THIN LAYER DRYING CHARACTERISTICS OF AMARANTH GRAINS IN A NATURAL CONVECTION SOLAR TENT DRYER

Abstract

This study aimed at determining thin layer drying characteristics of amaranth grains in a natural convention solar dryer. Initially, ttemperature  distribution in the dryer was evaluated using nine discrete points spread in two planes (Planes 1 and 2). Planes 1 and 2 were set at 0.75 and 1.5 m above the concrete base of the dryer. The drying characteristics were determined by drying the grains at two levels (Layers 1 and 2) in the dryer. The control treatment involved drying the grains in the open sun.  The mean temperatures and standard deviations for Plane 1 ranged from 38.2–38.4oC and 6.8–7.3oC, respectively. The corresponding values for Plane 2 were in the range of 38.8–39.2oC and 6.6–6.9oC, respectively. At 5% level of significance, there was no significant difference in temperature distribution within and between the planes. Further, the grains dried in the dryer attained an equilibrium moisture content of 7% d.b from an initial value ranging from 61.3–66.7% d.b after 4.5 hours of drying as opposed to 7 hours for the open sun. The effective moisture diffusivity of the grains ranged from 5.49×10-12–6.20×10-12 m2/s. The findings demonstrate the potential of natural convection solar tent dryers in enhancing drying of amaranth grains in vertical layers.