Micro/nano geometries with specified wall heat flux are widely encountered in electronic cooling and micro-/nano-fluidic sensors. In the present study, we introduce a new iterative technique to impose the desired (positive/negative) wall heat flux boundary condition in the DSMC method for Micro/Nano electro-mechanical systems (MEMS/NEMS) applications. In this algorithm, we use the non-dimensional difference between the computed and desired wall heat flux rates to iteratively improve an initial estimate of the wall temperature. A relaxation factor is applied to control the correction of wall temperature values. Effects of different numerical parameters such as number of simulator particles per cell and relaxation factor on the accuracy, performance and robustness of the iterative technique are investigated. We examine our iterative technique by analyzing heating and cooling processes in rarefied pressure-driven micro/nanoscale channel flows. Unique behaviors are observed. For example, contrary to the heating process, it is observed that cooling of micro/nanochannel walls would result in small variations in the density field. Upstream thermal creep effects in the cooling process decrease the velocity slip despite of the Knudsen number increase along the channel. Similarly, cooling process decreases the curvature of the pressure distribution below the linear incompressible distribution. Our results indicate that flow cooling increases the mass flow rate through the channel, and vice versa. We also investigate the effects of wall heat transfer on the hydrodynamics and thermal behaviours in the 2-D micro/nano cavity geometry.

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