ABSTRACT
The methods of measurement discussed earlier in this book have been developed for, and are generally applicable to, solid or liquid materials, homogenenous and isotropic with heat transferring equally well in all directions. Application of these principles to single units or particles of food and agricultural materials, with modifications to account for the geometry and other assumptions, can be the first step in understanding the heat and mass transfer phenomenon in these biological materials. However, such application to loose and granular materials in packed beds would at best produce a measure of bulk or effective thermal conductivity but not the particle conductivity (Otten, 1974). Nevertheless, most of the work reported in the literature on thermal properties of agricultural granular materials such as seeds and grains, packaged forage, and soils is based on the classical conduction methods discussed earlier with only a few investigators considering the principle of heat transfer in packed beds. The differences between these two methods of approach, together with the associated assumptions and relationships, are discussed as the work on agricultural and food materials is reported in the following sections.
