• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.04a
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• pp.82-86
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• 2002

The thermal characteristics of high-speed air spindle system with built-in motor are studied. Experiment and finite difference method analysis obtain temperature rise and temperature distribution of housing. For the analysis, air fluid film model is built and temperature rise and distribution in thermal steady state are computed for each rotational speed. Generally, it is said that the heat generation of air bearing is negligible. But the heat generation in air film by heat dissipation can not be negligible especially into high-speed region of the journal. In case that the heat generation of air spindle system is high, natural frequency of the spindle system becomes lower when the thermal state is in steady-state and it means the changes of air bearing stiffness due to the change of bearing clearance. It is shown that the temperature rise of air spindle system causes thermal expansion and induces the variation of bearing clearance. In consequence the stiffness of air bearing becomes smaller.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.23 no.6
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• pp.769-777
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• 1999

This paper presents models for the dynamic simulation of a regenerative gas turbine and describes dynamic behaviors of a small regenerative engine. A quasi-steady model is introduced where the inertia of the working fluid is assumed to be negligible compared with the mechanical inertia of the rotating shaft. Based on this quasi-steady model, the transient model for the heat exchanger is employed to simulate the unsteady heat exchange in the recuperator. The effect of the thermal inertia of the recuperator metal on transient behaviors is analyzed by comparing the predicted results of the transient and steady state heat exchanger models. For several load change modes such as sudden increase, decrease and periodic variation, engine dynamic characteristics are investigated by applying a fuel control logic for the constant shaft speed. It is found that the thermal inertia of the recuperator metal has a dominant effect on the whole engine dynamic behavior.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.435-436
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• 2017

This papaer is study on thermal analysis of the active-front-end(AFE) rectifier for solid-state-transformer(SST) applications. finite element analysis simulation model is combined by switching component model, power diode and heat-sink model. thermal model is calculated by computer program and feedback the result. using simulation result analysis switching loss and compare to thermal diffusion of the heat in the model for steady-state operation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.831-838
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• 2004

A fluid-solid conjugate solver has been newly developed and applied to an actual engine disk system. Most of the currently available conjugate solvers lack the special thermal modeling for turbomachinery disk system applications. In the present new code, these special models are implemented to expand the applicability of the conjugate method and to reduce the required computational resources. Most of the conjugate analysis work so far are limited to the axisymmetric framework. However, the actual disk system includes several non-axisymmetric components which inevitably affect the local heat transfer phenomena. Also the previous work devoted to this area usually concentrate their efforts on the steady-state thermal field, although the one in the transient condition is more critical to the engine components. This paper presents full 3D conjugate analysis of a single stage high pressure turbine rotor-stator disk system to assess the three-dimensional effects (Fig. 1). The analysis is carried out not only in the steady-state but also in the engine accelerating transient condition. The predicted temperatures shows good agreement with measured data.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.460-469
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• 2010

To develop coal gasfication system, many studies have been actively conducted to describe the simulation of steady state. Now, it is necessary to study the gasification system not only in steady state but also in dynamic state to elucidate abnormal condition such as start-up, shut-down, disturbance, and develop control logic. In this study, a model was proposed with process simulation in dynamic state being conducted using a chemical process simulation tool, where a heat and mass transfer model in the gasifier is incorporated, The proposed model was verified by comparison of the results of the simulation with those available from NETL (National Energy Technology Laboratory) report under steady state condition. The simulation results were that the coal gas efficiency was 80.7%, gas thermal efficiency was 95.4%, which indicated the error was under 1 %. Also, the compositions of syngas were similar to those of the NETL report. Controlled variables of the proposed model was verified by increasing oxygen flow rate to gasifier in order to validate the dynamic state of the system. As a result, trends of major process variables were resonable when oxygen flow rate increased by 5% from the steady state value. Coal flow rate to gasifier and quench gas flow rate were increased, and flow rate of liquid slag was also increased. The proposed model in this study is able to be used for the prediction of gasification of various coals and dynamic analysis of coal gasification.

• International Journal of Air-Conditioning and Refrigeration
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• v.12 no.2
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• pp.97-107
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• 2004

Wall/floor intersection is important parts of a building envelope system. These intersections can be sources of thermal bridging effects and/or moisture condensation problems. This paper provides a detailed analysis of the thermal performance of wall/floor intersection. In particular, two-dimensional steady-state and transient solutions of the heat conduction within the wall/floor joint are presented. Various insulation configurations are considered to determine the magnitude of heat transfer increase due to wall/floor joint construction.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.156.1-156
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• 1999

• The Journal of Engineering Geology
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• v.11 no.3
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• pp.255-267
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• 2001

A comparison study is performed to understand the coupling behavior of the thermal, hydraulic, and mechanical interactions in the vicinity of an underground radwaste repository, assumed to be located at a depth of 500 m, within a granitic rock mass with a 58$^{\circ}$ dipping fault passing through the roof-wall intersection of the repository cavern. The two dimensional universal distinct element code, UDEC is used for the analysis. The model includes a granitic rock meas, a canister with PWR spent fuels surrounded by the compacted bentonite inside a deposition hole, and the mixed bentonite backfilled in the rest of the space within a repository cavern. The coupling behavior of hydromechanical, thermomechanical, and thermohydromechanical interaction has been studied and compared. The effect of the time-dependent decaying heat, from the radioactive materials in PWR spent fuels, on the repository and its surroundings has been studied. A steady state flow algorithm is used for the hydraulic analysis.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.127-130
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• 2003

This paper presents the numerical thermal analysis for regeneratively cooled rocket thrust chambers. An integrated numerical model incorporates computational fluid dynamics for the hot-gas thermal environment, and thermal analysis for the liner and coolant channels. The flow and temperature fields in rocket thrust chambers is assumed to be axisymmetric steady state which is presumed to the combustion liner. The heat flux computed from nozzle flow is used to predict the temperature distribution of the combustion liner. As a result, we present the wall temperature of combustion liner and the temperature change of coolant.

• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.19-24
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• 1999

A two dimensional thermo elasto-plastic finite clement stress analysis was performed to study stress distributions in functionally gradient material. The upper $ZrO_2$ surface is heated at 1200K until a steady state is established and cooled at 300K. The influences on the thermal stress distributions due to the difference of compositional gradient exponent p were investigated. In this study, we obtained the thermal stresses are low for p=1.