To enhance the heat exchanger efficiency in a carbon dioxide energy storage system, a printed circuit heat exchanger (PCHE) was employed as the core heat transfer component, with binary nitrate molten salt (solar salt) serving as the cold-side fluid and supercritical carbon dioxide (S-CO₂) as the hot-side fluid. This study aims to investigate the key factors influencing the internal heat transfer process in PCHE and optimize the dominant structural parameters governing its thermal performance, thereby addressing the performance bottlenecks of heat exchangers in such energy storage systems.

Three key structural parameters of the Zigzag PCHE, such as channel diameter, turning angle, and number of turning cycles, were selected as independent variables. The overall heat transfer coefficient K (a core indicator of heat transfer capacity) and the ratio of the overall heat transfer coefficient to pressure drop K/ΔP (a key metric for evaluating the trade-off between heat transfer and flow resistance) were designated as response variables. A three-factor, three-level response surface methodology (RSM) was established to quantitatively analyze the effects of the three structural parameters and their pairwise interactions on the response variables. Parameter optimization of the heat exchange channels was subsequently performed based on the analytical results.

Within the specified parameter ranges (channel diameter: 1.0~2.0 mm, turning angle: 5°~30°, number of turning cycles: 6~10), the results indicate that reducing the channel diameter, increasing the turning angle, or increasing the number of turning cycles can effectively improve the heat transfer efficiency of the Zigzag PCHE. Statistical analysis shows that the channel diameter has a highly significant impact on both K and K/ΔP, and the interaction between the channel diameter and the number of turning cycles also significantly influences these two response variables. The optimal parameter set for achieving the maximum K value (1 313 W/(m²·K)) was determined to be a channel diameter of 1.003 mm, a turning angle of 29.71°, and 9.935 turning cycles. Furthermore, the optimal combination for the comprehensive performance factor K/ΔP was found to be a channel diameter of 2.0 mm, a turning angle of 9.407°, and 6 turning cycles, yielding a K/ΔP value of 0.453 7 W/(m²·K·Pa) and a corresponding K value of 801.7 W/(m²·K). A comparative analysis reveals that the optimized PCHE volume is reduced by approximately one-tenth compared to conventional shell-and-tube heat exchangers.

This study confirms that variations in the channel diameter, turning angle, and number of turning cycles significantly affect the thermal performance of zigzag PCHEs. The response surface methodology proves effective in optimizing the channel structural parameters to enhance heat transfer performance. Moreover, PCHEs demonstrate remarkable compactness advantages in CO₂ energy storage systems, making them well-suited for space-constrained operational environments. The findings provide reliable theoretical and data-driven support for the rational selection and engineering design of heat exchangers in related fields.