Study on Enhanced Heat Transfer and Flow Characteristics Outside the Tubes of a Molten Salt Hairpin Heat Exchanger

The molten salt hairpin heat exchanger, with its characteristics of safety, stability, and a compact structure, has shown a broad application prospect in the field of power generation. An in-depth study of its outside the tube bundle heat transfer characteristics is of vital importance for improving heat transfer efficiency. In this study, based on a Stirling power generation experimental platform, the molten salt hairpin heat exchanger was selected as the research subject, and computational fluid dynamics (CFD) technology was utilized for simulation calculations. Key thermodynamic parameters, including power, outlet temperature, and pressure drop, were obtained and compared with experimental data. The results indicate that the maximum deviation between simulation and experiment is controlled within 0.53%, fully verifying the accuracy and reliability of the simulation analysis. To further enhance the heat transfer capacity of the heat exchanger, this study optimized the structure of the traditional smooth tube hairpin heat exchanger. By comparing the heat transfer performance and resistance characteristics under different flow conditions, it was found that when the Reynolds number (Re) changes, the optimized structure with baffles significantly improves the heat transfer performance compared to the traditional smooth tube, while the flow resistance also increases accordingly. In the Reynolds number range of 500 to 15000, the ratio of the Nusselt number ranges from 1.17 to 1.49, and the ratio of the friction factor ranges from 1.29 to 1.56. Particularly, when the Reynolds number approaches 2000, the heat exchanger's heat transfer performance is optimal, with the Performance Evaluation Criterion (PEC) reaching a maximum value of 1.36.