CFD investigating thermal-hydraulic characteristics of FLiNaK salt as a heat exchange fluid

Concentrated solar thermal (CST) power plants are promising energy sources for electricity production in the near future. Thermal energy storage via a heat transfer fluid (HTF) is a crucial requirement to enable such plants to deliver electricity. With advantages of high boiling temperature, large specific heat, and low price, molten salts are very suitable for use as HTFs. Therefore, a computational fluid dynamics (CFD) methodology is proposed in this paper for investigating the thermal-hydraulic characteristics of FLiNaK salt. The proposed model is validated through comparison with existing correlations and experimental data of friction factor (fw), Nusselt (Nu) number, and hydraulic and thermal entrance length (Lh,Lth) in a simple round tube under various inlet Reynolds numbers (Re). Specifically, the predicted fully-developed fw corresponds well with that calculated by the Blasius correlation and the Moody diagram. The predicted Nu number is also in close agreement with that determined using Gnielinski’s correlation, revealing that this correlation is more suitable for predicting the heat transfer characteristics of FLiNaK salt.