• Proceedings of the SAREK Conference
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• 2007.11a
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• pp.52-57
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• 2007

The control characteristics for radiant panel heating system with automatic thermostatic valves were researched by computer simulation and experiment. The unsteady energy analysis using equivalent R-C circuit method and radiation heat transfer analysis of enclosure analysis method with simple structured rooms was performed. The results of flow rate changes of the simulation study are good fit with the ones of experimental one.

• Transactions of the Korean hydrogen and new energy society
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• v.5 no.2
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• pp.111-119
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• 1994

Analysis of heat loss is needed to achieve the high performance and high efficiency in hydrogen engine. So, cooling losses at each part of the direct injection hydrogen fueled engine were measured to evaluate the behavior and distribution of heat loss. Unsteady instantaneous temperature and heat flux at cylinder head were measured by use of instantaneous temperature prove. And these results were compared with those of gasoline engine.

• International Journal of Ocean System Engineering
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• v.3 no.4
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• pp.164-168
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• 2013

Tidal-current power is now recognized as a clean power resource. The turbine blade is the fundamental component of a tidal current power turbine. The kinetic energy available within a tidal current can be converted into rotational power by turbine blades. While in service, turbine blades are generally subjected to cyclic fatigue loading due to their rotation and the rotor-tower interaction. Predicting the fatigue life under a hydrodynamic fatigue load is very important to prevent blade failure while in service. To predict the fatigue life, hydrodynamic load data should be acquired. In this study, the vibration characteristics were analyzed based on three-dimensional unsteady simulations to obtain the cyclic fatigue load. Our results can be applied to the fatigue design of horizontal-axis tidal turbines.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.4
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• pp.24-31
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• 2019

In this paper, we simulated a new apartment building by using radon emission test values from various building materials used as interior finishing materials. The simulations evaluated the radon concentration in the room according to the radon emissions and the ventilations for each type of finishing material (gypsum board, stone, tile and concrete). Overall concrete finish simulation case showed the highest concentration than the case using other materials due to the effect of wall area at the center of each room and the mean radon concentration at 1.5 m above the floor was slightly lower than the mean value at each center. In the case of the porch, pantry and bathroom, the radon concentration was high even when the same materials were used as in the other rooms.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.359-364
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• 2003

Heat regenerator occupied by regenerative materials improves thermal efficiency of regenerative combustion system through the recovery of sensible heat of exhaust gases. By using one-dimensional two-phase fluid dynamics model, the unsteady thermal flow of regenerator with spherical particles, were numerically analyzed to evaluate the heat transfer and pressure losses and to suggest the parameter for designing heat regenerator. It is confirmed that the computational results, such as air preheat temperature, exhausted gases outlet temperature, and pressure losses, agreed well with the experimental data conducted from Chugairo. The thermal flow in heat regenerator varies with porosity, configuration of regenerator and diameter of regenerative particle. Assuming a given exhaust gases temperature at the regenerator outlet, the regenerator length need to be linearly increased with inlet Reynolds number of exhaust gases. It is considered that inlet Reynolds number of exhaust gases should be introduced as a regenerator design parameter.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.9
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• pp.799-807
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• 2005

The flow characteristics and the heat transfer rate on a surface by the interaction of a pair of vortices are studied numerically. To analyze the common flow up produced by vortex generators in a rectangular channel flow, the pseudo-compressibility viscous method is introduced into the Reynolds-averaged Navier-Stokes equation for 3-dimensional unsteady, incompressible viscous flows. To predict turbulence characteristics, a two-layer $k-\varepsilon$ turbulence model is used on the flat plate 3-dimensional turbulence boundary The computational results predict accurately Reynolds stress, turbulent kinetic energy and flow field generated by the vortex generators. The numerical results, such as thermal boundary layers, skin friction characteristics and heat transfers, are also reasonably close to the experimental data.

• International Journal of Aerospace System Engineering
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• v.3 no.2
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• pp.26-30
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• 2016

Experimental study on the unsteady aerodynamics analysis and power consumption of a folding wing is accomplished using a wind tunnel testing. A folding wing model is fabricated and actuated using servo motors. The flapping wing consists of an inboard main wing and an outboard folding wing. The aerodynamic forces and consumed powers of the flapping wing are measured by changing the flapping and folding wings inside a low-speed wind tunnel. In order to calculate the aerodynamic forces, the measured forces are modified using static test data. It was found that the effect of the folding wing on the flapping wing's total lift is small but the effect of the folding wing on the total thrust is larger than the main wing. The folding motion requires the extra use of the servo motor. Thus, the amount of the energy consumption increases when both the wings are actuated together. As the flight speed increases, the power consumption of the folding wing decreases which results in energy saving.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.3
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• pp.166-175
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• 2002

Tank track rubbers, which undergo dynamic stresses and strains under various road conditions, leads to a result of considerable internal temperature rise due to the heat generation. Since rubber materials are not fully elastic, a part of the mechanical energy is converted into heat because of the hysteresis loss. Heat generation without adequate heat dissipation leads to heat build-up, i.e. internal temperature rise which, if excessive, exerts a bad influence upon the performance and the life of the tank track rubbers. The purpose of this paper is to predict temperature distributions of the rubber components off tank track subjected to complex dynamic loads under various read conditions. In steady state analysis temperature fields are displayed in contour shapes, and in unsteady analysis the temperature variations of some important nodes are represented graphically with respect to the running time of the tank.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 1998.04a
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• pp.167-172
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• 1998

An algorithm of Thermal-elastohydrodynamic lubrication analysis for the piston ring is developed. This algorithm contains cavitation boundary condition so it automatically satisfies conservation of mass. 1-D Reynolds equation and 2-D energy equation are solved simultaneously by using Gauss-Jordan method and Newton-Raphson method. Minimum film thickness and friction force are calculated for 1 cycle. There is little difference between the results caculated by isothermal rigid and EHL analysis in entire cycle. In the results of THL, shear heating effect and temperature boundary condition affect the minimum film thickness and friction force prediction. The minimum film thickness and the friction force calculated by THL are lower than those caculated using isothermal assumption.

• The Journal of the Acoustical Society of Korea
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• v.36 no.5
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• pp.314-320
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• 2017

A pressure relief valve is generally used to prevent piping systems from being broken due to high pressure gas flows. However, the sudden pressure drop caused by the pressure relief valve produces high acoustic energy which propagates in the form of compressible acoustic waves in the pipe and sometimes causes severe vibration of the pipe structure, thereby resulting in its failure. In this study, internal aerodynamic noise due to valve flow is estimated for a simple contraction-expansion pipe by combining the LES (Large-Eddy Simulation) technique with the wavenumber-frequency analysis, which allows the decomposition of fluctuating pressure into incompressible hydrodynamic pressure and compressible acoustic pressure. In order to increase the convergence, the steady Reynolds-Averaged Navier-Stokes equations are numerically solved. And then, for the unsteady flow analysis with high accuracy, the unsteady LES is performed with the steady result as the initial value. The wavenumber-frequency analysis is finally performed using the unsteady flow simulation results. The wavenumber-frequency analysis is shown to separate the compressible pressure fluctuation in the flow field from the incompressible one. This result can provide the accurate information for the source causing so-called acoustic-induced-vibration of a piping system.