Introduction: Heat exchangers used in high-temperature environments require lightweight designs with high thermal resistance and efficiency. This study numerically investigates the thermal performance of a multi-channel compact cross-flow heat exchanger, focusing on geometric configurations and material selection.

Methods: Simulations were performed under steady-state conditions to reflect the operating conditions in typical micro gas turbine recuperators. The model featured a total mass flow rate of 0.01 kg/s, with hot air at 1223 K and cold air at 453 K. Five geometric configurations (baseline, conical flow diffuser, ramped ribs, semi-circular bumps, and turbulence promoters) and two materials (stainless steel and graphene-reinforced alumina ceramic composite) were compared.

Results: The implementation of these designs resulted in a 30.8% increase in efficiency for steel heat exchangers and a 33.4% increase for ceramic composite heat exchangers. A material change from steel to ceramic in the baseline geometry yielded an 11.3% effectiveness increase. However, geometric enhancements proved more impactful, with effectiveness increasing exponentially for both materials from baseline to the most complex geometry. This highlights geometric optimization as the primary driver of performance gains. Additionally, the ceramic material's 50% lighter weight offers advantages in weight-constrained applications.

Conclusion: These findings confirm that significant performance improvements in compact heat exchangers are achievable through geometric optimization and advanced materials. Geometric augmentations substantially boosted thermal effectiveness, with gains predominantly linked to geometric optimization. This study suggests that optimized flow channels and integrated internal features, facilitated by additive manufacturing, will be crucial for future high-performance heat exchanger designs.