Thermal-fluid-solid coupling analysis of vacuum brazing process for a titanium alloy plate-fin structure

Abstract

Vacuum brazing is the most significant step in the production of titanium alloy plate-fin heat exchangers, and its quality regularly determines the mechanical properties and service life. In response to the demand, the thermal-fluid-solid coupling method was established, which focuses on the temperature uniformity, fluidity of brazing filler metal, residual stress distribution characteristics, and deformation distribution characteristics of titanium alloy plate-fin structure (PFS). The multi-field coupling mechanisms involved the vacuum brazing processes were investigated. The formation mechanism during the brazing process was parametrically analyzed using the developed model. The temperature distribution on PFS during vacuum brazing was non-uniform with a maximum temperature difference of less than 70 K. The velocity of fluid flow varied considerably across various regions of the brazing layer during vacuum brazing. The temperature gradient acted as the main driving force for fluid flow. Stress concentration was present at the upper surface of fins and in the middle of the backside. The PFS experienced significant deformation in the Z-axis, reaching a peak value of around 1.1 mm. By verifying experimental measurement results of deformation, the analysis approached based on the multi-field coupling was feasible and highly accurate.