Rapid prediction and optimization of thermal performance for spiral-deflector jacketed molten salt steam generators

To address the high computational cost of coupled heat transfer simulations in a helical-baffle jacketed molten-salt steam generator, a 1D–2D axisymmetric bidirectional dynamic coupling model is developed. The model enables dynamic coupled calculations between molten-salt natural convection and in-tube flow boiling. The validation results show that the maximum deviation of the 1D flow boiling model is within 10 %, while the prediction deviation of the 1D–2D coupled model from the three-dimensional CFD results remains within 5 %. Compared with the conventional 1D–3D model, the proposed model reduces the computational time by approximately 83.97 %. The model therefore significantly improves computational efficiency while maintaining good prediction accuracy. Based on this model, the response surface methodology (RSM) and the NSGA-II multi-objective optimization algorithm are combined to perform parametric optimization. The sensible heat discharge ratio and pump work consumption are selected as the optimization objectives. Within the investigated design space, the interaction between the dimensionless baffle pitch and baffle height exhibits the strongest effect on the pump work consumption. In contrast, the coupled effect of and Reynolds number mainly determines the sensible heat discharge ratio. The interaction between the aspect ratio and the performance indicators remains relatively weak. Pareto-front analysis further identifies three representative optimal solutions, including two extreme solutions (Models A and B) and a knee-point solution (Model C). Model A increases the sensible heat discharge ratio and steam production by 40.53 % and 41.14 %, respectively, while the pump work consumption rises by 54.56 %, representing a heat-discharge-oriented optimization strategy. By comparison, Model B reduces the pump work consumption by 89.11 % while maintaining nearly unchanged steam production and sensible heat discharge capability, representing an energy-consumption-oriented optimization strategy. The knee-point solution Model C provides a balanced trade-off between heat discharge performance and flow energy consumption. These results demonstrate that different parameter combinations can achieve flexible trade-offs between thermal performance enhancement and energy consumption reduction. The proposed 1D–2D coupled model and multi-objective optimization method provide an effective tool for the rapid design and engineering optimization of molten-salt steam generators.