Abstract

The drying characteristics of chrome-tanned leather as a porous medium have been examined with particular reference to the falling rate period of drying between approximately 95% and 12% moisture contents. Samples 0.20 m² have been used with thicknesses ranging from 2.0 to 4.5 mm and with drying air velocities of 2.0 to 7.8 m/sec. Averaged drying rate and moisture content values have been computed from weight loss-time readings and the results plotted. Three findings emerged: first, and perhaps predictably, drying times are dependent on the 0.6 power of the velocity of the air flow over the leather surface according to conventional heat transfer theory. This relationship is true up to about 2.5 mm leather thickness and has important practical implications. Secondly, the moisture content-drying rate relationship can be represented by three straight lines with intersections at 30% and 18% moisture content and the system has three distinct falling rate periods. Thirdly, drying times for the system considered are linearly related, but not directly proportional to leather thickness. The last two of these observations indicate that the equations derived for the drying of a simple capillary system are limited in their application to the drying of chrome leather.