Development of compact sCO₂ heat exchangers

Diffusion-welded heat exchangers (Printed Circuit Heat Exchanger-PCHE) are a compact solution for recuperators and coolers in the sCO₂ power circuit (hydraulic diameters of up to 1 mm) due to the very small channels and at the same time achieve an extremely high resistance for the prevailing high-pressure environment. Since up to 90 % of the sCO₂ system costs are directly or indirectly caused by the heat exchangers, optimizing the design is of great importance. There are also challenges for the integration of PCHEs at high temperatures (> 600 °C). In the literature, designs with flow passages with straight channels, zigzag (wave-shaped) channels, channels with S-shaped fins and channels with airfoil-shaped fins are predominantly investigated. However, PCHE are limited by 2-dimensional flow paths, as the channels are etched into the plates. Here, additively manufactured plates instead of diffusion-welded plates offer the possibility of expanding the technical perspective and creating 3-dimensional flow structures. With sCO₂ coolers, heat conduction is often the performance limitation. Here, additively manufactured heat exchangers could be used, which utilize metal powder composed of materials with high strength characteristics and high thermal conductivity. In order to increase the competitiveness of these novel high-performance heat exchangers, issues relating to the design, production and material are addressed and the prototypes produced are tested experimentally.

References

• Guille-Bourdas, A. F.; Bangalore Mohankumar, M.; Unger, S.; Hampel, U.
  Numerical modelling of a primary heat exchanger in sCO₂ power cycles for thermal energy storage systems
  Journal of Engineering for Gas Turbines and Power - Transactions of the ASME 147(2025)6, 061025, DOI: 10.1115/1.4066892

Funding

Design and operation of energy plants with supercritical carbon dioxide (sCO₂) as working fluid - ESCO (BMWK, 03EE5157H). The authors are responsible for the presented content.