This paper presents the numerical simulation inside complex geometry drying spaces having hundreds of trays. A set of measurements taken in a laboratory experimental rig above one single tray, was used to validate the turbulence model most appropriate for the analysed configuration. Due to the change of the flow direction inside the investigated domain, the evaluation of velocity components was done using a five-hole tube connected with a "scanivalve" device and a differential pressure transducer. The comparison between the measured data and the predicted results from the numerical simulation of an identical arrangement, led to the conclusion that the standard k-epsilon is the most adequate turbulence model. Extensive simulation of the air flow inside the full-scale industrial dryer and the prediction of its parameters for different configuration helped in the optimisation of the drying space and finally led to a substantial improvement of the quality of the dried product together with considerable reduction of energy consumption. (c) 2005 Elsevier Ltd. All rights reserved.