On the Performance of Various Types of Solar Crop Dryers with Thermal Modelling and Simulated Studies

Various types of solar crop dryers are discussed and classified by passive solar-energy drying systems and active solar-energy drying systems. Solar energy dryers are broadly classified into direct, indirect and hybrid solar dryers. The working principle of these dryers is discussed. Energy balance equations have been written for various interactive components, such as top glazing, absorber plate and inside heated air for computing the collector heat-removal factor and thermal efficiency of selected dryer. Mathematical modelling of solar greenhouse dryer is also performed using energy-balance equations to compute convective heat-transfer coefficient, Nusselt number, Reynolds number and overall heat-loss coefficients. Various important conclusions have been drawn through simulation studies for optimising the performance of solar crop drying. Mechanical dryers are discussed which include fixed batch, re-circulation and continuous flow dryers. Biomass-based crop dryers are also discussed including design and thermal analysis of dryer performance.