• Journal of ILASS-Korea
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• v.16 no.4
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• pp.186-194
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• 2011

This study performed the numerical analysis of the internal nozzle flows including cavitation phenomena by using the automated body-fitted grid generator and the multi-fluid model. The effect of grid refinement and the validation of multifluid model were investigated using four computational meshes under two test conditions. The mesh #3 was chosen as the optimum which can reduce the computational time and have good prediction ability to identify the cavitation region simultaneously. In addition, the computed results using multi-fluid model were compared with the reference experimental observations and numerical simulation results using homogeneous equilibrium model. From the distribution of volume fraction and velocity field, the multi-fluid model predicted the internal nozzle flows well when the liquid quality parameters were selected as $1.0{\times}10^{12}$ for initial number density and 25 ${\mu}m$ for bubble diameter.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.948-951
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• 2000

This paper presents the analytical and experimental methodology for the prediction of aerosol concentration and size distribution due to cutting fluid atomization mechanism in turnining operation. The established analytical model which is based on atomization theory analyzes the cutting fluid motion and aerosol generation in machining process. The impinging and evaporation experiments were performed to know the particle size and evaporation rate of cutting fluid. The predictive models can be used as a basis for environmental impact analysis on the shop floor. It can be also facilitate the optimization of cutting fluid usage in achieving a balanced consideration of productivity and environmental consciousness.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.661-665
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• 2000

A method of considering the fluid induced external force in structural dynamic analysis is presented in this study. The fluid induced pressure distribution around a structure in discrete number of orientation. and velocity is calculated by using a CFD code and tabulated as resultant forces and moments in a database. These forces and moments are interpolated and employed as external forces during the dynamic analysis of structure. The reliability and usefulness of the present method is validated by using a simple discrete system example through transient analysis. The flutter speed is obtained and compared to the analytical solution. Comparing to the method in which structural dynamic and fluid flow analyses are performed simultaneously, the present method is very efficient to save computational effort.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.272-277
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• 2003

This paper reports the fluid flow and heat transfer around a module cooled by forced air flow generated by a piezoelectric(PZT) cooling fan. A flexible PZT fan with distortion in a fluid transport system of comparatively simple structure which was mounted on a PCB in a parallel-plate channel($450{\times}80{\times}700mm^3$) accelerates surrounding fluid locally. Input voltages of 20-100V and a resonance frequency of 23Hz were used to vibrate the cooling fan. Input power to the module was 4W. The cooling effect using a PZT fan was larger than that of free convection. Fluid flow around the module were visualized by using PIV system. The temperature distribution around heated module were visualized by using liquid crystal film(LCF). We found that the flow type was y-shaped and the cooling effect was increased by the wake generated by a piezoelectric cooling fan.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.959-963
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• 2006

A three-dimensional elastic blood vessel model with internal diameter variation is considered to investigate internal flow characteristics and effects of structural deformation. Also, computational analyses for both the rigid model and the fully-coupled FSI model have been conducted in order to compare the shear stress, pressure distribution, and flow velocity in detail. A 70% narrowing area of asymmetric blood vessel model was especially investigated to show the versatility of fluid-structure interaction phenomenon. The results reveal that effect of fluid-structure interaction is very important to accurately investigate the flow characteristics of the blood vessel.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.8
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• pp.796-802
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• 2001

The purpose of the present study is to examine the heat transfer characteristics of the U-shape heat pipe for the cooling of semiconductor in subway train. Perflouro-carbon(PFC) was used as working fluid. Temperature distribution on the surface and heat transfer coefficients were investigated according to the working fluid volume percent and heating rate. The results were as follows; Optimum volumetric percent of working fluid was from 80% to 90%, and hat transfer coefficients of evaporation and condensation were as follows, respectively. $\hbar_ie=0.37\times(\frac{P_i}{P_O})$l_c}^0.3$,$\hbar_ic-4.2(\frac{\kappa_l^3p_l^2gh_fg}{\mu_lq_c_l_c}^\frac{1}{3}

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.7
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• pp.571-580
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• 1998

The numerical model that can describe the ignition of pseudospark discharge using hybrid fluid-particle(Monte Carlo )method has been developed. This model consists of the fluid expression for transport of electrons and ions and Poisson's equation in the electric field. The fluid equation determines the spatiotemporal dependence of charged particle densities and the ionization source term is computed using the Monte carlo method. This model has been used to study the evolution of a discharge in Argon at 0.5 torr, with an applied voltage if 1kV. The evolution process of the discharge has been divided into four phases along the potential distribution : (1) Townsend discharge, (2) plasma formation, (3) onset of hollow cathode effect, (4) plasma expansion. From the numerical results, the physical mechanisms that lead to the rapid rise in current associated with the onset of pseudospark could be identified.

• Journal of Industrial Technology
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• v.11
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• pp.3-16
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• 1991

The lattice-fluid theory are adopted for modeling the phese equilibria in supercritical fluids, In order to investigate effects of the nonrandom distribution of holes in mixtures on the phase equilibria, the equation of state and the chemical potential of the binary miture are formulated with taking into account nonrandomness of holes distributions in the fluid mixture. The relations of phase equilibria formulated in this work are tested through predictions of solubility of heavy solids in supercritical fluids and predictions of high pressure phase equilibria of binary mixtures. Results obtained exhibit that the lattice fluid model with assumptions of nonrandomness of hole distributions is successful in quantatively mideling the phase equilibria of mixtures of molecules of dissimilar sizes, specifically solids-supercritical fluid mixtures.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.1020-1023
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• 2005

The fluid flow and thermal analysis were carried out by using the finite element program, Ansys. In analysis process, a electromagnetic analysis was accomplished. In afterwards, Fluid and thermal analysis was done. Fluid flow and heat could be produced by electromagnetic pump. In other words, A magnetic field which electromagnetic pump generates influences Liquid Material(Al alloy). This paper calculates the fluid flow and temperature distribution according to time. Using material is Al alloy(A356).

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.1
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• pp.24-30
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• 2006

Three liquid cooling heat exchangers for cooling of telecommunication equipment were designed and their cooling performances were tested. The liquid cooling heat exchangers had twelve rectangular channels $(5\times3 mm)$ with different flow paths of 1, 4, and 12. Silicon rubber heaters were used to provide heat flux to the test section. Heat input was varied from 75 to 400 W, while flow rate and inlet temperature of working fluid were altered from 1.2 to 4.0 liter/fin and from 15 to 3$30^{\circ}C$, respectively. The 4-path heat exchanger showed lower and more uniform average inner temperatures between heaters and the surface of heat exchanger than those of the others. To obtain optimal distribution of working fluid to each channels of liquid cooling heat exchangers, 2-3-2 and 4-3 type tube distributors were designed, and their distribution performances of working fluid were numerically and experimentally investigated. The distributor of the 2-3-2 type showed superior distribution performance compared with those of the 4-3 type distributor.