THEORETICAL STUDY OF INTERMITTENT DRYING (TEMPERING) IN PROLATE SPHEROIDAL BODIES.

The process of intermittent drying in prolate spheroidal bodies was simulated assuming liquid diffusion to be the sole mass transport process, a constant diffusion coefficient and equilibrium conditions at the surface. The mass diffusion equation in a prolate spheroidal coordinate system was used for a two-dimensional case. Due to the use of a dimensionless coordinate system, a Fourier number for tempering is defined, in order to determine the dimensionless time required to achieve a flat moisture content profile. Assuming that the drying process is stopped only once at a fixed point, the tempering Fourier number was determined for aspect ratios of 1.1, 2.0 and 5.0. Many cases were studied, changing the tempering Fourier and aspect ratio of the body. Focusing on the drying rate, the effect of one, two and four drying passes was studied for different interruption points in the process and aspect ratios of 1.1, 2.0 and 5.0, in all cases using the continuous process as a comparison. From the numerical results it was found that during the tempering process, the drying rate and the final mean moisture content are affected by the tempering Fourier number, multipass drying and geometrical dimensions of the body. [ABSTRACT FROM AUTHOR]