Centrifugal pumps are the workhorse of hydraulic conveying systems but their performance is derated when viscous non-Newtonian fluids, such as pastes and/or coarse solids are present. The reduced performance for purely viscous Newtonian fluids may be calculated using techniques such as the Hydraulic Institute method, but similar deration for non-Newtonian fluids is not so easy to apply. As part of the AMIRA P599 project investigating high concentration suspension pumping, centrifugal pump tests were systematically conducted on a wide range of non-Newtonian coarse particle suspensions. Suspensions up to 38% v/v of coarse particles with mean diameters in the range of 1.1 < d 50 < 3.4 mm suspended in carrier fluids with dynamic yield stresses of 0 < τγ < 17.2 Pa and shear thinning indices in the range 0.35 < n < 0.79 were examined. Techniques such as the Hydraulic Institute deration method require a characteristic shear rate to be assigned before application with a non-Newtonian fluid, and a method based on pump geometry, fluid rheology and flow rate is proposed. This method predicts the dramatic characteristic reduction in head at low flow rates that is often observed and explains why larger pumps are relatively insensitive to this form of head deration. Head deration due to the presence of coarse particles in non-Newtonian carrier fluids is seen to follow similar trends to that of Newtonian suspensions and often dominates the total deration procedure.
|Title of host publication||HYDROTRANSPORT 17 - The 17th International Conference on the Hydraulic Transport of Solids|
|Number of pages||15|
|Publication status||Published - 1 Dec 2007|
|Event||17th International Conference on the Hydraulic Transport of Solids, HYDROTRANSPORT 17 - Cape Town, South Africa|
Duration: 7 May 2007 → 11 May 2007
|Conference||17th International Conference on the Hydraulic Transport of Solids, HYDROTRANSPORT 17|
|Period||7/05/07 → 11/05/07|