Measuring/Modeling the drying process of porous materials

Have you ever wondered why molds grow much quicker on fresh bread than on a piece of dry toast? This everyday observation already shows that drying is a crucial step within the agri-food industry when producing quality products or materials. Drying is a complex process that involves water absorption, transport in porous media and ultimately evaporation. The interaction of these processes is complex which leads to various interesting fundamental and applied questions that require detailed study with modeling tools and advanced measurement techniques. Currently, the departments of Animal Nutrition (ANU) and Physical Chemistry and Soft Matter (PCC) are collaborating in a project, in which we are investigating how water migrates within pelleted animal feeds (Dutch: biks) during the pellet production process. However, feed pellets are made of many heterogeneous products. We would like to investigate the mechanisms behind the drying process of (porous) pelleted materials, by looking at simplified model systems composed of simple plastic spheres and various water absorbing agents such as hydrogels.

Your thesis project:

Figure 1: Project overview
Figure 1: Project overview

In this project you will be working with a capillary rheometer to produce 'synthetic' feed pellets composed of simple components. Combining hygroscopic particles, like hydrogels, together with hydrophobic particles, like plastic microspheres, we can make a pellet which is able to slowly release water when drying it under a certain air-flow. Modeling via finite element methods or Matlab based routines is an optional (or complete) part of the thesis.

The release of water can easily be analysed by the decreasing mass of a pellet, as well as by non-invasive methods like NMR-relaxometry. These complementary techniques will be used to model the drying process of a porous 'synthetic' feedpellet. Key parameters are the degree of porosity of the pellet, the moisture content of the hydrogels and diffusion speed of moisture from the hydrogels into air. The Instron SR50 capillary rheometer is available at one of the collaborating companies within Wageningen, so some company interaction will be involved as well. The results of this project will bring both a deeper understanding and a valuable contribution to the project in which we are investigating the moisture mobility within animal feed pellets.