• Journal of Power System Engineering
• /
• v.13 no.3
• /
• pp.27-32
• /
• 2009

Numerical analysis information of a complex discharge-passage will be very useful to improve hydrogen compression system. General information about an internal gas flow is presented by numerical analysis approach. Relating with hydrogen compressing system, which have an important role in hydrogen energy utilization, this should be a useful tool to observe the flow quickly and clearly. Flow characteristic analysis, including pressure and turbulence kinetic energy distribution of hydrogen gas from cylinder going to the chamber of a reciprocating compressor are presented in this paper. Discharge-passage model is designed based on real model of hydrogen compressor. Pressure boundary conditions are applied considering the real condition of operating system. The result shows pressure and turbulence kinetic energy are not distributed uniformly along the passage of the hydrogen compressing system. Path line or particles tracks help to demonstrate flow characteristics inside the passage. The existence of vortices and flow direction can be precisely predicted. Based on this result, the design improvement should be done. Consequently, development of the better hydrogen compressing system will be achieved.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.24 no.12
• /
• pp.999-1006
• /
• 2014

Mindlin plate theory includes the shear deformation and rotatory inertia effects which cannot be negligible as exciting frequency increases. The statistical methods such as energy flow analysis(EFA) and statistical energy analysis(SEA) are very useful for estimation of structure-borne sound of various built-up structures. For the reliable vibrational analysis of built-up structures at high frequencies, the energy transfer relationship between out-of-plane waves and in-plane waves exist in Mindlin plates coupled at arbitrary angles must be derived. In this paper, the new wave transmission analysis is successfully performed for various energy analyses of Mindlin plates coupled at arbitrary angles.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.5 no.3
• /
• pp.392-403
• /
• 2013

For the analysis of radiating noise problems in medium-to-high frequency ranges, the Energy Flow Boundary Element Method (EFBEM) was developed. EFBEM is the analysis technique that applies the Boundary Element Method (BEM) to Energy Flow Analysis (EFA). The fundamental solutions representing spherical wave property for radiating noise problems in open field and considering the free surface effect in underwater are developed. Also the directivity factor is developed to express wave's directivity patterns in medium-to-high frequency ranges. Indirect EFBEM by using fundamental solutions and fictitious source was applied to open field and underwater noise problems successfully. Through numerical applications, the acoustic energy density distributions due to vibration of a simple plate model and a sphere model were compared with those of commercial code, and the comparison showed good agreement in the level and pattern of the energy density distributions.

• Journal of the Korea Society for Simulation
• /
• v.6 no.2
• /
• pp.1-14
• /
• 1997

The characteristics of the flow and energy conversion in OMACON liquid-metal MHD system are investigated. Numerical simulation of two-phase flow in the OMACON system without magnetic field was carried out by the Phoenics code and the energy conversion characteristics are studied in association with the fact that the mechanical energy loss at the nozzle of the OMACON system are to be converted into electrical energy. In this system, working fluid (gas) is injected through the mixer located at the bottom of the riser, and is mixed with hot liquid metal. Therefore in the riser two-phase flow is developed under the influence of the gravity. In this study, the interaction between the gas and liquid is considered by the use of IPSA(InterPhase Slip Algorithm) where standard drag coefficient has been used. It has been assumed that in the flow regime the liquid is continuous and the gas is dispersed. For the liquid and gas, the continuity equations, momentum equations and energy equations are solved respectively in association with void fraction in the flow field. In order to calculate the energy conversion efficiency, firstly the ratio of the mechanical energy loss of liquid metal flow at the nozzle to the input thermal energy is considered. Secondly flow pattern of liquid metal in the generator has been analyzed, and the characteristics of the conversion of the mechanical energy into the electrical energy has been investigated. For an representative case where Hartmann number is 540 and magnetic field is 0.35 T, the present analysis shows that the energy conversion efficiency is 0.653. This result is considered to be reasonable in comparison with published experimental results.

• Nuclear Engineering and Technology
• /
• v.41 no.6
• /
• pp.797-806
• /
• 2009

The Multichannel Analyzer for Transient and steady-state in Rod Array - Liquid Metal Reactor for Flow Blockage analysis (MATRA-LMR-FB) code for the analysis of a subchannel blockage has been developed and evaluated through several experiments. The current version of the code is improved here by the implementation of a distributed resistance model which accurately considers the effect of flow resistance on wire spacers, by the addition of a turbulent mixing model, and by the application of a hybrid scheme for low flow regions. Validation calculations for the MATRA-LMR-FB code were performed for Oak Ridge National Laboratory (ORNL) 19-pin tests with wire spacers and Karlsruhe 169-pin tests with grid spacers. The analysis of the ORNL 19-pin tests conducted using the code reveals that the code has sufficient predictive accuracy, within a range of 5 $^{\circ}C$, for the experimental data with a blockage. As for the results of the analyses, the standard deviation for the Karlsruhe 169-pin tests, 0.316, was larger than the standard deviation for the ORNL 19-pin tests, 0.047.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.15 no.6 s.99
• /
• pp.674-679
• /
• 2005

Statistical Energy Analysis(SEA) has been considered as a Possible method for predicting responses of complex structures, especially at higher frequencies. In this paper, an SEA model of a vehicle was built using 138 energy storing subsystems connected together using 1019 Junctions. SEAM software program was used to build and calculate the model. To demonstrate the accuracy of the SEA model, predicted response levels were compared with measured levels. The source Input levels were measured at the engine mounting parts. There is good agreement between the estimated and the experimental results. This paper also identifies some dominant energy flow paths from sources. It is finally presented that the SEA model can optimize the design parameters of vehicles using model parameters and energy flow paths.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1287-1292
• /
• 2007

Recently, the frequency of unexpecting heavy rains has been increased due to abnormal climate and extreme rainfall. There was a limit to analyze 1D or 2D stream flow that was applied simple momentum equation and fixed energy conservation. Therefore, hydrodynamics flow analysis in rivers has been needed 3D numerical analysis for correct stream flow interpretation. In this study, CFD model on FLOW-3D was applied to stream flow analysis, which solves three dimenson RANS(Reynolds Averaged Navier-Stokes Equation) control equation to find out physical behavior and the effect of hydraulic structures. Numerical simulation accomplished those results was compared by using turbulence models such as ${\kappa}-{\varepsilon}$, RNG ${\kappa}-{\varepsilon}$ and LES. Those numerical analysis results have been illustrated by the turbulence energy effects, velocity of flow distributions, water level pressure distributions and eddy flows around the piers at Jangwall bridge in urbarn stream.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.51 no.3
• /
• pp.107-115
• /
• 2002

This parer presents the analysis of hot gas flow in puffer-type circuit breakers using FVFLIC method. For the analysis of arc-flow interaction, the flow field is analyzed from the equations of conservation for mass, momentum and energy with the assumption of local thermodynamic equilibrium state. The arc is represented as the energy source term composed of ohmic heating and radiation term in the energy conservation equation. Ohmic heating is computed by the electric field analysis only within the conducting plasma region. An approximate radiation transport model is employed for the evaluation of emission and absorption of the radiation. The analysis method was applied to the real circuit breaker model and simulation results such as pressure rise and arc voltage were compared with the experimental ones.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.211-212
• /
• 2008

As a result of environmental concerns, the production of electricity through renewable energy resources is rapidly increasing. Wind energy is among the fastest growing renewable energy resources now being integrated in the power system, and the penetration rate of wind generation has been gradually increased. For power flow analysis of the recent systems, thus, steady-state modeling of wind turbines and their application are of great importance. This paper presents the procedure we applied for implementation of a steady-state wind turbine model in power flow.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.6
• /
• pp.103-109
• /
• 2014

It is important to control the amount of supply water flow rate at all kinds of HVAC systems in order to maintain IAQ and energy efficiency. The most of buildings installed geothermal heat pumps is using fixed water flow rate in spite of the excellent performance of geothermal heat pumps. Especially when the air-conditioning load is low, the flow rate control may be possible to save energy to operate. However, it is effective to apply the variable flow control system in order to reduce energy consumption. Therefore, the purpose of this study, change a water flow rate and improve the whole performance of the geothermal heat pump. Geothermal heat pump system is modeled after the selection of the applied building, by setting the flow rate control to be analyzed through a simulation of performance evaluation. Building energy saving according to the flow rate of the ground circulating water analyze quantitatively and to investigate the importance of the flow control.