• Architectural research
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• v.14 no.4
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• pp.153-161
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• 2012

This paper presents an integrated procedure to predict the temperature and moisture distributions in hardening concrete considering the effects of temperature and aging. The degree of hydration is employed as a fundamental parameter to evaluate hydro-thermal-mechanical properties of hardening concrete. The temperature history and temperature distribution in hardening concrete is evaluated by combining cement hydration model with three-dimensional finite element thermal analysis. On the other hand, the influences of both self-desiccation and moisture diffusion on variation of relative humidity are considered. The self-desiccation is evaluated by using a semi-empirical expression with desorption isotherm and degree of hydration. The moisture diffusivity is expressed as a function of degree of hydration and current relative humidity. The proposed procedure is verified with experimental results and can be used to evaluate the early-age crack of hardening concrete.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.300-303
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• 2008

In the present study, the simple form of the heat transfer equation were suggested to estimate the temperature variation inside the oil pipe in order to determine the thickness of the insulating materials to retain the working oils below the critical temperature. The conservation of the thermal energy at arbitrary time were modeled to one dimensional unsteady equation with the empirical formula or data. The calculating results for non-insulation case showed that the temperature were very sensitive to the thermal convection by the velocity of the external wind. For insulation case, the insulation material which has higher density and specific heat, lower thermal conductivity should be chosen with more brighter coloring outside the pipe in order to retain the working oils below the critical temperature.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.133-152
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• 2015

Mathematical model has been developed for determination of temperature field in multilayer pavement and subgrade, which considers transfer of heat by conduction and convection, receiving of heat from total solar radiation and atmosphere emission, output of heat due to the emission from the surface of pavement. The developed model has been realized by the finite element method for two dimensional problem using two dimensional second order finite element. Calculations for temperature field have been made with the programme realized on the standard mathematical package MATLAB. Accuracy of the developed model has been evaluated by comparison of temperatures, obtained theoretically and experimentally. The results of comparison showed high accuracy of the model. Long-term calculation (within three months) has been made in pavement points in accordance with the data of meteorological station for air temperature. Some regularities have been determined for variation of temperature field.

• Journal of Energy Engineering
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• v.20 no.1
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• pp.1-7
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• 2011

The performance and life-cycle costs of electric vehicle(EV) and hybrid electric vehicle(HEV) depend inherently on battery packs. Temperature uniformity in a pack is an important factor for obtaining optimum performance for an EV or HEV battery pack, because uneven temperature distribution in a pack leads to electrically unbalanced battery cells and reduced pack performance. In this work, a three-dimensional modeling was carried out to investigate the effects of operating conditions on the thermal behavior of a lithium-ion battery pack for an EV or HEV application. Thermal conductivities of various compartments of the battery were estimated based on the equivalent network of parallel/series thermal resistances of battery components. Heat generation rate in a cell was calculated using the modeling results of the potential and current density distributions of a battery cell.

• Journal of Korean Society on Water Environment
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• v.24 no.5
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• pp.581-591
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• 2008

Most of our rivers are fragmented by the presence of at least one large dam. Dams are often the most substantial controller of the flow regimes and aquatic environments of natural river system. The quality of downstream water released from a stratified reservoir is highly dependent on upstream reservoir water quality. Thus, an integrated modeling approach is more efficient, compared to fragmented modeling approach, and necessary to better interpret the impact of dam operation on the down stream water quality. The objectives of this study were to develop an integrated reservoir-river modeling system for Daecheong Reservoir and its downstream using a two-dimensional laterally averaged hydrodynamic and water quality model, and evaluate the model's performance against field measurement data. The integrated model was calibrated and verified using filed data obtained in 2004 and 2006. The model showed satisfactory performance in predicting temporal variations of water stage, temperature, and suspended solid concentration. In addition, the reservoir-river model showed efficient computation time as it took only 3 hours for one year simulation using personal computer (1.88 Ghz, 1.00 GB RAM). The suggested modeling system can be effectively used for assisting integrated management of reservoir and river water quality.

• Journal of Korea Foundry Society
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• v.41 no.5
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• pp.445-453
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• 2021

Computational thermodynamics for various alloy systems is well known as the CALPHAD technique. Gibbs energy model parameters for each phase are obtained from experimentally measured thermodynamic properties and are mainly used to predict areas not experimentally measured and to analyze experimental results thermodynamically. In this study, the thermodynamic modeling of the Ni-Cr-Nb-C quaternary system is conducted for a thermodynamic analysis of the phenomena by which heat-resistant cast alloys (IN-657) are destroyed in certain areas after long-term use. The stable phases in the system according to the Cr content, phase fraction depending on the temperature, and long-range ordering parameters for the Ni₂Cr phase are calculated and compared to results obtained experimentally. The calculated thermodynamic properties suitably explain the experimentally reported fracture temperature range and the results of stable phases formed in the fractured areas. Thermodynamic modeling through the CALPHD method is expected to be useful for analyzing and predicting the thermodynamic behaviors of various cast alloys.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.12 no.1
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• pp.43-49
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• 2007

The methods of physical oceanographic surveys to examine the effect of thermal discharge from nuclear power plants in Korea have been reviewed and a standard guide to the survey is proposed. It is desirable that in situ observation and numerical thermal diffusion modeling are conducted simultaneously to describe the variation in temperature distribution affected by thermal discharge from a power plant because any observation or numerical modeling alone has limits to do so quantitatively. It is suggested that the field observation must be based on the concept of heat budget modeling considering all artificial and natural heat sources/sinks around the power plant. Any results from numerical modeling must reach to a certain statistical significance level to use for a standard temperature distribution. In addition, the development of standard numerical codes is proposed to improve the problems shown in the past numerical circulation and diffusion modelling.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.156-157
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• 2005

Gas hydrate is ice-like crystalline lattice, formed at appropriate temperature and pressure, in which gas molecules are trapped. It is worldwide popular interesting subject as a potential energy. In korea, a seismic survey for gas hydrate have performed over the East sea by the KIGAM since 1997. In this paper, we had conducted numerical and physical modeling experiments for seismic properties on gas hydrate with field data which had been acquired over the East sea in 1998. We used a finite difference seismic method with staggered grid for 2-D elastic wave equation to generate synthetic seismograms from multi-channel surface seismic survey, OBC(Ocean Bottom Cable) and VSP(Vertical Seismic Profiling). We developed the seismic physical modeling system which is simulated in the deep sea conditions and acquired the physical model data to the various source-receiver geometry. We carried out seismic complex analysis with the obtained data. In numerical and physical modeling data, we observed the phase reversal phenomenon of reflection wave at interface between the gas hydrate and free gas. In seismic physical modeling, seismic properties of the modeling material agree with the seismic velocity estimated from the travel time of reflection events. We could easily find out AVO(Amplitude Versus Offset) in the reflection strength profile through seismic complex analysis.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.3
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• pp.227-234
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• 2014

Fuel consumption rates of electric vehicles strongly depend on their battery performance. Because the battery performance is sensitive to the operating temperature, temperature management of the battery ensures its performance and durability. In particular, the temperature distribution among modules in the battery pack affects the cooling characteristics. This study focuses on the thermal modeling of a battery pack to observe the temperature distribution among the modules. The battery model is a prismatic model of 10 NiMH battery modules. The thermal model of the battery consists of heat generation, convective heat transfer through the channel and conduction heat transfer among modules. The heat generation is calculated by the electric resistance heat during the charge/discharge state. The model is used to determine a strategy for proper thermal management in Electric vehicles.

• Proceedings of the IEEK Conference
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• 2004.08c
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• pp.780-783
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• 2004

The two-dimensional modeling of the non-stationary thermal state and voltage responsivity of the sensitive elements usually used in solid-state pyroelectric focal plane arrays are presented. Temperature distributions under periodical thermal excitation and the response of the thermal imaging device, which is composed of the pyroelectric sensitive elements mounted on a single silicon substrate, are numerically calculated. The sensitive element consists of a covering metal layer, infrared polymer absorber, front metal contact, sensitive pyroelectric element, the interconnecting column and the bulk silicon readout. The results of the numerical modeling show that the thermal crosstalk between sensitive elements to be critical especially at low frequency (f < 10Hz) of periodically modulated light. It is also shown that the use of our models gives the possibility to improve the design, operating regimes and sensitivity of the device.