Numerical Analysis of Flow and Heat Transfer of Supercritical CO2 in Printed Circuit Heat Exchangers with Rectangular/semicircular Channel

The application of spoilers to rectangular printed circuit heat exchanger (PCHE) and the comparative assessment of their thermo‑hydraulic performance represents a relatively underexplored topic. In this work, a numerical investigation is performed on a rectangular PCHE and a conventional semicircular PCHE with hydraulic diameter (3.3mm) using supercritical CO₂ as the working fluid. The numerical model is validated against experimental data, with a maximum deviation of 16.0%, which is acceptable for engineering predictions. Simulations are conducted under low‑temperature recuperator conditions: hot side at 8–9MPa and 353–463K, cold side at 19.0–21.0MPa and 323–353K. Within the parameter ranges examined, the results indicate that heat transfer on the hot side is largely governed by specific heat capacity, whereas on the cold side, it is influenced by both specific heat capacity and thermal conductivity. The buoyancy‑induced secondary flow improves field synergy and heat transfer in the rectangular PCHE, but flattens the velocity profile and degrades heat transfer in the semicircular counterpart. Quantitative data indicate that, the rectangular configuration is recommended for the design of hot‑side channels in PCHE, as its comprehensive performance is expected to increase by 11.5% overall. Benchmarking classical supercritical CO₂ heat transfer correlations against simulation datasets reveals universal underprediction for the rectangular PCHE. Revised empirical correlations are separately developed for the hot and cold sides, yielding maximum deviations of 2.4% and 6.8%, respectively, from the simulation data.