Vapor diffusivity and hygroscopic expansion of corn kernels during adsorption
1990
Muthukumarappan, K. | Gunasekaran, S.
Moisture adsorption tests were conducted using two varieties of corn, locally grown K6400 and Dekalb 547, under the humid air conditions of 75, 85, and 95% relative humidity each at different temperatures of 25, 30, 35, and 40 degrees C. Vapor diffusivity values were estimated based on the Fick's law of diffusion assuming three kernel geometries, namely, infinite slab, infinite cylinder, and sphere. From the analyses, it was found that the infinite-slab model gave the best fit for predicting the adsorption behavior of the corn kernel. Vapor diffusivity of the kernel increased with increase in the absolute temperature of the humid air and followed an Arrhenius-type relationship. However, vapor diffusivity decreased with increase in the relative humidity. The ranges of diffusivity values obtained were from 0.803 X 10-7 to 4.318 X 10-7 m2/h for the K6400 variety and from 0.819 X 10-7 to 4.087 X 10-7 m2/h for the Dekalb 547 variety. Hygroscopic cubical and linear expansions of corn were found to vary linearly with the moisture content in the range of 13 to 24%. Expansion in kernel thickness was the greatest followed by expansion in width and length. Greater hygroscopic expansion and higher vapor diffusivity were observed in the denser variety of corn.
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