AbstractBACKGROUNDOscillatory baffled reactors have good prospect for use in batch to continuous transition for many industries. For reliable design and scale up it is essential to mathematically describe mixing and flow pattern of oscillatory flow. The aim of this study is to investigate the effects of operating conditions on residence time distribution (RTD) of liquid phase in a continuous oscillatory baffled reactor (COBR) and to propose a correlation that accurately describes the flow pattern.RESULTSAnalysis of results obtained for a wide variety of operating conditions in two geometrically similar reactors show that increase of oscillation frequency and amplitude both decrease axial dispersion, with a more prominent effect of amplitude. Proposed power‐law correlation is in very good agreement with all performed experiments. Peclet numbers predicted by this correlation are in reasonably good agreement with the literature experimental data and is much better than the ones obtained by the commonly used correlation, which contains more fitting parameters.CONCLUSIONResults show that relatively high amplitudes, low frequencies and low to moderate secondary non‐oscillatory flow should be used to ensure effective mixing with a low net flow in COBR. Developed correlation offers a simple, yet reliable way to predict the macroscopic flow pattern of liquid in COBR. © 2017 Society of Chemical Industry