细通道内R717沸腾干涸特性及关联式评价

The characteristics of dryout of R717 in a mini-channel during boiling and correlations evaluation

研究了R717(氨)在管内直径3 mm细通道内的沸腾传热及摩擦压降特性。从试验结果来看,干涸前后,传热系数与摩擦压降呈现截然相反的变化趋势,干涸前,随着干度的增加,传热系数与摩擦压降明显会逐渐增加。而在干涸后,随着干度的增加,传热系数与摩擦压降出现了不同程度的衰减。利用实测数据对现存的流动沸腾传热关联式和两相流摩擦压降关联式进行评价,评价关联式捕捉干涸后传热系数与摩擦压降衰减的能力。

The characteristics of boiling heat transfer and friction pressure drop of R717(ammonia)in the tube with an inner diameter of 3 mm are studied.From the experimental results,it can be seen that both the heat transfer coefficient and the friction pressure drop show diametrically opposite trends before and after dryout.Before the dryout,the heat transfer coefficient and the friction pressure drop will gradually increase with the increase of vapor quality.After the dryout,the heat transfer coefficient and friction pressure drop have different degrees of attenuation with the increase of vapor quality.The existing correlations of flow boiling heat transfer and friction pressure drop correlations of two-phase flow are evaluated using the measured data,and the ability of the correlations to capture the heat transfer coefficient and friction pressure drop attenuation after dryout is evaluated.