Modelling the mass transfer during convective, microwave and combined microwave-convective drying of solid slabs and cylinders

Abstract

In the present work, the mass transfer characteristics, namely moisture diffusivity and moisture transfer coefficient, of slab and cylindrical potato samples were evaluated by adopting the analytical model proposed by Dincer and Dost [Drying Technology, 13,1/2 (1995), 425]. As part of the experimental work, the moisture contents of slab and cylindrical potato samples dried under convective, microwave and combined convective–microwave conditions (air temperature, 30–60 °C; air velocity, 1–2 ms −1; microwave output power, 30–650 W) were measured. From the data collected the drying coefficients and lag factors were calculated and incorporated into the model. The results showed a reasonably good agreement between the values predicted from the correlation and the experimental observations; average error between experimental and predicted results less that 10%. The experimental system exhibited mass transfer Bi numbers in the range 0.038–11.4, thus indicating the presence of finite internal and external resistances. Moisture diffusivity values in the range 0.13×10 −8 to 24.22×10 −8 m 2s −1 were calculated.