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.

Mixing Performance of a Suspended Stirrer for Homogenizing Biodegradable Food Waste from Eatery Centers

“…Figure 2 shows the control volumes for a typical staggered grid discretization of the domain. Using the Semi-Implicit Method for Pressure-Linked Equations Consistent (SIMPLEC) algorithm [14,15], Ogedengbe et al [16] proposed Non-Inverted Skew Upwind Scheme (NISUS)-based multiple upstream nodes for convective interpolation. Since the detailed implementation of this formulation is covered elsewhere [15], the imposition of the Dirichlet boundary conditions is focused on here.…”

“…Because of the low shear rate of the liquid food used in the simulation, the viscosity can be assumed independent of shear rate, so that the fluid behaves as a Newtonian fluid. In the simulation presented here, it is assumed that the viscosity can be calculated as a function of temperature [16] The properties of carrot-orange soup used in the simulation are listed in Table 1. An impeller of diameter 0.16 m is used in the simulation.…”

Electro-Kinetic Pumping with Slip Irreversibility in Heat Exchange of CSP-Powered Bio-Digester Assemblies

“…Past studies of these mechanisms [4] have employed the principles of nonequilibrium thermodynamics. Consequently, increasing attention has been directed to the study of fluid flow and heat transfer in micro-channels, including the effects of slip irreversibilities [5].…”

“…This configuration has been proposed as effective and promising for cooling micro-electronic devices [6]. Also, increasing attention has been paid to the study of fluid flow and heat transfer characteristics in a single micro-channel [7,8]. Consequently, the application of these flow characteristics and heat recovery techniques can be leveraged for developing enhanced heat recovery and sustainable energy conversion systems, especially by using concentrating solar energy technologies.…”

Combined Effects of Pipe Diameter, Reynolds Number and Wall Heat Flux and on Flow, Heat Transfer and Second-Law Characteristics of Laminar-Transitional Micro-Pipe Flows

“…Celata et al [6] determined, for the micro-pipe diameter range of d < 100 μm with the non-dimensional roughness of ε * < 0.01, that friction factor tends to deviate from the Poiseuille law when Re > 1300, which can be attributed to the acceleration associated with compressibility effect. As energy conversion of near-wall microfluidic transport was numerically investigated for slip-flow conditions, including different channel aspect ratios, pressure coefficients and slip flow conditions, by Ogedengbe et al [7], Engin et al [8] studied wall roughness effects in microtube flows and evaluated considerable shifts from the conventional laminar flow theory. Laminar and transitional flow experiments in dimpled tubes were performed by Vicente et al [9], who reported a relatively low transition Reynolds number of 1,400 where the roughness induced friction factors were 10% higher than those of the smooth tubes.…”