Numerical simulation on the flow and heat transfer characteristics of molten salt nanofluid in the shell-side of helical baffle heat exchangers with elliptic tubes and circular tubes

In the energy field, molten salts are widely used due to their excellent heat transfer and thermal storage capabilities. However, there is limited research on the flow and heat transfer characteristics of molten salts in the shell-side of heat exchangers. Helical baffles not only guide the shell-side fluid flow but also reduce flow dead zones, further lowering pressure drop. The elliptic tube, with its streamlined structure, can significantly reduce the shell-side fluid pressure drop and optimize the flow characteristics of molten salts in the shell-side of the heat exchanger. In this study, the flow and heat transfer characteristics of molten salt nanofluid in helical baffle heat exchangers with elliptic tube and circular tube were investigated through numerical simulations. The results show that the heat transfer rate in elliptic tube heat exchanger increases by 5.45 %–8.51 %, the pressure drop is 56.55 % of that of the circular tubes, and the heat transfer coefficient per unit pressure drop is 1.85 times higher in elliptic tube heat exchanger. The comprehensive thermal performance factor (TPF) of the elliptic tube is 1.39 on average, indicating that elliptic tubes can improve the comprehensive performance of the heat exchanger, enhancing heat transfer while optimizing fluid flow. The research on the helical baffle heat exchanger with elliptic tubes presented in this paper provides valuable references for the design of future molten salt heat exchangers.