Thermal-hydraulic performance of printed circuit heat exchanger with supercritical carbon dioxide airfoil fin passage and molten salt straight passage

Highlights: • PCHE with S-CO₂ airfoil fin passage and molten salt straight passage is proposed. • Periodical fins dominate flow and heat transfer tendency but its heat flow is small. • Pressure of S-CO₂ periodically drops with sharp pressure loss in fin region. • Heat transfer coefficient in or near the head region of fin is much higher. • Parallel one has longer period, larger fluctuation and heat transfer coefficient. -- Abstract: Molten salt and supercritical carbon dioxide (S-CO₂) are promising heat transfer fluids, but heat exchanger between molten salt and S-CO₂ is seldom reported. By comprehensively considering low heat transfer coefficient of S-CO₂ and high pressure loss of molten salt, printed circuit heat exchanger (PCHE) with S-CO₂ airfoil fin passage and molten salt straight passage is first proposed and simulated in this paper. Because of fin, flow boundary of S-CO₂ is periodically broken, and there are wakes and vortices in downstream region of fin. Periodical fins dominate flow and heat transfer process, and the pressure of S-CO₂ periodically drops with sharp pressure loss in fin region for large flow resistance, while buoyancy force and turbulent kinetic energy have little effect on heat transfer. Heat transfer coefficients of molten salt and S-CO₂ both periodically change along the flow direction, and they have similar tendency in different regions. Heat transfer coefficient in head region of fin is highest, and that in tail region of fin is lowest for wakes. Heat flow in top and bottom surfaces determine heat transfer of the system, and the region near fin head has high heat transfer coefficient, while the region near fin tail region is lower. Compared with parallel arrangement, pressure and temperature in staggered one has shorter period and smaller fluctuation, and overall heat transfer coefficient and pressure loss will a little lower.