Numerical study of pulsating pipe flows and enhanced heat transfer of supercritical CO2

Supercritical fluids are extensively utilized in various industrial fields due to their excellent physical properties, where heat transfer plays a vital role. This study demonstrates that pulsating flow , characterized by periodic pulsation of inlet velocity , is an effective approach for enhancing supercritical heat transfer. Numerical simulations of pulsating laminar pipe flow of supercritical CO 2 with heat transfer are conducted using a high-order solver. Results show that pulsating flow disrupts the thermal boundary layer , significantly enhancing heat transfer. The spatially averaged bulk Nusselt number can reach up to 3.37 times the steady-state value, while the spatiotemporal average of wall temperature can drop by 114 K. The enhancement is attributed to the deformation at the interface between thermal boundary layer and bulk flow, driven by nonuniform acceleration and Kelvin–Helmholtz instability. This interface deformation exhibits both migration and superposition characteristics. Key factors such as velocity amplitude, heat flux, and time-averaged equivalent Reynolds numbers are examined for their influences on heat transfer. It is highlighted that increasing pulsation frequency and velocity amplitude can expand the mixing region and significantly improve heat transfer. Furthermore, higher heat flux and lower time-averaged equivalent Reynolds numbers amplify the effects of pulsating flow. • Periodic pulsation of inlet velocity is employed to enhance heat transfer to supercritical CO 2 flowing in a pipe. • Spatially averaged bulk Nusselt number can be enhanced, reaching up to 3.37 times its steady-state counterpart. • Nonuniform acceleration and Kelvin–Helmholtz instability are the underlying mechanisms. • Migration and superposition of disturbances govern the strength of heat transfer enhancement.