Modeling of Temperature of Grain During Storage with Aeration

Abstract

Two, 6.6-m-diameter steel bins were used to store wheat for observing seasonal grain temperature variations. Aeration in one bin was controlled by a programmable microprocessor and in the second bin, it was controlled manually with temperature limit settings. In each bin, 132 thermocouples were installed to measure the temperatures of grain at different depths and different radial distances from the bin center. Temperatures of the bin wall, bin floor, and air above the grain surface were also measured. Temperatures were recorded daily using a programmable data acquisition system. Each bin was filled with 99.3 t of Hard Red Winter Wheat to a depth of 3.66 m. Tests were started in May 1988 and ended in December 1990. A model was developed to predict the temperature of grain during storage. The model was based on a two-dimensional transient heat conduction equation with the associated boundary conditions and was solved using the finite difference method for a cylindrical geometry. The model included several sub-models which predicted temperature profiles of soil under the bins, solar radiation on bin wall at any time of day, and convective heat transfer coefficient for the bin wall. Local hourly weather data (air temperature, relative humidity, wind speed, and solar radiation on horizontal surface) and airflow rates during aeration periods were used as model inputs to simulate the temperatures of grain during storage. Predicted and measured grain temperatures were in close agreement for a test period of 32 months. Results indicated that the model and the parameter values used in the model are applicable for predicting temperature of stored wheat with and without aeration.