Dimensional analysis modeling of spraying operation – Impact of fluid properties and pressure nozzle geometric parameters on the pressure-flow rate relationship

Abstract

In food industry, atomization is an essential process as a large range of products are manufactured by spray drying of concentrated solutions. The pressure drop inside the nozzle, and its relation with the flowrate, is of prime importance to size an efficient continuous process. This work thus aims at both studying liquid atomization using pressure nozzles with throttle inserts and proposing a ready-to-use pressure/flowrate correlation from a series of experimental data. Beside the process parameters (flowrate) and fluid parameters (viscosity, density) of prime importance, the geometrical parameters of the nozzle were also accounted for to obtain a generic correlation. Using Newtonian maltodextrin aqueous solutions with viscosity ranging from 1 to 70.10-3 Pa s and eleven nozzle geometries, 264 experiments were performed. Through the use of a dimensionless pressure drop number (Euler number), all the experimental points gathered on a single Eu* vs. Re curve where conventional atomization regimes could be clearly identified. A comprehensive dimensional analysis, relying on the Vashy-Buckingham theorem, was performed. A set of dimensionless correlations, allowing to predict the pressure loss over a wide range of Reynolds number from parameters linked to the fluid, process and nozzle geometry, was then deduced from experimental data.