DESIGN, SIMULATION, CONSTRUCTION AND PERFORMANCE COMPARISON OF MIXED-MODE SOLAR CROP DRYERS WITH AND WITHOUT THERMAL STORAGE

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Department of Engineering

ABSTRACT
Agricultural products upon harvesting have high moisture content which makes it unsafe for storage as the moisture in the crops attracts microorganisms which result in deterioration of the products. The major shortcoming of multiple trays drying is uneven drying of the products being dried on different trays.Solar dryers with and without thermal storage materials were developed, simulated and tested under the same meteorological conditions of Zaria and their performance evaluation were carried out. The average drying rates, collector efficiencies, and drying efficiencies of the solar crop dryers with and without thermal storage are 2.82×10−5 kg/s and 2.55×10−5 kg/s, 78.25% and 42.20%, 29.15 % and 25.35% respectively. During the experiment, the drying rates do not vary much with the coordinate positions of the trays. The performances of the solar dryers were simulated under varying meteorological conditions of Zaria. TRANSYS 16.0software was used to simulate the collectors? outlet air temperatures with and without thermal storage. Since a drying model is not available in the TRNSYS library, MATLAB code was written to computes the weight loss of the yam slices in the drying chamber. The computed Nash-Sutcliffe Coefficient of Efficiency (NSE) values and its corresponding Root Means Square Errors(RMSE) between the modeled collector air temperature, and the observed collector air temperature, with and without thermal storage confirms that the model formulation using TRANSYS 16 software used here for the performance simulation of the system is valid and realistic owing to the good quality of fit between the experimental and the simulated results. Similarly, the computed NSE values and its corresponding RMSE between the modeled weight loss of yam slices, and the observed weight loss of yam slices, with and without thermal storage follow the same trend