• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.11 s.254
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• pp.1043-1050
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• 2006

An experimental investigation was performed to study flow boiling heat transfer of deionized water in a microchannel. Measurement and evaluation of boiling heat transfer coefficients were carried out using a single horizontal rectangular microchannel having a hydraulic diameter of $100{\mu}m$. Tests were performed for mass fluxes of 90, 169 and 267 $kg/m^2$s and heat fluxes of 200-700 $kW/m^2$. Test results showed that the measured boiling heat transfer coefficients had no dependence on mass flux and vapor quality. Most macro-channel correlations of boiling heat transfer coefficient did not provide reliable predictions.

• 한국전산유체공학회:학술대회논문집
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• 2004.10a
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• pp.3-6
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• 2004

In order to reduce the excessive numerical dissipation which is induced when a grid system is not aligned with a discontinuity, a new spatial treatment of cell-interface fluxes is introduced. The M-AUSMPW+ in this paper has the formula that has an additional procedure of re-defining transferred properties at a cell-interface, based on AUSMPW+. The newly defined transferred property could eliminate numerical dissipation effectively in non-flow aligned grid system of multi-dimensional flows.

• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.239-247
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• 2001

Measured radiative heat fluxes on the furnace exit plane of a heavy duty power boiler of steam output 1650 T/h are discussed. A high-ash pulverized bituminous coal was used. Such measurements are necessary to improve heat fluxes inside a steam boiler furnace was manufactured. An extra small heat radiation sensor was placed in the water cooled head of the probe. The sensor had no direct contact with furnace gases and measured only the radiant energy. There was no exposure to convective heat transfer. With the radiometric probe, one can obtain a spherical indicatrix of radiation intensity as well as hemispherical radiative heat flux incident on any surface passing through a measuring point inside the furnace. Thus, the quantity of radiation energy, passing through the furnace exit plane, to the convective heating surfaces and the quantity of radiation energy going in the opposite direction were measured. A formula for relative radiative heat flux on the furnace exit plane has been proposed.

• Journal of Power System Engineering
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• v.14 no.4
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• pp.11-16
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• 2010

The evaporation heat transfer characteristics of propane(R-290) in horizontal small diameter tubes were investigated experimentally. The test tubes have inner diameters of 1 mm and 4 mm. Local heat transfer coefficients were measured at heat fluxes of 12, $24\;kW/m^2$, mass fluxes of 150, $300\;kg/m^2s$, and evaporation temperature of $15^{\circ}C$. The experimental results showed that the evaporation heat transfer coefficient of R-290 has an effect on heat flux, mass flux, tube diameter, and vapor quality. The evaporation heat transfer of R-290 has an influenced on nucleate boiling at low quality and convective boiling at high quality. The evaporation heat transfer coefficient of R-290 increases with decreasing inner tube diameter. And the evaporation heat transfer coefficient of R-290 is about 1~3 times higher than that of R-134a.

• Journal of Environmental Impact Assessment
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• v.11 no.3
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• pp.173-187
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• 2002

토양 속에서 발생될 수 있는 용질과 용매의 복합 수송시스템을 대상으로 한 연구 중 회석상태로부터 포화상태에 이르기까지의 넓은 농도분포를 가지는 토양 용액에 적용될 수 있는 물리 화학적 이론에 입각한 지배방정식을 발표한 연구는 전무한 실정이다. 본 연구는 용매와 토양기체간 그리고 용질과 결정간의 상변화를 고려한 연립물질수지방정식을 제시하고, 여기에 타율적 대류를 포함하는 상호확산 분산수송방정식을 도입하여 대류와 확산에 관한 프럭스를 분리, 결정하는 것을 목적으로 한다. 대류 플럭스의 결정은 타율적으로 이루어지는 것이 이론적으로 타당하며, 이러한 타율적 대류 플럭스가 제공된다면 본 연구에서 제시된 지배방정식을 이용해서 토양용액의 복합수송 시스템을 범용적으로 해석, 예측할 수 있을 것으로 판단된다.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.26-31
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• 2014

Conventional TIG(C-TIG) welding process guarantees higher quality weldment when compared with other processes. However, C-TIG with inherent low penetration shows disadvantages in productivity, especially for thick-walled structure. To overcome these handicaps, active-flux TIG(A-TIG) welding has been introduced and studied widely in a motivation to improve both quality and productivity. Present study made a focus on optimum combination of oxide components to enhance arc contraction and penetration. Results indicated that arc contraction inducing enhancement of penetration could be possible when composition of active fluxes was well matched with base metal.

• Journal of The Korean Astronomical Society
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• v.36 no.2
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• pp.61-66
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• 2003

We have examined the relationship between the speeds of coronal mass ejections (CMEs) and the GOES X-ray peak fluxes of associated flares. Noting that previous studies were possibly affected by projection effects and random association effects, we have considered two sets of carefully selected CME-flare events: four homologous events and four well-observed limb events. In the respective samples, good correlations are found between the CME speeds and the GOES X-ray peak fluxes of the associated flares. A similarly good correlation is found for all eight events of both samples when the CME speeds of the homologous events are corrected for projection effect. Our results suggest that a close relationship possibly exists between CME kinematics and flaring processes.

• Journal of the Korean Ceramic Society
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• v.23 no.5
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• pp.86-92
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• 1986

As there is a growing trend to make high quality steel improving production efficiency and utilizing slag as resources the technologies of hot metal pretreatment have been progressed to meet these demands. Although mill scale $Na_2CO_3$ and CaO used as fluxes proved to be excellent agents then can severely corrode refractories such as chamotte and high alumina for torpedo or open ladle car. Thus it was considered necessary to develop new refractories which can endure suchy conditions. Desulfurization fluxes vastly used in POSCO are $CaCO_3$ and CaO Recent trials have been made by testing phenol resin bonded $Al_2O_3-SiC-C$ bricks in torpedo ladle car for hot metal pretreatment. The results showed that the life of this brick became about 1.2 times longer than that of foreign products. And the crushing strength M.O.R corrosion resistance and oxidation resistance were tested.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.4
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• pp.253-263
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• 2002

This paper presents an adaptive feedback linearization control scheme for induction motors using stator fluxes. By using stator flukes as states, overparameterization is prevented and control inputs can be determined straightforwardly unlike in existing schemes. This approach leads to the decrease of the relative degree for the flux modulus and thus yields a simpler control algorithm than the prior results. In this paper. adaptation schemes are suggested to compensate for the variations of stator resistance. rotor resistance and load torque. In particular, the adaptation to the variation of stator resistance with a feedback linearization control is a new trial. In addition, to improve the convergence of rotor resistance estimation, the differences between stator currents and its estimates are used for the parameter adaptation. The simulations show that torque and flux are controlled independently and that the estimates of stator resistance, rotor resistance, and load torque converge to their true values. Actual experiments on a 3.7㎾ induction motor verify the effectiveness of the proposed method.

• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.20-24
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• 2011

In this paper, numerical simulation of cavitation flow for modified NACA66 hydrofoil was made by using the multi-phase RANS equation based on pseudo-compressibility. The Homogeneous mixture model comprised of the mixture continuity, mixture momentum and liquid volume fraction equations was utilized. A vertex-centered finite-volume method was used in conjunction 2nd-order Roe's FDS to discretize the inviscid fluxes. The viscous fluxes were computed based on central differencing The Spalart-Allmaras one equation model was employed for the closure of turbulence. Reasonable agreements were obtained between the calculation results and the experiment for pressure coefficients on the hydrofoil surface.