Transient Temperature Variations in Stored Maize Bulk

Abstract
A two-dimensional transient heat conduction equation was solved by finite- difference method to predict temperature variations within the maize (Zea mays) bin. The mathematical model comprises the center, interior and exterior heat transfer equations. Variables used include bin diameter, bin-wall material, grain temperatures, grain thermal and air properties. Software was developed for the model in Visual Basic. Temperatures within the silo were predicted at radii 0.0m (silo center), 0.35m, and 0.7m (Silo Wall) and depths 0.0m (Silo Floor), 0.30m, 0.70m and 1.1m (Silo Top). To validate the model, a 1- ton capacity, 1.4m diameter and 1.1m height wooden silo was constructed to measure grain temperatures at the same radii and depths within the silo and ambient temperatures between July 1998 and March 1999 (9 months). Predicted and measured temperatures at the various radii and depths were in good agreement and not significantly different using F- test at 5% level of significance. Temperature gradient decreases from the wall towards the center and from the top to the floor. Wooden bin maintained lower temperatures than ambient temperatures at all seasons.

Keywords: Storage, maize, temperature gradient, transient.