Thin-layer rewetting rates of canola (Brassica campestris L.)
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Thin-layer rewetting tests were conducted for seeds of canola (Brassica campestris L.) in the temperature range of 7.5*C to 30.0*C at two relative humidities (80 and 90%) using a thin-layer wetting unit. Separate tests were done at 5.0, 7.0 and 10.0% initial moisture contents of seeds and 0.10, 0.25, and 0.43 m/s air velocities while the air was maintained at 30*C and 90% relative humidity. In the tests, a thin-layer (one to two kernels thick) of canola was held in the vertical plane and the conditioned air was passed through the layer, thus fully exposing the thin-layer of canola to the air. The gain in the mass of the thin-layer of canola with time was recorded using a micro-computer-based data acquisition system. The liquid diffusion equation for an isotropic and homogeneous sphere did not describe the rewetting rate of canola satisfactorily. The thin-layer rewetting rate data agreed well with Page's equation. The parameter n in Page's equation was assumed as a product-dependent constant which made it easy to compare the effects of independent variables on the rewetting rate without causing considerable error in predicting the rewetting rate for canola. A linear relationship was found between the parameter k, temperature and relative humidity. The initial moisture content, in the range from 5 to 10% wet mass basis, had no significant effect (p > 0.05) on the rewetting rate. The rewetting rate did not change significantly with air velocity in the range from 0.25 to 0.43 m/s (p > 0.05). The rewetting rate, however, was slower at 0.10 m/s air velocity. The thin-layer wetting model developed in this study will be of importance in predicting seed moisture changes during near-ambient air drying of bulks of canola.