Abstract:
The effect of environmental variables such as temperature, relative humidity, rainfall, sunlight and wind on the storability of grain in silos cannot be over emphasized. An evaluation of grain flow patterns and effect of environmental variables on stored grain inside a portable steel silo was carried out to analyze heat and moisture transfer. Parameters such as internal silo temperature, ambient temperature, ambient relative humidity, grain moisture content, discharge time, height of silo and weight of the grain were measured. The ambient temperature, relative humidity and initial grain moisture content were measured using digital thermometer, digital hygrometer and moisture meter respectively. The internal silo temperature and the moisture content of stored grain at five different points within the silo were measured using thermocouples and a data logger of model TC-800D.The discharge time was measured using stop watch. The height of the silo was measured using meter rule and the weighing balance was used to measure the weight of the grain. The flow pattern was observed using relevant modeled equations. The data collected over the storage period of 14 weeks were subjected to appropriate statistical analysis using SPSS version 21.0 and Microsoft excel. The results show that the internal silo temperature ranged from 20.20C to 39.00C while the ambient temperature ranged from 20.00Cto 34.20C. The minimum moisture content of grain was 11.5% (wb) and the maximum moisture content was 13.9% (wb) giving an increment of 2.4%. The highest values of grain moisture and temperature were obtained at the grains stored at the topmost part of the silo. Results show that the moisture migrated within the grains from the silo wall to the centre of the silo. The ambient relative humidity ranged from 74% to 93%.The grain level increased with decrease in coefficient of discharge, velocity of discharge, mass flow rate and volumetric flow rate. There was inverse relationship between mass flow rate and time of discharge. It is advised that the grain loaded into this silo should be of moisture content between 11.5% (wb) to 13.9% (wb) to prevent moisture migration and to enhance storability. It is recommended that the silo should be placed under shed to avoid rain and direct sun.
