Convective heat transfer of molten salt in circular tube with nonuniform heat flux

Convective heat transfer performances of molten salt in circular tube with nonuniform heat flux were experimentally investigated using unilateral copper coating tubes. Various experiments were carried out within the range of Reynolds number 10,000-67,000, Prandtl number 4.5-8, and the heat flux ratio of 1.0, 2.0 and 5.7. The results showed that there existed large wall temperature difference in the tube section with nonuniform heat flux, and associated Nusselt number of molten salt flow increased with Reynolds number and Prantal number. Compared with Sieder-Tate correlation, Nusselt number on the smooth side with lower heat flux was mostly larger, while Nusselt number on coating side with higher heat flux was mostly lower. Experimental heat transfer correlation for molten salt flow in circular tube with nonuniform heat flux was developed by least-squares method, and it very well fit with experimental data and classical correlations. In general, average Nusselt number of molten salt flow in circular tube had little relation with nonuniform heat flux, but Nusselt number difference on different sides increased with the heat flux ratio.