Modeling and Experimental Validation of Diffusion-Bonded Heat Exchangers with Arbitrary Geometries

This paper presents a robust and innovative thermal-hydraulic modeling methodology for compact diffusion-bonded heat exchangers with different channel cross-section geometries, including semi-circular, circular, and rectangular channel configurations. The proposed approach employs the square root of the channel cross-sectional area as the characteristic length scale in heat transfer and fluid flow analyses, enabling a unified treatment of different channel shapes using fundamental thermal and hydraulic correlations. A custom experimental facility was developed to validate the model under laminar, transitional, and early turbulent conditions. Experiments covered Reynolds numbers from 480 to 2683 for the water stream and from 799 to 3145 for the airstream. The heat transfer rate ranged from 1.22 to 4.36 kW, while the pressure drop varied from 154 to 1748 Pa for the cold stream and from 131 to 1191 Pa for the hot stream. The model was also validated against literature data for different channel geometries, showing good agreement with overall root mean square errors of 6.72% for heat transfer rate and 6.56% for pressure drop. The proposed framework provides a simplified and geometry-independent methodology for the preliminary and detailed design of compact heat exchangers across different operating regimes.