倾角变化的窄缝通道内CHF理论模型

对倾角变化的矩形窄缝通道的临界热流密度(CHF)进行分析,基于逆向对流限制(CCFL)机理建立相应的理论分析模型,并将该理论模型的预测结果与已有的实验结果进行对比。结果表明:当矩形窄缝通道尺寸为1 mm和2 mm,且倾角在范围在15°~90°时,预测结果与实验值符合得比较好;在倾角小于15°时,理论模型对CHF的预测明显小于实验值;修正的Katto-Kosho关系式可以比较准确地预测倾角小于15°时的CHF值;当通道尺寸为5 mm和10 mm时,预测值比实验值大,这表明基于CCFL机理的CHF预测理论模型仅适用于通道尺寸小于等于2 mm的窄缝通道。

Analytical Model for CHF in Narrow Gaps Concerning Surface Orientation

The CHF in rectangular narrow gaps have been investigated to develop a reasonable predictive model on CHF concerning surface orientation effects.The model is based on the counter current flow limita-tion(CCFL) by flooding of the flow entering gap.The results by the predictive model were compared with the experimental data by Kim and Suh(2003),and a good agreement was obtained in case of 1 mm and 2 mm gap size with surface inclination angle ranging from 10°-90°.However,when the surface inclination angle is less than 10°(nearly downward-facing position),the predictive model underestimated the CHF.The reason may be that the heating surface is covered by a stable vapor film and the vapor film is almost stationary,and that the effects of CCFL on CHF became smaller.A modified Katto-Kosho correlation was further proposed and it could predict the CHF well for inclination angle less than 10°.For gap size equaling to 5 mm and 10 mm,the predictive results were far larger than experimental data by Kim and Suh,which indicated that the validity of model based on CCFL controlled CHF was limited to gaps of less than 2 mm.