Study on Thermal–Hydraulic Characteristics of Novel Channels for Printed Circuit Heat Exchanger Using Supercritical CO₂

Two new types of printed circuit heat exchanger (PCHE) channels are proposed based on the typical airfoil fin PCHE channel proposed in literatures (standard channel) to further improve the thermal–hydraulic performances of airfoil fin PCHE channel. The small shuttle fins and oval fins are employed between the adjacent two airfoil fins of two novel channels, respectively. Using supercritical CO₂ as the working fluid, the thermal–hydraulic performances and enhancement mechanisms of the novel channels are numerically investigated. The results show that the channel with shuttle fins has the best comprehensive performance. The Nusselt number of the channel with shuttle fins is 6.7–26% larger, and the f-factor is 8.3–18.6% larger than that of the standard channel under the selected conditions, which leads to a 3–19.1% increase in the PEC (comprehensive performance evaluation criteria). The Nusselt number of the channel with oval fins is 9–27.3% larger, and the f-factor is 26.6–43.4% larger than that of the standard channel, which leads to a 1–15.3% increase in the PEC. The applications of small fins between the adjacent two fins can effectively reduce the low-velocity region area and enhance the local disturbance, thereby effectively improving the thermal–hydraulic performance. The enhancement mechanism of the novel fin PCHE channel structure can be well explained by the principle of field synergy. It can be found that the synergies of the temperature gradient field and the velocity field in two novel channels are significantly improved.