Study on Non-Newtonian liquid single phase flow in rectangular microchannel with sudden expansion

Abstract

The flow characteristics of the single-phase flow including the Newtonian and Non-Newtonian liquids were experimentally investigated in a horizontal rectangular micro-channel with a sudden expansion specifically the pressure changes across the expansion. The rectangular cross-sectional dimension has W_u × H_u (width × height) =0.50×0.50mm² on the upstream side and W_d × H_d(width × height) = 1.0 × 0.50mm² on the downstream side. Distilled water and three series of non-Newtonian shear-thinning liquid were used as the test liquid. The two different methods were used to determine the pressure change across the expansion. The expansion loss coefficient, K_e, was obtained from the pressure change data. The K_e for Newtonian liquid (water) is almost constant over a generalized Reynolds number tested. On the other side, the K_e for viscoelastic non-Newtonian liquids show unusual characteristics that are different from Newtonian fluids specially under low Reynolds number.