• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2009년도 추계학술발표대회 논문집
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• pp.404-408
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• 2009

The liquid desiccant air-conditioning system has been proposed as an alternative to the conventional vapor compression cooling systems to control air humidity. The complete system of liquid desiccant air-conditioning system is consisted two main components those are humidifier (regeneration) and dehumidifier. Humidifier part is connected to the load when summer season which is the air condition is hot and humid have to be turned into comfort condition on human. This paper purpose is performances study of air flow rate effect on a structured packed tower on cooling and dehumidifier system using liquid lithium chloride as the desiccant. Experimental apparatus used in this present study is consisted of three components those are load chamber, packed tower and chiller. Load chamber’s volume is $40m^3$, and packed tower dimension is cubic with length 0.4m occupied with packed column. Totally, 15 experimental has done using 5 times repeat on each variable of air velocity that varying on 2m/s, 3m/s and 4m/s with other conditions are controlled. Air inlet initial temperature and relative humidity are set respectively on $30^{\circ}C$ and 52%, desiccant flow rate is 0.63 kg/s, desiccant temperature is $10^{\circ}C$ and desiccant concentration is 0.4. The result of this study shows that averagely, the moisture removal rate and the heat transfer rate are influenced by the air velocity. Higher air velocity will increase the heat transfer and decreasing the moisture removal rate. At adiabatic condition the air velocity of 2 m/s respectively is having the higher moisture removal rate acceleration then the air velocity of 3m/s and 4 m/s until the steady state condition.

• 설비공학논문집
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• 제12권4호
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• pp.371-380
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• 2000

The turbulent heat transfer from a round oblique impinging jet on a concave surface were experimentally investigated. The transient measurement method using liquid crystal was used in this study. In this measurement, a preheated wall was suddenly exposed to an impinging jet while recording the response of liquid crystals to measure surface temperature. The Reynolds numbers were 11000, 23000 and 50000, nozzle-to-surface distance ratio was from 2 to 10 and the surface angles were a =$0^{\circ}\;15^{\circ},\;30^{\circ}and\;40^{\circ}$. Correlations of the stagnation point Nusselt numbers with Reynolds number, jet-to-surface distance ratio and dimensionless surface angle, which account for the surface inclined angle, are presented. The maximum Nusselt numbers, in this experiment, occurred in the direction of upstream. The displacement of the maximum Nusselt number from the stagnation point increases with increasing surface angle or decreasing nozzle-to-surface distance. In this experiment, the maximum displacement is about 0.7 times of the jet nozzle diameter when surface curvature, D/d is 10.

• 항공우주기술
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• 제8권1호
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• pp.17-25
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• 2009

복사전달식에서 흡수 계수의 정확한 계산은 액체 엔진 저부의 단열재 설계의 입력 값으로 사용되는 플룸의 복사 열전달을 예측하는데 매우 중요하다. 이를 위해서 가스 흡수 계수를 직접 모델링 할 수 있는 WNB 모델을 중요 인자의 선정을 위주로 설명하였고, 그 결과를 비교적 정확한 기준 값을 제공하는 SNB의 결과와 비교하였다. 비교 인자들은 총 방사율, 좁은밴드 복사강도 및 총 복사강도이며, 결과적으로 방사율의 경우 주어진 조건에서 3.1% 이내, 총 복사 강도역시 5%이내의 계산결과를 보여 이 모델의 타당성을 확인할 수 있었다. 추가적으로, 액체 엔진의 연소가스들의 성분비를 예측하고 이 조건에 대한 가스모델링 인자를 계산하여 데이터베이스를 구축하였다.

• Nuclear Engineering and Technology
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• 제27권2호
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• pp.189-202
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• 1995

계면 전단응력이 있을 때와 없을 때 가열 또는 응축되면서 하강하는 난류액막의 열전달 계수를 예측하기 위한 개선된 방법을 제시하였다. 특히 큰 계면 전단응력이 있을 때 하강하는 난류액막에 적용할 수 있도록 Mudawwar와 El-Masri의 준 실험적 난류모델을 수정하여 Yih와 Liu가 제안한 통합적 접근방법에 사용한 와류점성모델대신에 사용하였다. 광범위한 크기의 계면전단응력에 대해 액막 레이놀즈 수 대액체막 두께 및 접근적 열전달 계수를 개선된 방법과 다른 여러 기존 방법으로 예측하여 실험값들과 비교하였다. 그 결과 일반적으로 수정한 모델과 예측한 값이 다른 기존 모델로 예측한 값보다 실험 치와 더밀접하게 일치하는 것을 보여주었다.

• 대한기계학회논문집B
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• 제21권10호
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• pp.1314-1325
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• 1997

Experiments have been conducted to determine the flow and heat transfer characteristics for a two-dimensional turbulent wall attaching offset jet at different oblique angles to a flat surface. The distributions of the wall static pressure coefficient and time-averaged reattachment position for various offset ratios and oblique angles have been measured. The local Nusselt number distributions on the plate surface were also measured using liquid crystal as a temperature indicator. The new hue-capturing technique utilizing a true color image processing system was used to accurately determine the temperature of the liquid crystal. The experiments were carried out at Reynolds number, Re (based on D) of from 7300 to 21,300 with offset ratio, H/D from 2.5 to 10, and oblique angle, .alpha. from 0 deg. to 400 deg..

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.436-442
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• 2012

액체로켓 엔진의 제어 로직이나 제어 알고리즘을 설계하고 유량제어밸브의 작동 스킴을 결정하는데 있어서 엔진의 동특성을 파악하는 것은 무엇보다 중요한 일이다. 하지만 엔진의 동특성을 시험을 통해서 사전에 얻는 것은 상당히 어려운 일이기 때문에 해석적인 모델을 이용하는 경우가 많다. 이에 본 연구에서는 기존에 개발된 엔진의 정상상태 부근에서의 동특성 해석 모델을 이용하여 이러한 동특성 모델을 계산하였다. 해석 모델을 이용하여 외란을 가하여 얻어진 응답특성을 Levy 방법을 이용하여 엔진의 동특성 모델을 하나의 전달함수로 근사할 수 있음을 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3033-3038
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• 2007

In this research, Rayleigh instability of gas-liquid flow in annular pipe is studied in film boiling using viscous potential flow. Viscous potential flow is a kind of approximation of gas-liquid interface considering velocity field as potential including viscosity. A dispersion relation is obtained including the effect of heat and mass transfer and viscosity. New expression for dispersion relation in film boiling and critical wave number is obtained. Viscosity and heat and mass transfer have a stabilizing effect on instability and its effect appears in maximum growth rate and critical wave number. And the existence of marginal stability region is shown.

• 설비공학논문집
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• 제12권4호
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• pp.414-421
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• 2000

This study was discussed about the thermal characteristics of finned tube heat exchanger having two row used in the air-conditioning application. Pressure drop and heat transfer coefficient were measured and investigated for the 3 times models of plain fin. Also the temperature distribution and heat conduction in the fin was measured by using the liquid crystal method. The surface temperature of rear row was nearly constant, and heat conduction in the fin was stronger near the front row than the rear row.

• 에너지공학
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• 제10권4호
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• pp.342-348
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• 2001

A new design concept for a decay heat removal system in a liquid metal reactor is proposed. The new design utilizes a thermosyphon to enhance the heat removal capacity and its heat transfer characteristics are analyzed against the current PSDRS (Passive Safety Decay heat Removal System) in the KAL IMER (Korea Advanced LIquid MEtal Reactor) design. The preliminary analysis results show that the new design with a thermosyphon yields substantial increase of 20∼40% in the decay heat removal capacity compared to the current design that do not have the thermosyphon. The new design reduces the temperature rise in the cooling air of the system and helps the surrounding structure in maintaining its mechanical integrity for long term operation at an accident. Also the analysis revealed the characteristics of the interactions among various heat transfer modes in the new design.

• Journal of Mechanical Science and Technology
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• 제19권3호
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• pp.860-869
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• 2005

Local pool boiling on the outside and inside surfaces of a 51 mm diameter tube in horizontal direction has been studied experimentally in saturated water at atmospheric pressure. Much variation in local heat transfer coefficients was observed along the tube periphery. On the outside surface the maximum and the minimum are observed at ${\theta}=45^{\circ}$ and $180^{\circ}$, respectively. However, on the inside surface only the minimum was observed at ${\theta}=0^{\circ}$. Major mechanisms on the outside surface are liquid agitation and bubble coalescence while those on the inside surface are micro layer evaporation and liquid agitation. As the heat flux increases liquid agitation gets effective both on outside and inside surfaces. The local coefficients measured at ${\theta}=90^{\circ}$ can be recommended as the representative values of both outside and inside surfaces.