Modeling of Thin Layer Drying Characteristics of Cassava Grate in a Hybrid Solar Dryer.

Abstract

Cassava grate is a source of raw material for food and other bioprocessing industries. Drying the grate offers opportunities for value addition into novel products, reduction in transportation cost and increase in availability of farming space.  This study presented the mathematical models of the thin-layer drying behaviour of cassava grate using three varieties (TMS 96/1414, TMS 92/0326 and TMS 01/1368), temperature of 50^oC and 0.15m/s air velocity in a hybrid solar dryer which utilizes solar energy and an auxiliary heating system enabling drying at night or under other non-ideal irradiance conditions.  A total of seventeen drying models were used for choosing the best fitness model for describing the drying process; which helps to improve the efficiency of the dryer. The effective moisture diffusivity and activation energy were calculated using Fick’s diffusion equation.  The goodness of fit tests based on the criterion indicated that the Two-term exponential model was the optimum fitted to the drying data of cassava grate from TMS 96/1414, TMS 92/0326 and TMS 01/1368 respectively. The determined effective moisture diffusivity of the grate samples was 6.0984x 10^-8 m² s^-1, 7.2116 x 10^-8 m² s^-1 and 6.7184x10^-9 m² s^-1; the activation energy of the cassava grate samples was calculated as 36.82 kJ mol^-1.