Development of a portable device for the viscosity measurement of non-Newtonian fluids based on pressurized laminar flow

In this study, we focus on developing a simple and flexible rheometer based on pressurized laminar flow. The developed device uses pressure- and flow-rate measurements to calculate the shear rates and shear stresses on the pipe walls, based on the Herschel－Bulkley model. The rotational viscometer, an existing measurement device, struggles with measuring systems that contain large solid particles because of its narrow-gap assumption. Moreover, conventional fluid-delivery measurement devices require large pumps and multiple sensors, necessitating large-scale and expensive setups. In contrast, our device, comprising only a flow meter and a pressure gauge, is simple and can measure various fluids by changing the connected pipe’s diameter. We employed glycerin as a Newtonian single-phase fluid, polymer aqueous solutions as non-Newtonian single-phase fluids, and multiphase food fluids (low-oil-type mayonnaise and ketchup) to compare the rheological analysis data obtained from both the rotational viscometer and our device. Both devices delivered consistent results for Newtonian fluids and non-Newtonian fluids exhibiting shear-thinning behavior. Upon comparing the actual measured shear stresses and shear rates for single-phase fluids, the discrepancy between the results from our device and those from the rotational viscometer was up to ~6.6%, whereas discrepancies of 12.1% and 17.6% were observed for mayonnaise and ketchup, respectively. For the single-phase fluids, the measurement results delivered by both devices were similar; however, discrepancies were observed for the multiphase fluids. These discrepancies are attributable to the accumulated shear stress applied to the fluid and slippage on the tube wall, suggesting that our device enables simple and flexible rheological measurements.