An engineering model for single-phase flow in a multi-stage rotor-stator spinning disc reactor is presented. The model is based on residence time distribution data, obtained by tracer injection experiments. Measurements are done for gap ratios of G = 0.017 and 0.03, rotational Reynolds numbers of Re = 4.4 x 10(4) to 2.05 x 10(6) and superposed dimensionless throughflow rates of C-w = 127-421. A single rotor-stator cavity can be described by regions of radial plug flow at low radial disc positions, in combination with a single ideally mixed region at high radial positions. The radial position where transition between plug flow and ideally mixed regions occurs decreases with increasing rotational Reynolds number and gap ratio, and increases with increasing superposed throughflow rate. The resulting flow model is explained by the throughflow and rotation dominated regions observed in rotor-stator cavities with superposed throughflow. The model can be used to quantify performance characteristics of rotor-stator spinning disc reactors, without application of extensive numerical simulations. Results indicate that the model can be scaled up with any number of rotor-stator cavities in series, as well as with increasing disc radius and gap ratio. This makes it a valuable tool in scaling up production capacity of the spinning disc reactor. (C) 2014 Elsevier B.V. All rights reserved.