Abstract
Hybrid printed circuit heat exchangers have been designed for Gen-IV nuclear power applications. While microchannel devices are commonly fabricated using diffusion bonding, diffusion bonding of these hybrid heat exchangers is challenging due to non-uniform stress distributions across its structure during bonding, which can lead to bonded regions with varied joint properties that can compromise the performance and safety of these devices. In this paper, we delineate a method for determining whether diffusion bonding conditions exist for bonding hybrid printed circuit heat exchangers with maximum joint strength, minimum creep and without yielding or buckling. Diffusion bonding feasibility is determined in two steps. First, an improved pore elimination model is used to identify a feasible set of diffusion bonding parameters that can give acceptable bonded area and compressive creep. Second, a structural analysis is performed on regions in the structure susceptible to yielding and buckling that can constraint the maximum permissible bonding pressure. Diffusion bonding conditions were experimentally validated for bond strength, porosity and creep based on shear test and metallographic examinations as per ASME standards. Two sets of bonding conditions were found to satisfy nuclear boiling and pressure vessel code requirements. Future efforts will involve the diffusion bonding of a hybrid device structure capable of meeting the hermeticity and dimensional integrity requirements of the device.
Published Version
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