Diffusion and production of carbon dioxide in bulk corn at various temperatures and moisture contents

Abstract

The effective diffusion coefficient of carbon dioxide (CO2) through bulk corn was determined at various temperatures (10, 20 and 30 °C) and grain moisture contents (14.0, 18.8 and 22.2% w.b.). The diffusion coefficient measurements were conducted using a diffusion cell surrounded by a water jacket, which was used to control the bulk corn temperature in the diffusion cell. A source term (CO2 respiration rate) was introduced in the diffusion equation to account for CO2 production by corn during the diffusion process. Corn respiration rate increased when temperature and grain moisture content increased. As respiration rate increased, it had a larger effect on the diffusion pattern when measuring the effective CO2 diffusion coefficient. The effective CO2 diffusion coefficients through bulk corn ranged between 3.10 × 10−6 and 3.93 × 10−6 m2/s, depending on temperature and moisture conditions. As temperature increased from 10 to 30 °C, the effective CO2 diffusion coefficient through bulk corn increased from 3.21 × 10−6 to 3.76 × 10−6 m2/s. As corn moisture content increased from 14.0 to 18.8% (w.b.), the effective CO2 diffusion coefficient through bulk corn decreased from 3.59 × 10−6 to 3.39 × 10−6 m2/s, respectively. There was no difference observed in the effective CO2 diffusion coefficient when corn moisture content increased from 18.8 to 22.2%.