We utilized direct simulation Monte Carlo (DSMC) method to investigate the effects of boundary conditions on the thermal characteristic of the micro/nano mid-driven cavity in the slip and transition regimes. Monatomic argon gas confined in micro/nano isothermal and adiabatic lid-driven cavity is considered in this study. It is seen that hydrodynamic flow behaviors are similar for both cases, however, the adiabatic cavity encounters higher temperature rise in comparison to the isothermal cavity. Moreover, the directions of heat flux streamlines are quite different for the two cases. It is seen that in the slip regime the heat flux streamlines are generated from top left corner and are directed toward all walls of the isothermal cavity. In the adiabatic cavity the heat flux streamlines are only directed toward the driven-lid. Finally, the entropy distribution is calculated in the flow field. It is seen that direction of the heat flux streamlines agrees with the direction of the entropy isolines instead of temperature gradients in the domain. Fourier law, which assumes that heat always fluxes from hotter to colder region, loses its validity in the slip regime and beyond.

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