Numerical analysis of a helically coiled tube heat exchanger performance utilized in molten salt nuclear reactors for molten salt and He-CO2 working fluid conditions

In addition to the growing global energy demand, the intermittency of conventional renewable energy sources has increasingly directed attention toward nuclear energy. In this study, a heat exchanger responsible for circulating the coolant fluids in Molten Salt Reactors (MSR) was investigated, and the numerical analysis of a helically coiled tube heat exchanger was carried out. The numerical simulations were performed using the Computational Fluid Dynamics (CFD) approach and completed with ANSYS Fluent® software. Initially, analyses were conducted for pure CO₂ gas. Subsequently, CO₂ was mixed with 25 %, 50 %, and 75 % helium (He) gas, and analyses were completed for each case. Finally, pure He performance was evaluated. Each set of analyses was performed for Reynolds numbers (Re) of 50000 and 100000. The results indicate that an increase in the Re number significantly enhanced the heat transfer rate. The addition of helium notably increased the heat transfer rate, with the maximum rate being obtained using pure He gas. However, the transportation and cost of helium must also be considered. Ultimately, mixing CO₂ with He in the current model significantly improved system performance and could directly impact the power output of nuclear reactors. This approach enables higher coolant fluid temperatures to be achieved, thereby facilitating greater energy conversion efficiency.