Heat transfer and flow characteristics of supercritical carbon dioxide in nanochannels

Abstract

As the integration density of micro-nano electronic devices continues to increase, utilizing nanochannels for thermal management has emerged as a promising approach. Supercritical carbon dioxide (scCO₂) serves as an efficient coolant that can readily achieve a supercritical state within nanochannels, due to confinement effects and interactions with the channel walls. However, its behavior and applications in nanochannels have been less extensively explored. In this study, nonequilibrium molecular dynamics simulations were used to investigate how interface wettability, wall temperature, and applied force affect the heat transfer and flow characteristics of scCO₂ in nanochannels. The results indicate that interface wettability significantly affects the heat transfer characteristics and slip length at the wall-fluid interface. Under strong wettability, the interfacial thermal resistance is two orders of magnitude higher than those under weak wettability. Specifically, the interfacial thermal resistance is 3.01 × 10^-10 (K∙m²)/W under strong wettability and 5.22 × 10^-8 (K∙m²)/W under weak wettability. Similarly, the slip length is −0.204 nm under strong wettability and 0.755 nm under weak wettability. While the wall temperature and applied force exhibit minimal impact on interfacial heat transfer, they significantly influence the slip length. At 700 K, the slip length is 0.106 nm, whereas at 400 K, it decreases to −0.113 nm. Furthermore, when the applied force is increased fivefold, the slip length increases from −0.041 nm to 0.067 nm. Finally, the vibrational density of states, liquid structuring and density depletion length were analyzed to clarify the mechanisms governing interface heat transfer and flow characteristics.