Studies on Sun Drying of Raw Rough Rice (Part 1)

Thin layer sun drying model

Abstract

Thin layer sun drying experiments done in highly variable weather provided the needed data for subsequent studies on deep bed radiation drying of raw rough rice. The conditions during outdoor natural drying occasionally led to zero drying rates, making it inappropriate to specify a universally applicable model. The effect of radiation on moisture removal is shown by a direct and increasing relationship between incident radiation and vapour pressure difference. Using the least squares method, a drying constant of 0.384 per hour was obtained by plotting the drying rate against moisture difference (M-Me). In almost all the tests done, rough rice surface temperatures were always higher than ambient temperatures, except during overcast sky conditions when the reverse was true.