Abstract

High Knudsen (Kn) number flows are found in vacuum and micro-scale systems. Such flows are characterized by non-continuum behavior. For gases, the 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 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 (Nu) were examined. A simplified correlation for predicting Nu¯ as a function of Pe¯ and Kn¯ is presented.

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