PH—Postharvest Technology: Monitoring and Performance of a Commercial Grain Dryer

This paper presents detailed in situ experimental results for the performance of a commercial batch grain dryer under real operating conditions while drying barley. The distribution of key drying parameters of air temperature, relative humidity, airflow, grain moisture content, drying time and energy use are measured. For the two trials conducted, the overall cycle-averaged process thermal efficiency is 48·4 and 41·5%, respectively. This is achieved when the average initial moisture contents of the grain are, respectively, 15·7 and 17·2% and the highest plenum temperatures 41·4 and 34·0°C. During drying, unlike the stack-on temperatures, the exhaust air temperatures after the grain stack are fairly stable and only mildly affected by the variation of ambient conditions. After the initial heating period, the air enthalpy remains practically constant through the grain stack section. Close to the dryer centre, because of the presence of the auger, the air velocity is considerably lower than other parts of the dryer. The drying appears to be dominated by a drying front advancing through the grain stack. The reduction of grain moisture content is much faster during the last few hours of the drying process. The experiments highlight the importance of accurate measurement and representation of product moisture contents and airflow.