Simulation of solar air drying of rapeseed

Abstract

The feasibility of solar and combined solar-natural air drying of rapeseed was evaluated using computer simulations. Real-time hourly weather data of ambient air conditions and solar radiation for 1968, 1971, and 1974 have been used in the study. Simulations have been carried out for the three harvesting dates of 10 and 25 February and 10 March and the five moisture contents of 25, 22, 20, 18, and 14 %(d.b.) using an airflow rate of 180 m 3 (h m 2) −1. The complete drying of rapeseed having moisture contents of 20 and 18 %(d.b.) to a safe moisture content of 11.11 %(d.b.) was achieved at depths of 1 and 2 m, respectively, with both solar and solar-natural air drying at all the harvesting dates in all the years studied, except for the rapeseed harvested on 10 February 1974. Both total and actual drying times are increased with increasing depth and initial moisture content. The study of drying parameter profiles has shown that a faster and more complete drying is observed using solar-natural air drying. This is also reflected in the width of drying front being greater when solar-natural drying than when using solar drying alone. The solar-natural air drying regime appears to be superior to that of solar drying alone in respect of the required total drying time and in achieving complete drying within the safe storage time. A saving of actual drying hours is also observed.