper, the excellent consequences are found without using the existing decentralized control or hierarchical control method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3_1spc
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• pp.615-621
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• 2013

A blind system for window glass has been designed and manufactured as a CapStone Design project at Seoul National University of Science and Technology. This system automatically controls the interior illuminance to maintain a uniform temperature. The aim of this project was to support an air conditioning system and heating equipment to maintain a good indoor environment. Proportional integral differential (PID) control using cadmium sulfide (CdS) sensors was applied to control it. Polaroid film was attached to the new blind system to reflect sunlight. It was found that the system had the potential to reduce energy consumption and may be used with a building energy management system (BEMS).

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1303-1309
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• 2018

In the present paper, we study the entropy analysis of boundary layer flow over a slender stretching sheet under the action of a non uniform magnetic field that is acting perpendicular to the flow direction. The effects of viscous dissipation and Joule heating are included in the energy equation. Using similarity transformation technique the momentum and thermal boundary layer equations to a system of nonlinear differential equations. Numerical solutions are obtained using the shooting and fourth-order Runge-Kutta method. The expressions for the entropy generation number and Bejan number are also obtained using a suggested similarity transformation. The main objective of this article is to investigate the effects of different governing parameters such as the magnetic parameter ($M^2$), Prandtl number (Pr), Eckert number (Ec), velocity index parameter (m), wall thickness parameter (${\alpha}$), temperature difference parameter (${\Omega}$), entropy generation number (Ns) and Bejan number (Be). All these effects are portrayed graphically and discussed in detail. The analysis reveals that entropy generation reduces with decreasing wall thickness parameter and increasing temperature difference between the stretching sheet and the fluid outside the boundary layer. The viscous and magnetic irreversibilities are dominant in the vicinity of the stretching surface.