In order to minimize the operational time of atomic layer deposition (ALD) process, flow transports and film depositions are investigated in multi-outlet viscous flow reactors through reactor scale simulations. The simulation process is performed on depositions of Al2O3 films using trimethylaluminum and ozone as the precursors, and inert argon as the purge gas. The chemistry mechanism used includes both gas-phase and surface reactions. Simulations are performed at a fixed operating pressure of 10 Torr (1330 Pa) and at two substrate temperatures of 250 degrees C and 300 degrees C, respectively. Flows inside the reactors are following the continuum approach; as a result, the Navier Stokes, energy and species transport equations can be used to simulate transient, laminar and multi-component reacting flows. Based on the chemistry mechanism adopted in this study, the amount of oxygen atoms produced from the ozone decomposition is found to be the major reason for discrepancies in oxidation times and deposition rates at different ALD processes. A reactor with fewer outlets minimizes the ALD operational times by reducing both oxidation time and second purge time. In addition, higher deposition rates at a shorter time are obtained by using a reactor with fewer outlets. However, assigning a long enough time for the ozone exposure results in independency of ALD characteristics from the number of outlets such that the growth rates of around 3.78 angstrom/cycle and 4.52 angstrom/cycle are obtained for the substrate temperatures of 250 degrees C and 300 degrees C, respectively. (C) 2015 Elsevier Ltd. All rights reserved.