MINIMUM AIRFLOW RATES TO DRY CORN GRAIN WITH NATURAL AIR IN BOTUCATU-SP

Abstract

Minimum airflow rates are recommended to ambient air grain drying to reduce fan power requirements and grain overdrying. Historical weather records from 1971 were selected to determine airflow rates for drying corn with ambient air in Botucatu, São Paulo State. 1971 was the poorest drying year in the 10-year period from 1971 through 1975 and l977 through 1981. In the simulation of ambient air corn drying initial moisture contents, wet basis used were 22%, 20% and 18% within allowable storage periods of 7, 11 and 29 days, respectively, for monthly average dry bulb temperature of 23.40C, the upmost in the 10-year period. The average dry bulb temperature and relative humidity were calculated from the hourly data recorded at the Faculdade de Ciências Agronômicas, Botucatu county, São Paulo State, weather station. Due to impracticable continuous drying occurrence, only selective ambient air drying was considered, within daily periods from 9 a. m. to 5 p.m., 9 a. am. to 6 p.m. and 8 a.m. to 6 p.m. The simulation results showed that the minimum airflow rates decrease rapidly with decreasing grain equilibrium moisture content a few percentage points. Furthermore, the reduction in daily fan operation a few hours requires significant increases in minimum airflow rates to accomplish ambient air corn drying within the permissible storage time.