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

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^-6m²/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^-6m²/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^-6m²/s, respectively. There was no difference observed in the effective CO₂ diffusion coefficient when corn moisture content increased from 18.8 to 22.2%.