Transition and turbulent convective heat transfer of molten salt in spirally grooved tube

Transition and turbulent convective heat transfer performances of molten salt in spirally grooved tube were experimentally investigated using electric power through the testing tube. Various experiments were carried out within the range of Reynolds number 5000–15,000, Prandtl number 13.5–15.2, and relative groove height e/d was 0.0238, 0.0306, 0.0381 and 0.0475, respectively. The results showed that Nusselt number of molten salt flow in spirally grooved tube was higher than that of smooth tube, and the groove height increment can remarkably enhance heat transfer. Because the molten salt flow in spirally grooved tube was affected by spirally groove, its critical Reynolds number was less than that in smooth tube. Based on the experimental data and classical correlations by Sieder and Tate and Gnielinski, two modified correlations for molten salt flow in spirally grooved tube were developed by least-squares method. The modified correlations for transition and turbulent flow in spirally grooved tube had good agreement with experimental data, and their exponent of relative groove height was very close.

► Molten salt convection in spirally grooved tube was experimentally investigated.
► Spirally grooved tube can evidently enhance heat transfer of molten salt.
► Nusselt number increased with grooved height and Reynolds number.
► Critical Reynolds number of molten salt in spirally grooved tube decreased.
► Two modified correlations for transition and turbulent flow were developed.