ABSTRACT
To a first approximation the equations for heat-flow and matter diffusion are equivalent and it was obvious to Johns that the concepts which were developed in his paper [6.1] could be applied to both, provided that the distributed product (RdCd)−1 was set equal to the diffusion constant. There is some evidence that he presented details of the application to food engineering in 1984, but the first serious work was undertaken by M. Hendrickx as part of his PhD research on the absorption of water by white rice at the University of Louvain in Belgium [6.2—6.5]. The state of knowledge in the area of matter diffusion as at 1987 was then summarised by Johns and Pulko [6.6]. TLM has now been applied in other areas involving particle diffusion. Several of these are discussed here, although the chromatographic process is deferred to the next chapter since it combines diffusion with drift.
