Detection, causes and consequences of convection currents in bulk stored grain. A synopsis.

A simple theoretical model was derived to predict velocities of intergranular cyclic air convec­ tion currents in bulk stored grain for a given temperature difference between outer and inner vertical regions of the bulk. Using a tracer gas, the measured airflow in a laboratory simula­ tion was found to be in good agreement with theoretical predictions for differences in the range 17 to 25 °C. In tropical field trials in a metal silo, weather-induced intergranular air convection was, for the first time, detected and quantified in practical bulk storage. Signifi­ cant moisture content increases, proven here to be due to convective air transported moisture, were observed in the top of the grain bulk in laboratory and field experiments. In both cases, troublesome head space condensation occurred. One new way is recommended for reducing observed grain damage due to moisture and the scope for future academic work has been in­ dicated. to observe the physical changes in stored grain induced in the detected ways by and and to recommend ways to minimize these