Numerical investigation on heat transfer performance of molten salt in shell and tube heat exchangers with circularly perforated baffles

The molten-salt heat exchanger is a critical heat transfer device used in concentrated solar power systems. In this paper, molten salt heat-transfer performance characteristics and flow resistances in shell and tube heat exchangers with perforated baffles with a notch height of 0.25D (D is the baffle diameter) are simulated. Four opening schemes that use the same opening area (10% of the baffle area) are designed. The numerical results show that the baffle holes can shrink the molten salt flow dead zone significantly and greatly decrease the flow resistance on the shell side at the cost of a slight reduction in the heat-transfer performance. The comprehensive performance of each scheme after opening is higher than that before opening, and the comprehensive performance of Scheme 4 is the best. Next, a genetic algorithm is used to optimize the Scheme 4 opening diameter. The results show that the heat-flux density on the molten-salt side reaches a maximum of 17327 W/m2 when the opening diameter is 2.24 mm. We find that the opening diameter should be maximized to optimize the comprehensive performance at a given pump power. Finally, the data are compared to other correlations. The deviation decreases gradually as the Reynolds number increases. This is because the turbulence enhancement caused by structural change is not substantial at high Reynolds numbers.