Slip-flow irreversibility of dissipative kinetic and internal energy exchange in microchannels

Abstract

The mechanisms of near-wall velocity slip and their effects on energy conversion of fluid motion in microchannels are investigated. Unlike large-scale channels with no-slip boundary conditions, this paper predicts how streamwise temperature gradients and transverse velocity gradients contribute to velocity slip during intermolecular interactions near a microchannel wall. A numerical formulation is developed with a mass-weighted convection scheme (called NISUS; non-inverted skew upwind scheme) in a SIMPLEC finite volume method. The new convection scheme provides accurate upstream interpolation of convection variables, including robust pressure/velocity coupling near the slip-flow boundary. Numerical predictions of entropy production characterize the near-wall dissipation of kinetic energy. Effects of varying pressure ratios, accommodation coefficients, flow rates and channel aspect ratios are presented for nitrogen gas flows between Re = 0.001 and 0.003. This paper gives new insight regarding dissipative kinetic and internal energy exchange in microchannels, due to slip-flow behavior.