Thermal-hydraulic performance study of swiftlet-type fins for supercritical carbon dioxide precooler

The printed circuit heat exchanger has the advantages of compactness and high efficiency, and is one of the best candidates for precoolers in the supercritical carbon dioxide Brayton cycle. In this paper, for the precooler working condition, the swiftlet-type fin is proposed. The thermal-hydraulic performance of the fin is compared with that of the airfoil fin and the crossed airfoil fin under the same condition by numerical simulation. The flow and heat transfer mechanism of the fin is analyzed based on the field synergy theory and the flow line distribution of the longitudinal section. In the Reynolds number range of 5000 ~ 25000, the Nu of the swiftlet-type fin was improved by 44.5% ~53.0% and 12.1% ~16.6% compared to the airfoil fin and crossed airfoil fin, the f factor increased by 109.1% ~146.3% and 22% ~27%, comprehensive heat transfer performance PEC increased by 6.9% ~19.5% and 6.3% ~11.9%; By studying the effects of different length-to-width ratios (Lc), the widest position of the fin (n), and crossing distances at the tail of the swiftlet-type fin (Le) on convection heat transfer, the optimal structural parameters are derived, when the Reynolds number is less than 15,000, the optimal structure is Lc = 5 mm, n = 0.375, and Le = 1.5 mm; When the Reynolds number is more than 15,000, the optimal structure is Lc = 6 mm, n = 0.25, Le = 1.5 mm. This study can provide guidance for the application of printed circuit plate heat exchangers in precooler condition.