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충돌수분류에 냉각되는 고온 강판의 열전달에 있어 노즐높이의 영향에 대한 연구
이필종,최해원,이승홍,Lee, Pil-Jong,Choi, Hae-Won,Lee, Sung-Hong 대한기계학회 2003 大韓機械學會論文集B Vol.27 No.5
The effect of nozzle height on heat transfer of a hot steel plate cooled by an impinging liquid jet is not well understood. Previous studies have been based on the dimensionless parameter z/d. To test the validity of this dimensionless parameter and to investigate gravitational effects on the jet, stagnation velocity of an impinging liquid jet were measured and the cooling experiments of a hot steel plate were conducted for z/d from 6.7 to 75, and an inverse heat conduction method is applied for the quantitative comparison. Also, the critical instability point of a liquid jet was examined over a range of flow rates. The experimental velocity data for the liquid jet were well correlated with the dimensionless number 1/F $r_{z}$$^2$based on distance. It was thought that the z/d parameter was not valid for heat transfer to an impinging liquid jet under gravitational forces. In the cooling experiments, heat transfer was independent of z when 1/F $r_{z}$$^2$< 0.187(z/d = 6.7). However, it was found that the heat transfer quantity for 1/F $r_{z}$$^2$=0.523(z/d = 70) is larger 11% than that in the region for 1/F $r_{z}$$^2$=0.187. The discrepancy between these results and previous research is likely due to the instability of liquid jet.uid jet.
주변공기조건이 충돌수분류에 의한 고온강판의 냉각에 미치는 영향 연구
이필종,최해원,이승홍,Lee, Pil-Jong,Choi, Hae-Won,Lee, Seung-Hong 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.1
It is observed that the cooling capacity of impinging water jet is affected by the seasonal conditions in steel manufacturing process with large scale. To confirm this phenomena, the cooling experiments of a hot steel plate by a laminar jet were conducted for two different initial ambient air temperature($10^{\circ}C$ and $40^{\circ}C$) in a closed chamber, and an inverse heat conduction method is applied for the quantitative comparison. It is found that the cooling capacity under $10^{\circ}C$ air temperature is lower than that under $40^{\circ}C$, as is the saturated water vapor is more easily observed, and the amount of total extracted heat in the case of $10^{\circ}C$ is smaller by nearly 15% than that of $40^{\circ}C$ case. From these results, it is thought that the quantity of water vapor, which could be absorbed until saturation, effects on the mechanism of boiling heat transfer.
이필종,최호,이승홍,Lee, Pil-Jong,Choi, Ho,Lee, Seung-Hong 대한기계학회 2002 大韓機械學會論文集B Vol.26 No.6
The cooling heat transfer by impinging water spray jets on a rotating roll with a relatively large diameter has been investigated under various experimental conditions with 3 different sizes of flat type nozzle. The local heat transfer coefficients were calculated by finite difference method using measured surface temperatures of the circular cylinder as boundary conditions. Results show that a peak value of the heat transfer coefficient is located at the center of sprayed area and there may be a secondary peak at the downstream. The average heat transfer coefficients on the sprayed area were found to be 10 to 22 ㎾/$m^2$$^{\circ}C$, and were not related to spraying pressure, but approximately linearly to flow rate of sprayed water. Also it is found that increasing the distance from roll to nozzle could improve the cooling efficiency by increasing the sprayed area.
이필종,이승홍,최호 釜山大學校生産技術硏究所 1999 生産技術硏究所論文集 Vol.57 No.-
열간 압연과정에서 회전률에 충돌하는 스프레이 제트분사에 의한 열전단계수를, 3가지 크기의 평면 형태의 노즐을 사용하여 실험실의 다양한 실험 조건하에서 측정하였다. 열전달 계수는 유한 차분법에 의해 계산되었고, 그 결과들은 다른 실험결과들과 잘 일치하였다. 실험조건에서 냉각환경과 장치의 배열이 롤의 온도에 미치는 영향을 연구하였다. 분사된 영역에서 평균 열전달계수는 12에서 24 kW/m²K 범위이고, 분사압력의 0.4승에 비례한다. 열간압연 과정의 시뮬레이션 결과는 롤바이트 구에서 냉각 능력이 더욱 효과적임을 보여준다. The heat transfer coefficients on a rotating roll have been evaluated under various experimental, hot rolling conditions in the laboratory with 3 different sizes of flat type nozzles for impinging spray jets. The heat transfer coefficients were calculated by FDM and were in good accordance with other experinments. The effects of cooling conditions and configurations of spray device on the roll temperature have been investigated. The average heat transfer coefficients on the sprayed area are between 12 and 24 kW/㎡K, and proportional to the 0.4 power of the spraying pressure. The results of simulation for hot rolling process show that the enhancement of cooling capacity near the roll bite exit is most efficient.