A numerical study of simultaneously developing velocity and temperature fields in trapezoidal microchannels has been conducted in the slip-flow regime. A control-volume based numerical method is used to solve the Navier-Stokes and energy equations with velocity-slip and temperature-jump conditions at the walls. A wide range of channel aspect ratios (0.252α≤≤) and channel side angles (3090φ≤≤) have been considered for Reynolds numbers in the range of . Rarefaction effects as characterized by the Knudsen number (0110.Re≤≤01Kn.≤) are examined in detail for key flow parameters such as the friction factor and Nusselt number. Significant reductions in the friction and heat transfer coefficients are observed in the entrance region due to the existence of large velocity and temperature gradients near the walls. An interesting feature associated with the slip-flow regime is the existence of asymptotic inlet values for the heat transfer and friction coefficients, which depend strongly on Kn but are independent of the channel geometry and Re. Both coefficients are significantly affected by the degree of rarefaction and channel geometry in the fully developed region as well.

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