NEAR-AMBIENT DRYING OF STORED WHEAT USING VARIABLE AIR-FLOW - A SIMULATION STUDY

A control algorithm for near-ambient drying of stored wheat with varia ble airflows was slightly modified to improve its performance under th e Canadian Prairie climate and to facilitate the application of the al gorithm in a field situation. The original algorithm was designed to t ake advantage of large diurnal variations in relative humidity and to respond to the overall yearly weather patterns. Changes were made to t he stop conditions of the algorithm, to the reference fixed airflow, a nd to the airflow range. Optimal controlling parameters for the algori thm and a new fixed airflow of 26 L.s(-1).t(-1) were determined by rep eatedly running computer simulations using 30 years of Winnipeg weathe r data (1961 -1990). Using the optimized controlling parameters with t he modified algorithm resulted in a 30 year mean overall cost of dryin g of 1.11 Can$/t of wheat, compared with 2.28 Can$/t using the origina l algorithm and 2.94 Can$/t using a fixed airflow of 26 L.s(-1).t(-1). Cost savings were the result of reduced overdrying and electrical ene rgy costs. The spoilage index and the allowable time for drying were n ot exceeded using the new control algorithm in all 30 years of simulat ions.