低熔点熔融盐管内强迫对流换热的实验研究

利用课题组自行配制的二元混合熔融盐(KNO3-Ca(NO3)2)开展导热油与低熔点熔融盐的管内强制对流实验研究。通过实验得到导热油与低熔点熔融盐的总换热系数,并通过最小二乘法和Wilson分离法得到了管内低熔点熔融盐侧的对流换热系数及其准则关联式。与不同的经典传热关联式对比,最大偏差为+23%。考虑高温熔融盐的变物性特征,利用黏度项对Dittus-Boelter方程关联式进行修正。经过修正后的Dittus-Boelter方程与实验测试结果最大偏差为-15%,偏差值明显减小。过渡流实验数据和Hausen方程及Gnielinski方程的最大偏差均为10%,实验结果验证了传热关系式仍适用于高温熔融盐的结论。

EXPERIMENTAL STUDY ON FORCED CONVECTION HEAT TRANSFER WITH LOW MELTING POINT MOLTEN SALT IN SMOOTH TUBE

In this paper,the experimental study on the forced convection heat transfer between molten salt and heat transfer oil was carried out by using the binary mixed molten salt(KNO3-Ca(NO3)2)prepared by our group.The total heat transfer coefficient of the molten salt-heat transfer oil under different working conditions was obtained.The convective heat transfer coefficient and the convection criterion number correlation of the molten salt in the tube and the molten salt side under the fully developed turbulent flow and transitional flow in the tube were obtained respectively by the Wilson’s Separation Method and the Least Squares Method.The results show that the maximum deviation of turbulent experimental data is+23%compared with the classical correlation.By considering the variable properties of high-temperature molten salt,the viscosity equation is used to correct the Dittus-Boelter equation correlation.It is found that the maximum deviation between the modified Dittus-Boelter equation and the experimental test results is-15%.The deviation value is significantly reduced.The maximum deviation of the transitional flow experimental data from the Hausen equation and the Gnielinski equation is 10%.The test shows that the experimental results of this work are in good agreement with the classical heat transfer formula mentioned above,which isdications that the heat transfer relationship is still applicable to high temperature molten salt.