刀片式多排密集圆孔气体冲击射流冷却的实验研究

Convective Cooling of Blade-Type Multiply Intensive Circular Gas Impinging Jets

刀片式多排圆孔气体射流可用于受限表面的密集冷却。考察了喷射高度和雷诺数对密集圆孔气体射流冲击光滑平板换热效果的影响。应用热薄膜法测量壁面温度并利用等热流加热获得平均对流换热系数,在射流雷诺数(ReD)的取值范围为5000≤ReD≤48500、量纲为一喷射高度(H/D)分别为6.25、7.50、12.5时,平均努谢尔数随ReD增加而递增,并与H/D的0.606次幂成反比。建立了平均努谢尔数关于ReD、普朗特数(Pr)和H/D的准则关系式,以及密集气体冲击射流冷却的换热准数方程。实验结果与Martin公式的模拟结果比较表明:刀片式圆孔喷嘴密集布置喷孔后,开孔率提高,换热系数大幅提高,约为采用Martin公式得到的换热系数计算值的1.4倍。实验数据与Gardon公式的计算结果非常吻合,与Martin公式的计算结果差别显著,但引入修正函数后与后者能很好地拟合。

Blade-type multiply circular gas jets can be utilized for intensive cooling within limited area.The effects of impingement height H and jet Reynolds numbers on the heat transfer when multiply intensive circular air jets normally impinge on a smooth and flat surface are investigated experimentally.The average convective heat transfer coefficients are measured with heated thin foil technique which involves the detection of surface temperature and apples constant heat flux heating.When the jet Reynolds numbers(ReD)vary from 5000 to 48500 and normalized impingement height(H/D)is 6.25.7.50,12.5,respectively,an increase in jet Reynolds numbers will produce higher average Nusselt numbers,and normalized impingement height with an exponent of−0.606 also have a strong impact on it.The experimental results are compared with Martin’s correlation and about 40%higher is observed.It is indicated that intensive circular nozzle array can significantly enhance heat transfer rate due to its high open porosity.The experimental data are quite well fitted by the corrected Gardon's equation.Conversely,the correlation proposed by Martin is not suitable to deduce present data and a modified geometrical function is developed.