Investigation of CO₂ Flow Instability in a Heated Tube under Supercritical Pressure

In recent years, supercritical carbon dioxide (CO₂) has gained attention as a promising working fluid for power generation systems, enabling high-efficiency energy conversion from low-temperature heat sources. However, when CO₂ is compressed near its critical point, rapid variations in thermophysical properties can lead to unstable flow behavior. Understanding the onset conditions of such flow instabilities is crucial for the safe and efficient operation of these systems. In this study, we conducted heated flow experiments to investigate the behavior of CO₂ near the critical point, aiming to identify the thresholds at which flow instability occurs.