(311h) Influence of the Viscosity on the Velocity Propagation in Axial Direction in a Rietema Hydrocyclone
In the field of purification technology such as wastewater and sludge treatment, the rheological characteristics of the liquid media are significantly different from water . As a result, the optimum geometrical proportions may not be sufficient for these applications. Therefore, the velocity propagation in the hydrocyclone is evaluated by PIV (Particle Image Velocimetry) measurements and CFD simulations in different axial positions.
For the rheological modelling of the sludge a mixture of water and glycerol with a viscosity of 6 mPas  is used. The results of measurements and simulations are compared with a water-only system. The hydrocyclone was designed and manufactured according to Rietemawith a diameter of 100 mm and 500 mm in length.
For the water-only system the averaged VelMag/VelMagmax is 0.86 at axial middle position of the cyclone while the velocity ratio is 0.53 for the system with higher viscosity. The viscosity has a strong influence on the axial propagation of the circumferential velocity which leads to a limited efficiency along the conical separation chamber of the hydrocyclone. In conclusion, both Rietema and Bradleygeometrical hydrocyclone proportions may not be the optimum solutions for sludge processing. Further parametric studies on the cone angle and the cyclone length shall lead to optimization potential in the separation process.
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