Mathematical Modelling and Solar Tunnel Drying Characteristics of Yellow Maize

Abstract

Solar drying experiments of maizes were conducted at Gape- Kpodzi, in southern Togo. In this purpose, new type tunnel solar dryer was used. Solar dryer consist of an air collector, drying chamber and an air circulation system. Heated air in solar air collector was forced through the maizes by a blower. Yellow dent type maize was used for drying experiments. During the drying period, drying air temperature, relative humidity, air flow rates, solar radiation, and lose of mass were measured continuously in different levels of the dryer. Maize with initial moisture content of 0.37 dry basis (kg water / kg dry matter) were dried until they reached a final moisture content of 0.13 (kg water / kg dry matter) at different temperatures with respect to solar radiation variation. Drying time was examined with moisture content ratio as exponential and polynomial correlations. The effective diffusivity varied from 1.938x10-10 to 1.164x10-10 m2/s over the different level of temperature range. Fourteen different mathematical models available in literature were compared using their coefficient of determination to estimate solar drying curves. According to statistical analysis results, Midilli et al. drying model has shown a better fit to the experimental drying data of maize with a coefficient of determination R2 = 0.9975 as compared to other models. The results of this study revealed that the developed solar tunnel dryer can used for dehydration of maize crops under the climatic conditions of southern Togo.