Mathematical modeling and simulation of a solar agricultural dryer with back-up biomass burner and thermal storage

Solar drying is a cost-effective and environmentally friendly method for drying agricultural products. To design a proper solar dryer for specific products, thermodynamic relations for the dryer system need to be considered. Numerical simulations are commonly used for the design and operational control of dryers. This study presents the mathematical modeling and simulation of a solar agricultural dryer with back-up biomass burner and thermal storage. Thermodynamic and numerical simulations of the solar collector and drying chamber are performed, while back-up heater (biomass burner) operation is simulated with a computational fluid dynamics (CFD) simulation. For the solar collector, it was found that the presence of a glass cover significantly increases the temperature of the collector; however, increasing the number of glass covers from one to two does not significantly affect the temperature. Variation in thickness of the back insulation has negligible effects, especially for thicknesses over 3 cm. The results show that there is a small difference in temperature between the bottom three trays, while the temperature on the top tray is significantly higher. The CFD simulation showed that the average drying air temperature in the drying chamber was 56 °C, which is suitable for the drying of agricultural products.