Study on Heat Transfer and Flow Characteristics of Supercritical CO₂ of SLM Additive Manufacturing Heat Exchangers with Mini-channels

In recent years, additive manufacturing has gained significant attention in the production of high-temperature and high-pressure mini-channel heat exchangers. Among the various techniques, selective laser melting (SLM) is widely utilized in metal additive manufacturing. This study experimentally investigates the flow and heat transfer performance of rectangular and circular mini-channel heat exchangers produced by SLM. The experiments were conducted under pressure conditions ranging from 8 to 10 MPa and temperatures between 200 and 310°C. Heat transfer correlations for supercritical carbon dioxide (SCO2) in both rectangular and circular mini-channels were refined. Additionally, flow characteristics without heat transfer were analyzed, revealing that the Darcy friction factor in both types of mini-channels initially increases with the Reynolds number (Re), followed by a decrease, and stabilizes at higher Re values.