A simplified model for determination of moisture diffusivity of date from experimental drying curves

Experimental drying curves for Tunisia Deglet Nour dates were obtained in a laboratory dryer under different drying conditions. The air temperature wa s varied from 30 to 69 degrees C, relative humidity from 11.6 to 47.1% and air velocity from 0.9 to 2.7 m/s. A numerical method to obtain a solution o f a diffusion equation in which the diffusivity depends upon temperature an d moisture content has been proposed to investigate the moisture movement i n a date by assuming the sample to be a homogenous infinite cylinder. To fi nd the fitting moisture and temperature dependent diffusivity, the calculat ed drying curves are compared with the observed drying curves and an empiri cal equation for the moisture diffusivity of the date has presented as a fu nction of temperature and moisture. It has been shown that the moisture dis tribution in the date during drying can be obtained by using the empirical equation presented.