Poiseuille rayleigh-benard convective flow and compressible boundary effects of near-critical fluid in microchannels

Near-critical/supercritical fluids have been widely proposed in material process, energy conversion and chemical engineering, etc. The present study is focused on the near-critical CO₂ Poiseuille Rayleigh-Benard convective flow in microchannels. Careful numerical procedures are carried out by compressible Navier-Stokes equations, coupled energy and near-critical CO₂ fluid state equations. In the physical model, sudden application of boundary heat fluxes in the boundaries is assumed. The flow and heat transfer characteristics of such Poiseuille Rayleigh-Benard configuration in microscales are systematically explored. For the convection onset, strong near-critical vortex flows are found for a relative wide range of initial and input conditions in microchannels. It is found that typical near-critical thin, hot boundary layer (HBL) plays critical role in the basic stability evolution process. The hot boundary layer formation process and the characteristics of the transition phenomena, convection structure, heat transfer behaviors as well as future development are also presented in this paper. It is hoped that this study can contribute to near-critical hydrodynamics in microscales.