High Knudsen number (Kn) gas flows are found in vacuum and micro-scale systems. Such flows are usually in the slip or transition regimes. In this paper, the direct simulation Monte Carlo (DSMC) method has been applied to compute low pressure, high Kn flow fields in partially heated channels. Computations were carried out for nitrogen, argon, hydrogen, oxygen and noble gas mixtures. Variation of the Kn is obtained by reducing the pressure while keeping the channel width constant. Nonlinear pressure profiles along the channel centerline are observed. Heat transfer from the channel walls is also calculated and compared with the classical Graetz solution. The effects of varying pressure, inlet flow and gas transport properties (Kn, Reynolds number, Re and the Prandtl number, Pr respectively) on the wall heat transfer (Nusselt number, Nu) were examined. A simplified correlation for predicting Nu¯ as a function of the Peclet number, Pe¯ and Kn¯ is presented.

Issue Section:
Forced Convection
Keywords:
channel flow, Knudsen flow, heat transfer, microfluidics, flow simulation, computational fluid dynamics, Monte Carlo methods
Topics:
Computation, Flow (Dynamics), Heat transfer, Pressure, Simulation, Temperature, Monte Carlo methods, Ducts, Fluid dynamics
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