Compact and high-performance primary heat exchangers are essential for achieving high efficiencies in supercritical carbon dioxide (sCO 2 ) Brayton cycles for concentrated solar power (CSP). This study presents a numerical investigation of molten salt–to–sCO 2 primary heat exchangers based on triply periodic minimal surfaces (TPMS) for next-generation CSP systems, addressing a largely unexplored area. A validated numerical model is used to evaluate the thermal–hydraulic performance of gyroid, I-Wrapped package (IWP), and gyroid–primitive hybrid TPMS designs over a range of Reynolds numbers and inlet temperatures for both sCO 2 and molten salt. The results reveal that IWP achieves the highest overall heat transfer coefficient, exceeding the hybrid and gyroid designs by up to 69% and 13% in the cold channel and 85% and 11% in the hot channel, respectively. Geometry-specific correlations for the Nusselt number and overall heat transfer coefficient are developed to support system-level CSP design. The gyroid achieves the best cold-side thermal–hydraulic performance, with j / f 1/3 values 10–42% higher than the IWP and 20–40% higher than the hybrid design. The gyroid's enhanced performance under fixed pumping power conditions arises from curvature-induced secondary vortices and helical flow structures that intensify mixing and disrupt boundary layer development. The IWP design enhances heat transfer through primary flow impingement on the wall but incurs the highest cold-side pressure drop while maintaining an orderly low-velocity flow on the hot side. The hybrid design exhibits the lowest thermal–hydraulic performance. Overall, TPMS-based designs offer a viable high-performance alternative for next-generation CSP systems. • Systematic evaluation of TPMS MS – to – sCO 2 heat exchanger performance is performed. • Geometry-specific correlations for Nu and U are developed for the three TPMS designs. • Gyroid shows higher j / f 1/3 performance than the IWP and hybrid designs. • Secondary vortices and helical flows drive enhanced mixing in the gyroid design.
Shanmugam et al. (Sun,) studied this question.