Slip-flow and heat transfer in rectangular microchannels with constant wall temperature

Abstract

Rarefied gas flow and heat transfer in the entrance region of rectangular microchannels are investigated numerically 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. The effects of Reynolds number ( 0.1 ⩽ Re ⩽ 10 ), channel aspect ratio ( 0 ⩽ α ∗ ⩽ 1 ), and Knudsen number ( Kn ⩽ 0.1 ) on the simultaneously developing velocity and temperature fields, and on the key flow parameters like the entrance length, the friction coefficient, and Nusselt number are examined in detail. In the entrance region, very large reductions are observed in the friction factor and Nusselt number due to rarefaction effects, which also extend to the fully developed region (though at much lower levels). Current results show that the friction and heat transfer coefficients are less sensitive to rarefaction effects in corner-dominated flows as in square channels when compared to flows between parallel plates. Practical engineering correlations are proposed for the friction and heat transfer coefficients in rectangular and trapezoidal channels.