The air flow pattern in a co-current pilot plant spray dryer (diameter 2.2 metres) was modelled and measured for the case without spray. The swirl angle was zero and the modelling was done with a computational fluid dynamics package (FLOW3D by CFDS). The boundary conditions for the CFD-model (velocity and turbulence quantities at the inlet) were derived from measurements with a hot-wire probe. To validate the CFD model, air velocity magnitudes were measured at numerous locations in the spray drying chamber. To interpret the data, a novel approach was developed based on the interpretation of velocity distributions rather than time-averaging the signals. This was necessary because of flow reversals and large fluctuations in the air velocity. The measurements were compared with the CFD model results and the agreement between model and measurements was reasonable.