Using CFD to Model the Processing in the Dairy Industry
A Fundamental Study of Milk Ultrafiltration
Malavika Haribabu, David Dunstan, Greg Martin, Vicky Chen, Dalton Harvie, Malcolm Davidson and Dairy Innovation Australia Ltd.
Malavika is performing postgraduate study on this project. This work is supported by the Australian Research Council Linkage grant, `A Fundamental Study of Milk Ultrafiltration' (LP110200570) and is a collaboration between the University of Melbourne, University of NSW and Dairy Innovation Australia, Ltd.
During the ultrafiltration of skim milk, the permeate comprising serum proteins, lactose, salts and water leaves the system through a semi-permeable membrane, leaving behind larger particles (in the retentate) such as casein and whey proteins. Hence the concentration of the larger particles builds up near the membrane in a phenomenon known as concentration polarization (CP). CP contributes significantly to the resistance of the membrane, limiting the efficiency of the ultrafiltration process.
This study we are developing a comprehensive model of skim milk ultrafiltration that will be employed to improve filtration performance. Since casein is the major contributor to the proteins (80% by weight), we currently consider it as the primary constituent of the retentate. Most of the previous studies model ultrafiltration processes using a single-fluid approach, in which an advective-diffusive solids equation is superimposed over a single momentum (Navier-Stokes type) equation - this approach is strictly only valid in the dilute limit, and partially (at least) neglects particle-particle interactions on the overall momentum balance. Particle-particle interactions are particularly significant in regions of high concentration, for example in the efficiency limiting concentration polarization region formed during ultrafiltration. Our objective is to develop a multi-fluid model for milk ultrafiltration that accounts for particle-particle and fluid-particle interactions, and to validate this model using a concurrently running experimental program.