Experimental evaluation of drying kinetics of tomato (Lycopersicum Esculentum L.) slices in twin layer solar tunnel dryer

Abstract

In this study drying kinetics of tomato slices at different positions and trays in twin layer solar tunnel dryer was experimentally evaluated. The temperature profile, air humidity, and vapor pressure deficit of the drying air verse time along the length of the dryer at no-load and full load condition were studied. During full load experiment the dryer were loaded with 180 kg of 5.0 mm thick tomato slices. The moisture loss from the samples were monitored by weighing samples at 3 h interval from each upper and lower tray found at collector out let (0 m), middle of the dryer (8 m) and dryer outlet (16 m). Twin layer solar tunnel drying showed a considerable decrease in drying time with a 37.5‐57% decrease in total drying time as compared to sun drying to decrease the moisture content of tomato slices from 16.54 kg water/kg dry matter to 0.25 kg water/kg dry matter (94.3‐20% (wb)). The drying data were fitted to five drying models and statistical validity of the models were assessed and compared by using the coefficient of determination (R2), root mean square error (ERMS) and reduced chi-square (x2) obtained for these equations. The most suitable model for representing the drying characteristics of tomato slices in the twin layer solar tunnel dryer was the Page model. Effective moisture diffusivity (Deff) of tomato slices was also determined from the experimental drying data. Higher Deff values than open sun drying were obtained for twin layer solar tunnel dried tomato slices.