The direct simulation Monte Carlo (DSMC) method has been employed to analyze the rationality of the 2-D simplification for a 3-D straight rectangular cross-sectional channel. An implicit treatment for low-speed inflow and outflow boundaries for the DSMC of the microchannel flow is employed. The 3-D microchannel flows are simulated with cross aspect ratios in the range of 1 and 5. The calculated flow properties in the 3-D cases are compared with the results of the 2-D case. They show that when the aspect ratio <3, the two extra side walls in the 3-D case have significant effects on the heat transfer and flow properties. When the aspect ratio is increased, the flow pattern and heat transfer characteristics tend to approach those of 2-D results. The 2-D simplification is found to be reasonable only when the cross aspect ratio is greater than 5.
Numerical Heat Transfer, Part A: Applications 52(3), pp.239-250