• Tribology and Lubricants
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• 제11권3호
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• pp.31-39
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• 1995

Grease thermal elastohydrodynamic lubrication (TEHL) problems of line contacts are analyzed numerically. The effects of temperature and rheological paraineters on grease TEHL are investigated using the Herschel-Bulkley model as a theological model of greases. The pressure distribution, the shape of grease film, mean film temperature and surface temperature of solid wall in line contacts are obtained. It is found that thermal effects on the minimum film thickness become remarkable at high rolling speeds. The effect of yield stress of Herschel-Bulkley model on minimum film thickness is negligible, while the theological index and viscosity parameter have significant effects on minimum film thickness.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.99-100
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• 2002

Radial, tilting-pad proceeding bearings are applied in high speed rotating machines operating at stable small and mean loads and the peripheral speeds of proceeding reaching 150 m/s. The operation of bearing can be determined by static characteristics including the oil film pressure, temperature and viscosity distributions, minimum oil film thickness, load capacity, power loss, oil flow. The operation of 5-lobe tilted-pad proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions habe received by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss. oil flow, maximum oil film pressure, maximum temperature were computed for different sets of bearing geometric parameters as: bearing length to diameter ratio, pad angular length and width as well as pad relative clearance.

• Tribology and Lubricants
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• 제2권1호
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• pp.61-68
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• 1986

Effects of the ram-pressure on the THD-performance of pivoted pad thrust bearings are investigated experimentally. A sector-shaped tilting pad thrust bearing and a rotating disk are used. Temperature distribution on the disk surface as well as on the pad surface, distribution of the pressure generated within the fluid film, and the film thickness are measured continuously in the circumferential direction after thermal equilibrium is established. The ram-pressure is proportional to the mean pressure of oil film and to the rotational speed of the disk and affects the maximum pressure and the pressure distribution. The temperature rise on the mating surface of the disc and the pad, contacting with the oil film, is proportional to to the bearing load and the disk speed. The ram-pressure and the temperature rise on the disk surface are dominant factors that affect the THD-performance of pivoted pad thrust bearings.

• 설비공학논문집
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• 제6권4호
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• pp.453-462
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• 1994

An unsteady quasi one-dimensional model of momentum, heat and mass transfer in a falling film of a vertical plate absorber which is cooled by air was developed using the integral method. Energy conservation of the absorber wall is considered in the model. The model can predict absorption rate, film thickness and mean velocity as well as concentration and temperature profiles. Predictions of steady state temperature and concentration profiles for LiBr/water system for constant wall temperature condition are in good agreement with the two-dimensional finite difference method solutions. Effects of operating conditions, such as convective heat transfer coefficient between the cooling air and the absorber wall, cooling air temperature and film thickness at inlet, on absorption rate of water vapor into LiBr/water solution were shown.

• 한국연소학회:학술대회논문집
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• 대한연소학회 2003년도 제27회 KOSCO SYMPOSIUM 논문집
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• pp.167-173
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• 2003

An experimental study on the behavior of droplets impinging on a solid flat surface was carried out in the present study. Breakup of a liquid droplet impinging on a solid surface has been investigated experimentally for various fuels with different properties. The fuel temperature and incident angle were chosen as major parameters. And fuel temperature and incident angle varied in the range from $-20^{\circ}C$ to $30^{\circ}C$ and from $30^{\circ}$ to $60^{\circ}$, respectively, were investigated. It was found that the variation of fuel temperature influences upon droplet mean diameter which were bounced out from the solid surface. As the increases of incident angle, the break-out mass flow rate increases. This causes the decrease of liquid film flow rate. The larger incident angle gives less liquid film flow rate.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.687-694
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• 2006

We report on the fabrication of organic-based flexible displays using an amorphous IZO anode grown at room temperature. The IZO anode films were grown by a conventional DC reactive sputtering on the polycarbonate (PC) substrate at room temperature using a synthesized IZO target in a $Ar/O_2$ ambient. Both x-ray diffraction (XRD) and high resolution electron microscope (HREM) examination results show that the IZO anode film grown at room temperature Is complete amorphous structure due to low substrate temperature. A sheet resistance of $35.6\Omega/\Box$, average transmittance above 90 % in visible range, and root mean spare roughness of $6\sim10.5\AA$ were obtained even in the IZO anode film grown on PC substrate at room temperature. It is shown that the $Ir(ppy)_3$ doped flexible organic light emitting diode (OLED) fabricated on the IZO anode exhibit comparable current-voltage-luminance characteristics as well as external quantum efficiency and power efficiency to OLED fabricated on conventional ITO/Glass substrate. These findings indicate that the IZO anode film grown on PC substrate is a promising anode materials for the fabrication of organic based flexible displays.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.113-114
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• 2002

Radial, tilting 12-pad proceeding bearings are applied as the radial bearings of vertical rotors of water turbines. The mean loads are stable at the peripheral speeds of proceeding reaching 50 m/s. The operation of tilting 12-pads proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions have been obtained by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss, oil flow, maximum oil film pressure, maximum temperature have been computed for different load angle of bearing.

• 대한기계학회논문집B
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• 제29권3호
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• pp.330-339
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• 2005

An experimental study on the behavior of droplets impinging on a solid flat surface was carried out in the present study. Breakup of a liquid droplet impinging on a solid surface has been investigated experimentally for various liquids with different properties. The liquid droplet temperature and incident angle were chosen as major parameters. Liquid droplet temperature and incident angle varied in the range from $-20{\circ}C\;to\;30{\circ}C\;and\;from\;30{\circ}\;to\;60{\circ},$ respectively. It was found that the variation of droplet temperature influences upon the mean diameter and uniformity of droplets which were bounced out from the solid surface. With increase of incident angle the dispersion mass fraction increases, causing the decrease of liquid film flow rate. As the liquid temperature increases, dispersion mass fraction increases since the surface tension decreases.

• 대한기계학회논문집B
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• 제37권8호
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• pp.725-732
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• 2013

본 논문에서는 가는 열선 주위를 흐르는 나노유체의 대류열전달 특성을 실험을 통하여 검토하였다. 입자 혼합 농도가 다른 4개의 나노엔진오일에 대하여 열선온도가 증가하는 경우, 유체온도가 증가하는 경우 그리고 막온도가 일정하게 유지되는 경우 등 세가지 온도경계조건에 대하여 대류열전달계수를 측정하였다. 내부유동에서 나노유체의 대류열전달계수 상승이 열전도율 상승을 초과한다는 결과가 최근 발표되기도 했지만 본 연구에서는 이 결과를 확인할 수 없었다. 온도조건에 따른 대류열전달계수의 변화 거동을 분석함으로써 나노유체의 열전도율과 경계층두께의 관계를 설명할 수 있었다.

• 한국전산유체공학회지
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• 제5권1호
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• pp.33-42
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• 2000

The LiBr-H₂O absorption process on a horizontal tube has been analyzed numerically. The flow field, which was calculated in the authors' previous study by solving the fully elliptic Navier-Stokes equations with accurate free-surface-tracking method, is used to solve the temperature and concentration distributions in the absorption film. With the assumption that the absorbent is linear, calculations have been made for various inlet temperature and flow-rate conditions. For low inlet temperature, the absorption rate is large in the upstream region but the mean temperature also increases and as a result the absorption decreases as the film flows to downstream while high-inlet-temperature case does the opposite. The difference in the absorption rate due to the inlet temperature change becomes smaller in the downstream than that in the upstream. For large flow rate, the heat transfer to the wall becomes poor due to the thick film and so does the absorption rate. The analyses have also been carried out for multiple tube arrangement and the results show that the absorption rate converges after a few tube rows.