Elder, William Brian (1995) Numerical model for analysis and control of the quality of bulk-stored grain using cold air. Research Master thesis, Victoria University of Technology.

Abstract

Food grains that have been cooled can be stored for prolonged periods. This is because the rate population increase of insect pests can be slowed, seed viability is maintained, dry matter loss is reduced and the persistence of chemical pesticides can be improved. This thesis reports the development of a mathematical model of ventilated grain stores that enables optimal cooling strategies to be identified and developed. The model describes heat and mass transfer in two dimensions and it enables heat and mass transfer phenomena that occur in the boundary layers of grain stores to be examined in detail. This is achieved by first establishing the air flow distribution in the grain, and then solving the equations that govern heat and moisture transfer. It is believed that this represents an advance on models previously available. In addition to the physical phenomena, the model accounts for biological and chemical phenomena that occur in grain stores. The thesis also describes the development and operation of commercial mobile refrigerated grain cooling units that have been developed by the candidate. The mathematical model is used to determine the optimum strategy for moving the commercial grain cooler from one aeration duct to the other. The objective function is the number of insects in the grain bulk, although other measures such as seed viability and pesticide residue are also examined. Experiments were conducted on a commercially operated shed type store to validate the model using a commercial instrumentation system also developed by the candidate. The research shows that the optimum strategy is different from that of the grain cooling contractor and grain trader based principally on intuition.

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