• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.472-473
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• 2008

Flow boiling in parallel microchannels has received attention as an effective heat sink mechanism for power-densities encountered in microelectronic equipment. the bubble dynamics coupled with boiling heat transfer in microchannels is still not well understood due to the technological difficulties in obtaining detailed measurements of microscale two-phase flows. In this study, complete numerical simulation is performed to further clarify the dynamics of flow boiling in microchannels. The level set method for tracking the liquid-vapor interface is modified to include the effects of phase change and contact angle. The method is further extended to treat the no-slip and contact angle conditions on the immersed solid. Also, the reverse flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of channel shape and inlet area restriction on the bubble growth, reverse flow and heat transfer are quantified.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.2
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• pp.125-132
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• 2008

The bubble dynamics and heat transfer associated with nucleate boiling in parallel microchannels is studied numerically by solving the equations governing conservation of mass, momentum and energy in the liquid and vapor phases. The liquid-vapor interface is tracked by a level set method which is modified to include the effects of phase change at the interface and contact angle at the wall. Also, the reversible flow observed during flow boiling in parallel microchannels has been investigated. Based on the numerical results, the effects of contact angle, wall superheat and the number of channels on the bubble growth and reversible flow are quantified.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.1997-2000
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• 1999

본 연구에서 제시하는 기공세라믹(Porous Ceramic)에 의한 누설전류 측정법은 기공 사이즈가 일정한 Open Pore Cell내에서 도전성 물질 및 이온화된 물질이 기공 사이에 침투되었을 때 외부에서 전계를 가하므로 써 이들 이온화 된 물질이 chain처럼 배열되어 전기적 병렬회로를 구성시켜 미세한 누설전류를 흐르게 한다. 이 누설전류법에 의한 도전성분 검출을 여러 환경 배출가스에 대한 모의실험을 실시한 결과 기공세라믹인 센서 자체의 누설전류는 가스 온도 150 ($^{\circ}C$) 이상에서 급격한 변화를 보이고 200($^{\circ}C$)에서 센서 자체의 전류치와 가스를 주입하였을 때의 전류치와는 상당한 격차를 두고 변화됨을 알 수 있었다. 그리고 공장연돌이나 자동차 배기관에서 방출되는 가스 중 HC, CO, NO, $CO_2$, $SO_2$, $N_2$ 등에 대한 센서 특성이 각각 달리 나타남을 알 수 있었다.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.193-199
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• 1998

The mixtures of ultra-high molecular weight polythylene (UHMWPE), high density polyethylene (HDPE), process oil (mineral oil) and potassium hexatitanate whisker were melted and mixed at $150^{\circ}C$ for 30min, and prepared by compression molding to the specimen of separator of about $200{\mu}m$ thickness at the same temperature and 5000 psi. Thereafter the pores were formed by extracting process oil with organic solvents. In this study, the range of PR (the ratio polymer to process oil) was varied from 0.1 to 0.5 because the specimen turned into rubbery phase at which PR was below 0.1 whereas it changed into gel phase at which PR was above 0.5. When the specimen was treated with nonpolar organic solvents, process oil was extracted nearly 98%. Tensile strength was $31kg/cm^2$ at PR = 0.426, and resistance of specimen was $37m{\Omega}/cm^2$ at PR = 0.186, and $53m{\Omega}/cm^2$ at PR = 0.426. The $N_2$ adsorption-desorption isotherm showed a hysteresis representing regions of capillary condensation, and the surface area at PR = 0.186 was relatively large as $130cm^2/g$. Potassium hexatitanate whisker was randomly dispersed in between PE layers. It might be that the whisker is intercalated through the PE thin layers oriented by compression.