Transient mixing and heat transfer analysis of microchannel near-critical fluid flow

In recent years, micro-scale fluid flow and heat transfer have become one of the most promising and challenging topics in many engineering systems, such as chemical engineering, medical engineering, energy conversion systems, etc. Supercritical/near-critical CO₂ is a natural fluid, which has been widely used as a substitute fluid and has been proved to be advantageous in micro-scale with its preferable thermodynamic properties. The current study numerically studied the near-critical CO₂ horizontal flow and heat transfer performance in micro-scale channels. Due to the thermal-mechanical effects of critical fluid, abnormal thermal convection structure and transient micro-scale vortex mixing evolution mode are found in micro-scale channels. Along with the hot boundary vortex evolution, heat transfer of near-critical micro-scale channel flow is greatly enhanced, leading to fast thermal/heat transfer equilibrium process. The micro-vortex flow and self-expanding nature of the near-critical flow are also discussed into detail in this study.