• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.244-246
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• 1996

In an controlled electric machine, the variations of motor parameters such as stator and rotor time constant are caused by the temperature rise, thus it is needed to calculate the accurate parameter through the dynamic characteristic analysis considering the temperature variation. In this paper, the dynamic characteristic analysis method of vector controlled LIM is proposed using coupled magnetic & thermal 2D FEM taking into account the movement.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.12
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• pp.140-145
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• 2004

In this study, the design and analysis of a butterfly valve disk was performed to minimize the rubbing between the disk and the seat at opening and closing. The butterfly valve has double eccentric structure and the contact surface between the disk and the seat is a conical surface. At the instant of opening and closing the valve by the rotation of disk, the positions of zero contact point are changed. Also, if the cone surface is cut in the perpendicular direction to the rotation axis of the valve, the contour of cutting section is hyperbolic. Therefore minimum distance between the origin of the eccentric axis and the hyperbolic curve goes to the position of zero contact point. In order to consider the interferences between the disk and the seat, the thermal-structure coupled field analysis was performed by ANSYS.

• Tunnel and Underground Space
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• v.18 no.3
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• pp.175-184
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• 2008

In this study, state-of-the-art of $CO_2$ geological sequestration as a method of greenhouse gas reduction was reviewed. Thermal-Hydraulic-Mechanically(THM) coupled simulation technology and its application to a stability analysis of geological formation due to $CO_2$ injection as well as a leakage path analysis were investigated and introduced.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.1
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• pp.14-18
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• 2010

Car muffler has the role to form the exhaust gas from high temperature- pressure to lower level and reduce the generated noise. Because of this role, its durability decrease as deformation by heat is occurred. This study is to analyze the flow of exhaust gas inside muffler and its coupled thermal deformation with 3-D modeling and ANSYS. There is the fastest flow at the exit of muffler with the maximum velocity of 54 m/s. And the maximum deformation or equivalent stress is shown at this model respectively as 0.00435 mm or 3414.4 MPa by the influence of heat and pressure at part of intersection with inlet and body of muffler.

• Land and Housing Review
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• v.9 no.4
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• pp.25-32
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• 2018

Application of geothermal energy in buildings has been gaining popularity as it provides the benefits of both heating and cooling a building. Among the various types of geothermal energy systems, ground-coupled heat pump system is the most commonly applied one in South Korea. A ground heat exchanger plays an important role as a heat source in winter and a heat sink in summer. For the stable operation of a ground-coupled heat pump system, a ground heat exchanger should be sized so that it provides sufficient heating and cooling energy. Heating and cooling energies generated in ground heat exchangers mainly depend on the temperature difference between the heating medium in ground heat exchangers and the surrounding ground. In addition, the performance of ground heat exchangers influences the change in ground temperature. Therefore, it is necessary to consider this interrelation between the change in the ground temperature and the performance of ground heat exchanger for an accurate estimation of its performance. However, previous thermal analysis models for ground heat exchangers are not competent enough to allow a complete understanding of this interrelation. Therefore, this study proposes a three-dimensional equivalent, transient ground heat exchanger analysis model. First, a previous thermal analysis model for ground heat exchangers, including an analytical model, a g-function, and a numerical model are analyzed. Next, to overcome the limitations of the previous models, a three-dimensional equivalent, transient ground heat exchanger model is proposed. Finally, this study validated the proposed model with the measurement data of the thermal response test, sandbox test, and TRNSYS DST model. All validation results showed a good agreement. These findings helped us to investigate the thermal performance of ground heat exchangers more accurately than the analytical models, and faster than the numerical models. Furthermore, the proposed model contributes to the design of ground heat exchangers by considering the different operation conditions of buildings.

• Tunnel and Underground Space
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• v.4 no.2
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• pp.102-118
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• 1994

Thermomechanical analysis is conducted on the radioactive repository in deep rock mass considering the in-situ stress, excavation and thermal loading of a radioactive waste. Thermomechanical properties of a discontinuous rock mass are estimated by a theoretical method so called sequential analysis. Using the estimated properties as input for finite element analysis, the influence on temperature distribution and thermal stress is analyzed within the scope of 2-dimensional steady state and transient heat transfer and coupled thermal elastic plastic behaviour. Granitic rock mass is taken for this analysis. The analysis is done for two different rock mass conditions, i.e. continuous-homogeneous and highly jointed conditions, for the purpose of comparison. In the case of steady state, the extent of disturbed zone around the storage tunnel due to the heat production of the spent-fuel canister varies depending on the thermomechanical properties of the rock mass. In the case of transient analyses, the response of the jointed rock mass to the thermal loading after radioactive waste disposal varies significantly with time, resulting in dramatic changes in the both size and location of disturbed zone.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.1
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• pp.1-8
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• 2011

A coupled thermal/structural analysis of mechanical ablation is performed based on domain/boundary decomposition and finite element method. The ablative material non-linearity and boundary non-linearity can be easily localized within a few subdomains and/or on the boundary interfaces. An enthalpy method is applied to simplify the effect of heat of pyrolysis in the ablative subdomains. In addition, maximum in-plane shear stress is considered as a surface recession criterion for the mechanical ablation simulation. The basic characteristics of the proposed method are examined carefully through numerical experiments.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.4
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• pp.463-473
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• 2011

The warm shrink fitting process is generally used to assemble automobile transmission parts (shaft/gear). But the fitting process can cause the dimensions of addendum and dedendum of the gear to change with respect to the fitting interference and the profile of the gear. As a result, there may be additional noise and vibration between gears. To address these problems, we analyzed the warm shrink fitting process according to process parameters; the fitting interference between the outer diameter of the shaft and the inner diameter of the gear, the inner diameter of the gear, addendum and dedendum of the gear, the heating temperature. In this study, a closed form equation for predicting the amount of deformation of addendum and dedendum in the R-direction was proposed. And the FEA method to analyze the cooling process was proposed for thermal-structural-thermal coupled field analysis of the warm shrink fitting process (heating-fitting-cooling process).

• Nuclear Engineering and Technology
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• v.42 no.3
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• pp.259-270
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• 2010

New generation nuclear reactors are designed using advanced safety analysis methods. A thorough understanding of different interacting physical phenomena is necessary to avoid underestimation and overestimation of consequences of off-normal transients in the reactor safety analysis results. This feature requires a multiphysics reactor simulation model. In this context, a coupled dynamics model based on a multiphysics formulation is developed indigenously for the transient analysis of large pressurized VVER reactors. Major simplifications are employed in the model by making several assumptions based on the physics of individual phenomenon. Space and time grids are optimized to minimize the computational bulk. The capability of the model is demonstrated by solving a series of international (AER) benchmark problems for VVER reactors. The developed model was used to analyze a number of reactivity transients that are likely to occur in VVER reactors.

• Tunnel and Underground Space
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• v.8 no.1
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• pp.17-25
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• 1998

This paper investigates coupled thermal, mechanical and hydraulic phenomena in deep rock mass especially for underground heat storage system. Firstly, concepts of underground heat storage were presented and coupling phenomena in this area were illustrated. In order to understand the basic mechanism of thermal, hydraulic and deformation behavior in rock cavern disturbed by thermal gradient about 10$0^{\circ}C$, various numerical experiments were conducted using several codes. The study involves the behavior of fractured rock mass including rock joint. In spite of the limitation of codes modelling fully coupled effects, these codes could be applied in analysis of underground heat storage. The heat loss in rock mass, which is a major factor in heat storage, is insignificant in all results.