Adiabatic experiments were conducted to measure pressure drop for single-phase liquid and gas-liquid two-phase flows through a circular microchannel with an internal diameter of 100 μm. In order to study the effects of liquid properties on the pressure drop, aqueous solutions of ethanol with different mass concentrations (4.8, 9.5, 49 and 100 wt%) in distilled water and distilled water were used as the working liquid, while nitrogen gas was used for the gas phase. The surface tension of the working liquid ranged from 0.023 N/m (100 wt% ethanol) to 0.072 N/m (water), and viscosity from 0.9 mPa·s (water) to 3.4 mPa·s (49 wt% ethanol aqueous solution). For the single-phase flow experiments, the friction factor data were obtained for each working liquid used, over a Reynolds number range of 2 < Re < 800. For the two-phase flow experiments, pressure drop data were collected over 0.2 < jG < 7 m/s for the superficial gas velocity and 0.1 < jL < 1 m/s for the superficial liquid velocity. For single-phase flows, friction factor data were shown to be in reasonable agreement with conventional theory. Furthermore, early transition from laminar to turbulent flow was not observed over the present experimental flow conditions. For two-phase flows, Lockhart & Martinelli’s correlation was found to be capable of predicting the present pressure drop data irrespective of the working liquid tested, if an appropriate constant needed in the correlation is adopted.

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