Energy loss analysis of volute centrifugal pump handling non-Newtonian emulsions through entropy production theory

Abstract

Flow losses in centrifugal pumps handling non-Newtonian fluids are of great importance for design optimization, performance prediction, and energy savings. Traditional methods are very limited in determining energy losses due to the complex rheological behavior of such fluids. This study aims to investigate the hydraulic losses and performance degradation mechanism of centrifugal volute pumps handling non-Newtonian emulsions using the entropy production method, focusing on the influence of emulsion type on the loss mechanism. The influence of pump size on fluid’s non-Newtonian behavior and energy loss in a centrifugal pump is also investigated by comparing the entropy distribution in two geometrically similar pumps operating with different emulsions exhibiting shear-thinning behavior. The flow field and entropy production are predicted by computational fluid dynamics (CFD) based on the Reynolds-averaged Navier-Stokes (RANS) equations coupled with the k-epsilon turbulence model. The latter is used to acquire the dissipative entropic components of the flow. The results showed that for a non-Newtonian fluid, energy loss occurs primarily in the impeller, regardless of pump size and flow rate. In addition, the shear-thinning behavior of concentrated emulsions significantly affects hydraulic losses, especially in small-size pumps. Most importantly, small-size pumps generate relatively the highest entropy loss over the entire flow range and the entropy loss increases with the lower limit of the non-Newtonian plateau. This approach showed that the predominance of losses in centrifugal volute pumps operating with non-Newtonian fluids depends on the pump size. Thus, indicating that the hydrodynamic characteristics of two geometrically similar pumps do not scale when the liquid has non-Newtonian rheology.

Keywords

• entropy production
• emulsions
• non-newtonian
• cfd
• hydraulic losses
• pump size