Thermal diffusivity of granular and porous foods at low moisture content
1997
Kostaropoulos, A.E. | Saravacos, G.D.
Thermal diffusivity is an important transport property of foods, which is useful in computations, simulation and control of several unsteady-state food processing operations. Limited data on thermal diffusivity are available, especially at low moistures, which are of interest in drying and storage processes. Experimental values of the thermal diffusivity (alpha) in the low moisture range were obtained directly for freeze-dried coffee, potato and meat, using the transient method of Dickerson (1965), and indirectly for granular starch, flour, rice, and raisins, using thermal conductivities, obtained by the heated probe method. A nonlinear relationship was found between (alpha) and moisture content in granular and porous foods in the low moisture region. An evaluation of published data indicates a strong effect of physical structure (especially porosity) on the thermal diffusivity. A similar effect has been observed on the moisture diffusivity. These anomalies may be related to the state of water (adsorbed or capillary) in the porous structure of the low-moisture foods.
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