The macadamia processing units use different drying silos, for each drying stage, in order to reduce nuts-in-shell moisture content. Due to the need to quantify the resistance presented by the nuts submitted to different drying airflows, as well as, to evaluate the use of empiric models that predicted pressure losses from airflow, it was carried out several tests in laboratory to obtain experimental data and adjustment of models. Macadamia nuts (M. integrifolia) with 0.11 b.s. moisture content after cleaning and classification were placed into an apparatus constituted by a column of galvanized sheet (in different positions for measuring the static pressure), plenum and fan, being submitted to different airflows. The tests consisted of three repetitions (measures), with three lots of nuts, bringing up to nine measures of static pressure for each position in the column. The obtained results allowed to conclude that the tested airflows showed significant effect on the static air pressure in the macadamia column, which increased lineally with the depth. The experimental data adjusted very well to the Shedd and Hunter's models, suggesting their good suitability for macadamia.
gradient of static pressure; empiric models; macadamia nut
