Pressure drop of single phase flow in microchannels and its application in characterizing the apparent rheological property of fluids

The aim of this work was to experimentally examine apparent rheological properties of fluids in microchannels based on pressure drop. Pressure drops of Newtonian and non-Newtonian fluids in microchannels were measured using pressure sensors. The effects of flow rate, Reynolds number, and viscosity of fluids on the pressure drop of single phase flow in microchannels were investigated, and the measurements of pressure drop were compared with prediction models. For Newtonian fluids, the friction factor in the laminar regime is f/2 = 26/Re. The results show that the pressure drop of Newtonian fluid is in good agreement with the prediction formula proposed by Cornish. However, the pressure drop of non-Newtonian fluid deviates from the theoretical prediction. A power-law is proposed for the relationship between the apparent viscosity of non-Newtonian fluid and the characteristic shear rate in a microchannel based on the pressure drop measurement. This relationship between the apparent viscosity and the characteristic shear rate in a specific microchannel is completely different from the rheological curve measured by cone-and-plate rheometer, due to the heterogeneous distribution of shear rates at the radial direction for non-Newtonian fluids flowing in a microchannel.