Comprehensive knowledge of hydrodynamics inside the feeding channels of spira-lwound membrane modules is recognized as crucial for the efficient operation of such separation equipments. Slits are laboratory models widely used to mimic the fundamentals of hydrodynamics and mass transfer in spiral-wound membrane modules. In this work micro-PIV was the technique chosen to characterize fully developed laminar flows in a slit for both Newtonian and non-Newtonian fluids. Experiments with water, water-glycerol and water-glycerol-xanthan were carried out at different flow rates, ranging from 4.3. to 25.3 L/h. The ternary mixture water-glycerol-xanthan simulates the non-Newtonian rheological behavior of blood. The other fluids are Newtonian and exhibit different viscosities. The fluids rheology was characterized making recourse to a viscometer. Using micro-PIV, velocity maps at several depths of the channel were obtained. As expected, results showed that the Newtonian fluids flows exhibit parabolic profiles typical of laminar developed flows in slits. On the other hand, slightly flattened profiles characterize the non-Newtonian fluid flows. Comparisons with the analytical solutions for laminar developed flows in rectangular slits are very encouraging. and Obsahuje seznam literatury