PRINCIPLE AND APPLICATIONS OF DRYING CHARACTERISTIC FUNCTIONS

This article focuses on the concept of a 'drying characteristic functi on,' which is an effective way to correlate drying rate curves for con vective drying of homogeneous nonporous, hygroscopic porous and non-hy groscopic porous materials. The characteristic function, obtained by a certain transformation of a drying rate curve, is independent of dryi ng conditions and hence characterizes the transport kinetics in the ma terial. The principle and some applications of the functions are revie wed. The first application is estimation of drying rate curves. Becaus e any drying rate curve can be transformed into the characteristic fun ction and vice versa, the drying rate can be estimated for various dry ing conditions from a single drying experiment. Another application is determination of the moisture diffusivity. Using the 'flux ratio meth od,' an analytical expression of the characteristic function can be ob tained for any given moisture diffusivity. The expression enables one to determine the moisture diffusivity for a wide range of moisture con tent from a single drying experiment.