• 한국항공운항학회지
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• 제22권2호
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• pp.40-47
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• 2014

Heavy Rainfall event accompanying with Mesoscale Convective Systems(MCSs) inducing flash flooding and Muan and Kunsan Airport closing over Jeollabuk-do area was investigated this study. Comparing to previous study(I), this heavy rainfall event was characterized by much abundant moisture from Typhoon, strong conditional convective instability, and cluster type MCSs. It almost impossible to make accurate forecasting of precipitation amounts and life cycle of MCSs unless proper analysis.

• 대기
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• 제15권3호
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• pp.155-165
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• 2005

The characteristics of six precipitation systems occurred around Cheongju in 2002 are analyzed after the convective/stratiform radar echo classification using radar reflectivity from the Meteorological Research Institute"s X-band Doppler weather radar. The Biggerstaff and Listemaa (2000) algorithm is applied for the classification and reveals a physical characteristics of the convective and stratiform rain diagnosed from the three-dimensional structure of the radar reflectivity. The area satisfying the vertical profile of radar reflectivity is well classified, while the area near the radar site and the topography-shielded area show a mis-classification. The seasonal characteristics of the precipitation system are also analyzed using the contoured frequency by altitude diagrams (CFADs). The heights of maximum reflectivity are 4 km and 5.5 km in spring and summer, respectively, and the vertical gradient of radar reflectivity from 1.5 km to the melting layer in spring is larger than in summer.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.384-394
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• 2005

Important characteristics of impinging sprays intersected by a strongly convective gaseous cross flows were experimentally investigated. The breakup processes due to different Weber and Reynolds numbers of liquid and gas streams were visually examined with quantitative measurements of breakup lengths, penetration heights, and droplet sizes. Snapshot images and spay data evidenced that, at lower jet Reynolds number the breakup processes portrays the atomization profiles similar to typical column breakup of single orifice jet. At higher jet Reynolds numbers, disintegration of jet stream is significantly expedited by strong momentum transported from strongly convective gaseous stream. The breakup length and penetration height decreased as the convective flow increase. From the bottom the wall up, the SMD measured the centerline increase. The maximum SMD appeared the top of the SMD distribution

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2005년도 제25회 추계학술대회논문집
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• pp.395-406
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• 2005

Important characteristics of swirl sprays intersected by a strongly convective gaseous cross flows were experimentally investigated. The breakup processes due to different Weber and Reynolds numbers of liquid and gas streams were visually examined with quantitative measurements of breakup lengths, penetration heights, and droplet sizes. Snapshot images and spray data evidenced that, at lower jet Reynolds number the breakup processes portrays the atomization profiles similar to typical column breakup of single orifice jet. At higher jet Reynolds numbers, disintegration of jet stream is significantly expedited by strong momentum transported from strongly convective gaseous stream. The breakup length and penetration height decreased as the convective flow increase. From the bottom the wall up, the SMD measured the centerline first increases and then decreases before again increasing.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.118-123
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• 2000

This experimental study was conducted to figure out the characteristics of convective heat transfer in non boiling vertical downward flow with polymer additives. This experiment was studied in 26mm diameter, 800mm heating length and $1{\times}10^5W/m^2$ heat flux. The polymer concentration ranged from 0PPM to 500PPM with corresponding from Reynolds number $3.3{\times}10^4$ to $6.8{\times}10^4$ in non boiling vertical downward flow. Experimental results show that the characteristics of convective heat transfer was a strong function of polymer concentration and it has decreased with increasing the polymer concentration in non boiling vertical downward flow.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.71-76
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• 2000

This experimental study was conducted to figure out the drag reduction and convective heat transfer in vertical downward two-phase flow with polymer additives. The drag reduction effect were analyzed by using the difference of the pressure drop between the flow with polymer additives and without it. Experimental results show that the pressure drop with polymer additives is less than the pressure drop without polymer in vertical downward two-phase flow. And the convective heat transfer has decreased with increasing the polymer concentration in vertical downward two-phase flow.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1358-1363
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• 2004

The objective of this work is to propose calibration facility in which a thin film type heat flux sensor can be calibrated under convective flow condition by using a small wind tunnel with the constant temperature plate condition. A small wind tunnel has been built to produce a boundary layer shear flow above a constant temperature copper plate. 12-independent copper blocks, thin film heaters, insulators and temperature controllers were used to keep the temperature of flat plate constant at a specified temperature. Three commercial thin film-type heat flux sensors were tested. Convective calibrations of these gages were performed over the available heat flux range of $1.4{\sim}2.5kW/m^2$. The uncertainty in the heat flux measurements in the convective-type heat flux calibration facility was ${\pm}2.07%$. Non-dimensional sensitivity is proposed to compare the sensitivity calibrated by manufacturer and that of experiment conducted in this study.

• 설비공학논문집
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• 제11권6호
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• pp.912-920
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• 1999

The forced convective boiling heat transfer coefficients of R-407C were measured inside a horizontal tube 6.0mm I.D. and 4.0m long. The heat transfer coefficients increased according to an increase in heat flux at constant mass flux. Because nucleation was completely suppressed in the two-phase flow region with high quality, heat transfer coefficients in forced convective evaporation were higher than those in nucleate boiling region. Average heat transfer coefficients of R-407C were about 30 percent lower than the pure refrigerant correlation, due to mass transfer resistance at the gas-liquid interface. However, the total experimental data shows an agreement with the predicted data for ternary refrigerant mixtures with a mean deviation of 30%.

• 대한기계학회논문집
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• 제13권4호
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• pp.703-707
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• 1989

본 연구에서는 반무한체에 대하여 활성화 에너지가 매우 큰 경우의 점근법을 적용하여 이 두 변수의 시간에 따른 변화가 점화지연시간에 미치는 영향을 해석적으로 알아보고 참고문헌(1)의 실험치와 비교하고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.161.1-161.1
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• 2005