Resistance coefficients of fittings for power-law fluids in laminar flow

Abstract

The calculation of head loss in valves and fittings is highly to important design food engineering processes under several pumping conditions. Nevertheless, there are few data reported to predict pressure loss in accessories for non-Newtonian fluids in laminar flow, usually observed in many viscous fluid foods. In this study, experimental data of pressure drops as a function of the generalized Reynolds number were obtained to determine the resistance or friction loss coefficient(kf) of power-law fluids while pumped through 1-in. diameter stainless steel valves (butterfly and globe), and an assembly of four 90° bends. Aqueous dispersions of carboxymethylcellulose were used as a model of a shear thinning fluid. Results showed that for all the accessories evaluated, the kf values hold an inverse function with the generalized Reynolds, using the classical log-log plot. Results are in agreement with data reported in the literature for Newtonian and power-law fluids. The correlations obtained in this study were compared with results in previous works and they were found to be within the range reported.