45 research outputs found
Reference Correlation of the Viscosity of Cyclohexane from the Triple Point to 700 K and up to 110 MPa
Reference Correlation of the Viscosity of Cyclohexane from the Triple Point to 700 K and up to 110 MPa
Incorporating Emulsion Drop Coalescence into Population Balance Equation Models of High Pressure Homogenization
Recommended from our members
Experimental Studies and Population Balance Equation Models for Breakage Prediction of Emulsion Drop Size Distributions
A population balance equation (PBE) model for pure drop breakage processes was developed from homogenization experiments and used to investigate model extensibility over a range of emulsion formulation and homogenizer operating variables. Adjustable parameters in the mechanistic breakage functions were estimated from measured drop volume distributions by constrained nonlinear least-squares optimization. Satisfactory prediction of measured bimodal distributions was achieved by the incorporation of two different breakage functions that accounted for large drop breakage due to turbulent shear and for small drop breakage due to collisions between drops and turbulent eddies. Model extensibility to different emulsion compositions and homogenizer pressures was investigated by comparing model predictions generated with the base case parameters to drop volume distributions measured under different conditions. The PBE model satisfactorily accounted for changes in the dispersed phase volume fraction and the interfacial tension with the base case parameters. By contrast, significantly improved predictions for the continuous phase viscosity or multiple formulation variables were obtained through re-estimation of the model parameters using multiple data sets in which the associated variables were systematically varied. The model was not able to satisfactorily predict drop volume distributions resulting from homogenizer pressure changes, perhaps due to the assumption of a constant pressure throughout the homogenizer. We conclude that PBE models of drop breakage can be used to reasonably predict the effects of emulsion formulation variables on drop volume distributions and have the potential for guiding experimental efforts aimed at the design of novel emulsified products
Prediction of Emulsion Drop Size Distributions with Population Balance Equation Models of multiple drop breakage
Most population balance equation (PBE) models of emulsion drop breakage are based on the assumption of binary drop breakage. We previously developed such a PBE model for high-pressure homogenizers with a daughter drop distribution function exhibiting a maximum probability for two equal sized drops. In this paper, we present a PBE model accounting for multiple drop breakage and show that the model provides superior distribution predictions reflected by decrease in least-squares objective function for an oil-in-water emulsion processed in a pilot-scale high-pressure homogenizer. Following our previous work, two distinct rate functions for drop breakage, one due to turbulent eddies and another due to turbulent shear were used to reproduce the measured bimodal distributions. We found that multiple drop breakage was satisfactorily modeled with a uniform daughter drop distribution function if the assumed number of daughter drops formed was chosen to be sufficiently large. The PBE model with multiple drop breakage was shown to provide superior distribution predictions compared to the analogous binary breakage PBE model when adjustable model parameters were determined by nonlinear optimization. The multiple breakage PBE model was shown to be extensible to different emulsion formulations by using these base case model parameters to predict the effects of oil concentration, surfactant concentration, oil-to-surfactant ratio and emulsion premix distribution. Our experiments revealed that substantial breakage of the premix occurred during the first homogenization pass even under zero applied homogenization pressure operation, suggesting an unmodeled pressure independent breakage mechanism