熔盐圆管内湍流对流换热实验研究

Experimental study on turbulent convective heat transfer of molten salts in circular tubes

本文依托高温熔盐(High Temperature Salt,HTS)热工实验回路开展了硝酸盐(KNO3-53%,NaNO2-40%,NaNO3-7%)熔盐圆管内的强迫对流换热特性研究,通过威尔逊修正法获得了熔盐在圆管内充分发展湍流的对流换热系数,将实验结果与公开文献中的5种熔盐的实验结果合并后拟合,获得10 000<Re<50 000和4<Pr<26范围下适用于高温熔盐工质的管内充分发展湍流的实验关联式。另外,为验证熔盐的换热特性是否仍然符合经典关联式的换热规律,将不同种类熔盐工质与经典关联式Dittus-Boelter关联式、Sieder-Tate关联式、Hausen关联式以及Gnielinski关联式进行比较分析,实验结果与经典关联式符合得较好,偏差在25%以内。

[Background] With advantages of large thermal capacity, good chemical stability, high temperature, molten salt has recently been widely used in concentrated solar thermal power plants, nuclear reactors, chemical engineerings, and other fields.[Purpose] This study aims at the convective heat transfer characteristics and verifying the heat transfer laws of molten salt in a circular tube.[Methods] First of all, a thermal experimental loop of Nitrate (KNO3-53%, NaNO2-40%,NaNO3-7%) was built as basic experimental facility. The turbulent convective heat transfer coefficient of molten salt in circular tube for fully developed was obtained by Wilson's correction method. Then the experimental results combining with the experimental data of five kinds of molten salt in the open literature were fitted to get the experimental correlation of molten salt in the range of 10000<Re<50000 and 4<Pr<26 for the turbulent flow in the round tube. Finally, comparisons of different kinds of molten salt with classical correlation Dittus-Boelter correlation, Sieder-Tate correlation, Hausen correlation and Gnielinski correlation were conducted.[Results] The experimental data of molten salt agree well with the existing known relationship, and the deviation was below 25%.[Conclusion] The results show that the heat transfer characteristics of the molten salts still conform to the classical heat transfer relationship.