Dimensionless correlation for the heat transfer coefficient in a batch-indirect rotary drier

A batch-indirect rotary drier heated with steam was experimentally operated to obtain data of moisture content and temperature versus time for soy mea l and fish meal. Operation conditions were as follow: steam pressure (1 to 4 bar), rotation speed (3.7 to 11.6 r.p.m.) and rate of vapor extraction (0 .059 to 0.256 m/s). From experimental data the effective heat transfer coefficient between the hot surface and the bed of solids was determined. These data were correlate d by means of dimensional analysis as a function of the drying process vari ables. The equation obtained for the effective Nusselt number predicts adeq uately the effective heat transfer coefficient, for both substrates, in the range of the operating variables studied.